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Shift in Indian summer monsoon onset during 1976/1977

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Title Shift in Indian summer monsoon onset during 1976/1977
 
Creator SAHANA, AS
GHOSH, S
GANGULY, A
MURTUGUDDE, R
 
Subject SEA-SURFACE TEMPERATURE
EL-NINO
INTRASEASONAL OSCILLATIONS
INTERANNUAL VARIABILITY
SOUTHERN OSCILLATION
BOREAL SUMMER
PACIFIC
RAINFALL
OCEAN
ENSO
Indian monsoon onset
regime Shift of 1976/77
moisture dynamics of onset
 
Description The Indian summer monsoon rainfall (ISMR) contributes nearly 80% of the annual rainfall over India and has a significant influence on the country's gross domestic product through the agricultural sector. Onset of the ISMR displays substantial interannual variability and controls the crop calendar and hence the agricultural output. This variability is traditionally linked to sea surface temperature (SST) anomalies over the tropical Pacific Ocean. The tropical Pacific SST underwent a regime shift during 1976/77. Wereport a prominent delay in the Indian summer monsoon (ISM) onset following the regime shift. The onset dates are computed with the Hydrologic Onset and Withdrawal Index, based on vertically integrated moisture transport over the Arabian Sea (AS). The shift in onset is found to be due to the change in moisture availability over the AS. A delay in the development of easterly vertical shear reduces northward-propagating intraseasonal variability during May-June, limiting the moisture supply from the equatorial Indian Ocean (IO) to the AS. This, along with enhanced precipitation over the IO during the pre-monsoon, drives a reduction in moisture availability over the AS region from pre- to post-1976/77, delaying the ISM onset in recent decades. Our findings highlight the need for the re-assessment of the crop calendar in India, which is now based on the mean onset date computed from long-term data, without considering the regime shift or trends in onset.
 
Publisher IOP PUBLISHING LTD
 
Date 2016-01-15T08:23:15Z
2016-01-15T08:23:15Z
2015
 
Type Article
 
Identifier ENVIRONMENTAL RESEARCH LETTERS, 10(5)
1748-9326
http://dx.doi.org/10.1088/1748-9326/10/5/054006
http://dspace.library.iitb.ac.in/jspui/handle/100/18155
 
Language en