HR: 16:35h
AN: A54D-03    [Abstracts]
TI: Interannual Differences in Cloud Albedo and Cloud Height Measured by MISR
AU: * Davies, R
EM: Roger.Davies@jpl.nasa.gov
AF: Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 United States
AB: The Multiangle Imaging SpectroRadiometer (MISR) on the Terra satellite has been operating almost flawlessly since early 2000. Terra has fuel reserves that will last until about 2014, and the instruments are funded to remain operational at least through 2009. MISR provides homogeneous time series of cloud heights, albedos, and height-resolved cloud-tracked winds that are becoming increasingly relevant to climate change studies. The cloud height record is of special interest, as it is uniquely insensitive to the radiometric calibration issues that affect most other types of satellite-derived time series. In addition, due to the extremely large number of independent samples, the expected error in the mean cloud height, on a global annual basis, is less than 10 m, or about 0.3% of the mean height, allowing subtle interannual differences to be detected. By contrast, the albedo measurements have a relative temporal uncertainty that is limited by radiometric calibration to about 1% over the mission lifetime, together with an absolute calibration uncertainty of about 3%. Two complete 12-month periods, 5/00-4/01 and 5/04-4/05, together with several of the intervening months, have now been consistently processed, allowing assessment of MISR's ability to measure interannual differences. The albedo and height fields both show remarkably consistent seasonal and regional patterns for the two full years. The global annual mean albedos differ by less than 0.6%, well within the expected radiometric uncertainty, and the regional/seasonal patterns show no coherent difference. The global mean cloud heights, on the other hand show a measurable difference of 44 m, with a sampling uncertainty of only ±7 m. The regional/seasonal patterns for cloud height distribution also show coherent differences in the behavior of high tropical clouds associated with the Intertropical Convergence Zone.
DE: 0321 Cloud/radiation interaction
DE: 3305 Climate change and variability (1616, 1635, 3309, 4215, 4513)
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005