春夏季我国西北干旱区对周围大气环流和气候“热垫”作用的机理及数值研究

Arid region of Northwest China is a region of strong surface sensible heat transfer in spring and summer, and can be regarded as a "heating pad" region over the Eurasia. The sensible heat flux over this region has an important effect on the variability of the East Asia summer monsoon system, especially on the persistent drought in North China. However, study on the dynamical mechanism of this climatic "heating pad" effect is few at present. This project is going to reproduce surface sensible heat transfer over the arid region of Northwest China with an improved simple biosphere scheme (SiB2) as well as China Meteorological Administration (CMA) data, based on the understanding of thermodynamic parameterization which is determined from the observations by the air-land interaction experiments over the Gobi, desert and sparse vegetation surfaces in the arid region of Northwest China. Reasonable atmospheric reanalysis data will be further selected after a comparison of reanalysis sensible heat flux versus reproduced, and then the important influence of strong sensible heat flux over the arid region of Northwest China in spring and summer on East Asia summer monsoon system will be researched. The dynamical mechanism of its climatic effect will be proposed with a climate dynamics theory. A primary numerical simulation will be carried out to validate this mechanism by using a regional climate model. Therefore, the heating pad characteristics of this arid region in spring and summer and its important effect on the East Asia summer monsoon system should be idendified in this project, and new forecast factor might be supplemented to improve the prediction skill for the East Asia climate anomaly.

我国西北干旱区在春夏季有很强的感热输送，是欧亚大陆的一个"热垫"区域，此区域的感热对东亚夏季风系统的变异特别是华北地区的持续干旱有重要影响，目前对此气候热垫作用的动力机理研究还不多。为此，本项目根据对西北干旱区戈壁、沙漠和稀疏植被等下垫面陆-气相互作用观测试验的资料和热力学参数化的认识，通过陆面过程模式结合我国台站资料的模拟再现我国西北干旱区的感热输送；在此基础上，同再分析资料中感热的比较，选取合适的再分析大气资料，研究西北干旱区春夏季高感热对东亚夏季风系统的重要影响，并根据气候动力学理论揭示其气候效应的动力机理和进行初步的数值模拟。通过本项目研究，可以进一步认识春夏季我国西北干旱区的热垫特征及其对东亚夏季风系统的重要作用，并可能为提高东亚季风气候异常的预报水平增添新的预测因子。

我国西北干旱区在春夏季有很强的地表感热输送，是欧亚大陆的一个“热垫”区域，此区域内的感热变化对东亚夏季风的变异特别是华北地区和长江流域的降水变化有重要影响。本项目基于野外观测分析了我国西北干旱区陆-气相互作用，再现了我国西北干旱区的夏季感热变化，评价了六套再分析资料的地表感热通量，还分析了地表感热输送变化对大气环流的影响及其对东亚气候的影响。通过本项目的研究，进一步揭示了干旱区陆面过程参数的特征，特别是热力输送特征，有助于更好认识我国西北干旱区的感热变化，而且，也为优化陆面过程模式的参数化方案和改进陆面模式的模拟能力提供参考；评价了6套再分析的感热资料，结果显示ERA-Interim资料相对较为合理，这主要是由于相对合理的地表参数设置和通量参数化方案，此资料可以用于该区域陆-气相互作用研究；此外，西北干旱区地表感热输送与东部夏季降水异常可以通过沿欧亚大陆上空副热带急流传播的“丝绸之路”型遥相关波列相关联，这种大气遥相关模态对于研究干旱区的地表感热输送对东亚气候影响具有重要的意义。