Convective downdraft motions and related outflow wind considered as an eventual source of potential damage which can be more severe in the aviation sector. A great variety of atmospheric environments can produce these downdraft motions. These events are not easily detectable using conventional weather radar or wind shear alert systems, while Doppler radars are useful for identifying these Downbursts. In order to identify the situations that can cause these downdraft events different diagnostic tools are designed. Recently launched Indian satellite INSAT-3D, with atmospheric sounder and imager on board, is capable of identifying regions of downburst occurrence and can help in monitoring them in real time. Some Downburst events reported over different parts of India, during January-April period is investigated using Microburst Wind Speed Potential Index (MWPI) and thermodynamic characteristics derived from the NCMRWF GFS (NGFS) model. An attempt is made to make a short range prediction of these events using MWPI computed from NGFS model forecasts. The results are validated with in-situ observations and also by employing INSAT-3D data and it is shown that the method has a reasonable success. All the investigated downdraft events are associated with the hybrid Microburst environment.
Warm core is the characteristic that distinguishes tropical cyclones from its extra tropical counter parts, where the center of the cyclone is warmer than its environment. Two of the most common variables used to characterize the warm core are its strength and height. The strength is given by the magnitude of maximum perturbation temperature and the height is the level where the maximum perturbation temperature occurs. INSAT-3D, India's advanced weather satellite, is the first geostationary sounder over India and the surrounding Oceanic regions. INSAT-3D has 18 channel sounder with a resolution of 10 km to profile the atmospheric temperature and humidity. Brightness Temperatures (Tbs) from INSAT-3D sounder channels are used to analyze the warm core structure of Tropical cyclone Phailin (8–14 October 2013) over the North Indian Ocean. Only when the system becomes very severe cyclonic system, when the eye of the cyclone is clearer (fully cloud free), the sounder channel Tbs showed multiple maxima, with strong primary maximum in the middle level (600–500 mb) and the secondary maximum in the upper level (300–250 mb), unlike the conventional belief suggested warm core existence at 250 mb. Due to the high resolution of (10 km) INSAT-3D sounder channels, compared to the Micro wave channels (AMSU-A of 50 km resolution), the warm core structure below 10 km of the atmosphere is well resolved.
Satellite data is very important for model initialization and verification. A large number of satellite observations are currently assimilated into the Numerical Weather Prediction (NWP) systems at the National Centre for Medium Range Weather Forecasting (NCMRWF). Apart from Global meteorological observations from GTS, near-real time satellite observations are received at NCMRWF from other operational centres like ISRO, NOAA/NESDIS, EUMETCAST, etc. Recently India has become member of Asia-Pacific Regional ATOVS Retransmission Service (APRARS) for faster access to high resolution global satellite data useful for high resolution regional models. Indian HRPT at Chennai covers the APRARS data gap region over South East Asia. A robust data monitoring system has been implemented at NCMRWF to assess the quantity and quality of the data as well as the satellite sensor strength, before getting assimilated in the models. Validation of new satellite observations, especially from Indian satellites are being carried out against insitu observations and similar space borne platforms. After establishing the quality of the data, Observation System Experiments (OSEs) are being conducted to study their impact in the assimilation and forecast systems. OSEs have been carried out with the Oceansat-2 scatterometer winds and radiance data from Megha-Tropiques SAPHIR sensor. Daily rainfall analysis dataset is being generated by merging satellite estimates and in-situ observations. ASCAT soil wetness measurements from METOP satellite is being assimilated into the global model. Land surface parameters (LuLc and albedo) retrieved from Indian satellites are being explored for its possible usage in the global and regional models. OLR from Indian satellites are used for validating model outputs. This paper reviews the efforts made at NCMRWF in (i) assimilating the data from Indian/International satellites and (ii) generating useful products from the satellite data.