Influence of aerosol physico-chemical properties on cloud microphysical parameters perceived using in-situ high altitude observations

Variability in cloud microphysical parameters, aerosol physicochemical properties and their relationship were studied using in-situ ground observations from a high altitude site in Western Ghats, India, during monsoon season. Cloud microphysical parameters, such as cloud droplet number concentration (CDNC), liquid water content (LWC), and effective diameter (ED), have been analyzed. Aerosol–CCN (cloud condensation nuclei) number concentration and mass concentration of non-refractory particulate matter (NR-PM1) during summer monsoon also showed day to day and monthly variation. Cloud droplet size distribution (CDSD) showed a bimodal spectrum with two prominent peaks i.e. in 3–10 μm and 12–22 μm size ranges. The estimated spectral width of CDSD (σ) broadly varied from 0 to 4 μm and the effective radius ratio (β) from 0.6–1.8. Further, the effect of aerosol on cloud microphysical parameters and CDSD has been investigated. There was an apparent variation in CCN super saturation spectrum, aerosol chemical composition, and cloud microphysics during high and low aerosol loading days The aerosol chemical composition showed a higher sulphate and ammonium (organics) contribution during low (high) aerosol loading days. CCN concentration and CDNC (ED) were higher (less) during high aerosol days and vice versa during low aerosol days. A review of microphysical characteristics of monsoon clouds over various locations of the Indian region has shown that this is the first such report that provides observational evidence of how variation in aerosol physical and chemical properties affects the CCN and cloud properties derived explicitly from long-term ground-based observations.