CAIPEEX Phase III Ganga Basin experiment: probing the effect of pollution on monsoon clouds

Cloud Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX) illustrated that aerosol may impact the cloud microphysical and dynamical effects and their interactions in the monsoon environment. The CAIPEEX was carried out over Indian subcontinent at several locations during 2009-2011. CAIPEEX observations have indicated that locally, high aerosol loading change the vertical structure of clouds through modification of mixed phase cloud processes. During CAIPEEX, it was noted that increase in the aerosol number concentration lead to predominance of mixed phase cloud processes. However, observations were few and a detailed understanding of such cloud invigoration/vertical development is important in the monsoon regime as it may impact the vertical heating structure.

CAIPEEX Phase III in 2014 is focusing specifically on the aerosol-cloud interaction over the monsoon core region with an observational base over the central Indian region. The aerosol loading over this region is modulated through the dry and wet regimes by intra-seasonal variations of cloud and precipitation processes. Numerical studies and inferences from satellite data have indicated that aerosol may impact through the suppression/enhancement in the vertical development of clouds, and possibly modifying the vertical distribution of heating rates and changing the atmospheric dynamics.

As part of the 2014 experiment, a comprehensive set of ground based and airborne instrumentation are used over the central Indian region to derive information from the surface to the cloud layer. Ground based observations have started from the premonsoon conditions and were able to capture the gradual transition to monsoon conditions. The site characterized extreme conditions of heat wave conditions during the premonsoon conditions and gradual moistening in the middle layers. The vertical structure of monsoon onset and progression over the region is documented during the experiment. The role of mixed phase cloud processes within monsoon environment is the main focus of the observational campaign and will be investigated with co-located aircraft observations.