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The weather is a peculiar phenomenon. Every cloudscape is unique. Some are the harbingers of rain and the others of thunderstorms. The cycles range from minutes to millennia. A computer that simulated 1,000 years of the world’s weather would never see the same day twice. But it would not see any vast change in the weather’s broad characteristics either. The climate defines the limits within which the weather patterns would vary. A great deal of variation — storms one winter, bitter cold the next, a run of unusually dry summers — can all get accommodated within a stable climate. But the climate itself is not immune to the cycles of change seen in the weather. It changes slowly but surely.
Weather forecasting is not easy. Foretelling the arrival of the much-awaited monsoon or to point out approximately the place of destruction of an advancing cyclone requires measuring of various physical and structural areas of atmosphere around us. Environmental forces of varying degrees and different time scales dictate the final picture of the weather, whether violent or moderate.
The constituents of weather are pressure, temperature and wind speed. These forces constantly interact with each other. They have a combined ability to transform the terra firma at any given place instantly and without any warning.
For the weathermen, meteorology is a science which investigates the atmosphere, in particular, the physical process that occurs therein and in the connected systems of the lithosphere and hydrosphere. The subject includes the study of atmospheric content of moisture in it, clouds, and the sunshine.
Weather systems do not care for any geo-political boundaries and can move from one place to another affecting the weather. In order to forecast the weather conditions over any area it is necessary to know the meteorological conditions around it as much as possible. In India’s weather offices, weather maps generally covering the entire South Asia are prepared. As weather conditions change continuously, 4 to 5 maps a day are prepared at an interval of about 6 hours. Weather data taken at a number of observatories in different parts of the area of the map are collected at the forecasting offices and plotted on these weather maps. Observational data from ships plying in the sea are also plotted in these maps. Weather maps indicating the conditions in the entire troposphere are also prepared. The maps are analysed to reveal the significant weather features.
The Earth picture taken by weather satellites showing the cloud cover and existence of cyclonic storms etc. are an important and useful addition to the maps. The forecaster studies the maps carefully and prepares the forecasts.
Numerical weather prediction using computers to process the large volume of meteorological data available on a global scale at a very short time is one of the significant advances in weather forecasting.
To ensure sustainable agriculture in a region, knowledge of the local climate is vital. Climatic limitations are a strong indicator of agronomic potential and can be used to determine which crops are best suited for a particular region, as rainfall and temperature are two major variables affecting the crop type and yield.
In India, the onset of monsoon is expected in June or July. A weaker monsoon may spell death for oilseeds, grain and cotton in the south and in the east where much of the rice is dependent on rain. Planning the crop pattern is, therefore, crucial to get the maximum output from the weathermen’s projections for the monsoon season.
Strong monsoon can cause floods especially in the Gangetic region and the Indus basin. However, defying the vagaries of weather, India’s food production outpaced its population growth from the late 1970s. This was mainly because of the increase in the cultivated areas as well as the irrigation and fertilizer inputs. Advances in genetic research have been important in developing crops which would thrive in certain areas, balancing drought resistance and yield. In fact, some of the notable increases in production stem from germplasm, most notably wheat production, which has been more than quadrupled over the last nearly four decades.
The monsoon climate identified so far is still vulnerable to global weather, which in any given year could result in drought, flooding, or both. Research on the driving force behind the Indian monsoon has resulted in a better understanding of the weather extremes experienced throughout the tropics and their subsequent impact on agriculture in course of the last one century.
The India Meteorological Department (IMD), has been issuing long-range forecasts of the Southwest monsoon rainfall for a number of years using models based on a correlation between monsoon rainfall and the atmospheric and oceanic parameters. IMD has predicted a 98 per cent rainfall during the current monsoon season. The model has an error percentage of plus-minus five (5) per cent. By the latest reports, it seems the IMD has once again hit the right spot with rainfall or the precursor of the South-West monsoon being recorded in time over the Bay of Bengal and Kerala.
The failure to predict the last two droughts notwithstanding, IMD has been constantly updating its technology and broadening its data gathering which would enable it to accurately forecast how the Indian monsoon would behave. IMD is all set to master the lone-range forecast with the latest input from the remote sensing satellite technology. So the next time IMD predicts rain, do not forget to carry your umbrella or the raincoat.
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* Inputs from Krishna G. Sharma, Journalist
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