Cloud microphysical profile differences pertinent to monsoon phases: inferences from a cloud radar

Abstract

Microphysical evolution of tropical clouds in the core monsoon region of India is examined for the first time using ground-based cloud radar measurements. Combining high-resolution radar reflectivity (Z) profiles with empirical relations, cloud microphysical profiles in terms of cloud ice/liquid water content (IWC/LWC) during Indian summer monsoon (ISM) season are retrieved. Though the study is carried out using a point observation, it is shown that it represents the large-scale monsoon flow over the radar site. Cloud radar measurements during ISM period are classified into active and break ISM days. Radar-derived IWC profiles are validated against CloudSat, whereas LWC profiles are validated using the collocated microwave radiometer and microphysical observations from in situ aircraft measurements. The validated IWC and LWC profiles show significant differences between active and break ISM phases including their diurnal evolution. Larger (smaller) IWC values observed during active (break) days reveal the microphysical activity associated with the contrasting cloud vertical structure in the respective ISM phases. Observed discontinuity in the cloud vertical structure during break ISM days is attributed to the lack of moist convection. The significance of the present study lies in reporting the first ground-based radar measurements of cloud microphysical properties during active and break ISM period and discussing their distinctiveness.