Please use this identifier to cite or link to this item: http://hdl.handle.net/123456789/7816
Title: Internal feedbacks from monsoon-midlatitude interactions during droughts in the Indian summer monsoon
Authors: Krishnan R
Kumar V
Sugi M
Yoshimura J 
Keywords: Anticyclonic anomalies;Central Asia;Circulation patterns;Convective instabilities;East Asia;Eurasia;Extratropical circulation;Extratropical winds;High resolution;Indian summer monsoon;Interannual variation;Internal feedback;Large-scale circulation;Midlatitudes;Monsoon rainfall;Pakistan;Quasi-stationary;Rossby wave;Simplified models;Supplementary data;Thermal contrasts;Time-scales;Upper troposphere, Atmospherics;Drought;Ocean currents;Rain;Troposphere;Wind, Feedback, annual variation;atmospheric convection;atmospheric general circulation model;drought;midlatitude environment;monsoon;rainfall;sea surface temperature;summer;troposphere, Asia;Central Asia;Eurasia;India;South Asia
Issue Date: 2009
Publisher: Journal of the Atmospheric Sciences
American Meteorological Society
Source: Volume no: 66
Issue no: 3
Abstract: Results from a 20-yr simulation of a high-resolution AGCM forced with climatological SST, along with simplified model experiments and supplementary data diagnostics, are used to investigate internal feedbacks arising from monsoonmidlatitude interactions during droughts in the Indian summer monsoon. The AGCM simulation not only shows a fairly realistic mean monsoon rainfall distribution and large-scale circulation features but also exhibits remarkable interannual variations of precipitation over the subcontinent, with the 20-yr run showing incidence of four monsoon droughts.The present findings indicate that the internally forced droughts in the AGCM emanate largely from prolonged monsoon breaks that occur on subseasonal time scales and involve dynamical feedbacks between monsoon convection and extratropical circulation anomalies. In this feedback, the suppressed monsoon convection is shown to induce Rossby wave dispersion in the summertime subtropical westerlies and to set up an anomalous quasi-stationary circulation pattern extending across continental Eurasia in the middle and upper troposphere. This pattern is composed of a cyclonic anomaly over west central Asia and the Indo-Pakistan region, a meridionally deep anticyclonic anomaly over East Asia (?100E), and a cyclonic anomaly over the Far East. The results suggest that the anchoring of the west central Asia cyclonic anomaly by the stagnant ridge located downstream over East Asia induces anomalous cooling in the middle and upper troposphere through cold-air advection, which reduces the meridional thermal contrast over the subcontinent. Additionally, the intrusion of the dry extratropical winds into northwest India can decrease the convective instability, so that the suppressed convection can in turn weaken the monsoon flow. The sustenance of monsoon breaks through such monsoonmidlatitude feedbacks can generate droughtlike conditions over India.
URI: http://hdl.handle.net/123456789/7816
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