BOREAS AFM-06 NOAA/ETL 35-GHz Cloud/Turbulence Radar GIF Images Summary The BOREAS AFM-06 team from NOAA/ETL operated a 35-GHz cloud-sensing radar in the NSA near the OJP tower from 16-Jul-1994 to 08-Aug-1994. This data set contains a time series of GIF images that show the structure of the lower atmosphere. Table of Contents * 1 Data Set Overview * 2 Investigator(s) * 3 Theory of Measurements * 4 Equipment * 5 Data Acquisition Methods * 6 Observations * 7 Data Description * 8 Data Organization * 9 Data Manipulations * 10 Errors * 11 Notes * 12 Application of the Data Set * 13 Future Modifications and Plans * 14 Software * 15 Data Access * 16 Output Products and Availability * 17 References * 18 Glossary of Terms * 19 List of Acronyms * 20 Document Information 1. Data Set Overview 1.1 Data Set Identification BOREAS AFM-06 NOAA/ETL 35-GHz Cloud/Turbulence Radar GIF Images 1.2 Data Set Introduction This data set contains Graphical Interchange Format (GIF) images derived from radar data. The data were collected during July and August in the BOReal Ecosystem-Atmosphere Study (BOREAS) Northern Study Area (NSA) approximately 1 km northeast of the Old Jack Pine (OJP) tower. The images provide a visual depiction of the atmospheric structure during the data collection periods. Each .gif file contains two panels. The top panel is radar reflectivity in dBZ units (which are commonly used in radar meteorology). This is the intensity of the backscattered signal, and for water droplets it is related to the size and concentration of the drops. The hotter the color the, stronger the returned signal. The lower panel is the measured Doppler vertical velocity in units of m/s. Warm colors represent upward motion and cool colors signify downward motion. Often, the cloud image covers more area on the velocity image than on the reflectivity image because the radar's velocity measurements can detect weaker targets. 1.3 Objective/Purpose The field work objective was to measure turbulence characteristics of the outer boundary layer (above 100 m above ground level (AGL)) and the structure and kinematics of tropospheric clouds, including multiple cloud layer heights and thicknesses. The scientific analysis goal is to use these radar measurements, in combination with tower and aircraft flux measurements, to examine how clouds and outer boundary layer motions affect surface layer fluxes. The data may also be useful for extending the height-limited momentum flux measurements. 1.4 Summary of Parameters Parameters measured by the radar at every range gate include: radar reflectivity factor (dBZ) radial Doppler velocity (m/s) variance of the Doppler velocity spectrum (m2/s2) depolarization ratio (dB) Various other parameters, such as momentum fluxes, may be derived from these basic measurements. 1.5 Discussion National Oceanic and Atmospheric Administration (NOAA) Environmental Technology Laboratory (ETL) personnel operated a 35-GHz cloud-sensing radar in the BOREAS Northern Study Area throughout Intensive Field Campaign (IFC)-2 during midsummer of 1994. This work is one aspect of the research by the Airborne Fluxes and Meteorology (AFM)-06 team. The other aspect was the data collection by a 915- MHz wind profiler/Radio Acoustic Sounding System (RASS) in the Southern Study Area (SSA), as documented in a separate data set. The .gif files are time-height images of the structure and kinematics of clouds and other particulate scatters (such as insects) over the radar site for periods when the radar was pointing at the zenith. Thus, the images provide a history of the clouds, etc., as they passed over the radar. Insect echoes are limited to the boundary layer, usually less than 2 km above ground. Stratus clouds sometimes also occupied those low altitudes. 