青藏高原地表感热估算及对东亚副热带夏季风和中国旱涝的影响

The change of the surface sensible heat in Qinghai-Tibet plateau has an important effect on East Asia even the global atmospheric activities. In recent years, frequent droughts bring serious influence on the people's production and life in southwest area of China. The goal of this project is trying to get a better estimation scheme of regional surface sensible heat flux in the Qinghai-Tibet Plateau and study its influence mechanism on the East Asian subtropical summer monsoon activity and the droughts and floods in China. It is the key point of the surface sensible heat flux calculation that how to apply the surface thermal drag coefficient (Ch) from local values to regional scope. So we will do the following works: (1) Studying the estimation method of regional scope Ch in different underlying surfaces of Plateau using the ground meteorological observation data from field experiment over the Qinghai-Tibet Plateau in recent years and the normalized difference vegetation index (NDVI) data observed by the National Oceanic and Atmospheric Administration (NOAA) remote sensing satellites. (2) Estimating the surface sensible heat flux in plateau region by the optimal parameter fitting scheme and comparative analysis the temporal and spatial variation characteristics with the existing multiple surface sensible heat flux data of plateau. (3) According to the soaking rainfall standard, studying the relationship between the interannual and interdecadal changes of the East Asian subtropical summer monsoon activity and the droughts and floods in Eastern China. (4) Detailed studying the influence of surface thermal transfer anomaly in the plateau on the East Asian subtropical summer monsoon activity and drought and flood in China, forming a concept model and through the numerical test to verify it. The study results will provide important information for plateau climate dynamics, and provide theoretical foundation for short-term climate change and climate prediction research, and also provide scientific basis for disaster prevention and mitigation of China.

本项目试图得到青藏高原区域尺度地表感热较准确的计算方案，研究高原感热异常对东亚副热带夏季风活动和中国旱涝影响的物理过程。由于地表热力拖曳系数Ch值由“点”到“面”的推广研究是区域尺度地表感热计算的关键。为此，项目将（1）利用较新的青藏高原野外试验地面观测资料结合卫星遥感归一化植被指数（NDVI）资料，对高原不同下垫面区域尺度Ch值的估算方案进行探索研究；（2）利用得到的最优参数化方程计算高原长时间序列地表感热通量，并与现有多种高原感热资料进行时空变化特征的比较分析；（3）依据透雨量标准，研究东亚副热带夏季风活动的年(年代)际变化与我国东部旱涝分布的关系；（4）重点研究高原地表感热异常对东亚副热带夏季风活动和中国旱涝的影响及其途径，给出概念模型，并通过数值试验加以验证。研究结果将为高原气候动力学研究提供重要资料信息；为我国短期气候变化和气候预测研究提供理论基础，为国家的防灾减灾提供科学依据。

利用卫星遥感NDVI资料结合青藏高原野外试验地面观测资料，通过多种试验，确定了针对青藏高原中东部不同草甸下垫面的Ch-NDVI 参数化关系式；给出了各季高原中东部区域尺度地表Ch值的分布；完成了高原中东部地面感热通量的计算，得到了1981年7月至2012年12月历年各月地面感热通量序列；将其与再分析感热资料和阳坤等计算的感热序列进行了对比分析，在此基础上对其时空分布特征及异常变化规律进行了系统地研究；建立了可以较好表征高原中东部地面热状况的地表感热强度距平指数；研究了东亚副热带夏季风的爆发、推进和撤退过程和我国东部夏季雨型变化特征及其与青藏高原冬春季地面感热异常的联系和机制：当高原冬、春季地面感热异常偏强（弱）时，东亚副热带夏季风爆发时间异常偏晚（早），推进速度异常偏快（慢），北边缘带位置异常偏北（南），季风在北边缘停滞的时间异常偏长（短），中国东部夏季雨带异常偏北（南），多出现II（III）类雨型。建立了中国东部夏季雨型预测的概念模型，可为我国汛期降水预测和防灾减灾提供科学依据。