HR: 0800h
AN: A11C-0079    [Abstracts]
TI: Statistical Studies on Thin Cirrus Using MODIS Data
AU: * Li, R
EM: lirongr@climate.gsfc.nasa.gov
AF: GEST/UMBC, 1000 Hilltop circle, Baltimore, MD 21250 United States
AU: * Li, R
EM: lirongr@climate.gsfc.nasa.gov
AF: NASA/Goddard Space Flight Center, Code 913, NASA/Goddard Space Flight Center, Greenbelt, MD 20771 United States
AU: Kaufman, Y
EM: kaufman@climate.gsfc.nasa.gov
AF: NASA/Goddard Space Flight Center, Code 913, NASA/Goddard Space Flight Center, Greenbelt, MD 20771 United States
AU: Remer, L
EM: remer@climate.gsfc.nasa.gov
AF: NASA/Goddard Space Flight Center, Code 913, NASA/Goddard Space Flight Center, Greenbelt, MD 20771 United States
AU: Gao, B
EM: gao@nrl.navy.mil
AF: NRL, Remote Sensing Division, Code 7212, Washington, DC, 20375 United States
AB: The 1.38 um channel on the MODerate resolution Imaging Spectroradiomater (MODIS) is very sensitive to identify and quantify thin cirrus on a global basis. The channel is located in the center of a strong water vapor absorption band, that eliminates illumination from the earth surface and low clouds. This channel is used to produce the MODIS cirrus reflectance product and to mask clouds from the MODIS aerosol products. The aerosol product screens thin cirrus with the 1.38-um channel reflectance above a threshold of 0.01. This threshold can leave residual cirrus contamination that corresponds to aerosol optical thickness of up to 0.10. This contamination, though usually small, may generate significant biases in the seasonal-regional aerosol average optical thickness derived from MODIS. Here we develop a method to estimate this contamination and correct for it by distinguishing between thin cirrus clouds and the dark current noise in the channel. We analyze several years of Terra and Aqua data, over land and ocean to generate a systematic statistics of the presence and opacity of thin cirrus around the globe. The results can be used later on to correct the aerosol optical thickness and radiative forcing of climate.
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0320 Cloud physics and chemistry
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting