THIRUVANANTHAPURAM: The southwest monsoon is showing a decreasing trend in the state. The studies conducted by the research wing of the India Meteorological Department shows that of the 36 sub-divisions, only three, Kerala, Jharkhand and Chhattisgarh, show a decreasing trend.
According to Met Director K Santhosh, the normal rainfall in the state during the southwest monsoon period, calculated during 1961-1990, was 214 mm. However, the normal rainfall is 204 mm now. This is an average of the southwest monsoon during the period from 1971 to 2000. The period from June to September is considered as the southwest monsoon period. The normal rainfall is an average of the amount reported in 30 years.
The IMD study states that in Chhattisgarh, Jharkhand and Kerala significant decrease in rainfall is even observed in annual scale. Santhosh said the southwest monsoon in the state was showing a decreasing trend from 1985. “There is nothing alarming about that. Rainfall pattern in the country shows an epochal variation. By 2025, the amount of rainfall would reach the normal state and would show an increasing trend after that,” he said.
Studies proved that monsoon rainfall displays multi-decadal variations in which there is clustering of wet or dry anomalies. Santhosh said that the change was not part of any climatic variations and, so, not a matter of concern.
Kerala is considered as the gateway of monsoon to the whole country. Southwest monsoon usually sets in by June 1. Weather experts feel that the onset and withdrawal date of monsoon too are changing.
The number of depressions in the Arabian sea, which triggers rainfall in the country, too are diminishing. During last monsoon, the month of August was devoid of depressions.