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Laser Doppler Dust Devil Measurements NASA TECHNICAL NOTE NASA-. .TN 0-8429 d LASER DOPPLER DUST DEVIL MEASUREMENTS James W. Bilbro, Harold B. Jeffreys, John W. Kaivfman, and Edwin A. Weaver George C. Marshall Space Flight Center Marshall Space Flight Center, Ala. 35812 NATIONAL AERONAUTICS AND SPACE ADMINISTRATION WASHINGTON, D. C. FEBRUARY 1977 TECH LIBRARY KAFB, NM - - - - Illllll1lll1lllllllllllllllllllllllll11ll Ill1 - I REPORT NO. 2. GOVERNMENT ACCESSION NO. NASA TN D-8429 0134195 .-~ ~ ! - __ I TITLE AND SUBTITLE 5. REPORT DATE Laser Doppler Dust Devil Measurements r6. PERFORMING ORGANIZATION CODE 1. AUTHORIS) James W. Bilbro, .Harold B. JeEreys, John W. ORGANIZATION REPOR r # Kaufman, and Edmn A. Weaver .- - -_ - I. PERFORMING ORGANIZATION NAME AND ADDRESS TO. WORK UNIT, NO. I George C. Marshall Space Flight Center CONTRACT OR GRANT NO. Marshall Space Flight Center, Alabama 35812 13. TYPE OF REPORi' & PERIOD COVEREO 2. SPONSORING AGENCY NAME AND ADDRESS I Technical Note National Aeronautics and Space Administration Washington, D. C. 20546 SPONSORING AGENCY CODE __.- . ._ - 1 5. SUPPLEMENTARY NOTES Prepared by Electronics and Control Laboratory, Science and Engineering -.. ~ __ 6. ABSTRACT A Scanning Laser Doppler Velocimeter (SLDV) system was employed at a test site on the Gila River Indian Reservation south of Phoenix, Arizona, for the purpose of detecting, tracking, and measuring the velocity flow field of naturally occurring tornado-like flows (dust devils) in the atmosphere. Approximately 80 dust devils were observed with the system during the test period from August 10 through August 16, 1975. This report provides a review and general description of the dust devil phenomenon and outlines the test program, measurement system, and data processing techniques used to collect information on the dust devil flow field. The general meteorological conditions occurring during the test program are also described, and the information collected on two selected dust devils are discussed in some detail to show the type of information which can.be obtained with a SLDV system. The results from these measurements agree well with those of other investigators and illustrate the potential for the SLDV in future endeavors; consequently, recommendations are given for a comprehensive test program using a variety of sensors for obtaining a more complete description of the dust devil phenomenon. .~ 7.' KEY WORDS 18. DISTRIBUTION 5-ATEMENT Laser Doppler Cat 47 Dust Devil Velocity Profiles . 9. SECURITY CLASSIF. (of this repart) 120. SECURITY CLA! IF. (of this pa&) - 121. NO. OF PAGES I 22. PRICE Unclassified Unclassified 1 90 $5.00 ACKNOWLEDGMENTS The authors wish to express their appreciation to several people for their invaluable contribution to the program: Mr. R. M. Huffaker, formerly of NASA/MSFC, for his part in the instigation of this program; the personnel of Lockheed, who performed the data collection, including Messrs. Charles Craven, Edward Gorzynski, Robert Howle, and Michael Krause; the personnel of J3aytheon, who performed the data analysis, including Dr. Charles Sonnenschein, Mr. Charles DiMarzio, Mr. Douglas Toomey, and Ms. Dorothy Clippinger; and the personnel of the University of Arkansas, who were involved in processing of the data for three dimensional display, including Dr. Ron Skieth, Dr. Bill Ashmore, and Mr. Arato Kimura. Appreciation is also expressed to our MSFC colleagues, Messrs. Daryl Craig, Ron George, and Pete Marrero, for their support during this program. A special thanks is due Dr. Sherwood Idso of the United States Soil Conservation Service who provided a tremendous service throughout the test program by selecting and serving as local coordinator for the test site and by participating in the collection of the data. Dr. Idso's past experience in dust devil research was an important contribution in conducting this test program. The authors are extremely grateful to the Tribal Council of the Gila River Indian Reservation for allowing these tests to be conducted. TABLE OF CONTENTS Page I. INTRODUCTION ................................ 1 I1. DUST DEVIL PHENOMENON ....................... 2 A . Dust Devil Literature Review .................... 4 B. Reported Dust Devil Damage .................... 17 C . Idealized Dust Devil Model ...................... 20 I11. SYSTEM DESCRIPTION ........................... 23 IV. TEST PROGRAM DESCRIPTION ..................... 27 A . TestSite .................................. 27 B. Test Procedure ............................. 30 V. DATA PROCESSING/ANALYSIS ..................... 34 A . Description of the Data ........................ 34 B. Data Processing Techniques .................... 38 VI . ENGINEERING DATA ANALYSIS AND PRESENTATION . 44 A . Dust Devil Activity and Synoptic Features ............ 