c s^^Soa 3/SL Environmenta Satellites: Systems, Data Interpretation and Applicatid By Jimmie D. Johnson, Frances C. Parmenter, Ralph Anderson ^^ATES o^ "^ U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Environmental Satellite Service Washington, D.C. May 1975 PREFACE The National Environmental Satellite Service frequently is asked to provide information on the environmental satellite program of the National Oceanic and Atmospheric Administration. Part I of this report contains a reasonably detailed description of past, present, and future environmental satellite systems, their operations and types of data they provide. Part I also describes the various ground systems and data processing and handling methods used to obtain the information from the satellite and to disseminate the data to the users. Finally, the types of launch vehicles used to inject these spacecraft into orbit are briefly described. Part II contains a very thorough and timely presentation on satellite data interpretation and its applications to the users community. Included in this section are descriptions of various applications of satellite data to meteorology, oceanography, and hydrology. A series of slides identical to the pictures in the text accompany this report. They are available for loan upon request. 11 CONTENTS Page Preface ii List of Slides v Part I - Systems 1 I. Introduction l II. Satellites Systems 3 A. TIROS 3 B. TOS/ESSA 5 C . Nimbus ^ ' D. ITOS/NOAA 8 E. Geostationary Satellites 1^ F. LANDSAT 20 G . TIROS N 21 H. SEASAT-A 22 III. Ground Systems and Data Processing and Handling 23 A. Command and Data Acquisition (CDA) Stations 23 B. Satellite Operations Control Center (SOCC) 23 C. Data Processing and Analysis Facility (DAPAF) 24 ^ D. Automatic Picture Transmission (APT) System 24 ^ E. Central Data Distribution System (CDDS) 25 I F . Datalog and Muirhead Systems 27 IV. Launch Vehicles 27 Part II - Data Interpretation and Applications 28 V. Introduction 28 VI. Cloud Interpretation 28 ill CONTENTS — Continued Page VII. Application to Synoptic Scale Analysis 32 A. Circulation Patterns 32 B . Frontal Systems 33 C . Troughs and Ridges 35 >■ D. Jet Streams 36 E. Extratropical Cyclone Development 37 F. Meteorological Analysis and Satellite Data 39 G. Tropical Cyclones 42. H. Tropical Storm Classification 42 VIII. Application to Mesoscale Analysis and Forecasting 44 A. Fog and Stratus Distribution and Dissipation 44 B. Lake Effect Storms 45 C . Differential Heating 47 D. Squall Lines and Thunderstorm Growth 48 E. Mountain Effects 49 F . Air Pollution 51 IX. Hydrologic and Oceanographic Applications 52 A. Terrain Patterns 52 B . Snow Cover 53 C . Ice Surveillance 55 D. Oceanography 36 Selected References 38 Operational Satellite Summaries ^3 IV LIST OF SLIDES Slide No . D escription S].icle 1 - TIROS meteorological satellite system Slide 2 - TIROS operational satellite Slide 3 - Nimbus F satellite system Slide 4 - ITOS satellite Slide 5 - Comparison between Scanning Radiometer and Very High Resolution Radiometer images Slide 6 - Northern Hemisphere mosaic of Scanning Radiometer visible range images for June 8 and 9, 1974 Slide 7 - Northern Hemisphere mosaic of Scanning Radiometer infrared images for June 8 and 9, 1974 Slide 8 - Vertical Temperature Profile Radiometer coverage Slide 9 - SMS/GOES satellite area coverage Slide 10 - SMS/GOES satellite Slide 11 - SMS/GOES data collection system Slide 12 - Comparison of ATS- 3 and SMS- 1 imagery Slide 13 - Resolution of visible SMS-1 images at 4 km, 2 km, and 1 km Slide 14 - False color composite of LANDSAT 1 Imagery Slide 15 - TIROS N satellite Slide 16 - Wallops, Va. , Command and Data Acquisition station Sldie 17 - Automatic Picture Transmission ground receiving station Slide 18 - GOES Central Data Distribution system Slide 19 - Using satellite images in the weather station Slide 20 - Datalog system Slide 21 - Delta launch vehicle Slide 22 - Cloud types, within a frontal system, (A) visible and (B) IR, NOAA-2 VHRR, orbit 4369, 1533 GMT, September 29, 1973. LIST OF SLIDES — Continued Slide No. Description Slide 23 - Closeup of slide 1, (A) visible, (B) IR, NOAA-2 VHRR, orbit 4369, 1533 GMT, September 29, 1973. Slide 24 - Closeup of slide 1, (A) visible, (B) IR, NOAA-2, VHRR, Orbit 4369, 1533 GMT, September 29, 1973. Slide 25 - Wind estimates from geostationary satellites, visible, ATS-3, 1423 GMT, June 25, 1974. Slide 26 - Vortex and frontal system, visible, NOAA-2 SR, orbit 6388, 2124 GMT, March 9, 1974. Slide 27 - Upper level trough and ridge, visible, NOAA-2 SR, orbit 6371, 1310 GMT, March 8, 1974. Slide 28 - Jet stream and frontal band - Pacific, visible (with closeup) NOAA-2 VHRR, orbit 3347, 1944 GMT, July 9, 1973. Slide 29 - Development of a Pacific storm (A) visible, NOAA-2 SR, orbit 6426, 2214 GMT, March 12; (B) orbit 6439, 2307 GMT, March 13; (C) orbit 6451, 2209 GMT, March 14, 1974. Slide 30 - Satellite data input to NMC analysis, (A) IR, NOAA-3 SR, orbit 2870, 0620 GMT, June 26, 1974 and (B) 300-mb analysis 1200 GMT, June 26, 1974. Slide 31 - Hurricane Agnes, visible, ATS-3, 1431 GMT, June 19, 1972. Slide 32 - Cyclone patterns and wind speed and pressure estimates. Slide 33 - Radiation fog, visible, NOAA-2 VHRR, orbit 4506, 1416 GMT, October 10, 1973. Slide 34 - Great Lakes Snowstorms, IR NOAA-2 VHRR, orbit 4838, 0600 GMT, November 5, 1973. Slide 35 - Differential heating and convection patterns, visible ATS-3, (A) 1330 GMT and (B) 1930 GMT, June 13, 1973. Slide 36 - Squall lines and severe thunderstorms, visible DAPP, (A) 1636 GMT and (B) 1818 GMT, August 12, 1972. Slide 37 - Terrain effects, visible NOAA-2 VHRR, orbit 4670, 1632 GMT, October 23, 1973. VI LIST OF SLIDES — Continued Slide No. Description Slide 38 - Haze band east coast, visible, SMS-1, 2100 GMT, July 10, 1974 Slide 39 - Terrain features of the Rocky Mountains U. S., visible, NOAA-2 VHRR, orbit 1590, 1741 GMT, February 19, 1973. Slide 40 - Terrain features of the Southwest U. S., visible, NOAA-2, VHRR, orbit 1590, 1741 GMT, February 19, 1973. Slide 41 - Snow cover around the Great Lakes, visible, NOAA-2 VHRR, orbit 6247, 1517 GMT, February 26, 1974. Slide 42 - Great Lakes ice cover, visible, NOAA-2, VHRR, orbit 6172, 1531 GMT, February 20, 1974. Slide 43 - Gulf Stream, IR, NOAA-2, VHRR, orbit 5858, 1300 GMT, January 26, 1974. vii I ENVIRONMENTAL SATELLITES - SYSTEMS, DATA INTERPRETATION, AND APPLICATIONS JIMMIE D. JOHNSON, FRANCES C. PARMENTER, and RALPH K. ANDERSON NATIONAL ENVIRONMENTAL SATELLITE SERVICE NOAA WASHINGTON, D. C. PART I - SYSTEMS I . INTRODUCTION The Department of Commerce (DOC) is responsible for the establishment and operation of a national operational environmental satellite system. The National Environmental Satellite Service (NESS), a component of the National Oceanic and Atmospheric Administration (NOAA) , is charged with carrying out this responsibility. The operational system is based on space technology developed by government and industry. The National Aeronautics and Space Administration (NASA) procures and launches operational spacecraft as specified by the DOC and is reimbursed with Commerce funds. The objectives of the operational environmental satellite system are: To provide global images of the Earth and its environment regularly both by day and by night, and to provide direct readout of selected data to local ground stations within radio range of the satellites; to obtain quantitative data over the entire Earth on environmental variables such as temperature, moisture, radiation transfer, wind, and solar energetic particle flux for use in numerical analysis and forecast programs; to obtain near-continuous observations of the Earth and its environment, to collect data from remote observing platforms (buoys, ships, automatic stations, aircraft, and ballons) , and to broadcast environmental data to remote stations; and to provide satellite products for operational use and to develop practical techniques for applying these products to environmental service programs. The operational system consists of satellites, a Satellite Operations Control Center (SOCC) and Command and Data Acquisition (CDA) stations through which satellites are controlled and data are acquired, facilities for processing and analyzing of satellite products, and laboratories for developing satellite sensors and for developing operational and research applications of satellite data. Since April 1, 1960, when the first Television and Infrared Observation Satellite (TIROS) 1 was launched, environmental satellites have undergone some rather dramatic technical and conceptual changes. Satellites, control systems, orbital configurations, sensors, and data processing and handling systems have been modified, improved, and augmented by newly developed concepts or equipment. Several distinct systems of operational and experimental environmental satellites have been developed and used by the United States since 1960. These are: Polar-Orbiting Satellites - These spacecraft are placed in orbit so that they circle the Earth in a north/south direction in a near-polar orbit. The average altitude of most of these satellites is close to 1500 km; global images of the Earth and vertical temperature and moisture soundings of the atmosphere are obtained twice each day. However, there are some variations which will be described in greater detail later in the text. Satellites included in this category are: (1) TIROS; (2) TIROS Operational Satellite (TOS) also known as the Environmental Survey Satellite (ESSA) ; (3) Nimbus; (4) Improved TIROS Operational Satellite (ITOS) also known as NOAA; (5) Land Satellite (LANDSAT) ; and (6) TIROS N a new generation satellite. Goestationary Satellites - These spacecraft are placed in orbit approximately 36,000 km above the Earth's equator at a predetermined latitude. At this altitude, the period of circular orbit of the satellite is 24 hours. Since the Earth and the satellite turn through the same angular distance in the same time and in the same direction, the satellite continuously observes the same area on the Earth. Satellites included in this category are: (1) Applications Technology Satellites (ATS) and (2) Synchronous Meteorological Satellites/Geostationary Operational Environmental Satellites (SMS/GOES). -2- II. SATELLITE SYSTEMS -Fl R O S METEOROLOGICAL. SATELLITE DECEIVING ANTENNA p^-SOLAII CELlS .