THOOTHUKUDI: Though rainfall was predicted several times for the coastal district during this northeast monsoon, Thoothukudi has recorded over 30%short of the average rainfall usually received between October 1 and December 3. Weather researcher and professor T Raja attribute the low rainfall to the prevalence of negative IOD (Indian Ocean Dipole), which is the difference in sea surface temperature, over the Indian Ocean.
Rainfall data sourced from the Indian Meteorological Department between October 1 and December 3, shows that Thoothukudi has received only 257.7 mm of rainfall as against the usual figure of 368.6 mm. Though the district received surplus rains between March and September, the downpour was deficient during January and February months (23 mm recorded as against the usual figure of 41.44), and also during the current northeast monsoon season.
It may be noted that rainfall during the rabi season was highly erratic and only eight of the 228 irrigation tanks in the district got filled to their full capacity.
National Farmers Association president Renganayagulu told The New Indian Express that farm regions received less rain, while urban areas witnessed heavy downpours. "It's not yet ascertained how this pattern came to be, perhaps due to climate change," he added.
"As per the rainfall data available from January 1 and till December 3, however, the district received 89.6% of the usual rainfall of 588.2 mm," Raja said.
Raja attributed the deficiency of rain during the NE monsoon to the lower sea surface temperature in the Western Indian Ocean, which failed to attract the two depressions that formed over the Bay of Bengal in November's first and third weeks. "Also the absence of high-moisture easterly winds in the region may have played spoilsport. A new low pressure will be formed over the Bay of Bengal on December 5 which is expected to bring a good spell of showers to north Tamil Nadu, and another low-pressure formation in the third week of December, which may bring rains to south TN.
Predicting more rains in the coming days of the northeast monsoon, Raja pointed to the factors that the negative IOD is likely to become neutral; the Madden-Julian Oscillation (MOJ), an oceanic-atmospheric phenomenon which could trigger low-pressure formation to bring more rains; occurrence of Inter Tropical Convergence Zone at the south of Sri Lanka and the increased surface temperature over Gulf of Mannar. With these forecast downpours, the rain shortage will almost certainly get overcome