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Microphysics of clouds and rain over the Western Ghat

Konwar, M and Das, SK and Deshpande, SM and Chakravarty, K and Goswami, BN (2014) Microphysics of clouds and rain over the Western Ghat. Journal of Geophysical Research: Atmospheres, 119 (10). pp. 6140-6159.

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In an attempt to unravel the interactions between cloud microphysics and dynamics that make shallow clouds precipitate heavily in this region, some unique observations of rain and cloud microphysical parameters are presented here from two stations, Pune and Mahabaleshwar, one each on the lee and windward sides, respectively, of the Western Ghat (WG) mountains in peninsular India. To elucidate rain microphysics, we used the raindrop size distribution (DSD) by fitting three parameter Gamma functions to the observed raindrop spectra. Over Pune, during stratiform rain with bright band (BB) at 0°C isotherm; concave upward DSD shapes are observed below the BB which becomes concave downward at lower altitudes. It is due to breakup process of large raindrops which increases drop concentration at midsizes suggesting coalescence, collision, and breakup processes. Both slope and intercept parameters of Gamma DSD decrease during no BB condition as altitudes decrease, signifying collision and coalescence processes. Over Mahabaleshwar, bimodal and monomodal DSD are observed during light and heavy rainfall, respectively. With shallow storm heights, small raindrops mainly contribute to both types of rainfall. The DSDs are parameterized, and their radar reflectivity factor-rainfall intensity relationships are evaluated suggesting the dominance of collision-coalescence processes. Aircraft measurements of orographic clouds over the WG suggest interaction of cloud mass with the ambient updraft speed. The orographically forced updrafts foster rapid condensational growth of cloud droplets triggering coalescence process within few hundred meters of cloud depth. Hence, these clouds are dynamically forced to produce precipitation over the WG. Key Points CCB(CC) rain process in presence(absence) of bright band Shallow convective clouds with low R dominates over the WG Clouds grow by forced condensation process over the WG.

Item Type: Article
Additional Information: Copyright of this article belongs to American Geophysical Union.
Uncontrolled Keywords: Aircraft accidents; Clouds; Condensation; Drop formation; Meteorological radar; Physics, Cloud microphysical parameters; Collision and coalescence; Condensational growth; Intercept parameters; Radar reflectivities; Raindrop size distribution; Shallow clouds; Western ghats, Rain, cloud condensation nucleus; cloud microphysics; coalescence; convective cloud; droplet; isotherm; radar; raindrop; size distribution, India; Mahabaleshwar; Maharashtra; Pune; Western Ghats
Subjects: Meteorology and Climatology
Depositing User: IITM Library
Date Deposited: 09 Dec 2014 06:19
Last Modified: 09 Dec 2014 06:19

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