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Precipitation susceptibility of monsoon clouds to changes in aerosols has been studied initially by utilizing ground based observations from a High Altitude Cloud Physics Laboratory (HACPL), Mahabaleshwar, India collected during monsoon seasons and later compared with the results obtained from satellite observations. Cloud condensation nuclei (CCN) concentration, rain intensity and integrated liquid have been taken from ground based observations for calculating precipitation susceptibility. As a first step, we have analyzed the temporal variation of CCN concentration, rain intensity and integrated liquid water during monsoon season. It is observed that all three parameters exhibit strong diurnal variation with two peaks i.e. in morning and afternoon. CCN showed strong morning peak whereas other two showed during afternoon hours. Later precipitation susceptibility has been estimated using CCN as aerosol proxy and it is higher ∼0.65 for the integrated liquid water ranging from 0.6 to 0.8 mm. Secondly, we have compared ground based observation with satellite observations carried out using aerosol optical depth (AOD), rain rate and liquid water path. Satellite observations showed that precipitation susceptibility, S 0 , using AOD as aerosol proxy is higher (S 0  = 0.98) for liquid water path ranging from 800 to 1000 gm -2 . It is also seen that the results are in agreement with the earlier reported results especially with the report from tropical region. Present analysis also showed that the precipitation is getting suppressed at medium range of integrated liquid/liquid water path. This is the first such study from Indian region explicitly using ground-based observations. [ABSTRACT FROM AUTHOR]

Combination of radiosonde profiles with collocated in-situ ground and aircraft measurements is used for the first time to study the vertical structure and microphysics of clouds during southwest monsoon over the Western Ghats, India. The morphology of clouds is detailed with the help of radiosonde observations and classified as low, mid, and high-level clouds depending on the cloud base height. Radiosonde sounding profiles indicated occurrences of both single and multi-layered clouds with higher occurrences of single-layered (∼35%) clouds during monsoon transition period (June and September) and two-layered (∼42%) during core monsoon period (July and August). Dominance of low (∼30%) and high-level (∼60%) clouds were noticed compared to mid-level clouds over the observational site during the southwest monsoon. Warm cloud microphysics was investigated using collocated ground and airborne in situ measurements. Irrespective of the cloud type, the cloud liquid water content and the effective droplet diameter increased with altitude. One of the key results is the rapid broadening of the cloud droplet size distribution with height. The number concentration of droplets above 25 μm diameters showed a steep decrease at altitudes above 1800 m, suggesting active collision-coalescence. • Collocated observations of the vertical structure and microphysics of clouds over Western Ghats, India. • Cloud morphology is detailed using radiosonde observations over WG. • Warm cloud microphysics is investigated using collocated in-situ ground and airborne cloud measurements. • Rapid broadening of the cloud droplet size distribution with height was noticed. • This is the first such report over a complex terrain like Western Ghats in India. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The cloud droplet size distribution (CDSD) and microphysical properties prior to monsoon rain events is studied using in-situ ground observations over a high altitude site in Western Ghats, India. The cloud microphysical properties, such as cloud droplet number concentration (CDNC), liquid water content (LWC), cloud droplet spectrum, droplet effective diameter (ED), droplet mean radius (R m), spectral width (σ), and relative dispersion (ε) showed a considerable variation. A detailed analysis of CDSD before rain events showed single and multi-mode patterns which varied from case to case. An apparent variation in cloud microphysical properties is noted for both single and multi-mode cases. Large cloud droplets were found in both single and multi-mode clouds, and analysis revealed the possibility of entrainment of aerosols into these clouds leading to multi modes in the CDSD. Observed rain event duration indirectly suggested higher warm rain depths (D*) when multi-mode cases are observed. • Cloud droplet characteristics before monsoon rain event is studied using in-situ ground observations. • Single and Multi-modeal cloud drop size spectra observed before rain events. • CDNC, LWC, ED, R m , σ and ε, analyzed for single and multi-mode showed distinct variation. • Entrainment of aerosols from the cloud base probable cause of multi modes in the CDSD. [ABSTRACT FROM AUTHOR]