^^IR PACKAGE Slide 1. TIROS meteorological satellite system A, TIROS TIROS 1, the first meteorological satellite to provide photographs of the Earth and clouds, was launched on April 1, 1960 from Cape Canaveral (Kennedy) Florida. Since then, nine more TIROS satellites and nine ESSA (See II. B) satellites have been launched and used successfully. (See operational satellite summaries) The TIROS and ESSA (also known as TOS , or TIROS Operational Satellites) spacecraft were similar in appearance and nearly identical in size. Each weighed about 136 kg, was 57 cm high, and was 107 cm in diameter. The top and sides of these roughly cylindrical spacecraft were covered with more than 9,000 solar cells which provided the power to operate all onboard systems. The primary sensors were television cameras and low- and medium- resolution infrared radiometers. TIROS cameras used vidicon tubes 1.27 cm in diameter. The vidicon tube is similar in principle to those use in TV cameras; it has a photo sensitive face and with an internal scanning device that converts the image on the tube face to an analog signal. Five hundred scan lines were used in the 1.27 cm vidicon. The infrared radiometers and the Automatic Picture Transmission (APT) system are described later. -3- With orbits inclined at 48° to the Equator, the first TIROS satellites could obtain meteorologically useful data to about latitudes 55°N and 55°S. The next four TIROS, in orbits inclined at 58° to the plane of the Equator, could acquire data as far north and south as latitude 65°. TIROS 9 and 10 were launched into near polar, sun synchronous orbits. All TIROS (except TIROS 9) spun on their axis about ten times per minute to maintain a relatively constant attitude in space. TIROS 9 was a prototype of the TOS system (ESSA satellites) concept. Four different cameras were used on TIROS satellites. Their characteristics are listed in Table 1. Table 1. Vidicon camera types used on TIROS satellites TABLE 1 TV raster Best Vidicon Lens field Area in view* lines per resolution type of view (km) picture (km) Wide angle 104° Medium angle 80° Narrow angle 13° APT 108° 1208 725 121 1208 500 500 500 800 3.2 1.6 0.8 1.6 * Length of side of square area in vertical view from 765 km. TIROS 1 operated successfully for 79 days and acquired some 20,000 photographs. Both TIROS 1 and 2 were equipp-ed with one wide and one narrow-angle camera on each satellite. Experience showed that while the narrow-angle camera provided interesting details, the greater area viewed by the wide-angle camera was more useful for meteorological purposes. Thus, a decision was made to use two wide-angle cameras on TIROS 3. Other combinations were used experimentally on later spacecraft of the TIROS series, but all experience pointed toward the use of wide-angle cameras for optimal meteorological usefulness. Operating lifetime of the later satellites in the TIROS series increased steadily. TIROS 4 was the first spacecraft to exceed the design lifetime of 120 days. Operation of TIROS consisted basically of commanding the satellite to take pictures and to transmit the pictures and other data to the ground. The satellite control center computed the command signals to be sent to the satellite and passed this information to the CDA stations. The CDA station transmitted the commands to the TIROS as it passed overhead. When -4- the satellite reached the sunlit portion of the orbit, a clock system in the satellite started the camera. Every 30 seconds after start time the camera took a picture, until 32 pictures were recorded on magnetic tape aboard the satellite. A limit of 32 pictures per camera was imposed by the capacity of the magnetic tape storage. As the satellite returned to within telemetry range, the acquisition station commanded the satellite to transmit stored pictures and other data, to transmit direct pictures if the station was in daylight, and finally to set the clock for the next orbit. Slide 2. TIROS operational satellite B. TOS/ESSA The TIROS Operational Satellite (TOS) spacecraft were similar to, and based on, the technology proven in the TIROS experimental program. TOS system satellites were renamed ESSA after achieving orbit. There were nine successful ESSA launches. ESSA 8, launched December 15, 1968, continues to produce operational data; ESSA 9 took pictures for nearly five years until finally deactivated on November 29, 1973. The TOS system was designed to fill the need for a relatively low cost, fully operational weather satellite system. These "wheel" satellites were launched into near-polar, sun-synchronous orbits to provide worldwide photographic and infrared coverage of the Earth and its atmosphere. The distinctive feature of the ESSA "wheel" satellite was that the spin axis of the spacecraft was held perpendicular to the plane of the orbit so, in effect, the satellite "rolled" along its orbit on its "rim". With its two cameras mounted 180 degrees apart and looking out through the rim instead of through the base plate as in the standard TIROS, the Earth came into view directly below each camera once each revolution of the spacecraft. -5- Each picture covered an approximately square area 3330 km on a side; the resolution was about 3.8 km at the picture center, and about 7.4 km at the edge of the picture. The vidicon used was 2.54 cm in diameter; 800 scan lines were used to produce each picture. The TOS system went into operation in February 1966 with the launches of ESSA 1 on February 3 and ESSA 2 on February 28. The ESSA 1 was identical with the TIROS 9 spacecraft used to test the TOS system concept. The ESSA spacecraft were designed to operate at a 1388 km altitude with an orbital period of approximately 114 minutes. At this altitude and with the near-polar retrograde orbit, the satellite crossed the Equator at the same local sun time each day, and all parts of the Earth, except for those in polar darkness, were photographed at least once every 24 hours. The TOS system consisted of two ESSA satellites in orbit simultaneously. Odd numbered ESSA satellites (except ESSA 1) were equipped with two Advanced Vidicon Camera System (AVCS) cameras with associated tape recorders to store pictures for later high-speed transmission to the CDA stations in Alaska and Virginia. ESSA 3, launched October 2, 1966, was the first AVCS satellite of the TOS system. ESSA 1 did not contain the advanced version of the vidicon camera system. Even numbered ESSA satellites had two APT cameras to provide direct transmission to all ground stations equipped with suitable receivers. The AVCS satellite also carried low resolution infrared sensors to obtain information on the heat balance of the earth-atmosphere system. Operation of the ESSA series was much the same as that of the TIROS series. The near-polar, sun-synchronous orbits of the ESSA spacecraft permitted complete Earth coverage, so the necessity to choose where to photograph was not a factor. However, a command had to be given to the satellite when to photograph so that pictures were taken over the sunlit side of the Earth. The greater altitude at which these satellites were operated also made possible complete photographic coverage with only six pictures per orbital pass over the sunlit side of the orbit. Twelve pictures, with 50 percent overlap from picture to picture, were normally acquired on each pass. Thus, the satellite provided global coverage by means of 144 to 156 pictures every 24 hours. The use of 1.27 cm vidicons operated at a lower altitude, as was done with TIROS 9 and ESSA 1, required between 450 and 500 pictures for the same overlapping coverage. -6- NIMBUS F SPACECRAFT SOLAR ARRAY SUN SENSOR TRACKING &DAIA RELAY EXPERIMENT 1 1 iORCI ELECTRICALLY SCANNED MICROWAVE RADIOMETER (ESMRI RIGHT SOLAR PADDlf VERSATILE INFORMATION PROCESSOR IVIPl BEACON ANTENNA SCANNING MICROWAVE SPECTROMETER ISCAMSi COM^WND ANTENNA LIMB RADIANCE INFRARED RADIOMETER ILRIRI PRESSURE MODULATED RADIOMETER (PMRl .DIGITAL SOLAR ASPECT SENSOR IDSASI TEMPERATURE HUMIDITY INFRARED RADIOMETER ITHIRI HIGH RESOLUTION INFRARED RADIATION SOUNDER IHIRSI TROPICAL WIND ENERGY ' CONVERSION REFERENCE LEVEL EXPERIMENT IIWERLEI ANTENNA Slide 3. Nimbus F satellite system C. Nimbus Nimbus, the Latin word for cloud, identifies a more sophisticated NASA research and development spacecraft. Nimbus spacecraft are about three times the size and weight of the TIROS and ESSA. Originally conceived as the operational successor to TIROS, Nimbus turned out to be too complicated and expensive for that purpose and has since been used as a platform for testing new and improved cameras and sensors. Many of these sensors and other parts of the Nimbus system are shown in slide 3. Nimbus spacecraft in sun-synchronous, near-polar orbits provide global coverage twice in each 24-hour period. The spacecraft are butterfly-shaped, 3 m tall and 1.5 m in diameter. A circular structure forming the base of the spacecraft houses the major subsystems and experiments. A three-axis active attitude control subsystem mounted above the sensory ring keeps the spacecraft sensors oriented toward Earth's center with an accuracy of better than one degree. Two solar paddles track the sun during daylight operation and convert its energy into power for the spacecraft's subsystems. -7- The five Nimbus research spacecraft orbited to date (see table 2) have been used for development, test, and application of a variety of new and advanced meteorological and geophysical remote-sensing instruments and associated data-transmission and processing techniques. Nimbus satellites " flight tested the APT and AVCS systems used on the TIROS/ESSA series the high-resolution infrared scanning radiometers (HRIR) and the forerunner to the vertical temperature profile radiometers used on the ITOS series, and data relay devices and other instrumentation to be used on future satellites. It is worth noting, however, that the APT was first flight tested on TIROS 8. A wealth of new data applicable to meteorology, oceanography, geology, and hydrology have been transmitted to Earth from the Nimbus spacecraft. Slide 4. ITOS satellite D. ITOS/NOAA The improved TIROS Operational Satellite, ITOS 1, ushered in the second generation polar-orbiting operational satellite system. It dramatically exceeded the capability of the first generation TOS/ESSA operational system, and the national operational environmental satellite system moved closer to achieving its goals. ITOS coincided with the formation of the National Oceanic and Atmospheric Administration (NOAA) . In addition to previous concern with the atmosphere, NOAA has responsibility to describe and understand the oceans, the atmosphere, and the sun; to observe, describe, and predict the state of oceans and atmosphere; and to determine precisely the size and shape of the Earth. Satellite instrumentation systems are being developed to obtain measurements on sea-surface conditions, ionospheric conditions, soil, and snow and ice conditions. 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B CJ O- !-i 60 CJ (U >-i iH >-i (U 5-1 •H B >-i (U T) >-( CU iH CU H CU S o o 4-) (U CU 3 4J CO +J 4-1 CLJ m 4-1 :s > u CU O CU XI CU W CO •H CO B •H B (U B (U E o u +J 5-1 o >-l o 5-1 o to o S CO (U o (U •H 4J •H CO •H 3 CO 4-J ^ 4-1 CU o- Ti O 13 5-1 XI ^ m CO CJ rH iH B CO CU CO >4-< CO B M !>^ CO •H CU (U Pi iH Pi C Pi •H 3 CO CO P4 CO H W M S CO I C/3 P3 I I I I t> CAl Pi H c/^ H c/:3 Pi P^ H CO I I CO pi w u a CO -10- carried on the TTOS 1 and NO/Vf\ 1 spacecraft. A comprehensive survey of the possibilities for measuring and detecting occurrences such as earthquakes, seismic sea waves (tsunamis), volcanic activity, and many other phenomena from either manned or unmanned spacecraft h.as been made. TTOS 1, the !