Anticyclones, hanging even now over India, link warming to heat | Explained Premium

The record warming of 2023 has so far not been fully explained since it was much warmer than expected just from the superposition of El Niño on global warming; the rest could be due to anticyclonic circulations.

The complexities of the ways in which global warming manifests in local weather continue to underscore the need to model globally but predict locally.

The waning phase of the strong El Niño of 2023 brings the expected warm temperatures across the globe — while cooler temperatures spread from Pakistan across India to West Bengal during March. This band remained cool throughout 2023 even as record temperatures made relentless headlines.

What do the heat waves have to do with global warming?

Global warming also creates unique features locally that modulate heat waves on top of cool background temperatures. Heat waves over India have been of special concern this season because of the general elections. Some persistent circulation patterns have been creating heat waves and this pattern should serve as another focal point for improving predictions.

It was apparent in March that the anticyclonic circulations over the North Indian Ocean were the drivers of unusual rainfall over Odisha. An anticyclone has winds moving in a clockwise direction, with air sinking down in the middle of it. As this air hits the ground, it is compressed and warmed and can create a high pressure heat dome. An anticyclonic circulation could also explain the historic Dubai floods of April 17.

And these anticyclones exist over the North Indian Ocean and the Indian subcontinent even now.

The persistence of the anticyclones is not unusual in and of itself. During the pre-monsoon season, the upper-level Indian Easterly Jet (IEJ) begins to take shape in the upper atmosphere, at around the 10 degrees N latitude, across the Arabian Sea, peninsular India, and the Bay of Bengal. A strong westerly jet exists to the north around 30 degrees N, and the two together can generate an anticyclonic pattern over the Indian Ocean and the Indian subcontinent.