Retrieving the clear-sky vertical longwave radiative budget from TOVS: Comparison of a neural network-based retrieval and a method using geophysical parameters

At a time when a new generation of satellite vertical sounders is going to be launched (including the Infrared Atmospheric Sounder Interferometer and Advanced Infrared Radiometric Sounder instruments), this paper assesses the possibilities of retrieving the vertical profiles of longwave clear-sky fl uxes and cooling rates from the Television and Infrared Observation Satelli te (TIROS) Operational Vertical Sounder (TOVS) radiometers aboard the polar -orbiting National Oceanic and Atmospheric Administration satellites since 1979. It focuses on two different methodologies that have been developed at Laboratoire de Meteorologie Dynamique (France). The first one uses a neura l network approach for the parameterization of the links between the TOVS r adiances and the longwave fluxes. The second one combines the geophysical v ariables retrieved by the Improved Initialization Inversion method and a fo rward radiative transfer model used in atmospheric general circulation mode ls. The accuracy of these two methods is evaluated using both theoretical s tudies and comparisons with global observations.