A recent study published in Nature Communications has revealed a concerning decline in cyclone activity in the north Indian Ocean. The research, titled “Pacific Decadal Oscillation Causes Fewer Near-Equatorial Cyclones in the North Indian Ocean,” was conducted by a team of meteorology experts from various institutions, including Florida Tech, New York University Abu Dhabi, and McGill University.
According to the findings, there has been a significant 43% decrease in the number of low latitude cyclone formations (originating between 5–11 degrees) from 1981 to 2010, compared to the period between 1951 and 1980. This decline can be attributed to the weakened low-level vorticity influenced by the Pacific Decadal Oscillation (PDO) and increased vertical wind shear.
The PDO refers to a long-term fluctuation in the sea surface temperature of the north Pacific Ocean. It experiences cyclic variations approximately every 20 to 30 years, transitioning between “cool” and “warm” phases. During the cool phase, the number of cyclones in the north Indian Ocean decreases due to altered wind patterns and intensification processes.
Tropical cyclones are not known to form easily near the equator. However, wind patterns in the Indian Ocean contribute to the initiation of cyclone spin near the equator. The weakened wind shear caused by the Pacific Decadal Oscillation allows storms to move more easily and strengthen rapidly.
The research findings are crucial in developing better strategies for communities residing in cyclone-prone areas. By understanding the factors influencing cyclone intensification, communities can be better prepared and equipped to face these rapidly intensifying storms.
Associate Professor Pallav Ray, one of the co-authors of the study, hopes that this research will stimulate more interest in studying and preparing for these types of storms. He highlights that cyclone research has primarily focused on the Atlantic, where such storms are rare. However, the study demonstrates the urgent need to investigate cyclonic activity in other regions, particularly the north Indian Ocean.
The inspiration for this study came from Cyclone Okchi, a devastating storm that struck Sri Lanka and India in 2017, resulting in the loss of 884 lives. This event shed light on the frequency of storms originating close to the equator. The researchers delved into the data and discovered the decline in cyclone activity in this region.
While the recent findings highlight a decline in cyclone activity near the equator, the study acknowledges an increase in cyclonic activity away from the equator in the Indian Ocean. This indicates a complex and dynamic pattern in cyclonic formations in the region.
With the presence of warming along the equator and a favorable phase of the Pacific Decadal Oscillation, both the intensity and frequency of cyclones near the equator are expected to rise. The study emphasizes the importance of appropriate planning and mitigation strategies to address the changes in tropical cyclonic activity due to natural variability and climate change.
Previous research by Professor Ray has focused on understanding cyclonic formation, including the influence of the El Niño-Southern Oscillation on tropical cyclones in the Indian Ocean. This study specifically relates to the Bay of Bengal, revealing that the influence of this climate pattern is geographically limited. The findings provide valuable information for extending the lead time of seasonal predictions for cyclones in this specific region.
As the threat of tropical cyclones increases worldwide, it is crucial to understand the changing patterns of cyclone activity. The decline observed in the number of cyclone formations in the north Indian Ocean indicates a larger climate trend influenced by the Pacific Decadal Oscillation. This new research highlights the need for further investigation into cyclonic activity near the equator and the development of effective strategies to mitigate the impact on vulnerable communities.
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