^ASA prototype for the system, was launched on January 23, 1970 and became operational in June ]970. NOAA 1, the first NOAA operational spacecraft of the TTOS series, was launched December 11, 1970: it contained the same instrument package as TTOS 1. Since then, three more ITOS satellites have been placed in orbit, and a total of seven will be launched. Because the ITOS spacecraft was designed to do the work of a pair of FSSA spacecraft, both ITOS 1 and NOAA 1 had AVCS and APT capability. The required night tim.e capability was met by the addition of a Scanning Radiometer (SF) . SR data were stored on magnetic tape for later readout at the CDA stations and also were broadcast through the APT transmitter for local ground reception. These capabilities permitted operational day and night coverage for the first time. The original design lifetime was six months, but beginning with NOAA 2 the design lifetime was extended to one year. The ITOS spacecraft is considerably different in appearance from the earlier TIROS and TOS series. The spacecraft is 102 by 102 by 122 cm, weighs 284 kg, and carries three solar paddles, 91 x 160 cm, which generate 200 to 400 V7atts of electrical power. The satellite is earth-oriented; stabilization is provided by a flywheel rotating at 150 rpm. ITOS 1 and NOAA 1 each had two AVCS, two APT, two two-channel Scanning Radiometers, a Solar Proton Monitor, and a Flat Plate Radiometer (FPR) . The two-channel SR senses in the 0.5 to 0.7 micrometer (visible) region and the 10.5 to 12.5 micrometer (atmospheric infrared window) region to provide day and night viewing capability. The FPR furnished atmospheric heat balance measurements. The orbit for ITOS is similar to those of the TOS/ESSA series: sun-synchronous, near-polar, at an average altitude near ]470 km and an orbit period of about 115 minutes. The Solar Proton Monitor v/as the first non-meteorological instrument to be carried on operational satellites. Measurement of the solar proton flux is useful for estimating the degree of activity of the sun; this information can be used in forecasts of radio communications conditions. NOAA 2, launched October 15, 1972, was redesigned to incorporate two new instruments and to eliminate the APT and AVCS cameras and FPR. With the addition of the Very High Resolution Radiometer (VHRR) and t'ne Vertical Temperature Profile Radiometer (VTPR) , NOAA 2 became the first spacecraft to rely entirely on scanning radiometers for images and the first to carry an operational sensor capable of obtaining vertical temperature profiles of the atm.osphere over most of the Farth. NOAA 3 and NOAA 4, launched November 6, 1973 and November 15, 1974 respectively, were identical to NOAA 2. -11- The VHRR sensor measures cloud top temperatures or ground and sea surface temperatures in clear areas, both by day and by night, and transmits these data in real time to High Resolution Picture Transmission (HRPT) receiving stations. In addition, eight minutes of data per orbit may be programmed for storage in the satellites for later playback to the CDA stations. The operation of the two channel VHRR is similar to that of the SR, but the data acquired are of much higher resolution. One channel measures reflected visual radiation in the 0.6 to 0.7 micrometer range, and the second channel measures infrared radiation in the 10.5 to 12.5 micrometer range, both at 1 km resolution. The VHRR data provide more contrast between earth and clouds than do the SR data. G^E Slide 5. Comparison between Scanning Radiometer and Very High Resolution Radiometer images The resolution difference between the SR and WRR is clearly shown in Slide 5. The left portion of the slide is a visual image of eastern Canada, the eastern United States and the western Atlantic taken on May 1, 1974. To the right are two VHRR images of portions of the same area taken on the same day. The top image is in the visible wavelength and the bottom image is in the infrared wavelength. The detail shown in the VHRR images is quite superior to the detail shown in the SR image. For example, the ice cover and open water areas in Hudson Bay, James Bay, and Goose Bay are clearly delineated in the VHRR visible images; these conditions are barely discernible in the SR images. Similarly, the VHRR infrared image shows physical detail and temperature differences of the Great Lakes area that cannot be seen in the SR image. The St. Lawrence River, Cape Cod, and Long Island also are clear in the VHRR image. -12- Slide 6. Northern Hemisphere mosaic of Scanning Radiometer visible range images for June 8 and 9, 1974 Slide 7, Northern Hemisphere mosaic of Scanning Radiometer infrared images for June 8 and 9, 1974 Another method of displaying SR images is in the form of hemispheric mosaics. Slides 6 and 7 show a visible and an infrared mosaic of the Northern Hemisphere. These mosaics, derived from SR visible and infrared data for a 24 hour period are prepared by high speed computers. The scan-line signals are digitized, earth located, and reporduced on a standard polar stereographic map projection. Coastal outlines and 10° latitude- longitude lines are added by computer. Overlap between successive swaths is eliminated with the latest data retained. Similar mosaics of the Southern Hemisphere also are produced. -13- i 30 NOV 72 0000 GMT SHIP 4YJ 52 5N 20 OW 12 DEC 72 0214 GMT 70 OS 25 6W RADIOSONDE OBSERVATION (RAOB)- NOAA-2 VTPR Soundings Over 12-Hour Period Slide 8. Vertical Temperature Profile Radiometer coverage TEMPERATURE |K1 TEMPERATURE PROFILE COMPARISONS Slide 8 shows a typical area covered by VTPR soundings in a 12 hour period and some comparisons between temperature profiles obtained by VTPR and by radiosonde observation (RAOB) . The VTPR sensor makes radiance measurements in the 15 micrometer carbon dioxide band. These measurements are used to construct vertical temperature profiles of the atmosphere, from the Earth's surface to an altitude of 30 km, twice daily over most of the Earth. In addition to being used for making atmospheric soundings, a 12 micrometer "window" radiance measurement, a 19 micrometer water vapor band measurement, and six carbon dioxide band measurements are used secondaril}'^ to evaluate the amount of cloud cover. Measurements are made continuously day and night. VTPR data are recorded throughout the orbit and are played back when the satellite is over a CDA station. An innovation of NOAA 3 permits the direct broadcast of VTPR radiance data to ground stations equipped to receive such data. E. Geostationary Satellites Remarkable as the development of polar-orbiting satellites has been, it represents only half of the environmental satellite achievement. To achieve the objectives outlined in the introduction, it was necessary to develop the Geostationary Operational Environmental Satellite (GOES) system. -14- There is nothing theoretically new about placing satellites into geostationary orbits. As the distance between satellite and planet increases, the speed required to maintain an orbit decreases. At an altitude of about 35,903 km the orbital speed is down to about 10,948 km per hour and the period of circular orbit becomes 24 hours. It this 35,903 km orbit lies in the plane of the Earth's equator, the satellite and Earth revolve at the same rate so the satellite is always above the same point on the equator. Earth-synchronous, geosynchronous, and geostationary are terms used to describe such an orbit. By 1966, considerable expertise in achieving geostationary orbits had been developed on civilian communications projects, such as Early Bird (launched in April 1965) and on some military projects. The first environmentally important system was NASA's experimental series known as Applications Technology Satellite (ATS). The ATS spacecraft are cylindrical in shape, 137 cm long, 146 cm in diameter, and weigh 352 kg. Those designed to acquire environmental data are equipped with a Spin-Scan Cloud Camera (SSCC) . The SSCC has a field-of-view approximately 15,000 km in diameter. ATS-1, launched December 7, 1966, was placed into geostationary orbit over the Pacific Ocean at the equator at 150° West longitude. Four days later, the SSCC began transmitting continuous photographic coverage (complete picture approximately every 30 minutes) of the Pacific Basin and western United States. The camera had peak sensitivity in the green region of the visible spectrum which permitted maximum information to be obtained when the signals were converted to black and white photographs. Its resolution was about 3.2 km. The ATS-1 camera system operated until October 15, 1972. ATS-3, launched November 5, 1967, also was a major success. From its geostationary vantage point over the equator at 69° West longitude, the view from the satellite includes much of North America, the North and South Atlantic Ocean, all of South America, and the western edges of Africa and Europe. Important weather communications techniques were also tested on the ATS system. In the Weather Facsimile (WEFAX) experiment, weather data are transmitted from the Wallops CDA station to the satellite, which relays them to local APT receivers. Information transmitted on WEFAX consists of processed satellite data. The major shortcoming of the ATS was that it viewed the Earth only in daylight. However, ATS successes formed the technological base from which the SMS/GOES began. -15- Slide 9. SMS/GOES satellite area coverage On May 17, 1974 SMS 1 was launched into geosynchronous orbit over the equator at 45° West longitude to support the Global Atmospheric Research Program (GARP) Atlantic Tropical Experiment (GATE) . After the Gate experiment the spacecraft was moved to its nonimal position near 75° West longitude. NASA's second prototype, SMS 2 was launched on February 6, 1975, SMS 2 was placed in orbit over the equator at 115° West longitude. The first NOAA-funded operational spacecraft of the GOES series is scheduled for launch late in 1975. After the first GOES is launched, one satellite will be placed near 135° West longitude and the other at 75° W. With one satellite at each of these positions, the useful camera coverage and communications range will extend westward from western Europe and Africa to the Western Pacific Ocean and will include all of North and South America. -16- Slide 10. SMS/GOES satellite The SMS/GOES satellites (Slide 10) are cylindrical in shape and weigh about 305 kg; they are 191 cm in diameter and 231 cm high (exclusive of the magnetometer which extends 84 cm outside the spacecraft) . The principal instrument is the Visible and Infrared Spin-Scan Radiometer (VISSR) , which provides both day and night mapping capability; the resolution is 1 km in the visible channel and about 8 km in the infrared channel. The visible (0.54 to 0.70 micrometer) channel provides albedo measurements between 0.5 and 100 percent; and the infrared (10.5 to 12.6 micrometer) channel provides radiance temperature measurements between 180k and 315k. The SMS/GOES satellite also carries a Space Environment Monitor (SEM) . The SEM sensor measures solar energy particles, X-ray emissions, and magnetic field variations; all are important for use in planning for and the operation of high altitude and manned space flights and radio communications. SEM data are broadcast continuously for use in advisory and warning messages and also for use in forecasting and operational research. -17- ^ i' we, ,. M^ i L ^^I^S&» , «a«- -— — •' Slide 11. SMS/GOES data collection system The SMS/GOES satellites also are equipped with a Data Collection System (DCS) to collect and relay environmental data sensed by a variety of widely dispersed platforms such as automatic weather stations, river and rain gauges, tsunami stations, seismometers, tide gauges, buoys and ships. Each satellite can handle data from about 10,000 individual observing platforms within each 6 hour period. Each platform must be equipped with a Data Collection Platform Radio Set (DCPRS) to provide the communication link between the platform and the satellite. Both scheduled and interrogated data are transmitted from the platform to the VJallops CDA station via the satellite. Data are relayed from the CDA station to the World Meteorological Center, Washington, D. C. The raw data then are forwarded to the user community. The SMS/GOES satellites also include the WEFAX service described earlier. -18- Slide 12. Comparison of ATS 3 and SMS 1 imagery This comparison of ATS 3 and SMS 1 full disk visible images taken on June 28, 1974 at 1300 GMT shows the superior detail of SMS 1 pictures even though both are at 4 km resolution. For example, the cloud patterns in the low pressure center and associated frontal system over the eastern United States and western North Atlantic are much sharper in the SMS 1 image. The same is true of the clouds over the central portion of the Atlantic. '4 ul-M-; Qiao Ci?