<2 ss: /& : yc^-c v// - /i'. ■--■>'• y ' Uty ;, y. % NOAA Technical Report ERL 411-NHEML 3 >0 % £o> o r — ~^= — , t« c *„ j /■ ^rts of * Classification of Meteorological Radar Echoes by Their State of Motion During FACE 1970 Through 1978 Procedures and Results Francis J. Merceret Ronald L. Holle John B. Cunning July 1980 U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration Environmental Research Laboratories Digitized by the Internet Archive in 2013 http://archive.org/details/classificationofOOmerc NOAA Technical Report ERL 411-NHEML 3 MMOSPt, %««'»' Classification of Meteorological Radar Echoes by Their State of Motion During FACE 1970 Through 1978 Procedures and Results Francis J. Merceret Ronald L. Holle John B. Cunning National Hurricane and Experimental Meteorology Laboratory Miami, Florida July 1980 U.S. DEPARTMENT OF COMMERCE Philip M. Klutznick, Secretary National Oceanic and Atmospheric Administration Richard A. Frank, Administrator "5J Environmental Research Laboratories .^ Boulder. Colorado Wilmot N. Hess, Director For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 11 CONTENTS ABSTRACT 1 1. INTRODUCTION 1 2. CLASSIFICATION RULES 2 3. APPLICATION OF RULES TO FACE 1970 THROUGH 1978 DATA 4 4. SUMMARY AND CONCLUDING REMARKS 4 5. ACKNOWLEDGMENTS 5 6. REFERENCES 5 in CLASSIFICATION OF METEOROLOGICAL RADAR ECHOES BY THEIR STATE OF MOTION DURING FACE 1970 THROUGH 1978 PROCEDURES AND RESULTS Francis J. Merceret, 1 Ronald L. Holle, and John B. Cunning ABSTRACT. A procedure for the classification of radar meteorological echoes according to their state of motion is described. The procedure applies a set of objective rules for interpreting radar film. The eight rules and the reasons for their formulation are presented. The results of the application of this scheme to radar data from operational days during the Florida Area Cumulus Experiment (FACE) for 1970 to 1978 are presented, discussed, and compared with the results from the previous procedure of classification. 1. INTRODUCTION The Florida Area Cumulus Experiment (FACE) is a program designed to determine whether dynamic cloud seeding methods can be used to augment convective precipitation over 1.3 x 10 4 km 2 in south Florida (fig. 1). The program has been described in detail by Woodley and Sax (1976). Analysis of FACE rainfall has relied heavily on radar, and several covari- ales of precipitation have been used in the analysis. Echo motion determined from the radar images (Biondini, 1977; Woodley et al. , 1977) is important because a significant physical mechanism may be dynamic coupling of the clouds' in- ternal motions with the boundary layer. Such coupling is believed to b,e affected by upper- and mid-level wind-induced advection, but not by echo motion caused by propagation growth in a preferred direction. Propagation does not involve motion of the convective cells relative to the surface, but rather the development of new cells. (A detailed description of the physics and significance of echo motion is beyond the scope of this report.) Determination of radar echo motion necessitates a reliable, rational, and repeatable method. This paper describes such a method. Before 1978 echo motion classification was subjective and uneven. There were no explicit criteria, except that propagation was not considered motion. All days had to be designated as either "motion" or "no-motion." Different people did the classification in different years. Both the mandatory bimodal classification and the lack of objective criteria had been criticized informally, and FACE project scientists decided in 1978 to revise the procedure. Effective algorithms for automatic classification were much too time-consuming for existing resources, so a set of objective rules was devised. The new system has motion and no-motion categories and a third category called "other" to describe certain situations that do not fit neatly in the other two. As anticipated, some FACE days from 1970-1977 have been reclassified; 1978 days were all classified by the new system. The classification of all FACE randomized ("GO") days under both schemes is listed in section 3. 1 Research Facilities Center, Miami, Florida Figure 1. — The FACE 1970 through 1978 seeding target area in south Florida is shown by the hatched area northwest of Miami. The WSR-57 radar is at Coral Gables. The rain gage network area changes annually . 