中国干旱半干旱区降水集中度变化对陆面过程关键参量的影响研究

土壤湿度和地表蒸散是干旱半干旱区陆面过程最为关键的参量，其变化对该地区陆气相互作用过程有重要影响。近几十年中国干旱半干旱区的降水年内集中度显著减小，这势必会对该地区的土壤湿度和蒸散产生作用，但目前我们对其影响事实和作用机理仍缺乏全面认识和深刻理解。基于此，该项目拟利用观测、遥感、再分析资料及陆面同化数据（GLDAS）等多源数据，结合陆面模式的数值模拟，开展降水集中度变化对陆面过程关键参量土壤湿度和蒸散的影响研究。首先，利用观测资料，分析降水集中度及相关降水过程的变化特征；其次，通过多源数据的对比分析，研究降水集中度变化与土壤湿度和蒸散变化的关联性；最后，基于上述结果构建不同降水集中度和年降水量变化的试验方案，利用陆面模式数值模拟揭示土壤湿度和蒸散对降水集中度变化的响应机制。该研究的实施将深化对干旱半干旱区陆气相互作用过程及机理的认识，为该地区应对气候变化及区域可持续发展提供科学支撑。

Soil moisture and evapotranspiration play as the most crucial variables in land surface processes in arid and semi-arid region. Their variability directly affects the land-atmosphere interaction. During the recent decades, dramatic descending trends were observed in the intra-annual precipitation concentration degree over the arid and semi-arid region in China. However, their impacts on the regional soil moisture and evapotranspiration and the corresponding mechanisms remain unclear. In this context, this project aims to investigate to what extent and how the changes in precipitation concentration degree affect key variables in land surface processes over this region, using multi-source data from observation, remote sensing, reanalysis and the Global Land Data Assimilation System (GLDAS), combined with land surface modeling. Firstly, the characteristics of variations in precipitation concentration degree and the relevant precipitation processes will be revealed by analyzing the observational data. Secondly, their relationships with the changes in soil moisture and evapotranspiration will be examined by comparing multi-source data. Finally, based on these results, different sensitive experiments that vary in precipitation concentration degree and annual amount will be designed and conducted with a land surface model. These simulations will be investigated to reveal the responding mechanisms of the soil moisture and evapotranspiration under different precipitation concentration conditions. The results of this study would lead to a better understanding on the processes and mechanisms of land-atmosphere interaction over the arid and semi-arid region, providing information for addressing regional climate change and sustainable development.