With the launching of first weather satellite TIROS I (TIROS means Television and Infra- Red Observation Satellite) the field of meteorology entered the space age on April 1 1960. The TIROS 9 was the last weather satellite in the series. These satellites were a great success since they radioed back lakhs of data as well as the pictures of clouds to the earth.
Later, Nimbus satellites equipped with infra-red cameras were launched into space which was able to take cloud pictures even during the night.
Next followed the Polar satellites, better known as ‘Polar Orbiters’, which circled the earth in a north-to-south direction. These satellites orbited the earth at a height of only a few hundred kilometers, and required only 100 minutes per orbit.
These satellites drift about 15 degrees westward over the earth’s surface during the course of each orbit. Thus, it was possible for these satellites to take photographs of the whole earth twice each day. They could send back photos of a rather large section of the atmosphere in only a few hours.
Later on, in the year 1966 geostationary satellites were launched to be placed over the equator. Since the rate of orbiting of the satellites is equal to the rate of the earth’s rotation, they remain over a fixed point.
Hence their name “geostationary’ is justified. These satellites for technical reasons orbit the earth at a great distance of about 35,000 kilometers. The only disadvantage of placing them at this distance is that they are unable to pick up certain minute details on their photographs.
At present the total number of geostationary satellites launched by different countries is 5, out of which the number of such satellites launched by different countries is as under: U.S.A.<197>2 (GEOS- E placed at 75°W and GEOS-W at 135°W), India-1 (INSAT at 74°E), Japan<197>1 (GMS placed at 140HE longitude). These satellites, beside other tasks, serve as data relay stations for the earth.
It may be noted that these weather satellites are not weather forecasters. They are of invaluable aid to fill gaps in observational data, particularly over some parts of the oceans which otherwise would have remained unrepresented.
In addition, they have, to a considerable extent, added to our knowledge of the weather patterns. They are of special significance in detecting the developing violent storms before our ground-based weather observatories could discover them.
Infra-red photography from these weather satellites has made it possible to determine regions where precipitation is likely to occur within a cyclone.
On the contrary, photographs taken in the visible wave-lengths fall to distinguish one cloud type from another, so it is possible to predict which clouds may produce rain or snow and which clouds may be giving no precipitation at all.
The reason is obvious. In the infra-red photographs warm objects are shown as dark, whereas cold objects appear white. As we know, clouds with great vertical heights have their tops colder than those of the lower clouds.
Thus, this characteristic of the infra-red photography allows the geostationary satellites to distinguish between precipitation-yielding and non-precipitation yielding clouds.
Besides, geostationary satellites are sending back estimates of wind movements from cloud movements. They are also provided with instruments that measure temperatures in the atmosphere at different levels.
They are also being used in tracking and transmitting information obtained form instruments which are attached to balloons. Presently projects are ahead to enable the satellites to monitor the temperature and humidity measuring instruments carried by these sounding balloons as they move around the globe.
The geostationary satellites are likely to present a continuous view of the whole earth. The Polar Orbiters would monitor temperature and other atmospheric data.
Plans are under way to connect this system by electronic high-speed computers to the complete network of ground-based weather stations.
It is, therefore, hoped that in near future some of the current gaps in observational data will be filled. This will undoubtedly ensure more accurate and more reliable weather forecasts.
From the foregoing discussion of various weather forecasting methods it is clear that in order to predict the weather with any degree of certainty, a lot of raw information must be fed into computers in order to make the numerical analyses.
We know that our atmosphere resembles a huge engine, and to get a correct knowledge of its functioning weather data from all points of the world should be made available as inputs.
It is only then that significant improvement in weather prediction can be realized. Such prediction would require information on temperatures, heat transfer in the atmosphere, densities, pressures, winds, precipitation and evaporation from hundreds of thousands of points scattered all over our globe.
It is undoubtedly true that only artificial satellites can effectively and economically collect such large quantities of information on a global scale. Weather satellites have already proved their worth.
Automatic pictures transmitted from these satellites are gaining more and more popularity day by day. The benefits of such pictures are easy to understand.