2. CLASSIFICATION RULES Days were classified as motion, no-motion, and other, on the basis of observations from the Miami National Weather Service WSR-57 radar. Data were in the form of 35-mm black-and- white film; frames were taken at 5-min intervals. The radar film was viewed on a 35-mm stop- motion projector with variable speed control that was set at 15 frames per second. There are eight classification rules, which are presented below and explained. They are given in exactly the same order and wording used by the classifiers when the data presented in this paper were processed . Rule 1: If an echo is in the analysis area at any time during its lifetime, its whole path may be used. No echoes may be used that fail to enter the analysis area. The analysis area is the northwest quadrant of the Miami WSR-57 radar out to 100 nautical miles. Rule 2: Time [data period] of analysis is from 1600 to 0200 UT only Rule 3: Echo motions must be general and somewhat uniform in direction for the day to qualify as a motion day. Echoes must not be moving (except by propagation) to qualify the day as a no-motion day. Days on which echoes move in diverse directions, or on which some clouds move and some do not, will be classified separately. Direction changes with time do not make the motion nonuniform if all echo motions change together. Rule 4: On days in which the amount of echo motion changes with time, the day shall be classified as motion if a major portion of the analysis period qualifies for motion classification. It shall be classified as no-motion if a major portion of the analysis period qualifies for no- motion classification. If neither mode is clearly predominant, the day shall be separately clas- sified. When there is doubt as to classification under this rule, emphasis should be given to the status of motion from 1800 to 2200 UT . Rule 5: Categories of motion status are motion, no-motion, and other. The criteria for motion and no-motion are described in Rules 1-4 above. Rule 6: Days classified other shall be identified as to the reason for this classification. Reasons shall be selected from the following set: a) Diverse direction or motion status as described in Rule 3. b) Change of motion with time as described in Rule 4. c) Insufficient echoes or poor data quality that precludes echo tracking. d) Classifying personnel cannot agree on classification. Rule 7: A form containing these columns shall be used: Column 1 Column 2 Column 3 Date Category Remarks The form shall contain the names of the classification personnel. Rule 8: Instructions to the classification personnel shall include these rules and shall note that when category other is designated, the appropriate subcategory (i.e., a, b, c, or d) should be designated (e.g., other (b)). The comments column should be used to explain the classification more fully . The reasons for the rules are the following: Rules 1 and 2 determine the echoes to be used in the analysis and insure that different analysts use the same data. The northwest quadrant of the radar area was chosen for analysis because it consists mainly of the FACE seeding target area. The analysis time in Rule 2 in- cludes the typical period when convection is seeded and rain volumes are calculated, since the statistical results of FACE are based on analysis of rainfall from first seed time to first seed plus 6 hours. Rule 3 defines the motion and no-motion categories. Dynamic coupling of the clouds' in- ternal motions with the boundary layer may be the physical mechanism that distinguishes motion from no-motion situations. The coupling may be weakened by advection induced by winds above the boundary layer, but it is not modified by echo growth, even in a preferred direction. Advection involves relative motion between the active cells of the convection and the surface, whereas addition of new cells alone does not . It is the relative motion that affects the dy- namic coupling. Note that echoes that propagate, but are not advected in bulk, are considered to be not in motion for purposes of this rule. Propagation and advection are distinguished in the radar images subjectively by behavior of the echoes with time. If echoes