Overview
A recent study in Nature Communications warns that a shift to a cooler, negative phase of the Pacific Decadal Oscillation (PDO) could increase the frequency of equatorial‑origin cyclones during the post‑monsoon months. The last major event of this type was Cyclone Okchi (2017), which caused severe damage in Kerala, Tamil Nadu and Sri Lanka.
Key Developments
- The study finds a 43% decline in equatorial cyclones during 1981‑2010 compared with 1951‑1980, linked to a positive PDO phase.
- Since 2019, the PDO has entered a negative (cooler) phase, which may favour more cyclones near the equator.
- An ENSO is currently in an El Niño phase, causing rainfall deficits of 7% in central India and 17% in southern India.
- Researchers R.S. Ajayamohan and M. Rajeevan note that a negative PDO combined with El Niño could increase moisture and intensity of cyclones near the equator.
Important Facts
- La Niña typically leads to heavy rains, while El Niño causes deficits.
- The PDO’s positive phase (warmer Western Pacific, cooler Eastern Pacific) is detectable only after several years of ocean‑temperature monitoring.
- Equatorial cyclones are rare because the Coriolis force is weak near the equator; warm sea‑surface temperatures can overcome this limitation.
Exam Relevance
Understanding the interaction between PDO, ENSO, and regional cyclonic activity is crucial for several UPSC topics:
- GS II – Climate change and its impact on Indian agriculture and disaster risk.
- GS III – Water resources management, especially monsoon reliability.
- GS IV – Disaster management policies and early warning systems.
- GS I – International scientific collaboration and research institutions.
Way Forward
Policymakers should:
- Strengthen monitoring of long‑term oceanic oscillations like PDO and ENSO through agencies such as the Indian Institute of Tropical Meteorology.
- Integrate PDO phase forecasts into the Indian cyclone warning system to improve preparedness during the post‑monsoon period.
- Enhance coastal infrastructure and evacuation plans in states vulnerable to equatorial cyclones, especially Kerala, Tamil Nadu and Sri Lanka.
- Promote research on the combined effects of PDO and ENSO to refine climate models used for policy planning.
Proactive measures will reduce loss of life and economic damage if equatorial cyclones become more frequent in the coming decade.