Analysis of cloud impact on infrared and microwave atmospheric sounding performance using NAST

Data collected by airborne infrared (NAST-I, MAMS) and microwave (NAST-M) sensors during CAMEX-3 (Florida, summer 1998) are used to quantify the cloud impact on atmospheric sounding performance in several ways. First, the degrees of freedom introduced by clouds are estimated by applying principal component transforms to cloud-perturbed (clear minus cloudy) NAST spectra. These results are then compared to those obtained using radiances simulated using two-level clouds. Finally, the radiance cloud-clearing performance for NAST-type clouds is evaluated and compared with results for simulated two-level clouds.