6A.6 Using cloud radar to understand the vertical distribution of absorption in tropical clouds

Tuesday, 7 August 2007: 5:30 PM
Hall A (Cairns Convention Center)
Sally A. McFarlane, PNNL, Richland, WA; and J. H. Mather, Z. Liu, and T. P. Ackerman

Radiative heating is an important component of the total diabatic heating and dominates over latent heating in certain conditions, including cirrus anvils. Radiative heating acts to redistribute energy vertically in the atmosphere, which has important impacts on atmospheric dynamics. Although measurements of top-of-atmosphere and surface fluxes enable calculation of the total amount of absorption in the column, understanding how clouds act to redistribute energy within the atmospheric column requires measurements of clouds with high vertical resolution. In this study, we use cloud properties retrieved from cloud radar observations from the Atmospheric Radiation Measurement (ARM) program sites in the Tropical Western Pacific (TWP) to calculate estimates of the vertical distribution of solar radiation absorption in the atmosphere with high temporal and vertical resolution. Our calculations indicate that, on average, clouds increase the total column absorption by only a few W/m2 but they significantly redistribute the absorption vertically in the column. We compare the column absorption estimates based on the radar profiles to values calculated from satellite and surface flux measurements. The column absorption values calculated from the radar profiles show considerably less variability than those calculated from the surface and satellite observations. We discuss possible reasons for these differences.
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