1.6 Related Data Sets BOREAS AFM-05 Level-1 Upper Air Network Data BOREAS AFM-05 Level-2 Upper Air Network Standard Pressure Level Data BOREAS AFM-06 Boundary Layer Height Data BOREAS AFM-07 SRC Surface Meteorological Data BOREAS TF-08 NSA-OJP Tower Flux, Meteorological, and Soil Temperature Data 2. Investigator(s) 2.1 Investigator(s) Name and Title Robert Banta, Brooks Martner, James Wilczak NOAA/ETL 2.2 Title of Investigation Outer Boundary Layer Effects on Surface Fluxes of Momentum, Heat, Moisture, and Greenhouse Gases from the Boreal Forest 2.3 Contact Information Contact 1 ------------- Brooks E. Martner NOAA/ETL Boulder, CO (303) 497-6375 bmartner@etl.noaa.gov Contact 2 ------------ Jeffrey A. Newcomer Raytheon ITSS NASA GSFC Greenbelt, MD (301) 286-7858 (301) 286-0239 (fax) Jeffrey.Newcomer@gsfc.nasa.gov 3. Theory of Measurements The radar is an active remote sensor that transmits pulses of microwave energy and receives signals backscattered from targets in the beam. The Doppler shift caused by the targets' motions is determined by measuring and comparing the phase of the transmitted and received signals. In the BOREAS data set, the targets are primarily cloud hydrometeors and/or insects. Both are treated as tracers of the atmospheric motions. 4. Equipment 4.1 Sensor/Instrument Description The cloud-sensing radar is a 35 GHz (8-mm wavelength, Ka-band) Doppler, dual- polarization system developed at NOAA/ETL. Its Doppler capability allows the velocity of the backscattering targets to be measured, and its short wavelength (compared to storm-monitoring radars) gives it the ability to detect clouds as well as precipitation. It can also obtain measurements in the cloudless boundary layer from backscatter off of insects, bits of vegetation, seeds, and perhaps giant aerosols that are prevalent in warm seasons over continental locations. Two scanning modes were used in BOREAS: 1. Vertical. The antenna pointed continuously at the zenith. In this mode, high-resolution measurements were obtained of vertical velocity fluctuations in the boundary layer as a function of time and height. It also provided uninterrupted monitoring of cloud conditions over the site. 2. Conical. The antenna repeated a series of four elevation sweeps (35, 51, 69, and 90 degrees above the horizon) every 6 minutes. This mode allowed the horizontal components of the wind to be measured in addition to the vertical wind. Post-processing with velocity azimuth display (VAD) software computes profiles of the mean wind, momentum fluxes (u'w', v'w'), and higher order turbulence statistics for a large volume of air over the radar. NOAA/ETL 35-GHz Cloud/Turbulence Radar Range resolution = 37.5 m Range limits = 0.15-12.4 Temporal resolution = 3.33 Hz (vertical mode) (Complete hardware and operating characteristics table can be obtained from B. Martner, NOAA/ETL.) 4.1.1 Collection Environment Data were collected during a variety of weather conditions, as described in Section 7.2. 4.1.2 Source/Platform The radar was ground-based and mounted on two trailers. 4.1.3 Source/Platform Mission Objectives The purpose of the trailers was to contain and support the radar measurement equipment. 4.1.4 Key Variables Radar reflectivity factor (dBZ) Radial Doppler velocity (m/s) Variance of the Doppler velocity spectrum (m2/s2) Circular Depolarizaton Ratio (dB) 4.1.5 Principles of Operation Standard Doppler radar techniques 4.1.6 Sensor/Instrument Measurement Geometry Continuous, fixed-beam vertical scanning or continuous conical scanning (See Section 1.5). 4.1.7 Manufacturer of Sensor/Instrument NOAA/ETL 325 Broadway Boulder, CO 80303 4.2 Calibration Antenna gain and power patterns have been range-tested. Receiver calibrations are conducted before each field project. Typical measurement accuracies are +/- 1 dB for reflectivity and +/- 5-10 cm/s for radial velocity. 4.2.1 Specifications None given. 4.2.1.1 Tolerance None given. 4.2.2 Frequency of Calibration None given. 4.2.3 Other Calibration Information None given. 