Influence of land surface aridification on regional monsoon precipitation in East Asian summer monsoon transition zone

摘要

The East Asia summer monsoon transition zone, a unique area of transition from humid monsoon to arid continental climate, has the most prominent aridification in the world, and has experienced land surface aridification (LSA) in recent years. To investigate the influence of LSA on regional monsoon precipitation, two numerical experiments were run for vegetation degradation over a long period (30 years). Then, precipitation variation of different magnitudes was analyzed. After that, the mechanism of LSA influence on precipitation was studied. The results show that aridification reduced average summer precipitation by 5%. Additionally, LSA considerably changed the frequency of precipitation. Unlike aridification in North Africa caused by albedo variation, LSA in our study area mainly reduced surface thermal capacity, increased surface temperature, sharply increased the transport of surface sensible heat, and raised the atmospheric convective boundary layer. This reduces atmospheric moist static energy, which is not conducive to the generation of precipitation. LSA also increases the surface landscape gradient, local horizontal gradient of land surface turbulent flux, and probability of heavy convective precipitation. This paper reveals the mechanism by which land surface anomalies affect precipitation, which lays a foundation for follow-up studies.