HR: 1340h
AN: A43B-0078    [Abstracts]
TI: Daytime Land Cloud Detection Enhancements For The VIIRS Cloud Mask
AU: * Frey, R A
EM: richard.frey@ssec.wisc.edu
AF: Cooperative Institute for Meteorological Satellite Studies, 1225 West Dayton St., Madison, WI 53706 United States
AU: Heidinger, A K
EM: heidinger@ssec.wisc.edu
AF: NESDIS, Office of Research and Applications, 1225 West Dayton St., Madison, WI 53706 United States
AU: Hutchinson, K D
EM: keith.hutchinson@ngc.com
AF: Center for Space Research, University of Texas at Austin 3925 W. Braker Land, Ste. 200, Austin, TX 78759 United States
AU: Iisager, B
EM: Barbara.Iisager@ngc.com
AF: Northrup Grumman Space Technology, One Space Park, Redondo Beach, CA 90245 United States
AB: The first in a new series of polar-orbiting satellites, National Polar-Orbiting Operational Satellite System (NPOESS), is scheduled to be launched in 2008. The Visible/Infrared Imager/Radiometer Suite (VIIRS) is a major component of the series and will replace the AVHRR instrument on operational polar orbiters. A crucial piece of the VIIRS data processing chain is the VIIRS Cloud Mask (VCM). A high quality cloud detection system is necessary as a first step for most if not all of the algorithms which produce the 18 EDRs (Environmental Data Records) from VIIRS. A cloud detection scheme similar to the one developed for MODIS data (MOD35) will be implemented for VIIRS, but several enhancements have been investigated for daytime land scenes. During daylight hours over vegetated surfaces and in the absence of snow cover, use of the high contrast between clouds and surface in visible wavelengths offers the most sensitive clear/cloud discrimination. However, visible surface reflectances vary from about 10% over tropical rain forests to as high as 50% in arid regions, making the use of a single cloud test threshold very difficult. A set of reflectance thresholds based on NDVI and scattering angle has been developed from historical AVHRR data. Clear-sky NDVIs were accumulated as a function of scattering angle over a multi-year period and from morning and afternoon satellites, from which cloud test thresholds were developed. The thresholds were then tested on several AVHRR scenes. For extremely arid scenes, where visible reflectances from clouds and surface are similar, a cloud test using 0.4 æm data has been devised. This poster describes the development of both new cloud tests and associated thresholds, from initial tests using MODIS data to the calculation and implementation of the thresholds.
DE: 0321 Cloud/radiation interaction
DE: 0394 Instruments and techniques
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005