The effect of seasonally and spatially varying chlorophyll on Bay of Bengal surface ocean properties and the South Asian monsoon

Giddings, Jack, Matthews, Adrian ORCID: https://orcid.org/0000-0003-0492-1168, Klingaman, Nicholas, Heywood, Karen ORCID: https://orcid.org/0000-0001-9859-0026, Joshi, Manoj ORCID: https://orcid.org/0000-0002-2948-2811 and Webber, Ben ORCID: https://orcid.org/0000-0002-8812-5929 (2020) The effect of seasonally and spatially varying chlorophyll on Bay of Bengal surface ocean properties and the South Asian monsoon. Weather and Climate Dynamics, 1 (2). 635–655. ISSN 2698-4016

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Abstract

Chlorophyll absorbs solar radiation in the upper ocean, increasing the mixed layer radiative heating and sea surface temperatures (SST). Although the influence of chlorophyll distributions in the Arabian Sea on the southwest monsoon has been demonstrated, there is a current knowledge gap regarding how chlorophyll distributions in the Bay of Bengal influence the southwest monsoon. The solar absorption caused by chlorophyll can be parameterized as an optical parameter, h2, which expresses the scale depth of the absorption of blue light. Seasonally and spatially varying h2 fields in the Bay of Bengal were imposed in a 30-year simulation using an atmospheric general circulation model coupled to a mixed layer thermodynamic ocean model in order to investigate the effect of chlorophyll distributions on regional SST, the southwest monsoon circulation, and precipitation. There are both direct local upper-ocean effects, through changes in solar radiation absorption, and indirect remote atmospheric responses. The depth of the mixed layer relative to the perturbed solar penetration depths modulates the response of the SST to chlorophyll. The largest SST response of 0.5 ∘C to chlorophyll forcing occurs in coastal regions, where chlorophyll concentrations are high (> 1 mg m−3), and when climatological mixed layer depths shoal during the inter-monsoon periods. Precipitation increases significantly (by up to 3 mm d−1) across coastal Myanmar during the southwest monsoon onset and over northeast India and Bangladesh during the Autumn inter-monsoon period, decreasing model biases.

Item Type:	Article
Additional Information:	Funding Information: This research has been supported by the NERC (grant no. NE/L002582/1). The Bay of Bengal Boundary Layer Experiment (BoBBLE) is a joint programme funded by the Ministry of Earth Sciences (Government of India) and the Natural Environment Research Council (NERC, United Kingdom). Jack Giddings' PhD project was supported by the NERC EnvEast DTP (grant no. NE/L002582/1). Adrian J. Matthews, Karen J. Heywood, Benjamin G. M. Webber, and Manoj Joshi were supported by NERC (grant no. NE/L013827/1), and Nicholas P. Klingaman was supported by a NERC Independent Research Fellowship (grant no. NE/L010976/1).
Uncontrolled Keywords:	bay of bengal (bob),indian ocean,chlorophyll-a,radiant heating rate,south asian summer monsoon,solar penetration depth,atmospheric science ,/dk/atira/pure/subjectarea/asjc/1900/1902
Faculty \ School:	Faculty of Science > School of Environmental Sciences University of East Anglia Research Groups/Centres > Theme - ClimateUEA Faculty of Science > School of Natural Sciences
UEA Research Groups:	Faculty of Science > Research Groups > Centre for Ocean and Atmospheric Sciences Faculty of Science > Research Groups > Climatic Research Unit University of East Anglia Schools > Faculty of Science > Tyndall Centre for Climate Change Research Faculty of Science > Research Centres > Tyndall Centre for Climate Change Research
Related URLs:	http://www.scopus.com/inward/record.url?...
Depositing User:	LivePure Connector
Date Deposited:	20 Oct 2020 23:58
Last Modified:	15 Jun 2023 02:30
URI:	https://ueaeprints.uea.ac.uk/id/eprint/77380
DOI:	10.5194/wcd-1-635-2020

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