Mesoscale precipitation characteristics near the Western Ghats during the Indian Summer Monsoon as simulated by a high-resolution regional model

Wendilyn J. Flynn, Stephen W. Nesbitt, Alison M. Anders, Piyush Garg

Research output: Contribution to journalArticle

Abstract

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.

Original languageEnglish (US)
Pages (from-to)3070-3084
Number of pages15
JournalQuarterly Journal of the Royal Meteorological Society
Volume143
Issue number709
DOIs
StatePublished - Oct 2017

Fingerprint

monsoon
rainfall
orography
escarpment
summer
westerly
coastal plain
land breeze
TRMM
latent heat flux
sensible heat flux
gauge
land surface
spacing
spatial resolution
boundary condition
soil moisture
convection
moisture
topography

Keywords

  • India diurnal cycle
  • Indian summer monsoon rainfall
  • Western Ghats
  • diurnal cycle of rainfall
  • orographic precipitation

ASJC Scopus subject areas

  • Atmospheric Science

Cite this

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title = "Mesoscale precipitation characteristics near the Western Ghats during the Indian Summer Monsoon as simulated by a high-resolution regional model",
abstract = "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.",
keywords = "India diurnal cycle, Indian summer monsoon rainfall, Western Ghats, diurnal cycle of rainfall, orographic precipitation",
author = "Flynn, {Wendilyn J.} and Nesbitt, {Stephen W.} and Anders, {Alison M.} and Piyush Garg",
year = "2017",
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T1 - Mesoscale precipitation characteristics near the Western Ghats during the Indian Summer Monsoon as simulated by a high-resolution regional model

AU - Flynn, Wendilyn J.

AU - Nesbitt, Stephen W.

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AU - Garg, Piyush

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N2 - 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.

AB - 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.

KW - India diurnal cycle

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