5. Data Acquisition Methods Two scanning modes were used in BOREAS: 1. Vertical. The antenna pointed continuously at the zenith for long periods (several hours). In this mode, high-resolution measurements were obtained of the vertical velocity fluctuations in the boundary layer as a function of time and height. This mode also provided uninterrupted monitoring of cloud conditions over the radar site. 2. Conical. The antenna repeated a series of four elevation angle sweeps (35, 51, 69, and 90 degrees above the horizon) every 6 minutes. This mode allowed horizontal components of the wind to be measured in addition to the vertical wind. Post-processing with VAD software computes profiles of the mean wind, momentum fluxes, and higher order turbulence statistics for a large volume over the radar. 6. Observations 6.1 Data Notes The vertical data in this part of the cloud radar data set (Part I) are provided only in the form of images. The images are in GIF format, which can be displayed with various graphics packages. The image files are provided to give investigators a visual impression of the cloudiness (layer heights, thicknesses, intensities) and the strength of vertical motion fluctuations in the boundary layer as a function of time and height near the NSA-OJP site. Because the radar collects huge amounts of data (typically 100 megabytes per hour), a greatly reduced processed set of data is provided for distribution by the BOREAS Information System (BORIS). The original data are archived at NOAA/ETL on 46 8-mm digital video tapes in the Common Doppler Radar Data Exchange Format (also called "universal format") that is used by many radar meteorology research groups. 6.2 Field Notes Extensive field notes were recorded in an electronic log book by the radar crew. These notes contain comments about weather conditions, experimental events, equipment problems, etc. Each entry was automatically tagged with the time in Greenwich Mean Time (GMT), date, and topic category. The notes were recorded in WordPerfect format. The hardcopy printout totals about 100 pages. Notes for specific dates are available, upon request, from Brooks Martner (See Section 2.3). 7. Data Description 7.1 Spatial Characteristics 7.1.1 Spatial Coverage The North American Datum of 1983 (NAD83) coordinates of the site are: Lat. = 55 deg. 56 min. 00 sec. Long. = 98 deg. 36 min. 52 sec. Alt. = 290 m ASL This location is within the NSA, about 60 km west-northwest of Thompson and approximately 1 km northeast of the NSA-OJP flux tower. 7.1.2 Spatial Coverage Map Not applicable. 7.1.3 Spatial Resolution Beamwidth = 0.5 degrees Range resolution = 37.5 m Range limits = 0.15-12.45 km (= 328 range gates) 7.1.4 Projection Not applicable. 7.1.5 Grid Description Not applicable. 7.2 Temporal Characteristics 7.2.1 Temporal Coverage The radar operated in one of two modes, almost continuously, day and night, during IFC-2 and a few days earlier. The dates of radar operation and some general notes are included in the following table. Start End Date Time Date Time (GMT) (GMT) Weather; Scan mode ----------- ----------- --------------------------------------------- 07/16 22:21 07/17 14:21 mostly clear; vertical 07/17 16:40 07/17 22:10 clear skies; vertical 07/17 22:10 07/18 14:38 clear skies; vertical 07/18 15:50 07/19 00:01 mostly clear; conical 07/19 00:02 07/19 15:08 layer clouds, light rain; conical 07/19 15:14 07/19 21:40 rain; vertical and conical 07/19 21:50 07/20 15:00 rain then overcast; conical 07/20 15:14 07/20 23:15 clearing, cirrus & cumuli; vertical 07/20 23:16 07/21 14:54 cumuli then clear; vertical 07/21 15:15 07/21 22:28 clear; conical 07/21 22:29 07/22 14:33 clouds & showers; vertical 07/22 15:09 07/22 21:33 post-front clear & cloud; conical 07/22 21:33 07/23 15:03 variable cloudiness; conical 07/23 16:02 07/23 22:29 windy, cumuli then clear; vertical 07/23 22:29 07/24 14:33 cloud layers move in; vertical 07/24 14:45 07/24 21:54 stratus; vertical 07/24 21:54 07/25 15:25 cumuli, clear, layers; conical 07/25 15:35 07/25 22:39 showers, deep layer; conical 07/25 22:39 07/26 09:21 clearing; conical 07/26 14:48 07/26 22:47 clear, cloudy, clear; vertical 07/27 15:15 07/27 22:21 cirrus; conical 07/27 22:21 07/28 14:52 cirrus then clear; vertical 07/28 15:01 