DATASET: Electronically Scanned Microwave Radiometer (ESMR) IF YOU USE OUR DATA, PLEASE ACKNOWLEDGE: The production and distribution of this data set are being funded by NASA's Mission To Planet Earth Program. The data are not copyrighted, however, we request that when you publish data or results using these data please acknowledge as follows: "The authors would like to thank the Process Studies Program Office (Code SEP, NASA Headquarters) and the Distributed Active Archive Center (Code 902.2) at Goddard Space Flight Center, Greenbelt, MD 20771 for the production and distribution of these data, respectively. These activities were sponsored by NASA's Mission to Planet Earth Program." 1. GENERAL INFORMATION The ESMR data set is part of the atmospheric measurements collected in the intensive observation period of the Tropical Ocean Global Atmosphere- Coupled Ocean Atmosphere Response Experiment (TOGA-COARE). Dr. Thomas Wilheit of Texas A & M University is the Principal Investigator and the data set is archived as a member of the NASA/TOGA COARE Campaign Data Set at the Goddard DAAC. The Tropical Ocean Global Atmosphere-Coupled Ocean Atmospheric Response Experiment (TOGA COARE) is an international research program investigating the scientific phenomena associated with the interaction between the atmosphere and the ocean in the warm pool region of the western Pacific, a region roughly bounded by the latitudes 30N and 30S and the longitudes 140E and 160E. The field experiment phase of the program took place from November, 1992 through February, 1993 and involved the deployment of oceanographic ships and buoys, several ship and land based Doppler radars, multiple low and high level aircraft equipped with Doppler radar and other airborne sensors, as well as a variety of surface based instruments for in situ observations. The NASA component of TOGA COARE, while contributing directly to overall COARE objectives, emphasizes scientific objectives associated with the Tropical Rainfall Measuring Mission (TRMM) and NASA's cloud and radiation program. The ESMR instrument, which was mounted on NASA's DC-8 aircraft for the TOGA COARE Field Experiment, is a scanning radiometer that measures brightness temperatures in degrees Kelvin. It was operational during 13 mission flights of the DC-8 between January 11 and February 26, 1993. 2. INSTRUMENT INFORMATION 2.1 Science Objectives The objective for the ESMR instrument in the TOGA COARE Campaign was to provide observations to develop better radiative transfer models for used in rainfall retrieval algorithms to be used in the development of the TRMM research paradigm. The ESMR instrument, which was mounted on NASA's DC-8 aircraft for the TOGA COARE Field Experiment, is a scanning radiometer that measures brightness temperatures in degrees Kelvin. It was operational during 13 mission flights of the DC-8 between January 11 and February 26, 1993. 2.2 General Description The ESMR instrument is a 19.35 GHz scanning radiometer mounted aboard NASA's DC-8 aircraft. 2.3 Instrument Geometry The ESMR radiometer is nadir-mounted in the aircraft and scans in a plane perpendicular to the direction of flight with a swath of +/-50 degrees from nadir. Beam position (BP) 20 is at nadir during level flight; BP 1 is 50 degrees to the left, and BP 39 is 50 degrees to the right. The beam positions are distributed in equal divisions of the sine of the scan angle. When the pitch and roll of the plane are negligible, a simple algorithm can be used to obtain the latitude and longitude at each BP. If we define: - BP is the beam position (integer, 1-39) - sinBP is the sine of the scan angle of the BP - lat and lon are the aircraft position - ofsBP is the offset angle of the BP - hdg is the aircraft heading - alt is the aircraft altitude - latBP and lonBP are the latitude and longitude of the beam position Then execute the following calculations: sinBP = (sin(50/57.2)*(BP-20)/19) ofsBP = 0.1 * (sinBP/sqrt(1-sinBP*sinBP)) latBP = lat - ofsBP*sin(hdg)*alt/36000 lonBP = lon + ofsBP*cos(hdg)*alt/(cos(lat)*36000) 3. DATA ORGANIZATION 3.1 General Characteristics One data product consisting of 13 binary files of calibrated brightness temperatures in degrees Kelvin was produced by the ESMR instrument during the TOGA COARE Campaign. Each file contains data from 1 flight. The ESMR data totals ~12 MB in volume and has a typical file size of ~.8 MB. The following table relates ESMR data files to ER-2 and DC-8 flight numbers and dates for the 13 mission flights of the NASA/TOGA COARE campaign. The objectives column is included for the convenience of the user; the mission objective defaulted to Radiation unless Convection was forecast in the target area. Date(UTC) ER-2 Flight DC-8 Flight ESMR File Objective ------------------------------------------------------------------------- Jan 11-12 93-053 93-01-06 011.tbn Radiation Jan 17-18 93-054 93-01-07 017.tbn Convection Jan 18-19 93-055 93-01-08 019.tbn Convection Jan 25-26 93-056 93-01-09 025.tbn Radiation jan 31-Feb 1 93-057 93-01-10 031.tbn Radiation Feb 4 93-060 93-01-11 035.tbn Convection Feb 6 93-01-12 037.tbn Convection Feb 7 93-061 Feb 8-9 93-062 93-01-13 039.tbn Convection Feb 10-11 93-063 93-01-14 041.tbn Convection Feb 17-18 93-01-15 048.tbn Convection Feb 20-21 93-065 93-01-16 051.tbn Convection Feb 22-23 93-066 93-01-17 053.tbn Convection Feb 23-24 93-067 93-01-18 057.tbn Radiation 3.2 Data Format The TbN data format is as follows: bytes Type variable 1-39 unsign 1 byte Brightness Temp for each BP (add 100.) 