A new perspective on continental moisture recycling

There is a long ongoing debate on the extent to which precipitation at a given location depends on terrestrial evaporation. This moisture feedback mechanism over land is referred to as moisture recycling. Most of the research in the past focused on the contribution of evaporation to precipitation within a certain region only. This study makes use of new definitions to study the complete process of continental moisture recycling. Coupled maps are presented on which the regions can be identified which rely heavily on recycled moisture, and the corresponding major moisture supplying regions for precipitation over land. An accounting procedure based on ERA-40 reanalysis data is used to calculate moisture recycling ratios. As such, this research derives new information from existing data. It is estimated that on average 38 % of the precipitation over continents has evaporated from a land surface and that 52 % of all terrestrial evaporation returns as precipitation over land. China is exceptional as its water resources stem for 80 % from moisture evaporated from the Eurasian continent. In South America, the Rio de la Plata basin depends for 70% on evaporation from the Amazon forest. The main source of rainfall in the Congo basin is moisture evaporated over East Africa, particularly the Great Lakes region. The Congo basin in its turn is a major source of moisture for rainfall in the Sahel. Furthermore, this research demonstrates the important role of topography in the Andes and the Tibetan Plateau where local moisture recycling is a key process. The results of this study are particularly relevant to better understand global scale implications of regional land-use changes related to socio-economic developments (e.g. currently ongoing deforestation for energy crops).