Data Sources For Forecasting

The data required for forecasting and other services are provided by worldwide standard three-hourly synoptic reports (see Appendix 3); similar observations are made hourly in support of aviation requirements. Upper-air soundings (at 00 and 12 UTM), satellites and other specialized networks such as radar provide additional data. Under the World Weather Watch programme, synoptic reports are made at some 4000 land stations and by 7000 ships (Figure 8.5A). There are about 700 stations making upper-air soundings (temperature, pressure, humidity and wind) (Figure 8.5B). These data are transmitted in code via teletype and radio links to regional or national centres and into the high-speed Global Telecommunications System (GTS) connecting world weather centres in Melbourne, Moscow and Washington and eleven regional meteorological centres for redistribution. Some 184 member nations co-operate in this activity under the aegis of the World Meteorological Organization.

Meteorological information has been collected operationally by satellites of the United States and Russia since 1965 and, more recently, by the European Space Agency, India and Japan (see Box 8.1). There are two general categories of weather satellite: polar orbiters providing global coverage twice every twenty-four hours in orbital strips over the poles (such as the United States' NOAA and TIROS series (see Plates 2 and 3) and the former USSR's Meteor); and geosynchronous satellites (such as the geostationary operational environmental satellites (GOES) and Meteosat), giving repetitive (thirty-minute) coverage of almost one-third of the earth's surface in low middle latitudes (Figure 8.6). Information on the atmosphere is collected as digital data or direct readout visible and infra-red images of cloud cover and sea-surface temperature, but it also includes global temperature and moisture profiles through the atmosphere obtained from multi-channel infra-red and microwave sensors, which receive radiation emitted from particular levels in the atmosphere. In

Figure 8.6 Coverage of geostationary satellites and WMO data-collection areas (rectangular areas and numbers).

Source: Reproduced courtesy of NOAA.

Figure 8.6 Coverage of geostationary satellites and WMO data-collection areas (rectangular areas and numbers).

Source: Reproduced courtesy of NOAA.

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