Impact of aerosols (CCN and IN) on summer monsoon precipitating clouds over the Western Ghats: A regional climate modeling study

Aerosols, tiny particles present in the atmosphere, play crucial roles in weather and climate. It is generated primarily as solid particles, for example Asian dust, Saharan dust, sea salt or soot. Aerosols can have variety of impacts (e.g., direct and indirect effects) on the atmosphere, which can lead to earth's radiation budget. It has strong impact on the formation of clouds and precipitation processes also. The rainfall variability is characterized by the intraseasonal periodicity of about 30-60 days, which is essentially the manifestation of similar periodicity of the cloud organization, northward propagation and dissipation. Thus, the proper representation of clouds in climate models is one of the most important avenues toward reducing uncertainties in climate projections. Satellite observations are instrumental in exploring a wealth of information regarding cloud properties. These observations have also given a new insight in the role of aerosols, which act as cloud condensation nuclei (CCN) and ice nuclei (IN) and their interaction with regional and global hydrological cycle by modifying the cloud properties. This can be portrayed by the 'first indirect effect' where the increase of aerosols reduces the cloud droplet effective radius and the 'second indirect effect'. Cloud-aerosol interaction and its role for the invigoration of clouds through mixed-phase processes are also important. Therefore, the proper linkages between cloud microphysics, large scale dynamics and mixed-phase processes need to be indentified in order to reduce uncertainties in regional and global model prediction of summer monsoon precipitation. The present study focuses on the impact of aerosol (i.e., CCN and IN) on Indian summer monsoon precipitating cloud over Western Ghats. The number concentration of IN are taking from the in-situ measurement using SPectrometer for Ice Nuclei (SPIN). The model simulated cloud properties (e.g., cloud liquid/ice water, effective radius of liquid/ice), reflectivity are examined from observations (e.g., micro-rain radar, X-band radar etc.). Role of bio-aerosol and dust (that act as IN) in the formation of clouds and precipitation are also investigated. These results highlight the relative importance of cloud-aerosol interaction and its impact on ISM which is important for climate model.