Abstract:Aims Annual or long-term actual evaporation and its response to precipitation pattern are poorly known. Our aims are to estimate average annual surface evaporation of bare sand dunes and explore the relationship between precipitation pattern and annual evaporation variance. Methods Based on a meta-analysis of previous experiments, we used a process-based model to calculate the evaporation (EV) of bare sand dunes in Maowusu from day to multiyear scales. We also developed a simple Rainfall-EV model driven by amount and frequency of rainfalls, by which we explored the relationship between intensify of rainfall events and variance of annual evaporation. Important findings The process-based model yielded reasonable short-term evaporation pattern after rainfalls and accumulative evaporation. The long-term average of evaporation from 1959 to 1992 is 166 mm, accounting for 56% of annual precipitation. Although there is no significant change of annual precipitation, the actual evaporation increased significantly with a tendency of 1.30 mm•a－1. We suggested the significant increase (0.69 mm•a－1) of small rainfall events (<5 mm) was the dominant reason of the increase of annual actual evaporation. The frequencies and amounts of strong rainfall contributed more to annual precipitation than annual evaporation, while weak rainfall events (<12 mm) kept relatively constant among years, providing about 100 mm evaporation. These resulted in less variance of annual evaporation than precipitation. Since the precipitation pattern among years apparently will influence annual evaporation, the simple Rainfall -EV model is able to predict annual evaporation effectively.