El Niño-Southern Oscillation (ENSO) which is the climate pattern involving warming or cooling sea surface temperatures in the Pacific has immense influence on the formation of tropical cyclones globally. A new study involving Florida Tech shows that in the Bay of Bengal is a discovery that should help extend the lead time of seasonal predictions for cyclones that form in that region.
ENSO influence on Bay of Bengal cyclogenesis confined to low latitudes was published last month in the Nature journal npj Climate and Atmosphere Science. The study found that with little to no impact on cyclones that form further away from the equator.
40 percent of Bay of Bengal cyclones are near-equatorial cyclones. These storms can be extremely costly in terms of lives lost and damage done. A near-equatorial cyclone in November 2017 named Ockhitraveled over 1,200 miles and devastated parts of Sri Lanka and India with the loss of at least 218 people and $920 million in damages.
Any progress in understanding such cyclones can make a huge impact on the Indian subcontinent. It is said by Pallav Ray, a meteorologist and associate professor in ocean engineering and marine sciences at Florida Tech and a co-author of the study.
There is a second climatic phenomenon that has significant influences on year-to-year fluctuation in the tropical cyclone frequency in the Indian Ocean, the Indian Ocean Dipole (IOD). This is similar to ENSO in that it involves warming and cooling of the eastern and western equatorial waters. But this happens in the Indian Ocean.
The study found that the teleconnection between ENSO/IOD and Bay of Bengal cyclone frequency is confined in the near-equatorial region with little to no influence for cyclogenesis. Further away from the equator during ENSO and IOD except during negative IOD. Changes in the low-level winds in the equatorial region were found to be the most critical parameter influencing such cyclogenesis.