^ r.; Hlft'll Slide 13. Resolution of visible SMS 1 images at 4 km, 2 km, and 1 km -19- Slide 13 shows SMS 1 visible channel sectors at resolutions of 4, 2, and 1 km. In the frontal system extending along the east coast of the United States, and into the Gulf of Mexico the cloud detail increases considerably between the 4 km resolution image (above) and the 2 km resolution image (lower left) . The increase in cloud detail is especially striking in the 1 km resolution image (lower right) . F. LAND SAT LANDSAT spacecraft are NASA research and development satellites. Much of their data are used by NOAA for environmental applications. LANDSAT 1, originally known as ERTS (Earth Resources Technology Satellite), weighs nearly 909 kg. It was launched into a 918 km polar orbit on July 23, 1972. It makes 14 orbits per day, views a swath 200 km wide with 100 m resolution, and requires 18 days to obtain complete global coverage. LANDSAT 2 was launched on January 22, 1975. LANDSAT sensors consist of three Return Beam Vidicon (RBV) cameras which photograph the Earth in the green, red, and near-infrared portions of the electromagnetic spectrum, and the Multi-Spectral Scanner (MSS) which senses in four spectral bands, the visible green and red (0.5 to 0.6 and 0.6 to 0.7 micrometer) and two near infrared (0.7 to 0.8 and 0.8 to 1.1 micrometer) Slide 14. False color composite of LANDSAT 1 imagery -20- LANDSAT 1 is an experiinental spacecraft, intended to cemonstrate the usefulness of repeated global sensing of conditions on the Earth's surface, Investigators are evaluating the lANDSAT 1 data for applications in agriculture, cartography, forestry, geology, geography, hydrology, oceanography and meteorology. The photograph in slide lA is a false-color combination of simultaneous pictures from the RBV cameras showing the blue water areas of Chesapeake Bay on the right side of the picture. Light blue areas just to the left of center and top center show the positions of WasMrgton, D. C. and Baltimore, Maryland. The red portions are areas of more dense vegetation. Slide 15. TIROS N satellite G. TIROS N A third generation polar-orbiting satellite system is now being planned by NOAA and NASA. NASA's operational prototype for this system, TIROS N, is scheduled for launch early in 1978; it will be followed by the launch of the first NOAA operational spacecraft in this series later in 1978. TIROS N will overlap the current ITOS system for a short time to assure continued, uninterrupted service. -21- The TIROS N satellite will contain advanced sensors to provide improved temperature soundings. Microwave channels will be used to facilitate sounding retrieval in cloudy areas. This satellite will provide advanced multi-channel images and will have a data collection and platform location system on board. The design lifetime for this operational spacecraft is two years. During the lifetime of the TIROS N series, new sensors or instruments may be added or substituted for others, therefore the spacecraft is being designed for a growth capability of 25 percent in terms of weight, volume, power, command, and telemetry. TIROS N and the subsequent NOAA operational spacecraft of this series will carry a TIROS Operational Vertical Sounder (TOVS) with a Basic Sounding Unit (BSU) of 14 infrared channels, a Stratospheric Sounding Unit (SSU) of three infrared channels, and a Microwave Sounding Unit (MSU) of four channels. Radiance measurements from these units will provide temperature soundings accurate to 1°C from the Earth's surface to 50 km and water vapor soundings to 15 km. An Advanced Very High Resolution Radiometer (AVHRR) will provide data in four channels. The additional channels will improve delineation of land, water, melting and non-melting snow and ice, and improved sea surface temperature measurements in partly cloudy areas. AVHRR data will be broadcast directly at both 4 km and 1 km resolutions. A Space Environment Monitor (SEM) will provide for worldwide monitoring of solar proton and electron flux density and the total energy disposition in the near-earth environment. A Data Collection and Platform Location System (DCPLS) will receive data for later transmission to a central facility. The DCPLS also will have the capability of locating moving platforms . H. SEASAT-A SEASAT-A will be a polar-orbiting satellite dedicated to oceanographic research and development, and it will be designed to demonstrate the capability to measure global ocean dynamics and physical characteristics. SEASAT-A is now only in the planning stages, but the following instruments are planned to be carried by this spacecraft: a multifrequency microwave radiometer to measure high speed surface winds and sea state; a precision radar altimeter to measure sea surface topography and wave heights; a high resolution imaging radar to measure wave spectra and to map sea ice conditions; and a visible and infrared scanning radiometer to measure sea surface temperatures, ice conditions, and other oceanographic data. SEASAT-A data are expected to provide more accurate and longer term forecasting of storms and tidal conditions, high seas and adverse currents, and ice field conditions. Research applications of SEASAT-A data will be made to ship routing, ocean exploration, selection of criteria for design and location of offshore structures, and improvements in shoreline protection. NASA is providing the SEASAT-A spacecraft, launch vehicle, and launch services. Responsibility for data application will be assumed by the marine community of users. SEASAT-A is scheduled to be launched in 1978. -22- III. GROUND SYSTEMS AND DATA PROCESSING AND HANDLING Slide 16. Wallops, Va. , Command and Data Acquisition Station A. Command and Data Acquisition Stations (CDA) This CDA station (Slide 16) at Wallops, Va. , with its 26 m antenna system, is one of the two NOAA CDA stations. A similar station is located at Gilmore Creek, Alaska. The CDA stations are responsible for acquisition, command, and dissemination of data from environmental satellites. Gilmore Creek handles the polar-orbiting satellites only. Wallops Station handles the geostationary satellites as well. Spacecraft telemetry and sensor data are recorded in analog forra on magnetic tape and relayed from the CDA stations to NESS in Suitland. B. Satellite Operations Control Center (SOCC) SOCC duties include real-time monitoring and assessment of the spacecraft and CDA station operation, near real-time systems evaluation, origination of spacecraft command programs, magnetic attitude control programming, attitude determination, maintenance of engineering and other data records, and delivery of spacecraft operational environmental and engineering data to appropriate users. -23- C. Data Processing and Analysis Facility (DAPAF) This facility uses general and special purpose cornputers to locate, formate, and digitize the input data, and to produce scale-rectified digital map printouts and other summaries of environmental observations. For example, gridded visual displays of cloud cover are produced and distributed. DAPAF also processes spacecraft beacon data for use by SOCC. ANTENNA POSITION INDICATOR FM RECEIVER ANTENNA POSITION CONTROLLER WRITING DESK POWER DISTRIBUTION PANEL FACSIMILE RECORDER FACSIMILE PAPER STORAGE DRAWER STORAGE SPACE Slide 17, station Automatic Picture Transmission ground receiving D. Automatic Picture Transmission (APT) System The APT transmitter aboard an environmental spacecraft broadcasts data that can be read directly by any APT ground station within range of the broadcast. This system was originally tested with the TIROS 8 and the Nimbus 1 and 2 spacecraft. The APT system, as first conceived, was used on the ESSA, the ITOS 1, and the NOAA 1 satellites. APT ground systems (Slide 17) have since been modified to obtain direct readout of scanning radiometer data from the later ITOS spacecraft. The objective of the APT system is to make spacecraft images available at a minimum cost to anyone within radio range of the satellite. APT receiving stations are located in about 120 countries. -24- GOES CENTRALIZED DATA DISTRIBUTION SYSTEM (CDDS) SPSS SFO Sect<^s Western WSFO's SPSS MKC Sectors Central WSFO's NESS Central Kvis. Sector^ IR Low Resolution IR — ► To SPSS SFO IR IR IR To SFSS MKC ► To SFSS MIA ■ — ► To SFSS HNL SFSS DCA (WWB) ► Sectors SFSS MIA Sectors Eastern WSFO's SJU WSFO SFSS HNL Slide 18. GOES Central Data Distribution System E. Central Data Distribution System (CDDS) An integral part of the SMS/GOES system concept is the CDDS (Slide 18) . Stretched VISSR data are sent to the Satellite Field Services Station (SFSS) by the Wallops CDA station via the satellite and the Washington, D. C. Central Facility. The SFSS disseminates these data to regional environmental activities. Low resolution infrared images are transmitted directly to the SFSS from the CDA. -25- ^m^atm Slide 19. Using satellite images in the weather station A VISSR picture of the entire Earth disk is available every 30 minutes. Because the accumulation of data is too voluminous to transmit in real time, the data are divided into smaller geographical areas, or sectors, for local use. These sectors are transmitted to the using SFSS. Weather Service Forecast Offices receive sectors of the VISSR data from the SFSS for display and local use. The infrared data are reduced to video imagery at the SFSS for analysis and imterpretation. When the Earth is dark or when the sectorizing effort fails, infrared data are given to users in place of visible data. Slide 20. Datalog system -26- F. Datalog and Muirhead Systems In the Datalog System, picture signals received from the sectorizers are translated into sharply focused light impulses and recorded on a sheet of photo-sensitive paper on a rotating drum. At the end of each transmission, the Datalog photo recorder automatically stops, recycles, and the exposed photo paper Is ejected from the picture drum and a new sheet taken up. After 10 seconds the photo recorder is ready for the next transmission. Meanwhile, the exposed paper is being developed automatically After one minute, an original picture with very fine detail is available. Datalog is used primarily to produce the SMS/GOES images, but it also can display ITOS data although in a slightly distorted fashion because of the different scan rate. Datalog Systems can be used at any installation that can receive real-time SMS/GOES images. Another system used to process satellite pictures is the Muirhead Photo- Facsimile Recorder, which receives facsimile signals transmitted over telephone lines. Satellite images are recorded on photographic film wrapped aroung a rotating drum. IV. LAUNCH VEHICLES Slide 21. Delta launch vehicle -27- A two stage Delta Launch Vehicle is used to inject the polar-orbiting satellites into orbit. This type of launch vehicle has been used to launch a wide variety of scientific, comniunications, and earch resources spacecraft. Launch attempts have been successful more than 90 percent of the time. The present Delta Launch Vehicle is capable of boosting a 1,136 kg payload into a 805 km orbit. It is 33 m long, weighs 89,868 kg at liftoff, and has a maximum diameter of 2.44 m. The po].ar-orbiting satellites are launched from the Western Test Range at Vandenberg Air Force Base, California. The SNS/GOES are launched from the Eastern Test Range in Florida by a Delta Launch Vehicle (Slide 21) similar to that