Cyclones over Arabian sea on rise due to global warming
Date: 07 June 2020 Tags: Geography & EnvironmentIssue
The unusually high number of cyclones in the Arabian Sea, some of them extremely severe with high wind speeds, is a result of warming seas and changes in sea surface temperature distribution.
Background
According to India Meteorological Department, the ratio of cyclones in the Arabian Sea is normally 1:4. But this is set to change due to other new factors.
Details
-
The number of extremely severe cyclonic storms (ESCSs) over the Arabian Sea since 1998 is increasing especially during the post-monsoon season (October-December). The climate models suggest this increase is largely due to global warming.
-
Regarding the increase in ESCSs during the post-monsoon season, scientists 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 favorable for intensification of tropical cyclones.
-
But increasing greenhouse gasses also causes warming in the upper atmosphere, which makes the atmosphere more stable. This stable atmosphere is unfavorable for tropical cyclones.
-
Therefore, the frequency of tropical cyclone genesis would decrease when global warming proceeds. But once a storm generates, the storm can develop into an intense storm due to the warmed surface ocean.
-
The climate models suggest an increasing frequency of severe storms over the Arabian Sea during the post-monsoon season, especially during the post-monsoon season.