Cyclonic Storms in North Indian Ocean – UPSC GS1

Context: The intensity of severe cyclonic storms in the North Indian Ocean region has shown an increasing trend in the past four decades.
Why do we need to study the North Indian Ocean?
  • The impact of global warming due to climate change and its effect on extreme weather events such as frequency and high-intensity tropical cyclones formed over global ocean basins is a matter of concern.
  • Severe cyclonic storms have become more frequent in the North Indian Ocean, causing significant risk and vulnerability to the coastal regions.
  • In the recent decade (2000 onwards), an increasing trend in cyclone formation was found to be quite substantial in both Bay of Bengal and the Arabian Sea basins.
Key findings of the study related to North Indian Ocean:
  • The increasing intensity of severe cyclonic storms with major socioeconomic implications was due to atmospheric parameters. This includes parameters like
    • Higher relative humidity (RH), especially at mid atmospheric level,
    • Weak vertical wind shear (VWS)
    • Positive low-level relative vorticity (RV)
    • Suppressed outgoing long wave radiation
    • Warm sea surface temperature (SST).
  • The study also found that the RH, RV, VWS are distinct during pre-monsoon seasons of La Niña, and that favors the genesis of severe cyclone formation over this region.
  • Investigation of the role of additional parameters such as water vapour and zonal Sea Level Pressure gradients revealed the possible linkage of La Niña years on the increased severity of tropical cyclones.
  • The study reported an increased amount of water vapor content in the troposphere, and during the past 38 years at 1.93 times as compared to the base year 1979.
  • During the past two decades (2000-2020), the La Niña years experienced almost double the number of intense cyclones compared to the El Niño years.
Significance of the study:
  • The new findings from this study are expected to augment advanced research in tropical cyclone activity for the North Indian Ocean region
  • The study also provides the scope for a detailed investigation on the possible linkages and teleconnection with other climate indices over the North Indian Ocean.
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