used to launch the polar-orbiters . Injection into geostationary orbit is accomplished in three stages rather than the two stages used for the polar-orbiting satellites. PART II - DATA INTERPRETATION AND APPLICATIONS V. INTRODUCTION Today, our satellite systems provide more satellite data, at greater frequency, and covering greater areas, than ever before. A number of instruments designed to sense various parameters of meteorological and environmental interest have been tested experimentally. Currently, two sensors are being used operationally: the first senses in the visible spectrum (0.6 to 0.7 micrometers) and records the albedo or reflected light imagery of the underlying clouds, ground or ocean surfaces; the second senses in the infrared spectrum (10 to 12 micrometers) and provides temperature data of the viewed cloud tops, terrain or ocean surfaces. VI. CLOUD INTERPRETATION In the satellite data, each cloud type has a characteristic pattern and brightness or temperature return. Familarity with these cloud characteristics will facilitate the analysis or interpretation of the satellite data. Some of the satellite-observed details are described in these slides. -28- •H o Pi Pd c pa n3 42 •H •H > < 4-1 CO CO d n •H r^ ^ CTi (/} CN 0) a u >^ 0) o a. CO OJ s OJ •rH n -— I m LTj I— I -29- This visible, IR comparison shows the cloud system associated with a storm centered over Nebraska. The occluded front extends eastward from Nebraska to a point south of the Great Lakes and hence southward to the Louisiana Coast. In the visible data (left), most of the clouds appear uniformly white and must be identified by their shape, size, texture and pattern. In the IR display (right), the gray shades relate directly to the temperature of the emitting surfaces. The highest, coldest clouds are the brightest while the lowest, warmest clouds are the darkest. For example, the lowest clouds in this imagery are the stratocumulus (A) along the rear edge of the occluded portion of the frontal band. In the visible data, gray shade variations in this type of cloud depend on the thickness of the cloud as well as the sun angle. In the IR view, these same clouds are a dark gray which identifies them as being low. High cirrus is indicated by G, H, and I. Cirrus clouds can be in the form of a thick cirrostratus sheet, as fibrous streaks or thick convective cirrus spissatus elements. Cirrus is often difficult to detect in the visible data except by its shadow. Three areas of cirrus can be seen here: the first at (G) is a layer of semi-transparent cirrostratus; at (H) the cirrus is thicker, but still somewhat transparent; and at (I) the cirrus is somewhat convective in nature. These following two slides are close-up views of this same storm. The letters on all three slides relate to the same cloud formations. Slide 23. Closeup of slide 1, (A) visible, (B) IR, NOAA-2 VHRR, orbit A369, 1533 GMT, September 29, 1973. -30- The clouds In the center of this vortex are composed of altostratus (F) and cirrus clouds. Note how easily the cirrus can be detected in the IR data at points (G) and (H) where it overlies another cloud deck. The presence and the convective and fibrous character of the cirrus at (I) is certainly more obvious in the IR data. Use of the visible and IR data together permits the meteorologist to quickly assess the cloud structure of frontal systems. Slide 24. Closeup of Slide 1, (A) visible, (B) IR, NOAA-2 VHRR, orbit 4369, 1533 GMT, September 29, 1973. The frontal cloud band which spirals to a vortex center is usually composed of convective clouds and thick multiple layers of altostratus clouds. In the visible imagery, altostratus appears relatively bright when it is thick and often has a mottled appearance because of variations in cloud thickness caused by convection within the clouds. Thin altostratus of uniform thickness without underlying clouds will appear semi-transparent and quite gray. In the IR imagery altostratus appears uniformly gray. This view also shows various forms of cumulus. In the warm air ahead of the cold front, there is a field of very small, irregularly shaped fair weather cumulus clouds (B) . These clouds are frequently organized into lines or cellular patterns which are best detected in the visible data. In the IR, fair weather cumulus are hardly detectable at all because of the small temperature difference between the cloud tops and the Earth's surface, Under favorable conditions, some of these small clouds may grow to cumulus congestus such as at (C) or cumulonimbus clusters (D) . The taller clouds ■31- with colder tops appear brighter. The cumulus congestus (C) and cumulonimbus clusters (D,E) are easier to locate in the IR. Cirrus topped thunderstorms are usually the brightest (coldest) clouds in IR imagery. The cirrus-topped cumulonimbus clouds are also among the brightest clouds appearing in the visible satellite data. Characteristic to these clusters is a sharp upwind boundary with a filmy anvil edge downwind. These cumulonimbus clouds can appear singly, in lines, or be embedded in frontal bands such as at (E) . VII. APPLICATION TO SYNOPTIC SCALE ANALYSIS By analyzing the type of clouds that are present, the meteorologist can locate fronts, squall lines, jet streams, troughs, and ridges. Further, he can assess the stage and trend of development of mid-latitude and tropical storm systems. In many cases, it is possible to infer the presence of turbulence, the orientation of surface and upper-level winds, and the atmospheric stability. To a trained satellite meteorologist, many clues to the current state of the atmosphere are apparent just by visual inspection. The broad- scale patterns stand our clearly. Not so apparnet is the information implicit in the cloud patterns: quantities such as vertical velocity, vorticity, divergence, etc. Much progress has already been made in obtaining quantitative estimates of relative humidity, zero change in vorticity, wind vectors, etc., which can be used as observations for the computer forecast models. Some of these features are illustrated here. A. Circulation Patterns The various cloud elements described before can be used as targets to determine the ciruclation fields over the vast oceanic areas. The geostationary satellites provide data at 30-minute intervals; sequences of these views can be made into time lapse movies. These movies permit the analyst to track both high-level and low-level clouds and determine the wind fields at appropriate levels. The 24-hour availability of IR coverage enables the meteorologist to better assess the height or level of the clouds and to extract wind information at any time. Wind estimates are obtained by measuring cloud motion manually or, with computer programs. -32- Slide 25. Wind estimates from geostationary satellites, visible, ATS-3, 1423 cm, June 25, 1974. Slide 25 shows a 300 m.b level wind field that was derived from ATS-3 imagery. The wind directions and speeds, computed from pictures acquired between 1300 G^f^ to 1500 GMT on June 25, 1974, show a large upper level ridge located near Bermuda. The strongest winds are southwesterly at 55 knots along the frontal system lying along the east coast. They decrease as they turn north to northwesterly into the trough near 51°W and then to southwesterly around the bottom of the trough. A similar wind field can be extracted from the low level cloud elements. These data are used to supplement the conventional data in the National Meteorological Center (N>IC) HemispVieric and Global analyses. B. Frontal Systems Forecasting and analysis on the global scale can be made easier by the use of satellite data that show the large synoptic scale cloud patterns. Through these data, the meteorologist can assess current or imj^endine changes such as the development of waves on a front in response to an apprui^ching upper tropospheric vorticity maximum, the resulting new low center and frontal band, and, finally, the features characteristic of dissipation. -33- Slide 26. Vortex and frontal system, visible, NOAA -2 SR, orbit 6388, 2124 GMT, March 9, 1974. This view shows an occluded vortex and frontal system in the mid- Pacific. The cold front cloud band begins as a narrow line of clouds at (A) 23°N, 163°E, and becomes increasingly broader as it reaches 25°N. Another cloud band (B) joins the initial band near 30°N and from that point northward, the system is much more active, containing a number of bright globular cumulonimbus clouds (C) . The occluded portion of the front, from (D) to (E) , is composed of multiple, continuous cloud layers that curve cyclonically into the low center at (E) . Clearly identifiable frontal cloud bands such as this occur only in zones of strong baroclinicity . Warm fronts are usually not readily identifiable. In this case, the warm front could be analyzed at the southern edge of the clouds west of (F) . Note the presence of fog and stratus (G) in the warm sector of this system. While this cloud pattern is typical of an occluded system, it varies somewhat from the theoretical Norwegian model. The most marked difference between the satellite observed cloud patterns and the older theoretical models is the incursion of dry, cloud-free air into the low center. This dry slot is a good indicator of the stage of development of the system. A dry slot begins to appear as a system occludes. Continued movement of the dry air towards the vortex center indicates that the system has just about reached its mature stage. -34- A long clear, dry slot (J) can be seen immediately behind the frontal band. This area spirals into the low center at (E) and suggests that the storm has reached its maximum development. This slide also illustrates the effect of cold continental air passing over a relatively warmer ocean: large areas of small cumuliform clouds are produced. In this case, the cumulus congestus clouds form a ring-like or open cellular pattern (H) behind the storm system. Often small vorticity maxima can be detected by the appearance and organization of the cold air cumulus fields. The presence of these maxima is first indicated by the increase in brightness, which indicates an increase in the vertical development of the convective clouds. C. Troughs and Ridges Certain changes in the characteristics of frontal bands can be used for locating the positions of upper level ridges and troughs. These features can then be used with conventional data to locate the changes in wind direction and vertical motion. A 500 mb trough can be positioned extending from the center of the vortex southward to where the frontal band in visible imagery becomes ragged or full of holes. If a comma-shaped cloud area (evidence of a vorticity maximum) is present, the trough line should be drawn to the west of the comma cloud. Upper level ridge lines are determined from the distribution of middle and upper level clouds. A sharp ridge with small curvature will cause middle and high clouds produced upwind to end abruptly at the ridge line as the upward motion changes to dovmward. In this case, the ridge- line would be at the forward edge of the clouds. Medium and broad ridges produce a less distinct forward edge to the clouds and cirrus usually spills out ahead of the ridgeline. In such a case, the ridge is located westward of the cirrus edge, back where both middle and high clouds are present. Slide 27. Upper level trough and ridge, visible, NOAA-2 SR, orbit 6371, 1310 GMT, March 8, 1974. -35- This -/lev shows a well developed storm near Newfoundland, Using the criterir' described before, the upper-level trough would be located from the center of