VERA project to investigate impact of tropical forests on rainfall

LEAF scientists from the School of Earth and Environment have been awarded a NERC grant to study the complex interactions between tropical forests and rainfall. The Vegetation Effects on Rainfall in West Africa (VERA) project will be led by Professor Doug Parker and Dr Dominick Spracklen at the University of Leeds, in partnership with the Centre for Ecology and Hydrology (CEH) and the UK Met Office.

How the atmosphere responds to large scale vegetation, and changes to its distribution, is not completely clear. It has been shown that as air masses cross the continent they collect moisture from the forests they travel above, leading to more rain further downwind. Additionally, studies indicate that clearing patches of forest may actually increase rainfall over the cleared area, but reduce it over the remaining forest. Finally, 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 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 changed rainfall, and examine how the rapid greening of the savannah each year affects the monsoon rains.