07/28 22:18 clear; conical 07/28 22:18 07/29 14:11 clear, brief cirrus; vertical 07/29 15:05 07/29 22:16 clear, a few cirrus; conical 07/29 22:16 07/30 14:47 cirrus then clear; vertical 07/30 15:21 07/30 22:20 clear; conical 07/30 22:24 07/31 14:24 clear; vertical 07/31 14:40 07/31 21:15 clear; conical 07/31 21:15 08/01 14:45 clear then cirrus; vertical 08/01 14:56 08/01 22:25 cirrus; conical 08/01 22:25 08/02 14:56 layer clouds, virga; vertical 08/02 15:04 08/02 22:33 cold front clouds; conical 08/02 22:34 08/03 11:03 altostratus, stratus, clear; conical 08/03 15:37 08/03 22:07 cloud layers; vertical 08/03 22:08 08/04 14:08 stratus, clear, cirrus; vertical 08/04 14:19 08/04 22:31 clear; conical 08/04 22:31 08/05 00:54 clear; conical 08/05 15:06 08/05 22:18 cirrus, altostratus; mostly vertical 08/05 22:18 08/06 14:38 increasing clouds, rain; vertical 08/06 15:00 08/06 22:31 stratus; vertical 08/06 22:31 08/07 14:34 thin stratus; vertical 08/07 14:47 08/07 22:01 thin stratus; mostly vertical 08/07 22:01 08/08 10:14 thin stratus, clearing; vertical 08/08 14:38 08/08 18:39 clear, fair weather cumuli; conical 08/08 18:58 08/08 22:57 fair weather cumuli; conical 7.2.2 Temporal Coverage Map Not available. 7.2.3 Temporal Resolution Vertical mode: 20 beams/minute for routine averaged data (200 beams/minute for raw data) 30-minute volumes (= 600 beams/volume) Conical mode: 291 beams/sweep 1 sweep/90 seconds 4 sweeps/volume (= 1 volume every 6 minutes) 7.3 Data Characteristics 7.3.1 Parameter/Variable CLOUD HEIGHT DOPPLER VERTICAL VELOCITY RADAR REFLECTIVITY 7.3.2 Variable Description/Definition CLOUD HEIGHT Height of the clouds in km. DOPPLER VERTICAL VELOCITY Warm colors represent upward motion and cool colors signify downward motion. Often, the cloud image covers more area on the velocity image than on the reflectivity image because the radar's velocity measurements can detect weaker targets. RADAR REFLECTIVITY The intensity of the backscattered signal, and for water droplets it is related to the size and concentration of the drops. The hotter the color the stronger the returned signal. 7.3.3 Unit of Measurement CLOUD HEIGHT km DOPPLER VERTICAL VELOCITY m/sec RADAR REFLECTIVITY dbZ 7.3.4 Data Source Analysis of raw radar data. 7.3.5 Data Range CLOUD HEIGHT 0-12 km agl DOPPLER VERTICAL VELOCITY -40 to 17.5 RADAR REFLECTIVITY -40 to 17.5 7.4 Sample Data Record Not applicable. 8. Data Organization 8.1 Data Granularity The smallest unit of data tracked by BORIS is the entire set of GIF images. 8.2 Data Format(s) The entire set of GIF images is stored in a single Unix tar file. Within the Tar file are 603 GIF images. Each image shows a time series profile of the atmosphere as it passed over the radar site. 9. Data Manipulations 9.1 Formulae None given. 9.1.1 Derivation Techniques and Algorithms The image data contain direct measurements of radar reflectivity and vertical Doppler velocity as recorded by the instrument. The only processing of the measurements is temporal averaging of data. The displayed data have 3-sec resolution, which represents an average of 10 individual raw data beams that are recorded at the rate of one raw beam every 3/10 sec. 9.2 Data Processing Sequence 9.2.1 Processing Steps See Section 9.1.1. 9.2.2 Processing Changes None given. 9.3 Calculations 9.3.1 Special Corrections/Adjustments See Section 9.1.1. 9.3.2 Calculated Variables See Section 9.1.1. 9.4 Graphs and Plots The vertical data were provided to BORIS in the form of time-height plots. 10. Errors 10.1 Sources of Error One known source of error is the strong attenuation of the radar's microwave energy by rainfall. Rain or water on the antenna's waveguide feed window will usually invalidate the reflectivity measurements, although the velocity measurements remain accurate. Very strong targets may also cause saturation of the receiver used for the reflectivity data shown in these images. Range- aliasing (2nd-trip echoes) and velocity aliasing (folding) are not factors for these vertical data. 10.2 Quality Assessment 10.2.1 Data Validation by Source None given. 