Precipitation recycling using a new evapotranspiration estimator for Asian-African arid regions

Abstract

Local moisture recycling (precipitation recycling) plays a crucial role in precipitation. However, evapotranspiration, the key to precipitation recycling, is difficult to estimate. In this study, restrictions between the evapotranspiration ability and soil moisture (SM) supply are considered, and evapotranspiration estimations from 1981 to 2010 in Afro-Eurasia are examined. The results show that the improved evapotranspiration estimation obtained by correcting the potential evapotranspiration in Afro-Eurasia, especially in the Asia-Africa arid regions, ranges from 0.2 to 1.2 mm day−1, which was less than that obtained using the traditional Penman-Monteith evapotranspiration (PET, which ranges from 1.0 to approximately 11.0 mm day−1). Based on different evapotranspiration estimations, the characteristics of the precipitation recycling ratio (PRR) calculated using the dynamic recycling model (DRM) are analyzed and compared for three arid regions in the Asian-African continent, China-Mongolia (CM), West Asia (WA), and North Africa (NAF), during the precipitation season. A comparison with the results from the PET method reveals that the estimated evapotranspiration and precipitation recycling obtained using the corrected approach was more reasonable than that obtained using the Penman-Monteith method. Overall, the PRR in CM (about 0.7%) and NAF (about 0.5%) shows decreasing trends, whereas the PRR in WA (about 1.0%) increased, which implies that because the local moisture supply increased in WA and reduced in CM and NAF, the drought intensity increased in WA but weakened in CM and NAF. This trend was partially related to increased precipitation recycling that occurred with increased evapotranspiration in WA. Moreover, the negative PRR trend and alleviated drought intensity in CM and NAF implied that precipitation recycling had a negative effect when there was less local moisture supply in the region, and this alleviated the drought intensity in the Asian-African arid regions.