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Contrasting controls on convection at latitude zones near and away from the equator for the Indian summer monsoon

Masiwal, R and Dixit, V and Seshadri, AK (2023) Contrasting controls on convection at latitude zones near and away from the equator for the Indian summer monsoon. In: Environmental Research Letters, 18 (11).

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Official URL: https://doi.org/10.1088/1748-9326/ad0164


Understanding controls on convection on various timescales is crucial for improved monsoon rainfall forecasting. Although the literature points to vertically homogeneous vorticity signatures preceding rainfall during the Indian summer monsoon, we show using reanalysis data that, for rainfall associated with northward propagating intraseasonal oscillations (ISOs), different controls are present at different latitude zones. For the latitude zone close to the equator (5�N-14�N) and including the southern Indian region, a conventional dynamical control on rainfall exists with barotropic vorticity leading ISO rainfall by about five days. In contrast, for the latitude zone away from the equator (15�N-24�N; covering the central Indian region), thermodynamic fields control ISO rainfall, with barotropic vorticity following rainfall by two days on average. Over central India, the pre-moistening of the boundary layer (BL) yields maximum moist static energy (MSE) about four days prior to ISO rainfall. Analyzing the statistics of individual events verifies these observations. Similar thermodynamic control is also present for the large-scale extreme rainfall events (LEREs) occurring over central India. These high rainfall events are preceded by positive MSE anomalies arising from the moisture preconditioning of the BL. The resulting convection then leads to a maximum in barotropic vorticity 12 h after the rainfall maximum. Characterizing these influences on convection occurring over various timescales can help identify the dominant mechanisms that govern monsoon convection. This can help reduce climate model biases in simulating Indian monsoon rainfall. © 2023 The Author(s). Published by IOP Publishing Ltd.

Item Type: Journal Article
Publication: Environmental Research Letters
Publisher: Institute of Physics
Additional Information: The copyright for this article belongs to author.
Keywords: Atmospheric thermodynamics; Boundary layers; Climate models; Vorticity; Weather forecasting, Barotropic; Central India; Convection-circulation coupling; Extreme rainfall; Indian summer monsoon; Intraseasonal oscillations; Monsoon intraseasonal oscillation; Thermodynamic control; Time-scales; Vorticity evolution, Rain, atmospheric convection; boundary layer; climate modeling; latitude; monsoon; rainfall, India
Department/Centre: Division of Mechanical Sciences > Divecha Centre for Climate Change
Division of Mechanical Sciences > Centre for Atmospheric & Oceanic Sciences
Date Deposited: 28 Feb 2024 13:09
Last Modified: 28 Feb 2024 13:09
URI: https://eprints.iisc.ac.in/id/eprint/83671

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