Role of interaction between dynamics, thermodynamics and cloud microphysics on summer monsoon precipitating clouds over the Myanmar Coast and the Western Ghats
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Indian summer monsoon circulation can be characterized by mean tropospheric temperature (TT) gradient between ocean and land. Two major heat sources, one near the Myanmar Coast and the other near the Western Ghats play seminal role in defining this TT gradient. While both regions are characterized by very similar orographic features, there are significant differences in frequency of occurrence of precipitating clouds and their characteristics even when the amount of rain in June–July months is almost same in the two regions. Deeper (shallower) clouds appear more frequently over the Myanmar Coast (the Western Ghats). There is a sharp decrease in amount of rainfall from June–July to August–September in both the areas. Rather counter intuitively, during the June–July–August–September season, low and moderate rains contribute more to the total rain in the Myanmar Coast while heavy rains contribute more to the total rain in the Western Ghats. Western Ghats also gets more intense rains but less frequently. With significant differences in moisture availability, updraft, amount and characteristics of cloud condensate in the two regions, this study proposes that the nontrivial differences in features between them could be explained by linkages between cloud microphysics and large scale dynamics. Presence of more cloud liquid water and the role of giant cloud condensation nuclei reveals dominance of warm rain process in the Western Ghats whereas more cloud ice, snow and graupel formation in the Myanmar Coast indicates stronger possibility of cold rain coming from mixed phase processes. Stronger heating caused by mixed phase process in the mid and upper troposphere in the Myanmar Coast and its feedback on buoyancy of air parcel explains the appearance of deeper clouds. Thus, our study highlights importance of mixed phase processes, a major cause of uncertainty in GCMs.
KeywordsSummer monsoon Microphysics Dynamics Latent heating Aerosol
Indian Institute of Tropical Meteorology (IITM), Pune, is fully funded by the Ministry of Earth Sciences, Government of India, New Delhi. Authors duly acknowledge NASA for the data sets TRMM, AIRS, MERRA etc. We also acknowledge the MODIS mission scientists and associated NASA personnel for the production of the data used in this research effort. Some data used in this study were produced with the Giovanni online data system, developed and maintained by the NASA GES DISC. Authors duly acknowledge Dr. X. Jiang of JPL, NASA for providing CloudSat data. Authors also sincerely thank Mr. M. Mahakur for providing OLR data from Kalpana Satellite and Mr. V. Sasane for helping in drawing the Schematic Diagram.
- Houze RA, Jr (2012) Orographic effects on precipitating clouds. Rev Geophys 50:RG1001. doi: 10.1029/2011RG000365
- Kang I-S, Shukla J (2006) Dynamic seasonal prediction and predictability of the monsoon. In: B Wang (ed) The Asian monsoon, Ch. 15. Springer/Praxis Publishing Co., New YorkGoogle Scholar
- Kaufman YJ, Tanré D (1998) Algorithm for remote sensing of tropospheric aerosol from MODIS. NASA MODIS Algorithm Theoretical Basis Document, Goddard Space Flight Center 85Google Scholar
- Konwar M, Maheshkumar RS, Kulkarni JR, Padmakumari B, Morwal SB, Deshpande CG, Axisa D, Burger R, Piketh S, Rosenfeld D, Goswami BN (2012) Contrasting polluted and pristine cloud microphysical properties over the Arabian Sea and Bay of Bengal. International conference on OCHAMP-2012, OC-000112Google Scholar
- Meneghini R et al (1998) Estimates of path attenuation for the TRMM radar. Geoscience and remote sensing symposium proceedings. IGARSS’98, IEEE International, 4 IEEEGoogle Scholar
- Pruppacher HR, Klett JD (1997) Microphysics of clouds and precipitation. Kluwer Acad, NorwellGoogle Scholar
- Satheesh SK, Krishnamoorthy K, Das I (2001) Aerosol spectral optical depths over the Bay of Bengal, Arabian Sea and Indian Ocean. Curr Sci 81:1617–1625Google Scholar
- Sperber KR, Annamalai H, Kang I-S, Kitoh A, Moise A, Turner A, Wang B, Zhou T (2012) The Asian summer monsoon: an intercomparison of CMIP5 vs. CMIP3 simulations of the late 20th century. Clim Dyn. doi: 10.1007/s00382-012-1607-6
- Squires P, Twomey S (1961) The relation between cloud drop numbers and the spectrum of cloud nuclei. Phys Precip. Monograph, no. 5, pp 211–219, AGU, Washington, DCGoogle Scholar
- Tao W-K, Chen J-P, Li Z, Wang C, Zhang C (2012) Impact of aerosols on convective clouds and precipitation. Rev Geophys 50:RG2001. doi: 10.1029/2011RG000369
- Zhou YP, Tao W-K, Hou AY, Olson WS, Shie C-L, Lau K-M, Chou M-D, Lin X, Grecu M (2007) Use of high-resolution satellite observations to evaluate cloud and precipitation statistics from cloud-resolving model simulations. Part I: South China Sea monsoon experiment. J Atmos Sci 64:4309–4329CrossRefGoogle Scholar