40 " Hour 41 " Minute 42 " Seconds (integer part) 43 " Hundreths of seconds 44-45 signed 2-byte Julian Day 46-47 " Latitude(integer part) 48-49 " 1/10000ths of latitude 50-51 " Longitude (integer part) 52-53 " 1/10000ths of longitude 54-55 " Altitude (tens of feet) 56-57 " Heading (tenths of degrees) 58-59 " Roll (tenths of degrees) 60-61 " Pitch (tenths of degrees) 62-64 - Empty Note that the latitude and longitude fractions share the same sign; to obtain either variable, simply sum the integer and fractional parts without manipulating the signs. All of the integers are standard MS-DOS format. 4. DATA ACCESS 4.1 FTP access to ESMR data Data may be retrieved from the Goddard DAAC public FTP area by following the procedures below: o ftp daac.gsfc.nasa.gov o login - anonymous o password - your Internet address o cd pub/toga_coare/aircraft/nasa_dc8/esmr Please call TOGA-COARE user support to order ESMR data on tape. 4.2 Software 4.2.1 DOS Software. Read software in Turbo Pascal (RDTBNAV) was submitted by the ESMR instrument team. Display software used by the PI in processing the data has also been made available. It runs in a DOS environment and requires a Super VGA video card based on the Tseng chipset or a VESA standard compatible video card with appropriate drivers. Software to read and display the ESMR data on a DOS system resides in: toga_coare/aircraft/nasa_dc8/esmr/software/DOS_sftwr 4.2.2 UNIX Software. Program esmr_read.c was created by the GSFC DAAC to provide the functionality of the original Pascal read program to UNIX users. Porting the ESMR data set from a PC to the DAAC's Silicon Graphics machines required a byte swap when loading 2-byte data values into integers, an implementation dependent feature that may not be required on other systems. The program is self documenting. A validation file (ESMR.dat) displaying correct values from the first ten records in data file 011.tbn is offered to assist UNIX users in adapting program esmr_read.c to their environments. Software to read the ESMR binary data files on a UNIX system resides in: toga_coare/aircraft/nasa_dc8/esmr/software/unix_sftwr 5. DATA QUALITY ASSESSMENT In general, if the pitch or roll of the aircraft is greater than 5 degrees (pitch and roll are recorded in the data once for each scan) the data is not considered reliable, particularly at the extreme beam positions. 5.1.1 Times. All times are in UTC. The instrument clock was synchronized with the aircraft clock at the beginning of each flight. 5.1.2 Spatial Coordinates. Geo-referencing information was acquired from the aircraft's DADS system and is included in the data. 5.2 Noise Levels The noise threshold for this instrument is 4 Kelvin. Saturation did not occur during this campaign. 6. POINTS OF CONTACT For NASA/TOGA COARE user support, please contact: Pat Hrubiak EOS Distributed Active Archive Center(DAAC) Code 902.2 NASA Goddard Space Flight Center Greenbelt, Maryland 20771 Internet: hrubiak@daac.gsfc.nasa.gov (301) 286-1381 (voice) (301) 286-1775 (FAX) For detailed information about the sensor, contact: Principal Investigator: T. T. Wilheit Department of Meteorology Texas A&M University College Station, TX 77843-3150 Wilheit@ariel.tamu.edu (301) 286-8949 (voice) (301) 286-1761 (FAX) For ESMR data processing information, contact: Rick Russell Department of Meteorology Texas A&M University College Station, TX 77843-3150 rick-russell@tamu.edu (301) 286-9114 (voice) 7. DATA STATUS AND PLAN The Goddard DAAC will continue to archive and make these products available to TOGA COARE researchers. All NASA/TOGA COARE data products will be ingested into the DAAC IMS, becoming accessible to the earth science community. 8. REFERENCES a. TOGA COARE Science Data Workshop II Proceedings, March 15-17, 1994, page 4. b. Chang, A.T.C., A. Barnes, M. Glass, R. Kakar, & T.T. Wilheit, 1993: Aircraft observations of the vertical structure of stratiform precipitation relevant to microwave radiative transfer. J. Appl. Meteor. 32, 1083-1091. c. Wilheit, T.T., A.T.C. Chang and L.S. Chiu, 1991: Retrieval of Monthly rainfall indices from microwave radiometric measurements using probability distribution functions. J. Atmos. Oceanic Tech., 8, 118-136 d. Wilheit, T.T., {and 18 others}, 1994: Algorithms for the retrieval of rainfall from passive microwave measurements. Submitted to Reviews of REmote Sensing. See other subdirectories of FTP directory toga_coare for additional data products from the NASA/TOGA COARE field experiment. *94/07/09