significant 20th-c. advance
The launching of meteorological satellites revolutionized meteorology, in terms of the near-global view they provided of synoptic weather systems (see Plate H). The first meteorological satellite transmitted pictures on 1 April I960. The early television and infra-red observing satellites (TIROS) carried photographic camera systems and, due to their spin about an axis parallel to the earth's surface, they photographed the surface only part of the time. The types of images that were collected had been anticipated by some meteorologists, but the wealth of information exceeded expectations. New procedures for interpreting cloud features, synoptic and mesoscale weather systems were developed. Satellite pictures revealed cloud vortices, jet-stream bands and other mesoscale systems that were too large to be seen by ground observers and too small to be detected by the network of synoptic stations. Automatic picture transmission (APT) to ground stations began in 1963 and was soon in worldwide use for weather forecasting. In 1972 the system was upgraded to provide high-resolution (HRPT) images.
The operational polar-orbiting weather satellites in the United States were followed in 1966 by geostationary, sun-synchronous satellites positioned at fixed positions in the tropics. These give images of a wide disc of the earth at twenty-minute intervals, providing valuable information on the diurnal development of cloud and weather systems. The US geostationary operational environmental satellites (GOES) were positioned at 75°W and I35°W from 1974, and in 1977 the Japanese geostationary meteorological satellite (GMS) and European meteosat were added at I35°E and 0° longitude, respectively.
The early photographic systems were replaced in the mid-1960s by radiometric sensors in the visible and infra-red wavelengths. Initially, these were broad-band sensors of moderate spatial resolution. Subsequently, narrow-band sensors with improved spatial resolution replaced these; the Advanced Very High Resolution Radiometer (AVHRR) with 1.1km resolution and four channels was initiated in 1978. A further major advance took place in 1970 with the first retrieval of atmospheric temperature profiles from a Nimbus satellite. An operational system for temperature and moisture profiles (the High-resolution Infra-red Radiation Sounder (HIRS) became operational in 1978, followed by a system on GOES in 1980).
Satellite data are now routinely collected and exchanged between NOAA in the USA, the European Meteorological Satellite Agency (Eumetsat) and the Japanese Meteorological Agency (JMA). There are also ground-receiving stations in more than 170 countries collecting picture transmission by NOAA satellites. Satellite data collected by Russia, China and India are mostly used in those countries.
A vast suite of operational products is now available from NOAA and Department of Defense (DoD) Defense Meteorological Satellite Program (DMSP) satellites. The DMSP series are polar orbiting. They provide imagery from 1970 and digital products from 1992. NASA's Nimbus and Earth Observing System (EOS) satellites provide numerous additional research products including sea ice, vegetation indices, energy balance components, tropical rainfall amounts and surface winds.
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