The threat of tropical cyclones is a growing concern worldwide. However, an interesting phenomenon has been observed in the North Indian Ocean, where cyclone activity has experienced a significant decline. In a new study published in Nature Communications, researchers shed light on this decline and its potential implications. The study, titled “Pacific Decadal Oscillation Causes Fewer Near-Equatorial Cyclones in the North Indian Ocean,” provides insights into the factors contributing to this decline and explores the expected increase in cyclone activity in the coming decades.
The research, led by Pallav Ray, an associate professor of meteorology at Florida Tech, involved collaboration with researchers from prestigious institutions such as New York University Abu Dhabi and McGill University. By analyzing cyclone formations in the North Indian Ocean between 1951 and 2010, the study revealed a remarkable 43% decline in low latitude cyclones (originating between 5–11 degrees) from 1981 to 2010 compared to the previous three decades.
The Influence of Pacific Decadal Oscillation
The main factors attributed to this decline are the weakened low-level vorticity modulated by the Pacific Decadal Oscillation (PDO) and increased vertical wind shear. The PDO refers to the long-term fluctuation in sea surface temperature of the North Pacific Ocean, which undergoes “cool” and “warm” phases every 20 to 30 years. During the “cool” phase, cyclone formations are inhibited due to reduced low-level vorticity and stronger wind shear.
The Role of Equatorial Wind Pattern
Tropical cyclones are not easily formed near the equator but can intensify rapidly once initiated. The wind pattern in the Indian Ocean plays a crucial role in initiating cyclone spin near the equator. The presence of storm-weakening wind shear restricts the movement and intensification of cyclones. Therefore, understanding these wind patterns is vital for adequate preparedness in communities at risk.
The significance of this research lies in increasing awareness and preparedness for rapidly intensifying storms originating near the equator. Cyclone researchers primarily focus on the Atlantic, where such storms are relatively rare. By shining a spotlight on these types of storms in the North Indian Ocean, the study aims to generate more interest and facilitate better preparation strategies for communities at risk.
Origins of the Research
The inspiration for this study stems from the devastating 2017 Cyclone Okchi, which formed near the equator, passed through Sri Lanka and India, and caused the loss of 884 lives. Pallav Ray, a native of India and one of the co-authors, recognized the prevalence of storms originating near the equator for the first time. This realization sparked the investigation into the decline of cyclonic activity in that region.
Future Implications
Although there has been a decline in cyclone activity near the equator, the research also highlights an increase in cyclones away from the equator in the Indian Ocean overall. Natural variability and climate change contribute to these fluctuating patterns. In light of the expected increase in cyclone intensity and frequency due to warming along the equator and a favorable phase of the PDO, appropriate planning and mitigation strategies are necessary.
Previous Research on Cyclonic Formation
Pallav Ray has previously conducted research on cyclonic formation, including a paper published last year on the El Niño-Southern Oscillation in the Indian Ocean. This study contributed to understanding the influence of this climate pattern involving sea surface temperature fluctuations in the Pacific on the formation of tropical cyclones in the Bay of Bengal. The findings suggested that the impact of El Niño-Southern Oscillation is geographically confined to this specific region, which has implications for seasonal predictions and preparedness.
The decline in cyclone activity near the equator in the North Indian Ocean, as revealed by the study, highlights the complex interplay between climatic patterns, such as the Pacific Decadal Oscillation, and the formation of cyclones. As the threat of tropical cyclones continues to increase globally, understanding regional variations and forecasting their intensity and frequency becomes crucial for effective disaster management and preparedness. The findings of this study should serve as a call to action for further research and collaborative efforts to mitigate the risks associated with cyclones in the North Indian Ocean region.
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