Wide-Area Determination of Cloud Microphysical Properties from NOAA AVHRR Measurements for FIRE and ASTEX Regions

A method for satellite remote sensing of cloud optical thickness and effective particle radius has been developed to apply to NOAA AVHRR multispectral radiance data. Undesirable radiation components such as ground-reflected solar radiation and thermal radiation are guessed from satellite-received radiances in channels 1, 3, and 4 of AVHRR and subtracted from radiances in channels 1 and 3 to derive the reflected solar radiation of a cloud layer that includes information about cloud microphysical properties. This method can be applied to a broad range of water clouds from semitransparent to thick clouds. This method was applied to AVHRR data acquired over oceans during the First ISCCP Regional Experiment and the Atlantic Stratocumulus Transition Experiment. The authors found good agreement between satellite-derived and in situ microphysical quantities. The presence of drizzle droplets in optically thin clouds was also confirmed from the satellite observation. Furthermore, the results show that marine stratocumulus clouds were drastically modified by ship track effluents and dust-contaminated aifflow from the continent.