Tuesday, 24 January 2012
Inference of Ice Cloud Properties Using Hyperspectral Observations and a Fast Infrared Radiative Transfer Model
Hall E (New Orleans Convention Center )
We explore the development of a computationally efficient high spectral resolution cloudy-sky radiative transfer model (HISCRTM) for simulating upwelling radiances at the top of the atmosphere (TOA). A clear-sky transmittance database is calculated by using the rigorous line-by-line radiative transfer model (LBLRTM, version 11.7). Seven major absorbers (H2O, CO2, O3, O2, CH4, CO, and N2O) in the atmosphere are considered. A fast radiative transfer equation (RTE) solver is employed to couple with the transmittance database. The present model has inherent advantages to couple with high spectral satellite based observations, such as the Atmospheric InfraRed Sounder (AIRS) and the Infrared Atmospheric Sounding Interferometer (IASI). Moreover, the computational efficiency of HISCRTM ensures it can be applied to the operational retrieval of cloud properties, i.e., cloud optical thickness (τ) and effective particle size (Deff). For the ice cloud retrieval procedure, a retrieval algorithm for AIRS IR window bands is designed by simultaneous minimizing the differences between model simulated and satellite observed TOA brightness temperatures (BTs) and BT slopes in the spectral region between 800 and 1100 cm-1. Additional to τ and Deff, the retrieval also refines the cloud top altitude on the base of the Moderate Resolution Imaging Spectroradiometer (MODIS) collection 5 operational cloud products.ts.