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Bay of Bengal intraseasonal oscillations and the 2018 monsoon onset

Shroyer, E and Tandon, A and Sengupta, D and Fernando, HJS and Lucas, AJ and Farrar, JT and Chattopadhyay, R and de Szoeke, S and Flatau, M and Rydbeck, A and Wijesekera, H and McPhaden, M and Seo, H and Subramanian, A and Venkatesan, R and Joseph, J and Ramsundaram, S and Gordon, AL and Bohman, SM and Pérez, J and Simoes-Sousa, IT and Jayne, SR and Todd, RE and Bhat, GS and Lankhorst, M and Schlosser, T and Adams, K and Jinadasa, SUP and Mathur, M and Mohapatra, M and Rao, EPR and Sahai, AK and Sharma, R and Lee, C and Rainville, L and Cherian, D and Cullen, K and Centurioni, LR and Hormann, V and MacKinnon, J and Send, U and Anutaliya, A and Waterhouse, A and Black, GS and Dehart, JA and Woods, KM and Creegan, E and Levy, G and Kantha, LH and Subrahmanyam, B (2021) Bay of Bengal intraseasonal oscillations and the 2018 monsoon onset. In: Bulletin of the American Meteorological Society, 102 (10). E1936-E1951.

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Official URL: https://doi.org/10.1175/BAMS-D-20-0113.1


In the Bay of Bengal, the warm, dry boreal spring concludes with the onset of the summer monsoon and accompanying southwesterly winds, heavy rains, and variable air-sea fluxes. Here, we summarize the 2018 monsoon onset using observations collected through the multinational Monsoon Intraseasonal Oscillations in the Bay of Bengal (MISO-BoB) program between the United States, India, and Sri Lanka. MISO-BoB aims to improve understanding of monsoon intraseasonal variability, and the 2018 field effort captured the coupled air-sea response during a transition from active-to-break conditions in the central BoB. The active phase of the ~20-day research cruise was characterized by warm sea surface temperature (SST > 30°C), cold atmospheric outflows with intermittent heavy rainfall, and increasing winds (from 2 to 15 m s�1). Accumulated rainfall exceeded 200 mm with 90 of precipitation occurring during the first week. The following break period was both dry and clear, with persistent 10-12 m s�1 wind and evaporation of 0.2 mm h�1. The evolving environmental state included a deepening ocean mixed layer (from ~20 to 50 m), cooling SST (by ~1°C), and warming/drying of the lower to midtroposphere. Local atmospheric development was consistent with phasing of the large-scale intraseasonal oscillation. The upper ocean stores significant heat in the BoB, enough to maintain SST above 29°C despite cooling by surface fluxes and ocean mixing. Comparison with reanalysis indicates biases in air-sea fluxes, which may be related to overly cool prescribed SST. Resolution of such biases offers a path toward improved forecasting of transition periods in the monsoon. © 2021 American Meteorological Society

Item Type: Journal Article
Publication: Bulletin of the American Meteorological Society
Publisher: American Meteorological Society
Additional Information: The copyright for this article belongs to the American Meteorological Society.
Keywords: Atmosphere-ocean interaction; In situ atmospheric observations; In situ oceanic observations; Monsoons.
Department/Centre: Division of Mechanical Sciences > Centre for Atmospheric & Oceanic Sciences
Date Deposited: 23 Oct 2023 12:42
Last Modified: 23 Oct 2023 12:42
URI: https://eprints.iisc.ac.in/id/eprint/82773

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