Macrophysical and microphysical properties of monsoon clouds over a rain shadow region in India from ground‐based radiometric measurements

Abstract

AbstractThe important radiative properties of clouds such as cloud optical depth (COD) and droplet effective radii (Re) are retrieved from the simultaneous measurements by ground‐based multifilter rotating shadowband radiometer (MFRSR) and microwave radiometric profiler (MWRP), colocated at Mahabubnagar, a rain shadow region in southern Indian peninsula. Min and Harisson's (1996) retrieval algorithm is used for the first time to derive monsoon cloud properties in India. COD and liquid water path (LWP) retrieved from two independent instruments of MFRSR and MWRP showed reasonably good correlation. During monsoon (July to September) and postmonsoon (October) months, the maximum probability of occurrence of COD for overcast sky is 20. The maximum probability of occurrence of LWP is 100 gm−2 for water clouds during monsoon months, while October showed maximum occurrence at a lower value of 50 gm−2, where most of the times the cloud bases are above freezing level indicating mixed phase clouds. Maximum Re varied from 14–16 µm (10–12%) to 12 µm (9%) during monsoon to postmonsoon transition with very less probability of occurrence indicating the characteristic feature of this region. A case study showed that the mean Re from ground‐based and aircraft measurements are 12.0 ± 3.7 µm and 8.14 ± 1.4 µm, respectively, indicating a fairly good agreement within the experimental constraints. Intercomparison of ground‐based and Moderate Resolution Imaging Spectroradiometer (MODIS)‐Terra and MODIS‐Aqua‐derived COD, LWP and Re over the observational site for overcast and warm clouds indicates that on an average, MODIS‐retrieved mean COD and LWP are underestimated, while mean Re is overestimated as compared to ground retrievals.