‘Cyclones over Arabian Sea on the rise due to global warming’
NEWDELHI:THE unusually high number of cyclones in the Arabian Sea, some of them extremely severe with wind speeds higher than 167 kmph, are a result of warming seas and changes in sea surface temperature distribution, says Hiroyuki Murakami, a climate scientist at the US National Oceanic and Atmospheric Administration’ Geophysical Fluid Dynamics Laboratory, told
in an interview. His paper in the journal Nature in 2017 was among the first to make these linkages. According to India Meteorological Department, the ratio of cyclones in the Arabian Sea and the Bay of Bengal is normally 1:4. But this is set to change. both weak and intense storms) is two per year between 1998-2019 in the Arabian Sea.
Regarding the increase in ESCSS during the post-monsoon season, we found three factors may be related. One is the rising sea surface temperature, especially over the Arabian Sea. This warm ocean contributed to intensifying cyclones, leading to more severe storms in the Arabian Sea. The second factor is that onset of winter monsoon is delaying, leading to a longer storm season. The last factor is increases in anthropogenic aerosols, leading to changes in sea surface temperature distribution that in turn change monsoon circulation, resulting in more active storms.
In general, when global warming proceeds, the surface ocean gets warmer. This warm condition is favourable for intensification of tropical cyclones. But increasing greenhouse gasses also cause warming in the upper atmosphere, that makes the atmosphere more stable.
This stable atmosphere is unfavourable for tropical cyclones. But once a storm generates, the storm can develop into an intense storm due to the warmed surface ocean. Above discussion is generally applied to global tropical cyclones. But when we discuss regional tropical cyclones, it is more complex. Some regions get more active storms by changing circulation whereas some regions get less active. Expecting changes in regional tropical cyclones contain a lot of uncertainty.
Yes, especially during the post-monsoon season. Our climate models suggest an increasing frequency of severe storms over the Arabian Sea during the postmonsoon season, as we have reported in our paper.