enlarge in a preferential direction with identifiable elements remaining fixed, then propagation is taking place. If the echoes as a whole move, propagation is not occurring. Rule 4 refines Rule 3 for situations where the echo motion changes with time. The status of motion from 1800 to 2200 UT is important because most FACE activities, e.g., seeding, took place during this period. Rules 5 and 6 define the category other and are self-explanatory. Rules 7 and 8 are administrative rules to assure strict compliance with other rules and adequate documentation for each classification. Rules 1 through 8 were established and agreed upon by the authors and other FACE per- sonnel before the classification began. 3. APPLICATION OF RULES TO FACE 1970 THROUGH 1978 DATA Application of these rules to FACE data from 1970 through 1978 has resulted in a satis- factory definition of all cases. The rules, then, seem to provide a good framework in which to judge echo motion. The authors examined radar data for all GO days from FACE 1970 through 1978. A GO day is a randomized experimental day, which may be either seeded or unseeded. The two types of GO days are an A day, on which fewer than 60 flare drops are attempted, and a B day, on which 60 or more drops are attempted (Woodley et al. , 1977; Woodley and Sax, 1976). The category decision for each day was agreed upon after discussion. If agreement could not be reached the category other (d) was selected. Tables 1 through 6 present echo motion results by data for GO days. Assessment of motion type for the new category was made by the authors using the rules described in section 2. Classification of motion type for the former category is available in various FACE project reports, summaries, and data listings; in this classification system GO days were either motion or no-motion. The comments in tables 1 through 6 apply to the new category only. In tables 1 and 2, it is apparent that 1970 and 1971 film data were somewhat different from that of other years. During 1970 and 1971, the film covered a 200-nmi range, while in all other years it had a maximum range of 125 nautical miles. This resulted in a smaller FACE target area on the picture. Also during these 2 years, the Miami radar had no Video Integrator Pro- cessor (VIP) capability, so the intensity of radar signals was not apparent. Analysis was much more difficult in 1970 and 1971, without VIP. From 1973 through 1978 there were centers and smaller features on radar that could be identified and tracked, unlike the more diffuse echoes in 1970 and 1971. In table 6 there are no data listed under the former category, since the classification system given in section 2 was the only technique used at the end of FACE 1978. The numbers of changes between former and new categories of echo motion are given in table 7. The table shows that there were 22 changes in the 99 cases considered. When one considers that film data from 1970 and 1971 were more difficult to use, the agreement is quite good. This agreement lends confidence to the repeatability of the results, even when the in- formal technique is considered. If one removes the 12 changes to other, which was a nonexist- ent category under the former scheme, the overall result is 10 changes out of 87 cases, or 11%. From 1973 to 1976, the change rate (excluding changes to other) is only 8 of 79, or 10%. It should be noted that on 4 days there was insufficient or no film for determining echo motion with the new method (although the radar was operating), and these days were classified as other. The former classification had found echo motion from data and observations other than film; these sources were not used for the new category results. 4. SUMMARY AND CONCLUDING REMARKS A set of objective rules for the classification of radar meteorological echoes by their status of motion has been presented. Application of the scheme to FACE data from 1970 through 1978 shows that the system covers all classes of observed phenomena and produces fairly uniform acceptable results. This procedure also provides a satisfactory method for using echo motion to stratify precipitation statistics. The addition of a category for other preserves the purity of the motion and no-motion categories as covariates by removing doubtful cases. Some reword- ing and reordering of the rules might make them clearer or more concise, but their basic struc- ture should be maintained for the duration of FACE. 5. ACKNOWLEDGMENTS The authors thank John Flueck of Temple University, William Woodley of NHEML, Robert Sax of the Joseph Oat Corporation, and Joanne Simpson of the National Aeronautics and Space Administration for their suggestions and encouragement during the development of the system described in this paper. 