Removal of the 3.7 μm Solar Contamination in AVHRR Data

We have developed a numerical scheme for the removal of the solar contamination in the AVHRR 3.7 μm (Ch.3) radiance for the retrieval of cirrus cloud parameters during daytime. The scheme involves an iterative procedure coupled with the clear sky detection technique described by Saunder and Kriebel (1988) and the nighttime retrieval algorithm developed by Ou et al. (1992). In section 2, the removal scheme, based on the correlation between 0.63 and 3.7 μm solar reflectances, is presented. In section 3, we discuss a synthetic study using the midlatitude atmospheric profile and a sensitivity study involving the removal of the 3.7 μm solar component by adding random errors due to surface inhomogeneity and instrument noises. Application of the removal scheme to AVHRR data for inferring cirrus cloud parameters, and comparisons with available observations and retrieval results presented by other investigators are described in section 4. Finally, conclusions are given in section 5.