陆面反馈对西南干旱的影响

The droughts occurred frequently over Southwest China can have dramatic societal,economic, and ecological consequences. However, current models and methods show little skill in predicting Southwest China droughts on the seasonal timescale due to our limited understanding of key physical processes involved. Land surface conditions, in particular soil moisture and vegetation, can influence regional climate over Southwest China through their effects on exchanges of energy,moisture and momentum between the land surface and the overlying atmosphere and resulted changes in regional atmospheric circulations. However, the role of land-atmosphere interactions in Southwest China drought is not yet well understood. The goals of the proposal are to understand the role of land surface feedbacks in Southwest China droughts and to apply land surface information to improve seasonal prediction skills of the droughts by both statistical analyses to available data and high-resolution regional climate model simulations.We will investigate the relationships of Southwest China droughts to soil moisture and vegetation by using station observations,multiple sensor remote seasing data, land surface assimilation products, and reanalysis data.Then, we will explore the physical processes responsible for soil moisture and vegetation feedbacks on Southwest China droughts through both statistical analyses and high-resolution WRF simulations. Finally, we will develop empirical prediction models to test the role of antecedent soil moisture and vegetation conditions in improving the seasonal prediction skills of Southwest China droughts.

我国西南地区频繁发生的干旱灾害对社会、经济和自然生态系统造成了严重损失。但是，由于对影响西南干旱的关键物理过程认识不足，目前预测西南干旱的水平很有限，远不能满足国家和社会需求。陆地表面状况-尤其是土壤湿度和植被-调节着界面的能量、物质和动量交换，进而影响西南地区的气候。但是，目前对陆-气相互作用对西南干旱的影响尚缺乏足够的认识。本项目利用观测资料、卫星遥感数据、陆面同化数据和再分析资料分析前期和同期土壤湿度和植被状况与西南干旱的联系；通过高分辨率区域气候模式模拟结合统计分析，揭示陆面反馈影响西南干旱的物理过程；提出对预测西南干旱有先兆意义的土壤湿度和植被物理因子，并建立统计回归模型测试前期陆面因子对提高西南干旱季节预测技巧的作用。

我国西南地区的干旱灾害频仍发生，对当地的农业、水资源、生态系统和人民的健康产生严重影响。但是，由于对影响气候异常的关键物理过程的认识不足，在区域尺度上准确预测干旱仍是一个重要的科学挑战。陆地表面状况在季节及以上时间尺度上具有记忆气候异常的能力，因而对提高季节气候预测有潜在价值。本项目旨在揭示陆面因子包括土壤湿度、土壤温度和植被对我国西南干旱的影响，提出对预测我国西南干旱有先兆意义的关键陆面物理因子。利用站点观测、遥感数据、陆面同化数据与再分析资料的统计分析表明土壤湿度、土壤温度和植被变化与我国西南地区干旱存在滞后和同期相关关系。区域气候模式模拟表明，同期和前期的关键陆面因子能够对西南地区干旱产生重要影响。利用统计分析和区域气候模式长期模拟相结合的方法，揭示出陆面状况的改变对我国西南地区干旱具有局地和非局地的影响。土壤湿度、土壤温度和植被的异常能够对表面的能量和水分平衡产生重要影响，进而对西南地区的区域大气环流产生作用。筛选出了可用于西南干旱预测的前期关键陆面因子，主要包括西南地区和青藏高原南部的土壤湿度，西南地区、青藏高原东部以及中南半岛西部土壤温度和青藏高原东部以及四川北部的植被指数。建立了线性回归模型并测试了这些关键陆面因子的作用，后报试验表明这些前期陆面因子在我国西南干旱预测中的有用性。研究结果有助于提高预测西南干旱的能力，并降低干旱灾害的危害。