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Multiscale Interactions between Monsoon Intraseasonal Oscillations and Low Pressure Systems That Produce Heavy Rainfall Events of Different Spatial Extents

Nikumbh, AC and Chakraborty, A and Bhat, GS and Frierson, DMW (2021) Multiscale Interactions between Monsoon Intraseasonal Oscillations and Low Pressure Systems That Produce Heavy Rainfall Events of Different Spatial Extents. In: Journal of Climate, 34 (23). pp. 9523-9534.

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Official URL: https://doi.org/10.1175/JCLI-D-21-0231.1


The subseasonal and synoptic-scale variability of the Indian summer monsoon rainfall is controlled primarily by monsoon intraseasonal oscillation (MISO) and low pressure systems (LPSs), respectively. The positive and negative phases of MISO lead to alternate epochs of above-normal (active) and below-normal (break) spells of rainfall. LPSs are embedded within the different phases of MISO and are known to produce heavy precipitation events over central India. Whether the interaction with the MISO phases modulates the precipitation response of LPSs, and thereby the characteristics of extreme rainfall events (EREs), remains unaddressed in the available literature. In this study, we analyze the LPSs that produce EREs of various spatial extents (small, medium, and large) over central India from 1979 to 2012. We also compare them with the LPSs that pass through central India and do not produce any ERE (LPS-noex). We find that thermodynamic characteristics of LPSs that trigger different spatial extents of EREs are similar. However, they show differences in their dynamic characteristics. The ERE-producing LPSs are slower, moister, and more intense than LPSnoex. The LPSs that lead to medium and large EREs tend to occur during the positive phase of MISO when an active monsoon trough is present over central India. On the other hand, LPS-noex and the LPSs that trigger small EREs occur mainly during the neutral or negative phases of the MISO. The large-scale dynamic forcing, intensification of LPSs, and diabatic generation of low-level potential vorticity due to the presence of active monsoon trough help in the organization of convection and lead to medium and large EREs. On the other hand, the LPSs that form during the negative or neutral phases of MISO do not intensify much during their lifetime and trigger scattered convection, leading to EREs of small size. © 2021 American Meteorological Society. All rights reserved.

Item Type: Journal Article
Publication: Journal of Climate
Publisher: American Meteorological Society
Additional Information: The copyright for this article belongs to Authors
Keywords: Rain, Central India; Extreme events; Extreme rainfall; Intraseasonal oscillations; Intraseasonal variability; Low pressure systems; Multiscale interactions; Negative phase; Rainfall event; Spatial extent, Atmospheric thermodynamics
Department/Centre: Division of Mechanical Sciences > Divecha Centre for Climate Change
Division of Mechanical Sciences > Centre for Atmospheric & Oceanic Sciences
Date Deposited: 21 Dec 2021 05:49
Last Modified: 21 Dec 2021 05:49
URI: http://eprints.iisc.ac.in/id/eprint/70677

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