Estimates of land and sea moisture contributions to the monsoonal rain over Kolkata, deduced based on isotopic analysis of rainwater

Dar, Shaakir Shabir and Ghosh, Prosenjit (2017) Estimates of land and sea moisture contributions to the monsoonal rain over Kolkata, deduced based on isotopic analysis of rainwater. In: EARTH SYSTEM DYNAMICS, 8 (2). pp. 313-321.

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Abstract

Moisture sources responsible for rains over Kolkata during the summer monsoon can be traced using backward air-mass trajectory analysis. A summary of such trajectories between June and September suggest that these moisture parcels originate from the Arabian Sea and travel over the dry continental region and over the Bay of Bengal (BoB) prior to their arrival at Kolkata. We use monthly satellite and ground-based observations of the hydrometeorological variables together with isotopic data of rainwater from Bangalore and Kakinada to quantify the contributions of advected continental and oceanic water vapour in the Kolkata rains. The vapour mass is modified during its transit from its original isotopic value due to addition of evaporated moisture from the BoB, and further modification occurs due to the process of rainout during transport. The evaporated component is estimated using the Craig-Gordon equation. The rainout process is simulated using a Rayleigh fractionation model. In this simulation we assume that the initial isotopic composition of vapour originating from the continent is similar to the rainwater composition measured at Bangalore. In order to explain the monthly isotopic composition in southwest monsoon rainwater at Kolkata, we invoke 65-75% moisture contribution from the BoB; the remaining moisture is from the continental land mass.

Item Type:	Journal Article
Publication:	EARTH SYSTEM DYNAMICS
Additional Information:	Copy right for this article belongs to the COPERNICUS GESELLSCHAFT MBH, BAHNHOFSALLEE 1E, GOTTINGEN, 37081, GERMANY
Department/Centre:	Division of Mechanical Sciences > Centre for Earth Sciences
Date Deposited:	25 May 2017 09:29
Last Modified:	25 May 2017 09:29
URI:	http://eprints.iisc.ac.in/id/eprint/57049

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