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Is there an effect of Bay of Bengal salinity on the northern Indian Ocean climatological rainfall?

Krishnamohan, KS and Vialard, J and Lengaigne, M and Masson, S and Samson, G and Pous, S and Neetu, S and Durand, F and Shenoi, SSC and Madec, G (2019) Is there an effect of Bay of Bengal salinity on the northern Indian Ocean climatological rainfall? Deep-Sea Research Part II: Topical Studies in Oceanography, 166. pp. 19-33.

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Abstract

The northern Bay of Bengal (BoB) receives a large amount of freshwater directly from monsoonal rains over the ocean, and indirectly through river runoffs. It has been proposed that the resulting strong salinity stratification inhibits vertical mixing of heat, thus contributing to maintain warm sea surface temperature and high climatological rainfall over the BoB. In the present paper, we explore this positive feedback loop by performing sensitivity experiments with a 25-km resolution regional coupled climate model, that captures the main BoB features reasonably well. We confirm that salinity stratification tends to stabilize the upper ocean, thereby increasing the mixed layer warming due to vertical mixing by ∼+0.5 °C.month−1 on annual average. Salinity however also induces a compensating cooling by altering the mixed layer heating rate by air-sea heat fluxes, so that the net effect on climatological surface temperature is negligible. During and shortly after the southwest monsoon, this compensation predominantly occurs through increased cooling by upward latent heat fluxes. During boreal winter, it occurs because salinity favours a thinner mixed layer, which is more efficiently cooled by negative air-sea heat fluxes. These compensations result in a negligible climatological surface temperature and rainfall change at all seasons. This weak influence of salinity stratification on climatological surface temperature and rainfall in our model is robust when applying a flux correction to alleviate model biases, when neglecting the solar absorption below the mixed layer and when using different atmospheric radiation and convective parameterizations.

Item Type: Article
Additional Information: Copyright of this article belongs to Elsevier.
Uncontrolled Keywords: Atmospheric radiation; Climate models; Heat flux; Mixing; Oceanography; Rain; Surface properties; Surface waters, Air-sea heat flux; Coupled climate model; Flux corrections; Northern indian oceans; Positive feedback loop; Salinity stratification; Southwest monsoon; Surface temperatures, Atmospheric temperature
Subjects: Oceanography > oceanography
Depositing User: INCOIS Library
Date Deposited: 18 Sep 2019 08:54
Last Modified: 18 Sep 2019 08:54
URI: http://moeseprints.incois.gov.in/id/eprint/4633

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