Monday, 23 January 2012: 5:00 PM
On the Zenith Angular Effect of Residual Clouds and Aerosols in Clear-Sky IR Window Radiance Observations
Room 239 (New Orleans Convention Center )
Accurate satellite observations (OBS) and calculations (CALC) of top-of-atmosphere infrared (IR) spectral radiances are two necessary components required for the accurate retrieval of geophysical state parameters. Ideally, it is desired that systematic differences between OBS and CALC under well-characterized conditions be minimal, and because most environmental sensors must scan the earth surface to facilitate global coverage, this should include an unbiased agreement over the range zenith angles encountered. This presentation investigates the impact of the “clear-sky” observations commonly used in such analyses, which include “cloud-masked” data (as is typical from imagers), or alternatively, “cloud-cleared radiances” (as is typical from hyperspectral sounders). We have found that the likelihood of contamination by residual clouds and/or aerosols within clear-sky OBS can have a measurable “concave-up” impact (i.e., an increasing systematic CALC – OBS symmetric over the scanning range in the positive direction) on the angular agreement with CALC.