Meteorological Satellites and INSAT Meteorological Component (Especially for GATE-Geospatial 2022)

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Meteorological Satellites

  • Carry sensors that are pointing towards the ground, enabling them to have bird eye view of the globe from the space.
  • Meteorological satellites set out around the Earth allow a complete surveillance of the atmosphere. Satellite imagery gives a global and consistent view of the organization of atmospheric features in a great variety of scales over large areas.
  • These data are now operationally available in various spectral channels of three generations of geostationary satellite systems, and the operational updating rate of the images has increased with a cycle of repetition of 30,15, or even 5 min.
  • Such tools help the human forecaster in the early recognition of high-impact weather phenomena. In operational weather forecasting, satellite imagery is used in combination with other meteorological data, especially with relevant numerical parameter fields.
  • This combined use (see EUMeTrain/EUMETSAT, 2012; COMET 2016) is a major requirement for an optimal detection of ongoing physical processes as well as to overcome the problem of an excessive amount of material in the forecasting environment.
Image United States from the GOES-17 Satellite
  • Meteorological satellites are of two types viz. Polar orbiting and Geostationary Polar orbiting satellites pass approximately over the poles at a height of about 850 kms.
  • The whole surface of the earth is observable by these satellites which follow orbits nearly fixed in space while the earth is rotating beneath them. The areas scanned on each pass (swath) are nearly adjacent at the equator with overlapping areas further poleward.
  • The swaths are usually about 2600 km wide. These satellites complete 14 orbits per day and thus can provide global coverage twice in 24 hours. Some of the polar orbiting satellites are NOAA, IRS, ERS-1 &ERS2, TRMM (low inclination) , DMSP, Oceansat-1 etc.
  • Geostationary satellites orbit around the earth over the equator at a height of about 36000 kms. They complete one orbit in 24 hours synchronized with earth՚s rotation about its own axis.
  • Thus they remain over the same location on the equator. The main advantage of geostationary satellites lies in the high time-scale resolution of their data. A fresh image of the full earth՚s disc is available every 30 minutes. However they have limited spatial resolution as compared to the polar orbiting satellites in view of their distance from the earth.
  • Useful information is restricted to the belt between and south latitudes. Some of the examples of geostationary satellites are GMS (1400 E) , GOES-W, GOES-E, INSAT-1 and INSAT-2 Series. , GEOS, METEOSAT -5 (Positioned at ) , METEOSAT-6 etc.
Polar Orbiting and Geostationary Satellites

INSAT Meteorological Component

  • The Indian National Satellite (INSAT) is a multipurpose geostationary satellite, which carries both meteorological, and communications payloads. The INSAT-1D is located at and INSAT-2B is located at .
  • The VHRR (very high resolution radiometer) onboard the satellite has a visible (0.55 - 0.75 µm) and infra-red bands with resolution of 2.75 km and 11 km for INSAT-1 series, and 2 and 8 km respectively for the INSAT – 2 series.
  • The VHRR scans are taken every 3 hours on routine basis and half hourly to even less than that, for monitoring cyclones etc. One VHRR scan takes about 30 minutes to be completed and is made up of picture elements (pixels) in case of visible channel and pixels in case of IR channel. The meteorological component provides:
  • Round the clock, regular half-hourly synoptic images of weather systems including severe weather, cyclones, sea surface and cloud top temperatures, water bodies, snow etc. over the entire territory of India as well as adjoining land and sea areas.
  • Collection and transmission of meteorological, hydrological and oceanographic data from unattended data collection platforms.
  • Timely warning of impending disasters from cyclones and storms etc.
  • Dissemination of meteorological information including processed images of weather systems to the forecasting offices.
Cloud Cover over India as Seen by INSAT-3D
  • KALPANA-1 is located at 74 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.

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