Characteristics of deep cloud systems under weak and strong synoptic forcing during the Indian summer monsoon season

Phadtare, J and Bhat, GS (2019) Characteristics of deep cloud systems under weak and strong synoptic forcing during the Indian summer monsoon season. In: Monthly Weather Review, 147 (10). pp. 3741-3758.

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Abstract

Synoptic-scale weather systems are often responsible for initiating mesoscale convective systems (MCSs). Here, we explore how synoptic forcing influences MCS characteristics, such as the maximum size, lifespan, cloud-top height, propagation speed, and triggering over the Indian region. We used 30-min interval infrared (IR) data of the Indian Kalpana-1 geostationary satellite. Cloud systems (CSs) in this data are identified and tracked using an object tracking algorithm. ERA-Interim 850-hPa vorticity is taken as a proxy for the synoptic forcing. The probability of CSs being larger, longer lived, and deeper is more in the presence of a synoptic-scale vorticity field; however, the influence of synoptic forcing is not evident on the westward propagation of CSs over land. There exists a linear relationship between maximum size, lifespan, and average cloud-top height of CSs regardless of the nature of synoptic forcing. Formation of CSs peaks around 1500 LST over land, which is independent of synoptic forcing. Over the north Bay of Bengal, CSs formation is predominantly nocturnal when synoptic forcing is strong, whereas, 0300 and 1200 LST are the preferred times when synoptic forcing is weak. Long-lived CSs are preferentially triggered in the western flank of the 850-hPa vorticity gradient field of a monsoon low pressure system. Once triggered, CSs propagate westward and ahead of the synoptic system and dissipate around midnight. Formation of new CSs on the next day occurs in the afternoon hours in the wake of previous day’s CSs and where vorticity gradient is also present. Formation and westward propagations of CSs on successive days move the synoptic envelope westward.

Item Type:	Journal Article
Publication:	Monthly Weather Review
Publisher:	American Meteorological Society
Additional Information:	The copyright for this article belongs to American Meteorological Society.
Keywords:	Atmospheric thermodynamics; Crack propagation; Geostationary satellites; Storms; Tracking (position), Cloud top heights; Indian summer monsoon; Linear relationships; Low pressure systems; Mesoscale Convective System; Object tracking algorithm; Propagation speed; Vorticity gradients, Vorticity, algorithm; climate forcing; cloud microphysics; convective system; low pressure system; mesoscale meteorology; monsoon; summer; synoptic meteorology; trigger mechanism; vorticity, Bay of Bengal; India; Indian Ocean
Department/Centre:	Division of Mechanical Sciences > Divecha Centre for Climate Change
Date Deposited:	05 Dec 2022 06:54
Last Modified:	05 Dec 2022 06:54
URI:	https://eprints.iisc.ac.in/id/eprint/78236

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