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Some Aspects Of The Twentieth Century's Regional Hydrological Cycle - India

Congress: 2008
Author(s): A.A.L.N.Sarma,T.V.Lakshmi Kumar and A.Vijaya Kameswari*
Department of Meteorology and Oceanography, Andhra University, Visakhapatnam-530003,A.P, India. * D.NO.1-114- 11,M.V.P.Colony, Visakhapatnam-530017,A.P, India. E-mail: afamm@rediffmail.com

Keyword(s): Atmospheric and terrestrial branches, Water balance model, Humidity
AbstractIntroduction and Method It is the induced radiative forcing primarily from the level of human activity together with the internal dynamics of the Earth-Atmosphere system through global atmospheric teleconnections modulates the global with regional implications. The present investigation addresses the regional normal as well as the composites of the atmospheric AN and and and terrestrial branches of the hydrological cycle over India for the recent hottest, ENSO and LNSO event periods for the south -west monsoon period. The hydrological regime of India is studied through water balance concept. The present report pays attention in obtaining the advected moisture, which adds to the rainfall originating from local evaporation. The derived fields of humidity and aridity from water balance model are presented over India and the implications are discussed. Results The composite of hottest years precipitable water from normal,indicated small anomalies centered over Arabian sea Arabian sea and Bay of Bengal with a protrusion on to theland and was high compared to ENSO and LNSO years.The composite of ENSO and LNSO year’s precipitable water anomalies for the monsoon period were highly marginal from the normal. All along the Western and Eastern Ghats, the Indo-Gangetic plains and the north- east part of India the advection was strong but was weak over north-west part of India. The advection becomes weak in subnormal monsoon systems as was in 2002 and 2004. The interesting features that are observed when the summer monsoon system fails in the context of ENSO signal were i. The formation of a cell with 100 mm advection in case of 2002 over Madhya Pradesh and ii.the occurrence of two adjoint cells in 2004 over Madhya Pradesh and east of Uttar Pradesh and parts of Bihar and Jharkhand. The rainfall pattern over India during the monsoon period is not one to one agreement with spatial distribution of precipitable water but is coherent in climate extremities. The marginal anomalies in precipitable water in association with the weak advection of moisture trigger large-scale anomalies in rainfall pattern reflect in seasonal humidity and aridity as is observed in 2002 and 2004 over India. All along the Western Ghats and north -east of India the seasonal effectivity of moisture during the monsoon period supports large quantities of water surplus that feed the headwaters of the respective Indian river systems. The north-west part of India is devoid of any water surplus. The monsoon period of 2002 and 2004 witnessed large anomalies. The monsoon season of 2004 over north- east part of India could witness positive anomalies. The summer monsoon imparts less than 20% aridity over most of India with an exception to north-west part of India that harbors an aridity of 10-70 % across Rajasthan.The aridity status of the various climate zones over India during the monsoon season of 2002 is elevated above the normal over Rajasthan and Deccan Plateau excluding Indo-Gangetic plains and the Malabar Coast. The 2004 monsoon season lodged subnormal aridity over India with an exception to extreme western Rajasthan and central parts of Deccan Plateau.
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