Remote Sensing Of Atmospheric And Surface Parameters In A Cloudy Atmosphere Using Airs/amsu Sounding Data

Abstract

Introduction AIRS and AMSU are the prototype low Earth Orbiting Operational Sounding System which will first fly on the EOS PM Platform in 2000. AIRS (Atmospheric Infra Red Sounder) is a high spectral resolution IR sounder with spectral resolving power u / A u 21 1200 and roughly 3000 channels with essentially complete spectral coverage from 650 cm-' to 2700 cm-'. Figure 1 shows a simulated AIRS spectrum and indicates the principle absorbing species in each spectral region. AMSU (Advanced Microwave Sounding Unit) A, B contain approximately 20 channels with the majority centered around the 50 GHz oxygen cluster and 183 GHz water vapor line. The sounding goal for AIRS/AMSU is to provide temperature profiles with l 0 C RMS error in 1 km thick layer temperatures and water vapor profiles with 10% RMS error in layer precipitable water in 2 km thick layers throughout the troposphere. In addition, information will be obtained about ozone profile, surface skin temperature and spectral emissivity, cloud fraction, cloud top pressure, cloud spectral emissivity, and spectral components of OLR. We have developed a methodology for use in inverting a large number of channel radiances, which produces accurate results even under extensive partial cloud cover. In this methodology, the microwave and infrared channels complement each other. The AMSU-A microwave channels are used for cloud filtering because they are relatively insensitive to clouds. The AMSU-A microwave channels also have superior vertical resolution for retrieving the temperature profile in the stratosphere. Once the cloud filtering has been performed, the infrared channels, used in conjunction with the microwave channels, provide superior vertical resolution for retrieving temperature and water vapor profiles in the troposphere.