Four trends redefining the North Indian Ocean’s storm cycle, Pg11

Key Highlights:

• The frequency of cyclonic disturbances in the North Indian Ocean shows an inverted U-shaped trend from 1900-2025.
• The Bay of Bengal has seen a sharp decline in cyclonic disturbances, while the Arabian Sea has experienced an increase.
• The severity of cyclonic disturbances has intensified, with a higher percentage reaching severe cyclonic storm status.
• There's a shift in seasonality, with more disturbances in the Bay of Bengal originating in October-December.

Detailed Insights:

• From 1900 to 1920, the 10-year rolling average of cyclonic disturbances remained below 10, surging to over 15 by the 1930s, then declining sharply in the 1980s and 1990s, reaching a low in the 2000s.
• The overall decline in disturbances is primarily due to reduced activity in the Bay of Bengal, although it remains the primary source of disturbances in the North Indian Ocean.
• Disturbances originating in the Arabian Sea are historically more likely to intensify into severe cyclonic storms compared to those in the Bay of Bengal.
• Warmer ocean temperatures, particularly in the Arabian Sea, provide more energy to tropical storms, leading to stronger and less predictable cyclones.
• Before the 1980s, cyclonic activity in the Bay of Bengal was concentrated between July and September, but it has since shifted to October-December.

Key Concepts Involved:

• Cyclonic Disturbance: A low-pressure area in the atmosphere that can develop into a cyclone.
• Severe Cyclonic Storm: A cyclonic disturbance with wind speeds between 89-117 kmph.
• Seasonality: The timing and frequency of events that occur regularly during specific seasons.