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Mesoscale precipitation characteristics near the Western Ghats during the Indian Summer Monsoon as simulated by a high‐resolution regional model
Author(s) -
Flynn Wendilyn J.,
Nesbitt Stephen W.,
Anders Alison M.,
Garg Piyush
Publication year - 2017
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.3163
Subject(s) - weather research and forecasting model , orography , precipitation , mesoscale meteorology , monsoon , climatology , sea breeze , environmental science , submarine pipeline , escarpment , diurnal cycle , geology , atmospheric sciences , meteorology , geography , oceanography , paleontology
This study investigates (i) the role of orography in precipitation along and upstream of the Western Ghats (WG) and (ii) a diurnal cycle of precipitation in western India during the summer monsoon, using a high‐resolution meteorological model and a network of surface rain‐gauges over the WG. The Weather Research and Forecasting model (WRF‐ARW) was used to simulate the 2008, 2009 and 2010 summer monsoons at 5 km horizontal grid spacing and allows resolved convection, with initial and boundary conditions provided by ERAInterim. The highest daily mean precipitation is found immediate to the WG escarpment and coastal plain between 11.5° and 18°N, but areas receiving the most rainfall do not necessarily receive it most frequently. The greatest percentage of rainy days occurs over the escarpment of the WG and slightly inland, corresponding to the topography, and high percentages (over 75%) of rainy days occur along the coast, along the coastal plain and the WG. These findings are in agreement with several recent studies using high spatial resolution Tropical Rainfall Measuring Mission (TRMM) precipitation data. Analysis of WRF output at time increments of 30 min reveals a clear diurnal pattern of rainfall, with an early morning maximum offshore and afternoon maxima over inland regions that occur later in the day with distance inland. A weak land breeze circulation is observed, as nocturnal cooling of the land surface results in deceleration of westerly flow upstream of the WG. Offshore moisture convergence and destabilization of low‐level air results in the offshore morning maximum. Rainfall maxima over inland regions indicate that, while orography is the primary impetus for lift, rainfall is also convectively driven. Analysis of convective parameters and landsurface variables such as soil moisture and latent and sensible heat fluxes supports this weak land–sea breeze circulation embedded in prevailing westerly monsoonal flow.