India Meteorological Department (IMD) is the primary user of meteorological payload on INSAT satellites. The meteorological data from the satellites is processed and disseminated by INSAT Meteorological Data Processing System (IMDPS) operational at IMD, New Delhi. At present, KALPANA-1 and INSAT-3A satellites are supporting the meteorological imaging and data collections.
KALPANA-1 is located at 74 degree East and carries a Very High Resolution Radiometer (VHRR) capable of imaging the Earth in the visible, thermal infrared and water vapor bands. It is the main operational satellite and 48 scans of this satellite with a frequency of half an hour, are taken daily. The products derived from the satellite data include cloud images in the visible, infra-red and water vapour channels, atmospheric motion vectors, sea surface temperature, outgoing long-wave radiation, quantitative precipitation estimates and upper tropospheric humidity.
Cloud cover over India as seen by INSAT-3D
INSAT-3A satellite, located at 93.5 degree East, carries VHRR, Charged Couple Device (CCD) camera and Data Relay Transponder (DRT). 24 Scans of VHRR and 6 scans of CCD camera of INSAT-3A are taken daily. The products derived from CCD camera are Normalised Difference Vegetation Index (NDVI) and Aerosol Optical Depth (AOD).
The satellite images are being used for weather forecasting, both synoptic and numerical weather prediction. The monitoring of cyclone intensity, its location, and various other weather systems such as fog, thunderstorms, Western disturbances and Norwesters, etc., are done by Satellite images and data. A satellite bulletin is prepared every three hours describing images and products generated by the data and hourly bulletins are issued in the case of a cyclone. All images and products generated by satellite data are displayed on IMD website satellite page for users in real time. INSAT-VHRR imagery are used by Doordarshan during news coverage and by newspapers as part of weather reporting.
INSAT VHRR images and data are made available in near real-time at 40 Digital Meteorological Data Dissemination (DMDD) stations set up by IMD in various parts of the country as well as in neighboring countries of Nepal, Maldives and Srilanka and DMDD stations of Air force and Navy through CxS transponder on INSAT-3C. The availability of Satellite Imagery and Digital data through DMDD at Regional Meteorological Centre/ Meteorological Centre has improved the forecasting capability at regional levels.
IMD has installed 679 Automatic Weather Stations (AWS) and other agencies have installed about 1000 AWS all over the country. IMD has also installed 969 Automatic Rain Gauge (ARG) Stations. AWS and ARG services are operational by using Data Relay Transponders(DRT) of INSAT-3A having global receive coverage with a 400 MHz uplink and 4504 MHz downlink. Meteorological, Hydrological, Agro-Meteorological and Oceanographic data are relayed from unattended land and ocean based AWS. ISRO has taken up indigenous development of a low cost automatic weather station for deployment in the country in large numbers. The data collection is largely carried in TDMA mode.
For quick dissemination of warnings against impending disaster from approaching cyclones, specially designed receivers have been installed at the vulnerable coastal areas in Andhra Pradesh, Tamil Nadu, Odisha, West Bengal and Gujarat for direct transmission of warnings to the officials and public in general using broadcast capability of INSAT. IMD’s Area Cyclone Warning Centres generate special warning bulletins and transmit them every hour in local languages to the affected areas using Cyclone Warning Dissemination Systems (CWDS). 353 such receiver stations have been installed by IMD. Out of these, 101 are Digital CWDS (DCWDS) based on advanced technology. IMD is now upgrading all these existing network of CWDS/DCWDS by the ISRO developed DTH based Disaster Warning Dissemination Systems (DWDS). An MOU has been signed by ISRO, IMD and Doordarshan for the replacement of the existing network of CWDS by the new DTH based DWDS and the implementation of this project is under progress.