the low (F) southward to where the front changes from a broad c'Joud band (I) to a narrow cloud line at (G) . Cloudiness along the forward edge of this system Indicates a medium amplitude ridge. The axis of this ridge would be located westward of the higii cloudiness, along the forward edge of the middle clouds (J-K) . D. Jet Streams Jet streams or wind m.aximums can be accurately located from the satellite imagery, A large area of anticyclonically curved cirrus usually m.arks the equatorward side of the jet. On the poleward side, the cirrus cloud edge is quite sharp and can cast a shadow on the underlying cloud deck. If a shadow is not apparent on lower clouds, the edge of the cirrus shield can be located by noting the difference in the cloud texture; cirrus is the smoother cloud type in a frontal system. The jet system core lies parallel to and within 100 km of the poleward edge of the cirrus shield. Once the jet stream has been located, the meteorologist can then infer the wind direction, wind shear, areas of potential clear air turbulence and the horizontal temperature gradient. Slide 28. Jet stream and frontal band - Pacific, visible (with closeup), NOAA-2 VHRR, orbit 3347, 1944 GMT, July 9, 1973. -36- This satellite image shows p well developed stoi'in just off Lb.e California coast. The multilayered frontal band stretches fror", (Ii) n.oi thv;ard to 45°N and turns cyclonically into a center near (T). A higher deck of semi-transparent cirrus clouds (J->0 can be seen crossing the front. This typical anticyc] oni cally-sbaperi cirrus s^l.itvif' marks the position of the jet streani axis. Note that, in the area 0') (see enlargement) where the cirrus extends v/est of the front, the cirrus is so transparent that the ocean and a few low clouds can be seen throu};,h the clouds. Further north, at (L) the cirrus crosses the frontal band and casts a narrow shadow on the lower clouds to the west. The cirrus continues northv/ard onto the Canadian coast. The cirrus dissipates where the jet stream changes from an.ticycl oni c to cyclonic. The small amount of cirrus (M) advected over the ridgeline gradually dissipates as it moves into the sinking zone do\.'nwind frof il-t: ridge. E. Extratropical Cyclone Development Twice i. day surveillance by the visible and infrared sensors allowed meteorologists to monitor developing systems at 12-hour intervals. Now the geostationary satellites with their 24-hour surveillance allow hour-by- hour analysis of the stage of development of all systems. The typical sequence of events for a developing system are: the initial frontal wave, the deepening stage, the mature stage with or without secondary centers or secondary waves, and finally the decaying stage. The first three stages are shown in the accompanying slide. -37- a u S5 r H "— H ^U o ■X) • CM - J g O ^ o ^-\ 4-1 CJ m ^— ' o . »> •H m M-l iH •H O x^ m o o^ M v3 ^ S M-J #V O K r^ 4-1 O C (U (^ E o d, CO o CM iH 01 r. > C3> 0) CO Q o- vD • 4-1 a\ •H C^4 ^ 5-1 0) O T3 •H --^ .H pq CO v> -38- This slide shows the developmental stages of an extratropical cyclone in the mid-Pacific. Photographs were taken on three consecutive days by the NOAA-2 polar-orbiting satellite. On the first day, (fig. 29A) a large occluded front stretched from a low center (U) near Kamchatka Peninsula, then eastward and southward to near the dateline (V), and then southwestw'ard to (W) . This frontal band is composed mainly of low and middle stratiform clouds from (U) to (V) and more convective clouds southwestward from (V) to (W) . Looking to the south of the cyclone center and west of the frontal band, two bright comma-shaped cloud masses (Y and Z) are apparent. Such patterns have beem identified as being indicative of the presence of secondary centers of positive vorticity and positive vorticity advection (PVA) in the mid- troposphere . As one of these vorticity centers approaches a front, it will initiate a surface vave. In this example, the center at (Y) is close to the front and has caused a wave to form, at (T) . As the wave develops, the anti.cyclonic bulge of the cirrus north of (T) increases towards the cold air. Note that the most active (convective) portion of the front lies eastward of the vorticity centers. By March 13 (fig. 29B) , the less active portion of the front (north of V on March 12), was located just south of the Aleutians (G to 1!) and the wave (T) of yesterday is now the main system (I) in this area. The ongoing intensification of this system is indicated by the cirrus outflow (J) in the northern and eastern quadrants and the cloudy vortex center. The nearly clear, dry air behind the front has reached (K) ; intensification will continue until this day air spirals into the low center. An area of enhanced, more convective cloudiness, indicating the presence of a secondary vorticity center (L) can be seen behind the front. Figure 29C shows the fully occluded, mature stage of the storm. By this time, the clear dry air has made two complete revolutions into the vortex center (H) . The cirrus outflow apparent the day before is absent and only a narrow multilayered cloud band remains. A large field of cold air cumulus lies southeast of the center. F. Meteorological Analysis and Satellite Data The aforementioned satellite-observed cloud characteristics are routinely used to supplement the conventional surface or upper-air data. -39- Slide 30- Satellite data input to NMC analysis, (A) IR, NOAA-3 SR, orbit 2870, 0620 GMT, June 26, 197A and (B) 300 mb analysis 1200 GMT, June 26, 1974. This slide illustrates how satellite data are used to improve upper air analysis. The computer first-guess analysis (right) for 1200 GMT, June 26, 1974, (dashed lines) showed a trough extending southward from the Aleutians to near 35 °N, 180°W. Superimposing this trough line (C-D) on the satellite picture for 0620 GMT showed that this trough fell well into the clouds instead of west of them. Using the satellite data, the analyst positioned the trough line along the back edge of the clouds (E-F) . To correct the analysis to fit the clouds, the bogus wind reports shown on the map were given the computer to produce the analysis shown by the solid lines. This located the trough further west to agree with the clouds and reduced a potential error in the arrival of this system on the west coast. Satellite data taken 12 hours later, 1800 GMT, confirmed that the trough was moving slower than originally anticipated. -40- G. Tropical Cyclone's Perhaps tlie earliest use of satellite data was for locating and tracking tropical systems. Today, with the continuous coverage froiri the geostationary satellite, one can constantly monitor the progress of these potentially dangerous storms. Tropical cyclones undergo changes in their cloud patterns just as do the extratropical systemis. From these variations, one can estimate the wind speed and central pressure of the system and make some judgment as to its continued developm.ent and movement. These estimates are based on tlie organization, size, and banding of the tropical system. Slide 31. 1972. Hurricane Agnes, visible, ATS-3, 1431 GKT, June 19, Hurricane Agnes, the first hurricane of the 1972 season, developed in the Caribbean south of Cuba and came onshore June 19, 1972 near Appalachicola , Florida. This picture was taken just before the center or eye (F) moved onshore. Although the hurricane center was just approaching Florida, its associated cloudiness was affecting a tremendous area from Cuba to Florida, westward to Louisiana, and northward into Kentucky and Virginia. The bright line of thunderstorms (G) over Florida were in the surface cyclonic inflow area. A number of tornadoes were reported along this squall line through central Florida. At this time, the rain area of this storm extended northward to the edge of the thick, bright clouds (H to I). Further north, (H to J) the cloudiness is high level, somewhat transparent cirrus outflow on the leading edge of the storm. -41- H. Tropica] Storm Classification Tropical Storms are classified by the cloud features they exhibit. The classifications have been einpirically determined by com.paring the c].oud patterns with measiired storm data for a five-year period. A model of tropical cyclone development and weakening (Dvorak 1975) serves as guidance for the subsequent life expectation of the storm. The daily analysis of a cyclone is threefold. First the satellite data over the storm is analyzed for the clianges in cloud features between yesterday and today. Then the storm is given a T-number that describes the current intensity of the system in terms of its cloud features. Finally, the age and current intensity of the storm are applied to a model Xv'hich predicts the developmental trend over the next 24 hours. Hurricanes and typhoons exhibit a great variety of cloud patterns, but most can be described as having a comma configuration. The comma tail is com.posed of convective clouds that appear to curve cyclonically into a center. As the storm develops, the clouds form bands that wrap around into a center, producing a circular cloud system that often has a cloud-free, dark eye. Slide 32 shows some of the typical cloud patterns that these tropical systems exhibit. -42- Tl T2 PRE- STORM PATTERNS T3 T4 T5 T6 '■^ I - / - — •^ i^, I '% ^^ # (['V Q ONE HOOKING WIDE BAND TIGHT CURVE CF4 BFO CF4 BFI CF5 BFI (f( TWO HOOKING WIDE BANDS CURV IN OVCST CF3 BF 3\ ^^; K (g^- (r. CF4 BFI CF5 BFI o^'^ ^ vvpf"' (^' & (j 'CDO' CENTRAL TO WIDE BAND CF2 BFI CF3 BFI CF4 BFI CF4 BF2 KTS 25 30 45 65 90 115 Slide 32. Cyclone patterns and wind speed and pressui^e estimates -43- 1 The T-nuinber assigned stoi-nis range from Tl and T2 for developing, pre-storm patterns to T6 to T8 for fully developed hurricanes or typhoons. This slide shows, schematically, three of the cloud configurations typical to a developing and mature stor-ni. Below the schematics are actual satellite-observed cloud patterns. Note that in the pre-storm. state (Tl) the clouds form into a somewhat hooked-shaped area. As the storm starts to develop, the cloud becomes more comma-shaped and, as in type T4 , the cloud band completes one revolution into the center. The number and width of the bands, the solidness of the central dense overcast, and the presence of an eye all enter into the daily assessment of the storm,. The average maximum, wind speed for each T number is listed under each schematic . Hurricane Agnes (slide 31) was partially onshore and v;as classified as a TA.5. A large eye (F) and holes in the central dense overcast plus its over-land location indicated it had weakened and vjas a minimal hurricane at this tim.e. VIII. APPLICATION TO MESOSCALE ANALYSIS AND FORECASTING Higher resolution data and geostationary satellites have increased our understanding (and to some extent our forecasting abilities) of mesoscale weather systems. In particular, progress has been made in forecasting fog dissipation, afternoon thunderstorms, and lake effect snowstorms. Some of these new small scale forecasting techniques are discussed in connection with the following slides. A. Fog and Stratus Distribution and Dissipation Fog and stratus areas often blanket large areas of the coastal and plains states. The actual areal extent and times of formation or dissipation are often difficult to assess from conventional reporting stations. Satellite data can quickly shov/ the coverage and changes in these low clouds. Stratus clouds are uniformly textured clouds that vary from gray to white depending on their thickness and the angle of the sun. They often have irregular edges that conform to terrain