On uncommon cyclones in the Arabian Sea

Sub :Geo

Sec: Climatology

Context:

In August 2023, a rare cyclone, Asna, formed from a strong land-born depression transitioning to the warm Arabian Sea, marking the first August cyclone in the north Indian Ocean since 1981.
The depression was notable for its powerful growth over land, feeding off soil moisture from excess rainfall before gaining strength in the Arabian Sea.

Cyclones in the Arabian Sea and Indian Ocean:

The north Indian Ocean is crucial for the summer monsoon, supplying moisture through evaporation from the Arabian Sea and the Bay of Bengal.
Despite being warm tropical waters, the north Indian Ocean sees fewer cyclones compared to other global regions due to a mix of factors that both promote and suppress cyclone formation.

Cyclone Patterns:

The Arabian Sea cools significantly during the monsoon due to strong winds mixing surface waters with cooler subsurface waters.
Low-pressure systems form more frequently in the Bay of Bengal during the monsoon but rarely intensify into full cyclones due to vertical wind shear.
Cyclone activity over the north Indian Ocean occurs primarily in the pre-and post-monsoon seasons, with the Arabian Sea seeing fewer cyclones due to its cooler temperatures and less convective activity.
Despite some reports of increasing cyclone numbers since 2010, the Arabian Sea has been relatively calm in recent years.

Why does the North Indian Ocean have two cyclone seasons?

The Indian Ocean is distinctive for its monsoonal circulation and oceanic tunnels, connecting it to the Pacific and Southern Oceans.
The North Indian Ocean has two distinct cyclone seasons due to the unique monsoonal circulation patterns in the region:
- Pre-monsoon season (March-May): The Arabian Sea warms rapidly during this time as the sun crosses over to the Northern Hemisphere. The Bay of Bengal is relatively warmer and begins producing atmospheric convection and rainfall. This leads to cyclogenesis in both the Arabian Sea and the Bay of Bengal.
- Post-monsoon season (October-December): This is the northeast monsoon season for India. The Arabian Sea cools due to the strong southwesterly winds and mixing of cold subsurface waters. However, the Bay of Bengal remains favourable for The post-monsoon season is the major cyclone season in the North Indian Ocean.

Role of Climate Change:

Climate change intensifies the uniqueness of the Indian Ocean, bringing more heat from the Pacific and Southern Oceans.
Rapid warming in the Indian Ocean influences the global heat balance and cyclone formation, affecting how cyclones respond to climate drivers.

Source: TH