What ails India`s wind pattern study?
cyclone Gonu has showed up the chinks in India's wind pattern research. The cyclone lashed Oman on June 4, 2007, and delayed monsoon in India by a week. Indian scientists, including the India Meteorological Department (imd), failed to predict the wind disturbance on the Persian Gulf and its effect on the Indian monsoons. This was due to an inadequate system of studying wind systems over oceans.
Little known imd says sufficient data on the wind patterns over oceans is not available in India. Experts, however, say many countries, including the us and Australia, have advanced systems to study wind patterns. "Long-term wind data on land is available. Consistent data for about a decade which was collected from over the sea using satellites is there. We need at least 50 years' data to predict wind trends over oceans,' says J Srinivasan of the Indian Institute of Science, Bangalore.
Earlier, ships were used to collect data on winds, but there was no continuity in this system. For the last ten years, wind data from the sea has been collected through buoys. "Studies from various stations in the country show that wind speed is decreasing. But lack of data restricts prediction of long term trends,' Srinivasan adds.
Waning winds? Wind pattern is closely linked with the monsoon in India. The country has been receiving low-monsoons over the last decade; experienced droughts in 2002 and 2004. Studies have found changes in wind patterns over the Indian Ocean. However, scientists cannot link these two.
P V Joseph, former director of imd, in a paper published in Current Science (August 24, 2005), argued that the south westerly winds have decreased in speed. As a result, the paper said, weak monsoon spells have increased by 30 per cent between 1995 and 2003.
A study by M Rajeevan, director of imd's National Climate Centre in Pune, and team, in Current Science (August 10, 2006), said no such evidence was found. It was just a weak monsoon epoch, the researchers claimed.
According to S K Dash of iit Delhi, the difference in force between the south westerlies and south easterlies is decreasing, weakening depressions over the Indian Ocean. His study in Current Science, (May 25, 2004) said while the frequency of low pressures is increasing; the frequency of depressions is decreasing. (see box: Wind way).
Gonu and after imd had predicted southwest monsoon would hit Kerala on May 24, but it reached four days late due to the wind disturbance caused by Gonu. By May 29, it covered south Karnataka and south Tamil Nadu, and the wind pattern over the region became irregular. Instead of moisture-laden monsoon wind, northern parts of the country got hot west-winds from Pakistan and the desert of Rajasthan, intensifying the heat wave.
The influence of Gonu waned only by June 7. The Arabian Sea flow started building up and the Bay of Bengal got the first showers.
imd said Gonu's influence on monsoon was an isolated event, though there have been past instances of stormy developments in the Arabian Sea slowing down the advancement of the monsoon. A similar disturbance was marked over the Arabian Sea in 1979 when a storm disrupted wind advancement over the Indian Ocean, but according to experts, no specific wind pattern has emerged from such occurrences.
Experts say that alame system to study wind patterns can cause much trouble to the country which heavily relies on the monsoon for farming. It is time imd got serious in recording and studying wind data when such aberrations take place.