Interaction of Low-Level Flow with the Western Ghat Mountains and Offshore Convection in the Summer Monsoon

Grossman, Robert L.; Durran, Dale R.

doi:10.1175/1520-0493(1984)112<0652:iollfw>2.0.co;2

Cited by 193 publications

(147 citation statements)

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“…Studies by Grossman and Durran (1984) have confirmed the persistence of Highly Reflecting Cloud Cover (HRCC) along the west coast of India during monsoon season. The persistent zone of convection along the west coast, make this belt a major source of monsoon latent heat release.…”

Section: Seasonal Characteristics Of Vertical Structure Of Atmospherementioning

confidence: 87%

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Analysis of large‐scale conditions associated with convection over the Indian monsoon region

Bhowmik

Roy

Kundu

2007

Intl Journal of Climatology

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This paper examines the thermodynamics of the atmosphere in relation to occurrence of convective rainfall over the Indian region. Various thermodynamical and kinematic parameters such as convective available potential energy (CAPE), convective inhibition energy (CINE), equivalent potential temperature and relative vorticity field are computed based on model analysis field of the limited area model of India Meteorological Department. The data period of this study is from 15 March 2001 to 28 February 2002. The study shows that the spatial distribution of CAPE in pre-monsoon and monsoon season exhibits a belt of high CAPE along the east coast extending north up to Gangetic West Bengal and another zone of high CAPE along the southwest coast. During post-monsoon and winter seasons, the belt of maximum CAPE shifts over the extreme southern Peninsula. The annual variation of CAPE over all stations is bi-modal in nature with twin peaks each at the beginning and at the end of the monsoon season. Magnitude of CINE on the other hand is nearly zero during the monsoon season. The result shows that presence of strong thermodynamic environment is not sufficient for the occurrence of deep convection. Factors like proper dynamic conditions play a very important role in controlling the occurrence of deep convection. The surface warming during the pre-monsoon season destabilizes the atmosphere, but large-scale moist convection, generally, does not take place until CINE becomes close to zero (in the monsoon season). Preceding the monsoon season, the land sea contrast heating strengthens circulation in the lower atmosphere, which in turn leads to the moistening and destabilization of lapse rate. This process starts about a month prior to the actual start of the monsoon rainfall, allowing moisture to build up to lead to the widespread monsoon rainfall. During winter months, rainfall occurs over northwest India in association with high negative value of CINE and over southern Peninsula in association with high value of CAPE. Substantial changes are noticed in the equivalent potential temperature (θ e ) and vorticity profiles between days with and without rainfall over northwest India (Delhi). The results suggest that the increase in moisture in association with the occurrence of rainfall over Delhi is of advective origin. Where as, other regions (Kolkata, Mumbai and Thiruvananthapuram) display relatively smaller changes in the vertical profiles of θ e , indicating an in situ presence of moisture.

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Section: Seasonal Characteristics Of Vertical Structure Of Atmospherementioning

confidence: 87%

“…This helps in decreasing the inhibition energy (CINE). The Himalayan orography interacts with this low level circulation to provide the dynamic lift upstream of the mountains (Grossman and Durran, 1984). When both factors, i.e.…”

Section: Seasonal Characteristics Of Vertical Structure Of Atmospherementioning

confidence: 95%

Analysis of large‐scale conditions associated with convection over the Indian monsoon region

Bhowmik

Roy

Kundu

2007

Intl Journal of Climatology

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“…Deep convection off the west coast of India is partly due to an upstream blocking effect caused by the interaction of the low-level flow with the Western Ghats mountain range, which in turn decelerates the wind causing a gentle lifting well offshore. If this lifting occurs in conditionally unstable air, deep convection could be initiated depending upon the thermodynamic and dynamic structure in the mid-troposphere (Grossman & Durran 1984). There are many studies that explain the causes for the initiation of deep convection and its maintenance over the tropics.…”

Section: Introductionmentioning

confidence: 86%

“…The Ghats run parallel with the coast about 50 km inland, between latitudes 8.5 • N and 21 • N, and have a mean altitude of 800 m, though individual peaks are much higher. A persistent feature of the surface pressure field over the Arabian Sea is an eastward increase of pressure as observed during the Summer Monsoon Experiment (SMONEX) in June 1979 which does not seem to depend upon the presence of offshore convection (Grossman & Durran 1984). The axis of the pressure ridge is either coincident or just upstream of the ridge line of the Western Ghats.…”

Section: Introductionmentioning

confidence: 99%

Moist convective instability over the Arabian Sea during the Asian summer monsoon, 2002

Murthy

Sivaramakrishnan

2006

Meteorological Applications

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“…on the WCI, the convective systems form windward of the terrain of Western-Ghat Mountain as an orographic response to the southwesterly monsoon flow, which develops inward of coast line. Earlier observational studies indicated that the ISM cloudiness over this region is mostly convective (Romatschke and Houze, 2011;Grossman and Durran, 1984). These studies noted that since the convection over this region is non-extreme in nature, they do not develop large stratiform outflows.…”

Section: Variation Of Cloud Pattern During Active and Break Phasementioning

confidence: 99%

Intra-seasonal variability of cloud amount over the Indian subcontinent during the monsoon season as observed by TRMM precipitation radar

et al. 2014

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The intra-seasonal variability of the Indian summer monsoon, which manifests in the form of "active" and "break" phases in rainfall, is investigated with respect to the variability of the convective and stratiform precipitating cloud pattern over the region. Long period data from TRMM PR satellite (2A23 and 3B42 datasets) for the monsoon season of 2002 to 2010 over the Indian subcontinent is used for this purpose. The study reveals that the most significant spatial variation in convective and stratiform cloud amount in relation to the active and break phase occurs over the monsoon trough region in central India. The active phase is characterized by positive convective (~5%) and stratiform (~20%) precipitating cloud anomalies over this region. However, the maximum of the former precedes the latter by 1-2 days leading up to the active phase, indicating that the stratiform build up, is due to the gradual organization of the convective cloud systems over the region. The days leading up to the break phase are marked by negative anomalies in the convective and stratiform fractions of cloudiness over this region, which are in phase with each other, unlike the lead-up to the active phase. Analysis of the pattern of atmospheric heat source and sinks over the region from the NCEP-NCAR re-analysis data indicates that the engine for the growth/decay of convection over the monsoon trough region lies primarily in the Bay of Bengal and adjacent east India. The active phase is preceded by a heating pattern that promotes large scale, organized convective cloud growth over the Bay of Bengal preceding the actual onset, while the heating pattern leading up to the break phase promotes the formation of isolated convective clouds and decay of cloud organization over the monsoon trough region.

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Interaction of Low-Level Flow with the Western Ghat Mountains and Offshore Convection in the Summer Monsoon

Cited by 193 publications

References 0 publications

Analysis of large‐scale conditions associated with convection over the Indian monsoon region

Analysis of large‐scale conditions associated with convection over the Indian monsoon region

Moist convective instability over the Arabian Sea during the Asian summer monsoon, 2002

Intra-seasonal variability of cloud amount over the Indian subcontinent during the monsoon season as observed by TRMM precipitation radar

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