Tropical Rain Affects Ocean Stability | 04 Aug 2025

Source: TH 

A new study challenges the belief that tropical rain always makes the ocean surface more buoyant (floating), even though freshwater is less dense than seawater. It reveals that rain can sometimes increase surface stability instead of promoting mixing. 

• Heavy Rain and Role of Cold Pools: A study finds that, during heavy rainfall, the ocean surface becomes heavier and more stable due to cold pools (cold, dry air accompanying rain clouds) that cool the surface by blocking sunlight and transferring heat from the ocean to the atmosphere.  
  • This process counteracts ocean water mixing, leading to more stable conditions. 
• Light Rain Promotes Mixing: For light rainfall (0.2-4 mm/hr), the buoyancy flux is positive, making the ocean surface less stable and promoting mixing of ocean waters. 
• Night vs Day Impact: Rainfall at night is more likely to cause ocean instability compared to daytime rainfall. 
• Geographic Variations: Cold rain zones (Western Pacific & Indian Oceans) have higher heat loss, more stability. The hot rain zone (Central Pacific) has less heat loss. 
• Climate and Weather Predictions: Understanding how rainfall affects ocean stability is crucial for accurate weather and climate predictions, as ocean mixing helps regulate climate by transporting heat, carbon, and nutrients.