| Session Details | |
| Section | AS - Atmospheric Sciences |
| Session Title | Severe Thunderstorm Observation and Regional Modeling (STORM) |
| Main Convener | Prof. Uma Charan Mohanty (Indian Institute of Technology, India) |
| Co-convener(s) | Dr. Someshwar Das (SAARC Meteorological Research Centre, Bangladesh) Prof. Taiichi Hayashi (Kyoto University, Japan) |
| Session Description | Thunderstorm, resulting from vigorous convective activities, is one of the most spectacular weather phenomena in the atmosphere. This is a mesoscale system with space scale of a few kilometers and time scale of some minutes to few hours. Many parts of Indian region experiences thunderstorms at higher frequency during pre-monsoon months (March-May). During April and May, the eastern and northeastern states of India (i.e., Gangetic West Bengal (GWB), Jharkhand, Orissa, Bihar, Assam) get affected by higher frequency of severe thunderstorms, that form and move from northwest to southeast, locally known as “Kal-baishakhi” or “Nor’westers”. Strong heating of landmass during mid-day initiates convection over Chhotanagpur Plateau, which moves southeast and gets intensified by mixing with warm moist air mass. These severe thunderstorms associated with thunder, squall lines, lightning, torrential rain and hail cause extensive loss in agriculture, damage to property and also loss of life. The casualties reported due to lightning associated with thunderstorms in this region are the highest in the world. The strong wind produced by the thunderstorm is a real threat to aviation. The highest numbers of aviation hazards are reported during occurrence of these thunderstorms. In India, 72% of tornadoes are associated with Nor’westers. These severe thunderstorms have significant socio-economic impact in the eastern and northeastern parts of the country. An accurate location specific and timely prediction is required to avoid loss of lives and property due to strong winds and heavy precipitation associated with these sever weather system. Department of Science and Technology, Govt. of India has been organized a national coordinated programme on ‘Severe Thunderstorm Observation and Regional Modeling (STORM)’ and carried out field experiments in the pre-monsoon season of 2006 and 2007, to improve the understanding and prediction of “Nor’westers” over East and North-East regions of India and their socio-economic impact. STORM programme focus is on a comprehensive observational and modeling study on genesis, evolution and life cycle of intense tropical convective activities over east and northeast regions of India during pre-monsoon period through meso-network of observations and mesoscale analysis and prediction systems. Extensive observations with modern instruments / sensors viz., Doppler Weather Radar (DWR), wind-profilers, Automatic Weather Stations (AWS) etc. has been used in providing a better understanding of the physical, dynamical and thermo-dynamical characteristics of these thunderstorms. The INSAT and METEOSAT hourly imageries and INSAT cloud top temperature data were very useful. An initial pilot experiment was conducted during 13 April to 31 May, 2006 and a second phase of pilot experiment was conducted during 15 April to 31 May, 2007. It was observed that about 50% of thunderstorms were well organized while remaining were sporadic in nature. The convectional tracks of these thunderstorms were from NW to SE predominately, with 1-2 super-convective cells. As the Nor’westers also affect Bangladesh, Nepal and Bhutan, therefore, in 2009 the field experiment was extended to cover these countries as well. A coordinated field experiment named ‘SAARC STORM’ was conducted jointly with 4 countries during 1-31 May 2009. The first phase of the field campaign will be continued through 2012. In the second and third phases other SAARC (South Asian Association for Regional Cooperation) countries namely Pakistan, Afghanistan, Sri Lanka, and Maldives will be included for collecting intense field observations on different types of convective regimes namely, dry convection such as dust storms, maritime convection, and continental deep moist convection. This programme has great significance in view of the recent international scientific programs, such as the Asian Monsoon Year (AMY) and the Year of Tropical Convection (YOTC) sponsored by the World Meteorological Organization (WMO). The intensive observations collected during the 3 pilot experiments form a good data base for assimilation into mesoscale Numerical Weather Prediction (NWP) models, improve our understanding of the finer structure of the Nor’westers, and enhance our capability for their warning in well advance. The observations are being used for understanding the life cycle of the severe thunderstorms, investigate the synoptic and mesoscale environments conducive for their occurrences, the planetary boundary layer processes, convective dynamics, aerosols, cloud microphysics and electrifications of these violent storms. We welcome contributions to the session that will address these issues. We expect overwhelming response to the session as it covers an important topic of wider interest involving all the countries of South Asia and beyond. |