Tamil Nadu, for the first time in 110 years, has experienced a continuous run of seven years of positive departure of rainfall during north-east monsoon, Y.E. A. Raj, Deputy Director General of Meteorology, said on Thursday.
Since 2004, the State has recorded excess rainfall in four years – 2005, 2007, 2008 and 2010 and normal rainfall in three years – 2004, 2006 and 2009.
According to meteorological standards, normal rainfall is regarded if the deviation from the anticipated rainfall is in the range of minus 19 per cent to plus 19 per cent. For excess, the deviation has to be 20 per cent and more while, for deficient, it has to be in the range of minus 20 per cent to minus 59 per cent.
The figures of deviation of rainfall for the State are: one per cent (2004); 79 per cent (2005); 15 per cent (2006); 21 per cent (2007) and 31 per cent (2008) 13 per cent (2009) and 42 per cent (2010).
Dr. Raj was addressing a seminar organised by the Chennai chapter of Indian Meteorological Society on the 2010 monsoon.
Emphasising that the State had been witnessing one of the best epochs of north-east monsoon rainfall, he said the other good spells were 1911-1915, 1929-1932 and 1976-1979 when rainfall departure remained on the positive side for four consecutive years. He also pointed out that the State, during 1947-1955, experienced a negative epoch of north-east monsoon rainfall when the departure was on the negative side in all the years with five deficient years. From 1988 to 1992, the State had seen yet another negative spell.
Attributing the delayed arrival of the monsoon last year to the prevalence of La Nina and positive Southern Oscillation, Dr. Raj said that the two factors coupled with anticipated correction in the time series of monsoon rainfall made a section of meteorologists to expect that the 2010 monsoon would be, at best, near normal.
However, what had happened showed that one parameter, howsoever influential, could not help predict accurately the monsoon behaviour.
S.R. Ramanan, Director of the Area Cyclone Warning Centre, said interior parts of the State registered higher rainfall in the early phase of the 2010 north-east monsoon due to various reasons including upper air circulation.
S. Santhanagopalakrishnan, Deputy Director of the State Agriculture Department, said that against the originally programmed food grain production of 112 lakh tonnes, it was now estimated that the actual production would be in the range of 90 lakh tonnes to 98 lakh tonnes.
