Atmospheric Science

Chairman, ISRO approved the proposal for establishing a facility for monitoring local weather, severe thunderstorm and providing agromet services in the North Eastern Region (NER) of India on August, 2008 under the Atmospheric Science Programme of ISRO. With this NESAC initiated research and services in the area of atmospheric science with the following primary objectives:

  • Providing Weather Advisory Services (WAS) for the farmers of the NE Region.

  • Short and medium Range Numerical Weather Prediction using WRF model. Customization of the models by assimilating data from Automatic Weather Station (AWS), sonde, satellite radiance, satellite derived wind, etc.

  • Satellite based near real time rainfall estimation.

  • Development of flood forecasting model for major river basins of NER.

  • Dissemination of the services through Village Resource Centres and other satellite based networks established by NESAC and also thru web.

Agriculture is the primary livelihood of Assam and it supports 53% of the total working force of the state. The physiographic and micro-climatic variations are ideally suitable for cultivation of a variety of agricultural crops. Timely disseminated weather forecasting could be very helpful to farmers for planning their activities, thereby minimizing risk of crop damage. However, providing weather forecasting for each of the agro-climatic zone and crops and disseminating the information to the needy farmer in time remains a challenging task. The Internet and satellite communications are providing new opportunities to connect people, to obtain and disseminate information and thus bring a new revolution in agriculture.

ISRO has a programme called Village Resource Centres (VRC) to disseminate the range of services emanating from the space systems directly down-the-line to the rural communities. VRCs facilitate interactions between local people and experts at knowledge centres like agricultural universities and other technical organizations on a wide range of subjects on agriculture and other allied sectors. There are some 35 VRCs already functional in the NER including one expert node at NESAC. In the initial stages of development, the ten VRCs covering two agroclimatic zones namely north bank plan zone and upper Brahmaputra valley zone (fig 1) are utilized for disseminating the weather advisories produced at NESAC.

The Bulletin is prepared incorporating IMD’s daily weather forecast (both numerical and synoptic) that is available from the IMD website, weather forecast from NESAC (based on weather research and forecast model run), information about the prevailing weather system over the study areas using KALPANA-1 satellite data in Visible (VIS), Thermal Infrared (TIR), and water vapor (WV) channel and various satellite derived products like cloud motion vectors, relative vorticity etc. Rainfall data is collected from IMD web site and from ISRO/NESAC installed automatic weather station network. The bulletin contains data on cumulative rainfall of last week, past 24 hours and rainfall forecast for next 24 hours (as on date of issue). Weekly agro-meteorological bulletins (in English and Assamese Languages) issued jointly by IMD and Assam Agricultural University, Jorhat for the respective VRCs are also enclosed along with the daily weather bulletin (fig 2). Based on Central Water Commission (CWC) observation daily weather bulletin on flood warning is also issued for the VRCs located in flood prone areas during the peak flood season. In addition to daily weather bulletin, climatological information and their changing scenario over the years are prepared and made available for advising the farmers on the choice of crops or any other agricultural planning purposes.

Weather Forecasting

The Weather Research and Forecasting (WRF) model is being run at NESAC to give 24 hour weather forecast specifically for Flood Early Warning System (FLEWS) project and weather advisory services. The model is presently run at a resolution of 27 km for a domain covering NER by assimilating data from AWS and satellite derived wind.

The centre has developed methodology for estimation of weekly rainfall from satellite data. Estimation of hourly rainfall from satellite data exclusively for the region (dominated by orography induced rainfall) is being attempted presently. The centre has also developed and demonstrated flood forecasting technique by suitably integrating inputs from different organizations and platforms.