The response of the atmosphere to changes in the distribution of vegetation is not completely understood. The Vegetation Effects on Rainfall in West Africa (VERA) project will combine satellite observations with the latest weather and climate models to improve our understanding of how vegetation affects rainfall.
It has been shown that as air masses cross the continent they collect moisture from the forests they travel above, leading to more rain several hundreds of kilometres further downwind. Additionally, there are indications that clearing patches of forest may increase rainfall over the cleared area, but reduce it over the remaining forest. Finally, by controlling the balance between heating and moistening of the atmosphere, the presence of vegetation can affect the pattern of winds that are responsible for bringing moist air from the ocean to the land. This can delay, or extend, the rainy seasons that are so important in shaping the tropical climate.
Atmospheric scientists have struggled for a long time to accurately represent the types of thunderstorms that dominate rainfall in tropical regions (i.e., cumulonimbus storms) within large-scale computer models of the climate system. However, recent advances mean that it is now possible to simulate the entire seasonal cycle at a spatial scale detailed enough to capture these storms properly.
In partnership with the Centre for Ecology and Hydrology (CEH) and the UK Met Office, VERA will be led by Professor Doug Parker and Dr Dominick Spracklen from the School of Earth and Environment at the University of Leeds. In the VERA project, data from satellites will be used, together with the latest weather and climate models, to improve our understanding of how vegetation affects rainfall.
VERA will focus on West Africa, one of the most climatically sensitive regions of the world, and will use observations from the past 30 years to detect whether deforestation has altered rainfall patterns, and examine how the rapid greening of the savannah each year affects the monsoon rains.