12-14 September, 2011, Lucknow - Earth Science India

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National Conference on Science of Climate Change and Earth’s Sustainability: Issues and Challenges ‘A Scientist-People Partnership’ 12-14 September, 2011, Lucknow was controlled by westerly air flow under cold and dry conditions. Climatic amelioration, the post LGM warming seem to have taken place ca. 17.5 and 12.5 ka BP, can be suggested to document strong chemical weathering, strong hydrodynamics and organic enrichment in the lake under the raised precipitation conditions. A weak monsoon between ca. 12.5 and 11.3 ka BP is inferred by the presence of low Kaolinite, Illite, LOI, SiO 2 and high Muscovite, K, Ti, Fe, MgO, TiO 2 , Na 2 O and positive δ 13 C. The lake level started to rise from about ca. 11.3 ka BP onward due to intensified glacier melt and the onset of summer monsoon moisture supply. Summer monsoon influence weakened after ca. 10.8 to 7.2 ka BP and fostered a return to dry conditions with the increasing influence of westerly disturbances. The period between ca. 7.2 and 5.8 Ka BP is interpreted as strengthening of monsoon, chemical weathering, accumulation of fine grained material and eutrophic conditions and may suggest high precipitation regime. The lake shrank gradually after ca. 5.8 ka BP towards its lowest stand at about ca. 4.2 ka BP, as an abrupt decrease in monsoon precipitation. Our results indicate that the orbitally driven regional climate variability is well reflected in the Yunam basin by hydrological cycles. Extensive summer monsoon moisture seems to have influenced the area only during the early Holocene. The soft sediment deformation structures from four prominent horizons within the profile, approximately ca. 25.3-24.8 ka BP, ca. 20.8-19.5 ka BP, ca. 18.0-17.5 Ka BP, and ca. 12.5-12.0 ka BP in age are incorporated. These dates constrain the palaeoseismic activity during Quaternary as manifestations of the ongoing tectonic processes. SIMULATION RESULTS FROM A MATHEMATICAL OCEAN MODEL Anshu Prakash Mishra 1,2 , S. Rai 1 and A.C. Pandey 1 1 Department of Atmopsheric and Ocean Studies, University of Allahabad, Allahabad 2 Central Water Commission, Sewa Bhawan, R.K.Puram, New Delhi. email: anshu_786@rediffmail.com A z-coordinate numerical ocean model with free surface rigid lid approximation has been implemented for global domain and driven at surface by NCEP/NCAR wind stress climatologies and executed for 25 years. Several results of interest were studied mainly for the Southern Indian Ocean region spanning from 60°S-10°N, 30°E-120°E including Antarctic Circumpolar Current (ACC) region (40°S to 60°S). The fidelity of the model is examined for sub-surface horizontal circulation, sub-surface vertical velocity (overturning circulation), transport phenomenon, heat fluxes including statistical estimation for Sea Surface Temperature (SST). Statistical estimation of SST 16
National Conference on Science of Climate Change and Earth’s Sustainability: Issues and Challenges ‘A Scientist-People Partnership’ 12-14 September, 2011, Lucknow include studying Model Error (ME)(bias), Root Mean Square Error (RMSE), Correlation coefficient (R) and Skill Score (SS). The results show high correlation over the region of study between model/observed SST with annual mean error between 0 to 1° C. It is noticed that in the upper ocean, the zonal transports are eastward that may directly follow the surface currents. MONSOON AND CYCLONES: ROLE OF CLIMATE CHANGE M.R. Ramesh Kumar Physical Oceanography Division, National Institute of Oceanography, Dona Paula, Goa – 403 004. Monsoon and cyclones are the two prominent meteorological attributes of the Indian subcontinent. The southwest monsoon contributes about 60-80% of the mean annual rainfall of various meteorological sub divisions, where as the northeast monsoon contributes to the rainfall of the southeast peninsular India region. There are important aspects which make each monsoon unique, they are the a) monsoon onset over Kerala b) activity within the monsoon life cycle (i.e active and break in monsoon conditions) and c) the quantum of monsoon rainfall. Out these it is the activity within the monsoon life cycle which decides the fate of each monsoon. A prolonged break can cause severe droughts as is the case in recent years of 2002 and 2009. Causes of disruption in monsoon rainfall during the peak monsoon months of July and August for the period 1951-2007 are investigated using a suite of in situ, satellite and reanalysis data sets. Most of the prolonged breaks in recent decades were associated with convective activity over southern hemispheric equatorial trough region (SHET). The association between prolonged break events and convective activity over Bay of Bengal, SHET and North West Pacific (NWP) regions were further explored. The convective activity was found to be more intense over SHET and NWP during the prolonged break in monsoon conditions. Further, it was found that the number of convective systems over NWP were twice the number of systems in Bay of Bengal during deficit and break in monsoon conditions. Thus it is found that the ocean atmospheric processes over the tropical Indian Ocean was found to play a major role in the prolonged break events in recent decades over the Indian subcontinent. The cyclones over the north Indian Ocean form during two seasons, namely a) pre monsoon season and b) post monsoon season. In the present study we look at the role of the various ocean atmospheric parameters on the cyclogenesis of the convective systems over the north Indian Ocean. Further, we have looked at mostly only on the Bay of Bengal region as the bay has about 2 to 3 times more convective storms than the Arabian Sea. An analysis of the various cyclogenesis parameters over the Bay of Bengal 17
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12-14 September, 2011, Lucknow - Earth Science India

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