NEW DELHI: Even before the possible threat of El Nino in the latter half, the building up of the negative Indian Ocean Dipole (IOD) event over the Indian Ocean is expected to weaken the monsoon.
The IOD, which affects the strength of monsoon over the Indian subcontinent, is an irregular oscillation of sea-surface temperatures in which the western Indian Ocean becomes alternately warmer and colder than the eastern part of the ocean.
“There are two phases of IOD – negative and positive. While the positive phase assists rains, the negative phase doesn’t. There is a threat that IOD, which is currently slight positive, may turn to negative or neutral,” said DS Pai, director, long-range forecasting, meteorological department.
The IOD phenomenon was first identified by climate researchers in 1999. The positive phase sees greater-than-average sea-surface temperatures and greater precipitation in the western Indian Ocean region, assisting the movement of clouds over India, while the negative phase does the opposite. However, Talim – a tropical depression developed near South China sea – has moved away farther to Japan, minimising the threat to the monsoon.
Talim could have interfered with the monsoon by sapping its energy before fizzling out.
“Talim has gone. Now there will be no influence of Talim on the monsoon. But there are several such tropical activities happening in the Pacific that may influence the monsoon. We can’t count on every activity,” he said.
IMD, which is likely to come out with its updated forecast on Friday, will give a detailed account on phenomena like El Nino and IOD. It will also forecast a region-wise break-up of rainfall besides predicting the behaviour of monsoon in July and August, which are crucial for farming.
Monsoon on Wednesday didn’t show much progress from its Tuesday’s advancement over parts of Vidarbha, Orissa, West Bengal & Sikkim, more parts of Chhattisgarh, south Madhya Pradesh, Bihar and Jharkhand.