Ocean-Atmosphere Connection Causing Unprecedented Rains in Telangana: Meteorologists

Update: 2023-07-27 18:30 GMT
The progress of Tropical Intraseasonal Oscillations over Indian Ocean that brought the heavy spells of rain over Telangana. Currently, the TIO phenomenon is in Phase 5 (PH5). The blue indicates moisture laden cloud bands moving northward from the Equator and onto India bringing heavy rains. The orange and red bands following in Phase 6 to Phase 8 indicate a break phase in the monsoon. ( Image Courtesy: Dr Akshay Deoras, Research Scientist, University of Reading.)

Hyderabad: The extremely heavy rainfall experienced during the past two days has to do with how bands of moisture moved north from the Equator over the Indian Ocean as a result of tropical instraseaonal oscillations that are caused by what meteorologists describe as the “atmosphere and the ocean communicating with each other.”

The rains over Telangana have “definitely been insane,” Dr Akshay Deoras, research scientist at the National Centre for Atmospheric Science, department of meteorology, University of Reading, said on Thursday. Similar heavy spells of rain were experienced in Chennai in 2015 when the metropolis went under water rainfall ranging between 300mm and 500mm in a day, he said.

During an active intraseasonal oscillations (fluctuations) period, with more than the normal cloud bands ranging northwards from the Equator, a lot of moisture is brought with them influencing rainfall when the bands move over coastal India resulting in an active monsoon. This phenomenon also helps in formation of low-pressure systems as was seen over the past few days over the Bay of Bengal resulting in more rain, he said.

Meanwhile, with the atmospheric component of the El Nino, the warming of waters off the western coast of South America was not well established in July which is why the monsoon has not been affected. However, there could be a break in the rains in August and September because the Indian Ocean Dipole —  a complex series of measurements of water temperature and atmospheric interactions along Ethiopia off Africa’s east coast on the one side, and Indonesia on the eastern wing of the Indian Ocean on the other — has not yet turned positive.

“There are no triggers to make the IOD positive. If it turns positive, then the impact of El Nino may not be felt. If it remains in the negative, then El Nino’s impacts are possible resulting in a less active second half of the monsoon,” Dr Deoras explained.


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