Mathematics – Logic
Scientific paper
Dec 2001
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001agufm.a11a0016l&link_type=abstract
American Geophysical Union, Fall Meeting 2001, abstract #A11A-0016
Mathematics
Logic
1610 Atmosphere (0315, 0325), 1640 Remote Sensing, 3359 Radiative Processes, 9310 Antarctica
Scientific paper
Recent analysis of fourteen years of Total Ozone Mapping Spectrometer (TOMS) UV-A reflectivity data, published by NASA Goddard Space Flight Center, has suggested that cloud reflectance may be increasing over large parts of the Southern Ocean. This potentially indicates an increase in cloud amount or cloud opacity, in response to a climate warming scenario. The TOMS program comprises a well-calibrated series of instruments that has provided useful information on top-of-atmosphere (TOA) reflectance since late 1978. The major limitation with analyzing TOMS data alone is that backscattered radiances at the conservative scattering UV-A wavelengths depend strongly on the albedo of the underlying sea ice as well as the clouds. The effects of sea ice and clouds cannot be separated, and trends in TOA reflectance as measured by TOMS by itself cannot be attributed unambiguously to purely atmospheric phenomena. In this work, we have combined TOMS data with Special Sensor Microwave Imager (SSM/I) passive microwave observations of sea ice concentration, to identify TOMS pixels in maritime Antarctic regions that lie over open ocean, and over various concentrations of sea ice. We have also extended the trend analysis to encompass two decades worth of TOMS data. As a whole, Antarctic sea ice concentration has been increasing slightly, although there is considerable variability in Antarctic sea ice trends (including changes in sign) with longitude. We find similar regional variability in TOMS reflectivity trends. There are some regions where upward trends in cloud reflectance can be separated from trends in sea ice, and in these regions the TOMS data may indicate a response to a changing atmosphere. These regions include parts of the Marie Byrd Land, Queen Maud Land, and American Highland sectors of the Southern Ocean. Regions where trends in TOMS reflectivity are zero or slightly negative include the Wilkes Land sector of the Southern Ocean, and the Weddell and Bellingshausen Seas. These results are discussed in terms of meteorological phenomena, changes in sea ice concentration, changes in sea ice reflectance, and the resulting changes to the shortwave and longwave radiation balance.
Lubin Dan
Morrow Esther
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