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 CLIMATE CHANGE AND TROPICAL CYCLONES IN THE INDIAN SEAS O.P. Singh India Meteorological Department, New Delhi On an average, about 5-6 tropical cyclones form in the Indian seas every year, of which about 2 may reach the severe stage. About 80% of the total number of tropical cyclones of the Indian seas form in the Bay of Bengal. Most of the severe cyclones of the Indian seas form during the post-monsoon season in the months of October and November. A few severe cyclones also form during May. The east coast of India and the coasts of Bangladesh, Myanmar and Sri Lanka are vulnerable to the incidences of tropical cyclones of the Bay of Bengal. Every year these cyclones inflict heavy loss of life and property in this region. The average frequency of cyclones in the Arabian Sea is relatively less, ie approximately 1 cyclone per year. The Arabian Sea cyclones generally affect Maharashtra and Gujarat coasts. Sometimes, these cyclones travel northwest and strike Pakistan and Oman coasts. Global climate change resulting from anthropogenic activity is likely to manifest itself in the weather and climate of the Indian Ocean region also. The long-term trends in the frequency and intensity of tropical cyclones of the Indian seas during intense cyclonic months May, October and November is one such problem which has been addressed in the present paper. Utilizing the existing data of 129 years (1877-2005) pertaining to the tropical cyclone frequency and intensity in the Indian seas during May, October and November, a study was undertaken to investigate the trends in the frequency of severe cyclonic storms ( SCS ) during past decades. The results of the trend analysis reveal that the SCS frequency over the Bay of Bengal has registered significant increasing trends in the past 129 years during the intense cyclonic months. It may be emphasized that these are longterm trends for more than hundred years based on statistical analyses which do not necessarily imply that SCS frequency has increased continuously decade after decade. The intensification rate during November, which accounts for highest number of intense cyclones in the Indian seas, have registered a steep rise of 26% per hundred years, implying that a tropical depression forming in the Bay of Bengal during November has a high probability to reach the severe cyclone stage. A regional climate model simulation revealed the enhanced cyclogenesis in the Bay of Bengal during May, October and November as a result of increased anthropogenic emissions in the atmosphere. 26
National Conference on Science of Climate Change and Earth’s Sustainability: Issues and Challenges ‘A Scientist-People Partnership’ 12-14 September, 2011, Lucknow SOLAR IRRADIANCE FORCING OF TERRESTRIAL CLIMATE: AN UNDENIABLE FACT EVEN IN THE ANTHROPOCENE ERA Rajesh Agnihotri 1 , Koushik Dutta 2 and B.C. Arya 1 1 Radio and Atmospheric Science Division, National Physical Laboratory, New Delhi 110012 2 Large Lakes Observatory, University of Minnesota – Duluth, Duluth, MN 55812, USA email: rajagni9@gmail.com, agnir@nplindia.org Despite continued skepticism, solar intrinsic forcing has emerged as key factor governing natural climate variability on decadal to centennial timescales (Gray et al., 2009). Several important advancements in the field of sun–earth climatic connection have been made in last few years that have eventually led scientific community to incorporate solar forcing component in modeling of terrestrial climate (Meehl et al., 2009). Sustained efforts are required for quantitative estimation and sensitivity analysis of internal climate drivers against this external forcing for making realistic climatic projections in the present era when greenhouse gas forcing is suspected to have taken a dominant role governing terrestrial climate. Here we present (i) how temporal variations of solar irradiance govern inter-decadal variability of Indian monsoon (Agnihotri et al., 2011) and (ii) brief review of recent major investigations carried out across the globe that collectively reinforcing a definite role of solar intrinsic variability governing natural climate variability in the recent past (Mauas et al., 2008, 2010; Stager et al., 2007). It is attempted to address a few important knowledge gaps in the sun-climate relationship desired for successful delineation of natural versus anthropogenic forcing of recent climate change in the present Anthropocene era. LONG TERM CHANGES OF TOTAL OZONE COLUMN CONTENTS OVER TROPICAL STATION I.E., UDAIPUR Brij Mohan Vyas and Abhishek Saxenna Department of Physics, M.L.Sukhadia University, Udaipur – 313001 (Rajasthan) email: bmvyas@yahoo.com After the great scientific discovery of the “Ozone Hole”, assessment of long term trends of total ozone contents over different parts of the world has now become frontier research topics, which is seriously concerned to global environment. In the past one decade, extensive studies based on various ground and satellites measurements of Total 27
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