Cloud Absorption Radiometer BRDF (Bidirectional Reflectance Distribution Function) data of various surfaces and of clouds were collected during twenty-one flights over southern Africa during the SAFARI 2000 Dry Season Aircraft Campaign from August14 to September 16, 2000. Airborne data were collected over five different SAFARI measurement sites and include a set of cloud measurements over Namibia.
The Cloud Absorption Radiometer (CAR) is an airborne multi-wavelength scanning radiometer that can perform several functions including determining the single scattering albedo of clouds at selected wavelengths in the visible and near-infrared, measuring the angular distribution of scattered radiation, measuring bidirectional reflectance of various surface types, and acquiring imagery of cloud and Earth surface features. The CAR instrument was developed at the NASA Goddard Space Flight Center by Dr. Michael King.
The CAR now operates from a position mounted in the improved nose cone on a Convair CV-580. In addition to its traditional starboard viewing mode, the CAR instrument can be operated in zenith viewing, nadir viewing, and BRDF mode. The instrument can be switched between each of these four modes during flight.
During the SAFARI 2000 research field campaigns, the CAR was flown in concert with an array of cloud microphysics, aerosol, atmospheric chemistry, and general meteorological instruments under the direction of the Department of Atmospheric Sciences at the University of Washington (Hobbs 2004).
Additional information on the CAR, BRDF measurements, and the Convair CV-580 are in the companion file [http://daac.ornl.gov/daacdata/safari2k/remote_sensing/CAR_BRDF/comp/car_brdf_cv580_doc.pdf ]. Detailed flight maps and logs and additional browse images may be accessed via links in this companion file.
For more information about the 21 CAR missions in support of SAFARI see: http://car.gsfc.nasa.gov/data/safari.php.
Cite this data set as follows:
King, M. D., C. Gatebe, and S. Platnick. 2004. SAFARI 2000 Cloud Absorption Radiometer BRDF, Dry Season 2000. Data set. Available on-line [http://www.daac.ornl.gov] from Oak Ridge National Laboratory Distributed Active Archive Center, Oak Ridge, Tennessee, U.S.A. doi:10.3334/ORNLDAAC/709.
Gatebe, C. K., M. D. King, S. Platnick, G. T. Arnold, E. F. Vermote, and B. Schmid. 2003. Airborne spectral measurements of surface atmosphere anisotropy for several surfaces and ecosystems over southern Africa. J. Geophys. Res. 108(D13): 8489, doi:10.1029/2002JD002397.
Hobbs, P. V. 2004. SAFARI 2000 CV-580 Aerosol and Cloud Data, Dry Season 2000 (CARG). Data set. Available on-line [http://www.daac.ornl.gov] from Oak Ridge National Laboratory Distributed Active Archive Center, Oak Ridge, Tennessee, U.S.A.
King, M. D., M. G. Strange, P. Leone, and L. R. Blaine. 1986. Multiwavelength scanning radiometer for airborne measurements of scattered radiation within clouds. Journal of Atmospheric Oceanic Technology 3: 513-522.
CAR BRDF data of various surfaces and clouds were collected in southern Africa during the SAFARI 2000 Dry Season Aircraft Campaign (August 14 - September 16, 2000). Data were collected over five different sites and include a set of cloud measurements over Namibia as well. The data have been zip compressed for each site. Within the zip archive are Level 2a and Level 2c files. The Level 2a product represents top of the atmosphere reflectances on a 1 x 1 degree radial-azimuthal surface. The Level 2a product is derived from CAR Level 1b data, which is time-referenced instrument data at full resolution that have been corrected with radiometric coefficients and corrected for aircraft pitch and roll and located by position on the Earth surface. The Level 2c data are derived from Level 2a by correcting for atmospheric absorption and scattering.
Level 2a data files are named for the target location and date of measurements. For example, the file for Skukuza is named: skukuza_20000829_l2a.asc. In each file a header describes the format and includes latitude/longitude and time, followed by data for channels 1 to 8 (at 0.34, 0.38 .47, .68, .87, 1.03, 1.22, and 1.27 microns).
Level 2c data are named and formatted in a manner different from the Level 2a data. Each channel is a separate ASCII gridded file. The file names begin with the prefix CAR, followed by date and time of measurements, brdf, and channel number. For example, the file car_20000829_1350_brdf01.asc is CAR BRDF data for channel 1 measurements taken on August 29, 2000, starting at 1350 UTC over Skukuza. Each Level 2c file contains 181 x 181 data points on an x-y grid. Because the data are in spherical coordinates (181 points along the diameter), points outside the diameter but within the x-y grid are assigned a fill value of -8421. Consequently, the central values represent nadir, and the principal plane is from mid-point left (forward scattering plane) through nadir (center) to mid-point right (backward scattering plane).
The format for these data should be considered preliminary. Alternative data formats are available from Tom Arnold (firstname.lastname@example.org) or Charles Gatabe (email@example.com) or from the CAR web site (http://car.gsfc.nasa.gov/).