One might think that as the planet gets warmer and soil becomes more parched, droughts would become more common. However according to new research from Britain’s Centre for Ecology and Hydrology the opposite may be true. The UK team published a study in Nature this week stating that as soil becomes more parched, afternoon storms are more likely to develop, meaning that droughts are less likely to occur.

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The new research examined hydrological processes across six continents and revealed important implications for the future development of global weather and climate models which, the team believe, may currently be simulating an excessive number of droughts. Looking at imagery from weather satellites, the team tracked the development of storm clouds across the globe and noted when new storms appeared and how dry the ground was. The results were surprising.

Dr Chris Taylor from NERC Centre for Ecology & Hydrology said, “We had been looking at storms in Africa and knew that rain clouds there tended to brew up in places where it hadn’t rained in the previous few days. We were surprised to see a similar pattern occurring in other regions of the world such as the US and continental Europe. In those less extreme climates, with more vegetation cover, we expected the soil wetness effect would be too weak to identify.”

All of their research essentially contradicts existing models which state that rain occurs over wetter soils. The implication is that existing climate models are more likely to go into a vicious circle whereby dry soil decreases rainfall, leading to even drier soil conditions.

Dr Taylor added, “Both heat and moisture are critical ingredients for rain clouds to build up during the afternoon. On sunny days the land heats the air, creating thermals which reach several kilometres up into the atmosphere. If the soil is dry, the thermals are stronger, and our new research shows that this makes rain more likely.”

+ Britain’s Centre for Ecology and Hydrology


Images: USDAgov and bunnygoth