• Investment World
• eWorld
• Catalyst
• Mentor
• Life
• Canvas
• Praxis
• Urban Pulse
• Brand Quest

Vinson Kurian

Thiruvananthapuram , Nov. 16

TROPICAL weather, with its constantly evolving nature, has proved a typical bother for meteorologists of all hues. Significantly so in a country like India, a vast majority of whose population depends on rain-fed farming for sustenance and who contribute to as much as 35 per cent of the GDP.

The large-scale dynamics of the tropical atmosphere with the sun and the vast expanse of seas in constant interaction, and the sparse availability of data make forecasting a difficult proposition.

According to Dr Akhilesh Gupta and Dr L. S. Rathore of the New Delhi-based National Centre for Medium Range Weather Forecasting (NCMRWF), many people who travel to advanced countries (mostly the extra-tropics) argue that the weather forecasting in these countries is quite accurate presumably due to country's advancement in the field.

But the basic fact is that weather systems are quite well behaved in these latitudes. Extra-tropics have single scale of atmospheric systems that travel in defined path and have preferred areas of development and intensification. Their forecasting therefore becomes much easier. The tropics are on the other hand do not enjoy this blessing. The fundamental laws of fluid dynamics do not apply in tropics. These regions are dominated by all scales of motion beginning from less than a km to tens of thousands of km.

Moreover, the convective development in the tropics could be quite sudden and erratic as compared to those in extra-tropics. As already mentioned, the tropical areas are covered with ocean where little data are available. These factors are responsible for poor accuracy of weather predictions in tropics. It has been shown mathematically that while weather systems in extra-tropics can be predicted with adequate accuracy up to 7-10 days in advance, the limit of predictability for tropics is only 3 days.

Scientists have long understood the basics of convection: warm, moist air bubbles up through colder air aloft. It's the complex interplay of convection with the atmosphere around it, sometimes at a great distance, that remains a challenge.

According to some experts, understanding tropical convection will help weather prediction in mid-latitudes because the effects of tropical convection ripple across to mid-latitudes within a few days. What is learned about the tropics, in other words, can be applied to the entire earth.

The NCMRWF specialises in numerical weather prediction (NWP) models and is working on strategy for progressively enhancing the time range of its weather predictions for farmers from five to seven days in the next 5 years.

According to Dr Gupta and Dr Rathore, short range forecasts may be useful for certain applications, but are inadequate for planning weather-based agricultural practices because of longer lead time required for implementing the desired precautionary measures.

Explaining the circumstances that led to the setting up of the centre, they said that during April-May 1983, unusual persistent cloudiness in some parts of the country resulted in excessive losses of wheat crop. The then Prime Minister, Mrs Indira Gandhi, suggested serious examination of variations and fluctuations in the weather and exploration of ways and means to adjust the cropping pattern according to likely weather conditions. The apex committee set up to examine these aspects, recommended setting up the NCMRWF with a capability to forewarn farmers several days in advance.

Information on impending weather about a week in advance could be vital to ensure optimum effectiveness of modern farming practices such as sowing of weather-sensitive high yield variety of seeds, need based application of fertilisers, pesticides, insecticides, efficient irrigation and harvest planning.

Devastating events like hails, squally winds, tornado and flash floods have damaging impacts on the standing crop. Other events like unseasonal rains, long wet and dry spells, ground frost and other inclement weather conditions also have adverse effects on crop growth as well as crop yield.

Article E-Mail :: Comment :: Syndication

Stories in this Section
Attestation counters sought for overseas jobseekers

Copyright © 2003, The Hindu Business Line. Republication or redissemination of the contents of this screen are expressly prohibited without the written consent of The Hindu Business Line