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Classification of mid-tropopsheric cyclones over the Arabian Sea and western India

Kushwaha, P and Sukhatme, J and Nanjundiah, RS (2023) Classification of mid-tropopsheric cyclones over the Arabian Sea and western India. In: Quarterly Journal of the Royal Meteorological Society .

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Official URL: https://doi.org/10.1002/qj.4466


The formation of mid-tropospheric cyclones (MTCs), responsible for a large portion of annual precipitation and extreme rainfall events over western India, is studied using an unsupervised machine learning algorithm and cyclone tracking. Both approaches reveal four dominant weather patterns that lead to the genesis of these synoptic systems. Specifically, re-intensification of westward-moving synoptic systems from the Bay of Bengal (type 1, 51), in-situ formation with a coexisting cyclonic system over the Bay of Bengal that precedes (type 2a, 31) or follows (type 2b, 10) genesis in the Arabian Sea, and finally in-situ genesis within a northwestward-propagating cyclonic anomaly from the south Bay of Bengal (type 2c, 8). Thus, a large fraction of this region's rainy middle tropospheric synoptic systems form in association with cyclonic activity in the Bay of Bengal. The four variants identified also show a marked dependence on large-scale environmental features. In particular, type 1 and type 2a MTC formation primarily occurs in phases 4 and 5, and type 2b and type 2c MTCs form mainly in phases 3 and 4 of the boreal summer intraseasonal oscillation. Further, though in-situ formation with a Bay of Bengal cyclonic anomaly (types 2a and 2b) mostly occurs in June, downstream development is more likely in the core of the monsoon season. Out of all categories, type 2a is associated with the highest composite rain rate (60 mm (Formula presented.) day (Formula presented.)) over western India and points towards the dynamic interaction between a low-pressure system over the Bay of Bengal and the development of MTCs over western India and the northeast Arabian Sea. This classification, identification of precursors, connection with cyclonic activity over the Bay of Bengal, and dependence on a large-scale environment provide an avenue for a better understanding of rain-bearing MTCs over western India.

Item Type: Journal Article
Publication: Quarterly Journal of the Royal Meteorological Society
Publisher: John Wiley and Sons Ltd
Additional Information: The copyright for this article belongs to John Wiley and Sons Ltd
Keywords: Atmospheric thermodynamics; Hurricanes; Learning algorithms; Machine learning; Tropical cyclone; Tropics; Troposphere, Arabian sea; Bay of Bengal; Cyclonic activities; Extream rainfall; In-situ formations; Mid-tropospheric cyclone; Monsoon; Monsoon low; Synoptic systems; Tropical cyclone, Rain
Department/Centre: Division of Biological Sciences > Centre for Ecological Sciences
Division of Mechanical Sciences > Divecha Centre for Climate Change
Date Deposited: 15 Jun 2023 10:30
Last Modified: 15 Jun 2023 10:30
URI: https://eprints.iisc.ac.in/id/eprint/82063

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