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Reduced availability of GMS-5 imagesThe Japan Meteorological Agency (JMA) has announced that from 4 July 2001
there will be a reduction in the satellite imagery available from its
Geostationary Meteorological Satellite GMS-5. The changes will comprise: 
Figure showing the new extent of GMS-5 images
Australia has been extremely fortunate to have the benefits of satellite imagery from Japan’s weather satellite program for over two decades. The program is a key part of the Global Observing System of the World Meteorological Organization. GMS cloud images have been of vital importance to the operations of national meteorological services in the Asia-Pacific region. The reduced satellite imagery will affect both the Bureau’s forecasting and warning services and its data access services.
Satellite pictures are used in several ways in routine weather forecasting and warning. Forecasters are able to interpret the pattern of clouds in the satellite pictures to get better information on such features as the position of fronts, low pressure systems and tropical cyclones, and the type of rainfall that might be produced in some areas. The satellite images are also used to derive information for high up in the atmosphere - winds and temperatures for example - which are then fed into computer models (numerical weather prediction models or NWP models) which simulate the evolution of the atmosphere over a number of days ahead; forecasters use these as guidance in deriving their forecasts of weather. Satellite imagery is therefore an extremely important tool for weather forecasting services. There is almost certain to be some impact on the quality of forecasting services due to the reduction in availability of satellite data. This will be relatively small for the current reduction in coverage and frequency, but if the satellite were to fail completely, the impact would be much more significant. It is important to remember however that many other types of data are also used in weather forecasting and warning services, so the latter are by no means entirely dependent on satellite-derived information. The aspects of services likely to be affected most are the positioning of tropical cyclones well off the coast and the timing of summertime cool changes in southern Australia. In addition the daily solar radiation service will be disrupted.
Some of the Bureau’s data access services will also be affected. Any service providing hourly frequency of pictures will now be updated less frequently, and any service currently including “full disk” pictures which show the whole earth hemisphere, will show a black area south of 49S with no information.
JMA has endeavoured to minimise the impact of the reduced observations on forecasting and warning by ensuring that they cluster images around the times in a day when input to computer models is most important. In addition, in the case of further reductions in GMS5 data, the Bureau is examining “substitute” satellite images produced by other satellites including the United States’ NOAA polar orbiting satellites, and other geostationary satellites to the east of Australian longitudes. The substitute satellite pictures will be used to supplement the Bureau's forecasting and warning and data access services to the extent possible if GMS fails. These images will not be as frequent or as convenient as those from GMS-5, which is a geostationary satellite (effectively stationary above the equator) located in Australian longitudes, and so shows the full disk of the earth with Australia very close to the centre of the picture. However, they can be used quite effectively in the forecast process.
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Impact on Bureau products and services