Effects of surface wind speed decline on modeled hydrological conditions in China

Abstract

Abstract. Surface wind speed decline in China has been widely reported, but its effects on hydrology have not been fully evaluated to date. In this study, the effects of wind speed change on modeled hydrological conditions are investigated using the Variable Infiltration Capacity (VIC) hydrological model for China during the 1966–2011 period. Two model experiments, i.e., VIC simulations with the observed (EXP1) and detrended wind speed (EXP2), are performed over the major river basins in China. The differences between the two experiments are analyzed to assess the effects of wind speed decline. Results show that wind speed has decreased by 29% in China. The wind speed decline would have resulted in a decrease in evapotranspiration of 1–3% of mean annual evapotranspiration and an increase in runoff of 1–6% of mean annual runoff at most basins in China. The sensitivities of evapotranspiration and runoff changes to wind speed change are larger in humid areas than dry areas, while the sensitivity of soil moisture change to wind speed change is situation dependent. The wind speed decline would have offset the expansion of the drought area in China. It has contributed to reducing drought areas by 8.8% of the mean drought area (i.e., approximate 106 × 103 km2 out of 1.2 × 106 km2) over China. The reductions of soil moisture drought induced by wind speed decline are large (more than 5% of the mean drought area) in most basins, except in the Southwest and Pearl River basins.