features such as river valleys, mountain foothills, or coastal plateaus. During the day there is a natural erosion of the low clouds caused by daytime heating. Sequential ATS-3 pictures show that fog and low clouds dissipate first at their outer edges, gradually eroding into the center. It has also been noted that there are som.e variations in brightness, thus thickness in these cloud areas. Gurka (1973) shows that the early morning bright areas are usually the last areas to dissipate. He has advisfed a scheme by which one can predict the dissipation of radiation fog and stratus by measuring the brightness gradients present in the early morning pictures. -44- Slide 33. Radiation fog, visible, NOAA-2 VHRR, orbit 4506, 1416 GMT, October 10, 1973. This early morning view shows a large area of fog in the lower Great Lakes Region. Since the sun is low on the horizon, the fog looks very uniform in texture and quite gray. There are a number of interesting features in this view. First, looking northward toward Lakes Erie and Ontario, fog can be seen along the southern shore of Lake Ontario (M) and eastward from Lake Erie. Eastward of the lakes is a typical veined pattern to the fog (N) as it settles into the winding river valleys in upstate New York. Some brighter, thicker areas of fog can be seen in the Ohio River Valley (0-P) and the inter-mountain valleys (Q) in Maryland and Pennsylvania. Using the prediction techniques mentioned above, one could predict the dissipation of fog to be last in the valley areas such as (N, 0, P, and Q) where the depth of the valley allows a deeper (brighter) area of fog to persist. B. Lake Effect Storms One of the most well-known and studied local effect is the Greal Lakes snowstorm. During the winter months, cold continental air passes over the warmer waters of the Great Lakes and produces a large field of fine cloud lines that extend over the adjacent land areas. These cloud lines are usually oriented parallel to the low-level winds. Once formed, they remain stationary and produce dreary skies and copious amounts of snow on adjacent land areas. Frequently these bands receive additional heating -45- and pick up additional condensation nuclei as they pass over the large, industrialized centers such as Detroit; these cause an increase in the cloud line size and could affect their downwind excursion. Satellite data can quickly show detail of the downwind extent and the area affected by these local snowstorms. W Slide 34, Great Lakes snowstorms, IR NOAA-2 VHRR, orbit 4838, 0600 GMT, November 5, 1973 The formation of cloud lines over the downwind of the Great Lakes is most pronounced during the late fall and early winter when the air-water temperature differences are the greatest. This infrared view shows the temperature contrast between the land and water. In this case, the upwind shores of Lakes Superior and Michigan are cloud-free. As the cold, dry air passes over these warmer water bodies, it is heated and becomes unstable, as small cumulus develop . These grow increasingly larger until the spacing between the cloud lines is barely detectable. The initial position of cloud formation is a function of air-water temperature differences, wind speed, and the presence of an upwind pollution source. Note that some of the cloud lines begin closer to the northern shore of Lake Superior (S) . Looking further upwind it appears that Rainy Lake along the Minnesota- Canada border is the source of this longer cloud line. Notice that the cloud lines form closer to Green Bay in the northern portion of Lake Michigan and closest to the eastern shore in the southern portion of the lake (T) . Cloud lines from Lake Michigan brought precipitation as far east as Lansing, Michigan (U) . Looking north again, the clouds from Lake Superior cross the extreme northeast portion of Lake Michigan and much of -46- Lake Huron southward to Lake Erie (V) finally breaking up as wave clouds in the Appalachians (W) . Although relatively small in size, the Great Lakes can affect a large portion of the eastern U. S. C. Differential Heating The formation and distribution of convection, from the smallest fair weather cumulus to large cumulonimbus clusters, is often a function of surface heating alone. For instance, given uniform atmospheric conditions, fair weather cumulus will form over quickly heated land areas, leaving the cooler water surfaces such as lakes and rivers cloud-free. A similar pattern is created when low clouds persist over an area during the morning heating hours. In a situation where solar heating is the controlling mechanism for thunderstorm formation, presence of an early morning cloud cover will keep the underlying surface cooler. This cooler air, being more dense, sinks and spreads outward, lifting the warmer and more unstable air about its perimeter. This causes the thunderstorms to form along the perimeter of the early morning cloudiness. Even after the dissipation of the morning cloudiness, the surface heating lags behind and tends to keep this region free from convection for the remainder of the day. A squall line passing over an early morning clear area is often enhanced by this increased heating and instability. Slide 35, Differential heating and convection patterns, visible, ATS-3, (A) 1330 GMT and (B) 1930 GMT, June 13, 1973. -47- These two satellite views taken six hours apart show the importance of early morning cloudiness on thunderstorm development. Note in the A section of this slide the large area of low cloudiness from northeastern Mississippi to Georgia (A, B, C) . Another area of multilayered clouds, associated with an approaching low, covers Arkansas and Lousiana eastward ' into Mississippi (D) and there is a narrow cloud-free area (E) . By 1930 GMT, (15B) thunderstorms had formed in the clear area (E) , terminating abruptly near the early morning cloud edge. Further south, a line of thunderstorms formed in the near-coastal areas from Louisiana to Georgia (F, G, H) . These thunderstorms were the result of both the sea breeze in Mississippi and Alabama and differential heating along the Florida and Georgia borders. D. Squall Lines and Thunderstorm Growth Thunderstorms often form along squall lines along or ahead of a frontal zone. The development along these lines is affected by the stability of the air through which it moves. If the line passes over an early morning clear zone, the added instability will cause the thunderstorms to develop rapidly. High resolution pictures have revealed the presence of long arc-shaped cumulus congestus lines along the forward edge of thunderstorms clusters. These arcs are usually produced along the forward edge of out-rushing, rain- cooled air and mark the boundary of the mesohigh produced by the thunderstorm. These arc accelerate away from the main showers. Arc lines often intersect old frontal boundaries or other arcs. Augmented lifting at such intersection points can result in intense, and often severe thunderstorms . Slide 36. Squall lines and severe thunderstorms, visible DAPP, (A) 1636 GMT and (B) 1818 GMT, August 12, 1972. -48- The two satellite views shown here were taken nearly two hours apart, but show the dramatic changes that can take place. In the earlier view (1636 GMT)) an old squall line (AB) was moving southward through Illinois and Kentucky. A second mesohigh was developing behind the forward edge of the thunderstorm cluster at (C) to the rear of the initial squall line. The latter became lost in the conventional data, but remained easily detectable in the satellite data. When the second squall line at (C) moved southward, overtaking the old squall line, a rapid development occurred at the intersection point at Cape Girardeau, Missouri (D, 1818 G>rr) . This severe storm produced high winds and hail at that location. As the old squall line (AB) moved southward into Tennessee, new activity began to form in the previously clear areas at E, F, and G. The storm near Nashville (F) brought high winds and damage to the area. E. Mountain Effects Under various conditions, mountains are barriers to loiv clouds or are the initiating points for middle and high level clouds. When the flow at the mountain top is perpendicular to the ridges and greater than 40 knots, wave clouds, suggesting turbulent conditions, can form downwind of the ridges. Upslope motion of moist air along the eastern slopes of the Appalachians or the Rockies produces large areas of fog and stratus along the windx^7ard sides of the lower slopes. In the fall and winter, strong surface highs with low-level easterly flow settle into the Plains states. This, together with long nights and strong nocutrnal radiation, causes tbe fog to thicken and persist for days. The areal extent of this low cloudiness can easily be determined from the satellite data. Satellite data has shown that wave clouds, short parallel stratocumulus or altostratus cloud bands, are quite frequently observed in the mountainous regions. A newer phenomenon observed is the role of the mountain peaks in generating and increasing middle and high cloudiness downwind from mountain ranges. It is particularly noticeable when thin cirrus clouds enter the West Coast and become increasingly thicker and broader after crossing mountain ridges. The production of these clouds can affect the weather downwind by decreasing the solar heating or the amount of nocturnal radiation -49- Slide 37. Terrain effects, visible, NOAA-2, orbit 4670 1632 GMT, October 23, 1973. Both mountain wave clouds and cloud plumes can be seen over the western U. S. on this day. The low (L) located in eastern Oregon has a well-defined frontal band that crosses southward from Idaho into Nevada. The clouds along the southern edge of the front (M) are broken up by the mountains into num.erous parallel bands or wave clouds. Further south an area of cirrus cloud plumes begin (M to 0) downwind of the Sierra Nevada Mountains in California. These clouds become brighter as additional high and middle level lenticular clouds are produced over the Wasatch Range (V) in central Utah. The cloud amount decreases beyond the Wind River Range (Q) in Wyoming, but still is sufficient to affect the surface heating as far east as Kansas (R) . The' source and extent of these clouds can best be assessed by using satellite data. -50- E, Air Pollution During the summer months, large high pressure areas with nearly calm and clear conditions become stationary over the East Coast. Under these conditions, natural atmsopheric dispersion decreases and gaseous and particulate matter becomes concentrated in the lower layers of the atmosphere. The extent of the haze or pollution is best seen when tl;e viewing angle of the satellite and the position of the sun are such that forward scattering in the atmosphere is maximized. If conditions are extremely hazy, normal land marks, such as the Great Lakes or East Coast, cannot be recognized. Slide 38, Haze band east coast, visible, SMS-1, 2100 OH', July 10, 1974, During the early weeks of July, a settled over the East Coast. Stron day and night, and little wind comb pollution. On this day, a front wa As is typical of summertime fronts, band. This view shows a large area off the Atlantic Coast near (A) wes (B to C) . The haze lies in the sta obscures coastal features, especial sun and the sun is low on the horiz in the afternoon, as has happened i large, cool and dry high pressure area g subsidence, clear skies during tht ined to contain the locally produced s moving southward down the East Coast, there was no well-defined frontal cloud of whitish haze that exter.ds from tv7ard towards the mid-Atlantic coast gnent warm air mass. Eaze such as this ly when the satellite view is tov.