10.2.2 Confidence Level/Accuracy Judgment None given 10.2.3 Measurement Error for Parameters For typical conditions the reflectivity measurements are accurate within +/- 1 dBZ, and the vertical Doppler velocity measurements are accurate to within +/- 5-10 cm/s. 10.2.4 Additional Quality Assessments None given. 10.2.5 Data Verification by Data Center BORIS Personnel visually reviewed several randomly selected images. All reviewed images appeared to reflect the description found in Section 11.4. 11. Notes 11.1 Limitations of the Data None given. 11.2 Known Problems with the Data None given. 11.3 Usage Guidance The time-height images are provided to BORIS in order to allow scientists to obtain a general impression of the evolution of cloudiness and boundary layer vertical motions near the NSA-OJP site. The principal investigators should be consulted for a more quantitative use of the vertical data. 11.4 Other Relevant Information There is one profile of data every 3 seconds, 600 of which are assembled side by side in chronological order into these half-hour images. Each image covers 30 minutes of time (the x-axis) and 0-12 km of height above ground (the y-axis). A few specific times are shown at periodic intervals near the top of each image, with the time mark corresponding to the left-hand edge of those time numbers. There is some additional nondata blank space at the end of the y-axis in each image beyond the 30-minute mark, which accounts for the extra pixels. The start time in Universal Time Code (UTC) of each half- hour is shown in the header strip at the top of each image. Thus, the file k01aug94.0815.gif contains the radar data for 08:15-08:45 UTC on 01-Aug-1994 and shows all radar echoes that passed over the radar during that period between the ground and 12-km height. 12. Application of the Data Set The data may be useful for extending the height-limited momentum flux measurements. 13. Future Modifications and Plans None given. 14. Software 14.1 Software Description None given. 14.2 Software Access None given. 15. Data Access 15.1 Contact Information Ms. Beth Nelson BOREAS Data Manager NASA GSFC Greenbelt, MD (301) 286-4005 (301) 286-0239 (fax) Elizabeth.Nelson@gsfc.nasa.gov 15.2 Data Center Identification See Section 15.1 15.3 Procedures for Obtaining Data Users may place request by telephone, electronic mail, or FAX. 15.4 Data Center Status/Plans The AFM-06 GIF images are available from the EOSDIS ORNL DAAC (Earth Observing System Data and Information System) (Oak Ridge National Laboratory) (Distributed Active Archive Center). The BOREAS contact at ORNL is: ORNL DAAC User Services Oak Ridge National Laboratory (865) 241-3952 ornldaac@ornl.gov ornl@eos.nasa.gov 16. Output Products and Availability 16.1 Tape Products The complete data set (approximately 48 gigabytes) is archived at NOAA/ETL on 46 8-mm digital video (Exabyte-type) tapes. The data are on tape in the Common Doppler Radar Data Exchange Format used by many radar meteorology research groups. 16.2 Film Products None. 16.3 Other Products None. 17. References 17.1 Platform/Sensor/Instrument/Data Processing Documentation Barnes, S.L. 1980. Report on a meeting to establish a common Doppler radar data exchange format. Bull. Amer. Meteor. Soc., 61, 1401-1404. 17.2 Journal Articles and Study Reports Frisch, A.S., B.E. Martner, and J.S. Gibson. 1989. Measurement of the vertical flux of turbulent kinetic energy with a single Doppler radar. Boundary Layer Meteor., 49, 331-337. Frisch, A.S., B.W. Orr, and B.E. Martner. 1992. Doppler radar observations of the development of a boundary layer nocturnal jet. Monthly Weather Rev., 120, 3- 16. Frisch, A.S., B.B. Stankov, B.E. Martner, and J.C. Kaimal. 1990. Doppler radar measurements of vertical velocity in the convective boundary layer. Gibson, J.S. and B.E. Martner. 