Cloud microphysical properties over Indian monsoon regions during CAIPEEX-2009

Cloud microphysical data collected from an instrumented aircraft in the Cloud Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX-2009) during May–September 2009 have been used to examine the nature of cloud drop size distributions (DSD), cloud drop effective radius (RE) and their height variations at different locations during tropical Indian monsoons. Single mode drop size distributions were observed over Pathankot, Hyderabad and Bengaluru regions and bimodal DSD were recorded often over Guwahati and Bareilly regions. DSD spectral width showed height variation, being narrow at lower heights and broadening with increasing height. DSD spectra were narrow even at higher levels over Pathankot during pre-monsoon season and were very broad at Bareilly and Guwahati during the active phase of monsoon. The total concentrations of cloud droplets and percentage contribution of cloud droplet of radii≤10 μm (small) and >10 μm (large) showed interesting height variations and were different over different regions. The RE showed nearly linear increases with height over all the regions. However, the droplet growth rate is observed to be different over different regions, being less over north (Bareilly and Pathankot: 1.3–1.46 μm/km), intermediate over central (Hyderabad: 1.74 μm/km) and highest over northeast (Guwahati: 1.92 μm/km) and south (Bengaluru: 1.99 μm/km) India.For the first time an attempt has been made to collect and explore cloud microphysical characteristics using in-situ aircraft observations during Indian monsoon conditions.

► First time in-situ cloud parameters collected during CAIPEEX-2009.
► DSD were monomodal and narrow (bimodal, broad) during pre (active) monsoon.
► DSD were narrow at lower heights and broadened with increasing height.
► Percentage of small cloud drops is high (low) during pre (active) monsoon.
► Growth rate of RE is less (medium) over N (central) and high over S and NE India.