-ard the on either early in the morning or late n this case. -51- IX. ITYDROLOGIC AND OCEANOGRAPHIC APPLICATIONS The foregoing slides showed, in general, the use of satellite data for meteorologiral purposes. In addition, there are various hydrologic and oceanographic uses for the high resolution data. A. Terrain Patterns , In the visible range data, vegetation-covered mountains and flatlands have a low albedo or reflective properties and so appear dark. Desert areas or treeless fields appear white; White Sands, New Mexico, is the brightest such feature in the U. S. Recognizing the shape and appearance of terrain features permits the meteorologist to quickly determine the location of the image and is useful in gridding the pictures. Snowfall produces distinct patterns and makes mountain ranges and river valleys easier to identify. Slide 39. Terrain features of the Rocky Mountains U. S., visible, NOAA-2 VHRR, orbit 1590, 1741 GMT, February 19, 1973. Both snow covered and bare terrain features of the western U. S. can be seen in slide 39. The snow cover seen in slide 39 accentuates the varying terrain features about the Great Salt Lake (A) in Utah. Snow cover on flatlands or plateaus appears uniformly white (N) . Trees and brush along river beds create thin dark line patterns across the snow cover. This can be seen in the area south of the Unita Mountains (E) where the Green and Price Rivers cross. -52- Large stands of trees, especially evergreens, will hide the snow covered ground and produce a dark scene. Areas that lie above the timberline or those which have been cleared or burnt will appear white then snow covered. The treeless mountain tops and tree covered slopes and valleys produce the dendritic pattern seen on the Unita Mountains (E) and Wastch Range (D) . Another distinctive feature is the smooth- looking snowfield in the Colorado River Valley (F to G) . Changes in these large snow patterns are usually slow. By looking at these areas daily, the hydrologist can assess areas of new snow and areas of melting or sublimation; such information can be useful in determining the water content of the snow cover, which in turn can be used to estimate downriver water levels. Slide 40, Terrain features of the Southwest U. S., visible, NOAA-2 VHRR, orbit 1590, 1741 GMT, February 19, 1973. Slide 40 shows the snow-free southwestern deserts. The main feature is the dark Salton Sea (B) . The dark and light patterns east of the sea are caused by the alternating vegetated mountains and more reflective desert valleys. B. Snow Cover Newly deposited snow often lies in a long strip parallel to the track of the surface low center that produced it. The band of snow can be narrow enough to lie between reporting stations and so be unobserved, its presence is important for forecasting maximum and minimum temperatures and cloudiness over and downwind of the snow cover. The use of satellite data is excellent for detecting areas of snow cover totaling one inch or more. -53- The pattern and reflectivity of the snov cover varies with its age, depth, and the characteristics of the terrain. Old snow is less reflective than fresh snow because old snow may have a layer of dust or dirt on it. may h.tve been subjected to internal or -'-rface melting or nav have been subjected to recent rainfall. The roughness of the terrain produces a recognizable pattern that allows one to easily distinguish snow from clouds, Tree covered areas, whether coniferous or deciduous, produce a dark image as the snow usually covers only the ground surfaces. (The reverse could be true in very wet spring storms when the snow sticks to the trees.) Often snow field boundaries are detectable though by thin cirrus or stratus overcasts. Slide 41, Snow cover around the Great Lakes, visible, NOAA-2 WRR, orbit 6247, 1517 GMT, February 26, 1974. A band of new snow was deposited over the Lower Great Lakes States on February 25, 1974. The absence of clouds allows one to map the area of snow cover from Missouri (A) to Ohio (B and C) . Snow also covers Wisconsin, Iowa and northern Missouri (D) and most of Michigan (E) . Note the differences in the appearance of this snow cover: the snow appears brightest at (B) suggesting the greatest depth there; the area near (A) is less reflective and would probably be 1 to 4 inches in depth. Farther north in northern Michigan (E) , areas of coniferous forest obscure the snow, so, no estimate of snow depth can be made for the dark forested areas, Finally, the isolated area of snow to the south of Lake Michigan (F) was produced by local convection under conditions similar to those depicted in Slide 24. -54- A number of river valleys can be seen in this view. Stands of trees along these rivers produce the dark veined look of the Illinois River (H) , and Mississippi River (I). Cities often appear as dark areas, where there is either dirt-covered snow or no snow. The cities of Cincinattl (CIN) , Dayton (DAY), and Columbus (COL), Ohio, and Flint (FLT) and Ann Arbor (ANN), Michigan, appear dark in this view. C. Ice Surveillance Areas of snow-covered ice that have not begun to melt or have not been subjected to rainfall will appear smooth and bright. Newly formed ice that is quite thin or overlaid with water (puddled) will appear quite dark. Ice that has been subjected to strong winds will contain cracks and leads that are visible in the high resolution data. Strong winds can cause the ice to break away from the shore, leaving easily navigable waters that appear dark in the satellite imagery. Ice charts of the Great Lakes and the Arctic regions are prepared routinely from' the high resolution satellite imagery. These charts indicate areas of fast ice, pack ice, newly formed ice, leads, and floes that can be discerned in the satellite data. Information about these items is used operationally by shipping interests in the Great Lakes and northern oceanic regions. Slide 42. Great Lakes ice cover, visible, 1531 GMT, February 20, 197A. N0Ay\-2 VHRR, orbit 6172, -55- This view shows the smooth, bright snow-covered fast ice in the North Channel (A), Strait of Mackinac (B) , Green Bay (C) , Thunder and Black Bay (D), and Lake Nipigon (E) . A number of cracks or leads can be seen in the southwestern portion of Lake Superior (F) . In the near shore areas near Duluth, the ice takes on a much darker appearance suggesting some melting is taking place. Another area of very thin, smooth, and dark ice can be seen in the area from south of Heron Bay to Isle Royale (H) , Finally, areas of dark ice-free shore lines can be seen along much of the northern and western shores of Lake Superior from Heron Bay (H) southward to Isle Royale (I) and another area from Silver Bay down towards Duluth. The area to the lee of Keweenaw is also ice-free. Even in the area of thin cloudiness at (J) , one can still assess the presence of ice in the lakes and bays in upper Michigan. D. Oceanography Infrared data provide a valuable third dimension for mapping the sea surface temperature. The positions of the various currents, such as the Gulf Stream, are important to commercial shipping and fishing interests. At present, the high resolution data are used to map the position of the Gulf Stream as well as the presence of cold and warm water eddies. These weekly charts serve a wide audience, ranging from racing enthusiasts to oil tanker operators, who use the clockwise or counterclockwise currents to speed them to their destination. Slide 43. Gulf Stream, IR, NOAA-2 VHRR, orbit 5858, 1300 GMT, January 26, 1974. -56- I This satellite view shows a portion of the Gulf Stream off the north- eastern U. S. coast. The Gulf Stream, being much warmer than the shelf or slope waters, appears as a dark water feature. In this view the Gulf Stream (G) has a split in flow (arrows) with one branch heading east northeast and the other turning counterclockwise to initiate a new warm eddy. Further west is a large warm eddy (WE) with a counterclockwise circulation. Other details include the slightly cooler slope waters (SLW) and the colder shelf waters (SHW) . Acknowledgement » We would like to express our appreciation to Larue Amacher of the Applications Group who did the illustrative work for Part II, to Betty Nobles who typed the various draft copies including the final draft, and finally to Robert Pyle and Paul Lehr v.'hose editorial reviews and comments contributed much to the successful completion of this report. -57- Selected References Agee, Ernest, "Note on ITCZ Wave Distrubances and Formation of Tropical Storm Anna," Monthly Weather Review , Vol. 100, No. 10, October 1972, pp 733-737. Agee, E. M. and Dowell, K. 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Bjerknes , Jacob, et al., "Satellite Mapping of the Pacific Tropical Cloudiness", Bulletin of the American Meteorological Society , Vol. 50, No. 5, May 1969, pp 313-322. Bonner, William D. , and Winninghoff, Frank, "Satellite Studies of Clouds and Cloud Bands Near the Low-Level Jet", Monthly Weather Review , Vol. 97, No. 7, July 1969, pp 490-500. Booth, Arthur L. , and Taylor, V. Ray, "Mesoscale Archive and Computer Products of Digitized Video Data from ESSA Satellites", Bulletin of the American Meteorological Society , Vol. 50, No. 6, June 1969, pp 431-438. Bristor, C. L. , Callicott, W. M. , and Bradford, R. E., "Operational Processing of Satellite Cloud Pictures by Computer", Monthly Weather Review , Vol. 94, No. 8, August 1966, pp 515-527. Carlson, Toby N. , "Some Remarks on African Distrubances and Their Progress over the Tropical Atlantic", Monthly Weather Review , Vol. 97, No. 10, October 1969, pp 716-726. 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Gaby, Donald C. , and Poteat, Kenneth 0., "ATS-3 Satellite Derived Low-Level Winds: A Provisional Climatology", Journal of Applied Meteorology , Vol. 12, No. 6, September 1973, pp 1054-1061 (COM-74-10134) Gruber, Arnold, "Estimating Rainfall in Regions of Active Convection", Journal of Applied Meteorology , Vol. 12, No. 1, February 1973, pp 110-118 (COM073-11088) Gurka, James J., "Using Satellite Data for Forecasting Fog and Stratus Dissipation", Preprint Volume, Fifth Conference on Weather Forecasting and Analysis, March 4-7, 1974, St. Louis, Mo., American Meteorological Society, Boston, Mass., pp 54-57. -59- Hilleary, D. T. , et al. , "Indirect Measurements of Atmospheric Temperature Profiles from Satellites: III. The Spectrometers and Experiments", Monthly VJeather Review , Vol. 94, No. 6, June 1966, pp 367-377. Huang, Chin-Hua, Panofsky, H. 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Krishna, "A Procedure for Estimating Cloud Amount and Height From Satellite Infrared Radiation Data", Monthly Weather Review , Vol. 101, No. 3, March 1973, pp 240-243. Kornfield, J., et al., "Photographic Cloud Climatology from ESSA 3 and 5 Computer Produced Mosaics", Bulletin of the American Meteorological Society , Vol. 48, No. 12, December 1967, pp 878-883. McClain E. Paul, "On the Relation of Satellite Viewed Cloud Conditions to Vertically Integrated Moisture Fields", Monthly Weather Review , Vol. 94, No. 8, August 1966, pp 509-514. McClain E. Paul and Baliles, Maurice D. , "Sea Ice Surveillance from Earth Satellites", Mariners Weather Log , Vol. 15, No. 1, January 1971, pp 1-4. McClain, E. Paul, Ruzecki, Mary Ann, and Brodrick, Harold J., "Experimental Use of Satellite Pictures in Numerical Prediction", Monthly Weather Review , Vol. 93, No. 7, July 1965, pp. 445-452. McClain, E. 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