The Hindu Business Line : El Nino may hit monsoon next year

Latest indications that El Nino conditions are intensifying and may likely continue through April-June 2007 are likely to cast a spell over next year's (2007) Indian monsoon.

Expectations were that the nascent El Nino would die out early next year, ensuring `safe passage' for the ongoing northeast monsoon and the southwest monsoon that followed six months hence.

But latest updates from the US National Oceanographic and Atmospheric Administration (NOAA) seem to suggest otherwise. It said that based on recent trends and majority model forecasts, El Nino conditions should intensify during the next three months and will likely continue through April-June 2007.

ON ALERT

This is enough to make climatologists sit up and take notice, says Dr Akhilesh Gupta of the Department of Science and Technology.

A developing El Nino has to be put on a constant `monitoring-cum-prediction' mode and assessed for intensity and likely impact on global and regional climate, he said.

Allowing for a lag effect of one month from the time of the latest assessment, the likely El Nino shadow should ideally not grow past a threshold timeline of March/April of 2007. Anything beyond this should naturally be cause for some worry.

Which is likely to be the case, given NOAA's projections extending into April-June 2007. The fact that there is still no conclusive evidence of a direct cause-effect connection between an El Nino and a prevailing Indian monsoon provides cold comfort.

LOCAL SYSTEM

A more crucial signal to look forward to will be the Indian Ocean Dipole (IOD), says Dr Gupta. This is a localised, seesaw ocean-atmosphere system developing in the equatorial Indian Ocean. IOD will have immediate impact on the evolving weather in the region. It has a `positive' phase and a `negative' phase as wind patterns change in the equatorial Indian Ocean from April-May and the dipole peaks in October.

A positive dipole will have winds blow from east to west. These anomalous winds drive changes in the ocean currents, making the Arabian Sea off the Somali coast in Africa unusually warm, enhancing cloud formation, while eastern Indian Ocean around Indonesia becomes colder than normal and more dry.

In a negative dipole year, the reverse happens and the Arabian Sea near Africa becomes cooler and less cloudy while the Indian Ocean is warmer and wetter around Indonesia. This would adversely impact rainfall over India.

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