44 B. Analysis of Run 5. Day 235 ...................... 52 C . Analysis of Run 9. Day 238 ...................... 66 VI1. CONCLUDING REMARKS .......................... 78 REFERENCES ................................. 81 iii I I I I111111Ill I1 I I I I I I I I I .......... LI ST OF ILLU STRATI ONS Figure Title Page 1. Idealized model of a dust devil .................... 21 2 . Laser beam path ............................. 24 3 . Laser Doppler velocity measurement .....+ ......... 24 4 . Illustration of optical heterodyning ................. 25 5 . SLDV system composite ........................ 26 6 . SLDV block diagram ........................... 28 7 . Dust devil test site ............................ 29 8. SLDV scan pattern ............................ 30 9. Dust cloud caused by Earth mover .................. 31 10 . Dustdevil .................................. 32 11 . Significance of dust devil spectra .................. 35 12 . Dust devil signal spectrum (translated) .............. 36 13 . Dust devil signal spectrum (untranslated) ............ 36 14. Typical spectra from a single dust devil and the atmospheric wind ............................. 37 15. Variations in signal amplitude .................... 40 16 . x-y plot of a given velocity cell .................... 41 17. Velocity versus range and angle ................... 42 18. Intensity versus velocity and range ................. 43 19 . Averaged wind speed data for a 5'day period ........... 47 iv ,.--..., .......L._....I...­..-l...ll..l.lnllllls........I' . 'IT.11 .... I 1 I LIST OF ILLUSTRATIONS (Concluded) Figure Title Page 20. Average differences of wind speed data for a 5 day period . 48 21. Velocity versus azimuth ........................ 53 22. Dust devil angular transport. ..................... 58 23. Angular core width time history ................... 58 24. Peak velocity time history ....................... 59 25. Dust devil backscatter intensity profile .............. 60 26. Dust devil peak integrated signal time history .......... 65 27. Dust devil peak signal transport ................... 66 28. Velocity versus azimuth ........................ 67 29. Dust devil angular transport. ..................... 71 30. Dust devil core width time history. ................. 72 31. Velocity time history dust devil No. 1 ............... 73 32. Velocity time history dust devil No. 2 ............... 73 33. Dust devil backscatter intensity profile .............. 74 34. Peak integrated signals versus time ................ 77 35. ,Dust devil peak signal transport ................... 78 V Li ST OF TABLES Table Title Page 1. Hourly Air Temperature Data as Recorded on August 22-26, 1975, at the Sky Harbor International Airport at Phoenix .................................... 46 2. Periods of Maximum Dust Devil Activity .............. 48 3. Wind Aloft Data for August 22-26, 1975, Tuscon International Airport, Arizona ..................... 50 vi LASER DOPPLER DUST DEVIL MEASUREMENTS 1. INTRODUCTION Those members of the meteorological community concerned with tornados and related flow fields have long recognized that detailed velocity information on the dust devil flow field would be a significant contribution to their studies. Because of the interest of the National Oceanic and Atmospheric Administration (NOAA) in these studies and the potential benefit to many people in the United States, the Technology Utilization Office of NASA sponsored a program to remotely measure the dust devil velocity flow field using a Scanning Laser Doppler Velocimeter (SLDV) system developed by Marshall Space Flight Center (MSFC) . This system, originally developed for research on wing-tip vortices, was modified to provide a horizontal scan plane and was set up at a test site on the Gila River Indian Reservation south of Phoenix, Arizona. Approximately 80 dust devils were observed with the SLDV during the test period from August 10 through August 26, 1975. These dust devils were observed and measured daily between approximately 11 a.m. and 3 p. m. when the ambient temperature was approximately 38°C and the soil surface tem­ perature was in excess of approximately 63°C. The dust devils were observed in varying wind conditions from 0 to approximately 5 m/s during the test period. Cloudy conditions existed for several days and one thunderstorm occurred in the test area during the test period. The occurrence of dust devils on cloudy days and on the days following the thunderstorm was reduced to zero until the soil had dried and reached or exceeded what appeared to be the critical 63°C ground surface temperature. Several of the dust devil data records were processed and analyzed at the Raytheon Company in Sudbury, Massachusetts, with additional analyses occurring at the University of Arkansas, Fayetteville,
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