6. REFERENCES Biondini, R. (1977): The use of predictors in analyzing FACE. Preprints, Sixth Conf. on Planned and Inadvertent Weather Modifications , Oct. 10-13, 1977, Champaign-Urbana, 111. Amer. Meteor. Soc. , Boston, Mass., 210-213. Woodley, W. L. , and R. I. Sax (1976): The Florida Area Cumulus Experiment: rationale, design, procedure, results, and future course. NOAA Tech. Rep ERL 354-WMPO 6, 120 pp. Woodley, W. L., J. Simpson, R. Biondini, and J. Berkeley (1977): Rainfall results, 1970-1975: Florida Area Cumulus Experiment. Science 195:735-742. Table 1. — Results of classification of radar echo motion by two methods for GO days, FACE 1970 Date Julian Type of day Go day Category New Former Change Comments 29 June 30 June 2 July 7 July 8 July 18 July 180 181 183 188 189 199 B Motion (N) B Motion (NNE) B Motion (E) B Other (d) B No-motion B No-motion Motion (W) No-motion X No-motion X No-motion X No-motion No-motion No VIP, 200-nmi range film No VIP, 200-nmi range film No VIP, 200-nmi range film No VIP, 200-nmi range film: too complex, may be no-motion No VIP, 200-nmi range film No VIP, 200-nmi range film; sparse intermittent data Table 2. — Results of classification of radar echo motion by two methods for GO days, FACE 1971 Date Julian day Type of Go day Categc ry Change Comments New Former 16 June 167 B Motion (WSW) Motion (WSW) No VIP, 200-nmi range film; sparse echoes 1 July 182 B Motion (SE) Motion (ESE) No VIP, 200-nmi range film 12 July 193 B Other (a) No-motion X No VIP, 200-nmi range film; converging sea breeze lines 13 July 194 B Other (b) Motion (E) X No VIP, 200-nmi range film; SE until 2300 UT, then still 14 July 195 B Other (d) Motion (E) X No VIP, 200-nmi range film; chaotic; maybe weak W with strong propagation 15 July 196 B Motion (S) Motion (SSE) No VIP, 200-nmi range film Table 3. — Results of classification of radar echo motion by two methods for GO days, FACE 1973 Date Julian Tvpe of Category Change Comments day Go day New Former 5 July 186 7 July 188 16 July 197 17 July 198 20 July 201 25 July 206 30 July 211 6 August 218 8 August 220 9 August 221 12 August 224 13 August 225 22 August 234 25 August 237 27 August 239 28 August 240 9 Sept. 252 12 Sept. 255 A B R B B B A B A B A A B B B B B A Motion (W) Motion (NW) No-motion Motion (E) Motion (ESE) Motion (NE) Motion (S) No-motion Motion (NE) Other (b) Motion (ESE) Motion (SE) Motion (W) Motion (SE) Motion (ENE) Motion (NNE) No-motion No-motion Motion (WSW) No-motion No-motion Motion (E) Motion (E) Motion (E) Motion (S) motion ion (ENE) ion (ENE) No Mot Mot Motion (E) Motion (E) Motion (W) Motion (SSE) Motion (ENE) Motion (NE) Motion (WSW) Motion (WNW) X X Later from N Weak; accelerates later to SSW Later ENE Still to 2200 UT; then motion from NE X X Few echoes Table 4. — Results of classification of radar echo motion by two methods for GO days, FACE 1975 Date Julian Type of Category Change Comments day Go day New Former 16 June 18 June 21 June 22 June 24 June 25 June 27 June 28 June 30 June 7 July 9 July 167 169 172 173 175 176 178 179 181 188 190 16 July 197 18 July 199 19 July 200 20 July 201 23 July 204 24 July 205 25 July 206 26 July 207 29 July 210 30 July 211 13 August 225 15 August 227 16 August 228 17 August 229 19 August 231 25 August 237 28 August 240 3 Sept. 246 11 Sept. 254 12 Sept. 255 14 Sept. 257 A B B B B B A B A B B B B B B B A B B B B B B A B B B A B B A No-motion Motion (ESE) No-motion Motion (E) Motion (NNW) Motion (W) Motion (SW) Motion (WSW) No-motion Motion (SW) Motion (S) Motion (SE) Motion (SE) Motion (SE) Motion (SSE) Motion (ENE) Motion (ENE) No-motion Motion (SE) Other (a) Motion (E) No-motion Motion (ESE) Other (c) Other (c) No-motion Other (c) Motion (NE) Motion (SE) Motion (E) Motion (e) Motion (NE) Motion (SE) Motion (ESE) No-motion Motion (E) No-motion Motion (W) Motion (WSW) Motion (WSW) No-motion Motion (WSW) Motion (S) Motion Motion (SE) (E) Motion (ESE) Motion (S) Motion (E) Motion No-motion Motion (E) Motion (SSW) Motion (E) No-motion Motion (ESE) Motion (E) No-motion No-motion Motion (E) Motion (ene) Motion (SE) Motion (E) Motion (E) Motion (E) X A typical chaotic propaga- tion Cirrus from W X Slow Slow; later from NW Systematic propagation from NE TO SW Film double-exposed; difficult to analyze Film double-exposed; direction imprecise Fill 2200 to 0200 UT only Superimposed on propaga- tion from E SE to SSE Slow Film begins 1800 UT; rapid random propagation Slow X West half from SW; east half from SE Active propagation X Film 1600 to UT only; no echoes X No film Radar intermittent; changes to ENE after 0000 UT X No film ENE later Slow E later ■Table 5. — Results of classification of radar echo motion by two methods for GO days, FACE 1976 Date Julian day Type of Go day Category Change Comments New Former 3 June 155 B Motion (SSW) Motion (S) 4 June 156 A Other (c) Motion (SW) X No film 1600 to 0400 Ut 6 June 158 B No-motion No-motion Maybe weak NE hidden in propagation 8 June 160 B Motion (SW) Motion (W) 25 June 177 A Motion (ESE) Motion (W) 26 June 178 B Motion (SE) Motion (E) 27 June 179 A Motion (ENE) Motion (E) 28 June 180 B Other (a,b) No-motion X N-fixed; W-still, then motion; S-motion, then still 29 June 181 B No-motion No-motion 30 June 182 B Motion (SSW) No-motion X Slow 5 July 187 B Motion (SE) Motion (S) 6 July 188 B Motion (SE) Motion (SSE) 11 July 193 A Motion (SW) Motion (S) AP in NW target area; late-stationary or NW 14 July 196 A Other (c) Motion (W) X One small brief echo only 16 July 198 B No-motion No-motion Much AP; fuzzy echoes; ma be slow hidden motion 17 July 199 B No-motion No-motion 18 July 200 B No-motion No-motion 19 July 201 A Motion (SE) Motion (SE) 20 July 202 B Motion (ESE) Motion (SE) 21 July 203 B Motion (NE) Motion (ENE) 23 July 205 B Motion (SE) Motion (ESE) 24 July 206 B Motion (SE) Motion (SE) 25 July 207 B Motion (ESE) Motion (ENE) Turning to NE 26 July 208 B Motion (ENE) Motion (E) 30 July 212 A Motion (E) Motion (E) Quite weak 31 July 213 B No-motion No-motion 5 August 218 B No-Motion No-Motion 6 August 219 B Motion (N) No-motion X 10 August 223 A Motion (SSW) Motion (S) No film after 2100 UT 11 August 224 A Motion (ENE) Motion (E) Fast; no film before 1900 UT 15 August 228 15 No-motion No-motion Few echoes 16 August 229 B No-motion No-motion Radar intermittent 21 August 234 B Motion (SW) Motion (S) 22 August 235 A Motion (NW) Motion (NW) 26 August 239 B Motion (ENE) Motion (E) 30 August 243 B Motion (E) Motion (ENE) Table 6. — Results of classification of radar echo motion with new method for GO days, FACE 197 t Date Julian day Type of GO day New Category Comments 29 June 180 B Motion (E) 30 June 181 B Other (a) Center-still; extreme N and S-from E 1 July 182 B No-motion 2 July 183 B Motion (WNW) 3 July 184 B Motion (SW) Weak 5 July 186 A Motion (SW) Much AP 10 July 191 B Motion (SE) 18 July 199 A Motion (WSW) Heavy AP and anvil rain 25 July 206 B Motion (SE) Short-lived echoes 29 July 210 B Motion (W) Propagation in same direction also 4 August 216 B Motion (E) 5 August 217 A Motion (SE) Slow 10 August 222 B Motion (SE) 11 August 223 B Motion (SSE) Turning to SSW 12 August 224 B Other (a,b) Chaotic, diverse in space and time 13 August 225 B Motion (SSE) Slow 14 August 226 B Motion (E) 16 August 228 B Motion (ESE) A few stationary echoes 17 August 229 B Motion (SE) 18 August 230 A No-motion 29 August 241 B Motion (SE) A few stationary echoes Table 7 .--Summary of changes in classification of echo motion Year Total days GO Changes Total changes Percent To motion To other To no-motion total changes 1970 6 2 1 3 50 1971 6 3 3 50 1973 18 1 1 2 4 22 1975 32 1 4 1 6 19 1976 37 3 3 6 16 All years 99 7 12 3 22 22 is GPO 1980—677-096/1265 LABOR AT ORIES The mission of the Environmental Research Laboratories (ERL) is to conduct an integrated program of fundamental research, related technology development, and services to improve understanding and prediction of the geo- physical environment comprising the oceans and inland waters, the lower and upper atmosphere, the space envi- ronment, and the Earth. 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