1995. Interactive auxiliary real-time display system for NOAA/ETL Radars. Preprints, 11th Intl. Conf. on Interactive Information Processing (IIPS), Dallas, TX, Amer. Meteor.Soc. Kropfli, R.A. 1986. Single Doppler radar measurement of turbulence profiles in the convective boundary layer. J. Atmos. & Ocean. Tech., 3, 305-314. Kropfli, R.A., B.W. Bartram, and S.Y. Matrosov. 1990. The upgraded WPL dual- polarization 8.6-mm Doppler radar for microphysical and climate research. Preprints, Conf. on Cloud Physics, San Francisco, Amer. Meteor. Soc., 467-472. Kropfli, R.A., S.Y. Matrosov, T. Uttal, A.S. Frisch, B.E. Martner, and J.B. Snider. 1994. Studies of radiatively important clouds with 8-mm wavelength Doppler radars. Preprints, Intl. Geosci. & Remote Sensing Symp., Pasadena, IEEE, 657-659. Martner, B.E. and R.A. Kropfli. 1993. Observations of multi-layered clouds using K-band radar. AIAA Paper 93-0394, 31st Aerospace Sciences Meeting, Amer. Inst. Aero. & Astronautics, Washington, DC, 8 pp. Martner, B.E., A.S. Frisch, and R.M. Banta. 1995. Diurnal evolution of boundary layer turbulence over a boreal forest as observed by Doppler radar. Preprints, 27th Conf. on Radar Meteorology, Vail, CO, Amer. Meteor. Soc., 485-487. Matrosov, S.Y., T. Uttal, J.B. Snider, and R.A. Kropfli. 1992. Estimation of ice cloud parameters from ground-based infrared radiometer and radar measurements. J. Geophys. Res., 97-D11, 11567-11574. Sellers, P. and F. Hall. 1994. Boreal Ecosystem-Atmosphere Study: Experiment Plan. Version 1994-3.0, NASA BOREAS Report (EXPLAN 94). Sellers, P. and F. Hall. 1996. Boreal Ecosystem-Atmosphere Study: Experiment Plan. Version 1996-2.0, NASA BOREAS Report (EXPLAN 96). Sellers, P., F. Hall, and K.F. Huemmrich. 1996. Boreal Ecosystem-Atmosphere Study: 1994 Operations. NASA BOREAS Report (OPS DOC 94). Sellers, P., F. Hall, and K.F. Huemmrich. 1997. Boreal Ecosystem-Atmosphere Study: 1996 Operations. NASA BOREAS Report (OPS DOC 96). Sellers, P., F. Hall, H. Margolis, B. Kelly, D. Baldocchi, G. den Hartog, J. Cihlar, M.G. Ryan, B. Goodison, P. Crill, K.J. Ranson, D. Lettenmaier, and D.E. Wickland. 1995. The boreal ecosystem-atmosphere study (BOREAS): an overview and early results from the 1994 field year. Bulletin of the American Meteorological Society. 76(9):1549-1577. Sellers, P.J., F.G. Hall, R.D. Kelly, A. Black, D. Baldocchi, J. Berry, M. Ryan, K.J. Ranson, P.M. Crill, D.P. Lettenmaier, H. Margolis, J. Cihlar, J. Newcomer, D. Fitzjarrald, P.G. Jarvis, S.T. Gower, D. Halliwell, D. Williams, B. Goodison, D.E. Wickland, and F.E. Guertin. 1997. BOREAS in 1997: Experiment Overview, Scientific Results and Future Directions. Journal of Geophysical Research. 102(D24): Dec. 1997, 28,731-28,770. 17.3 Archive/DBMS Usage Documentation None. 18. Glossary of Terms None given. 19. List of Acronyms AFM - Airborne Fluxes and Meteorology AGL - Above Ground Level ASCII - American Standard Code for Information Interchange BOREAS - BOReal Ecosystem-Atmosphere Study BORIS - BOREAS Information System CD-ROM - Compact Disk-Read-Only Memory DAAC - Distributed Active Archive Center EOS - Earth Observing System EOSDIS - EOS Data and Information System ETL - Environment Technology Laboratory GIF - Graphical Interchange Format GMT - Greenwich Mean Time GSFC - Goddard Space Flight Center IFC - Intensive Field Campaign NAD83 - North American Datum of 1983 NASA - National Aeronautics and Space Administration NOAA - National Oceanic and Atmospheric Administration NSA - Northern Study Area OJP - Old Jack Pine ORNL - Oak Ridge National Laboratory PANP - Prince Albert National Park RASS - Radio Acoustic Sounding System SSA - Southern Study Area TF - Tower Flux URL - Uniform Resource Locator UTC - Universal Time Code VAD - Velocity Azimuth Display 20. Document Information 20.1 Document Revision Dates Written: 01-Dec-1994 Last Updated: 17-Feb-1999 20.2 Document Review Date BORIS Review: 29-Jan-1999 Science Review: 20.3 Document 20.4 Citation Radar images (and/or data) provided by Brooks Martner NOAA/ETL 20.5 Document Curator 20.6 Document URL Keywords: Radar reflectivity Vertical Doppler velocity AFM06_GIF_Imgs.doc 05/07/99