青藏高原全天空地表辐射收支与热状况的卫星遥感估算研究

Land surface radiation budgets over the Tibetan Plateau is the power source of the land-atmosphere mass and energy exchange process. They have important impacts on the land surface radiation balance, energy balance, the formation and change of weather or climate. But for a long time, the accuracy of the surface radiation balance components cannot meet the needs of practical application. Especially,there is a lack of times series data of surface radiation flux and soil heat flux under all sky conditions, which further limits the quantitative understanding of the Tibetan Plateau's surface heating effects. Therefore, based on multi-source satellite data (MODIS, SPOT and AMSR-E) and in situ bservation network(CAMP/Tibet,TORP), by using remote sensing retrieval, satellite parameterization and statistical analysis methods, a set of parameterization scheme for land surface radiation components and soil heat flux under all sky conditions will be developed and validated. The time series data of surface radiation components, soil heat flux and surface heating field with high spatial resolution and precision will be constructed as well. The spatio-temporal variations of plateau surface radiation balance and surface heating field will be revealed. What will also be identified are effects of soil water freezing and thawing process on the surface energy budgets and heating field during seasonal transition periods.Therefore this research will improve the simulation accuracy of the atmospheric circulation model and regional climate model. It will also make contribute to give an insight into energy and water cycle processes over the Tibetan Plateau and their influences on weather and climate.

青藏高原地表辐射收支是地气系统物质和能量交换过程的源动力，对地表辐射平衡、能量平衡和天气气候的形成和变化具有重要影响。但长期以来，地表辐射平衡各分量的精度难以满足实际运用的需求，尤其是缺乏全天空条件下的地表辐射各分量和地表土壤热通量时间序列资料，这也进一步限制了对青藏高原地表热源作用的定量理解。为此，本研究将在多源卫星数据（MODIS、SPOT、AMSR-E）和高原野外观测网络（CAMP/Tibet,TORP）的支持下，采用卫星遥感参数化和统计分析相结合的方法，发展全天空条件下青藏高原地表辐射平衡分量和土壤热通量的参数化方案，建立高分辨率、高精度地表辐射分量、土壤热通量及地表加热场的时间序列资料，揭示全天空条件下高原地表辐射收支和热源时空变化规律及季节转换时段土壤水分冻融过程对地表辐射收支和加热场的影响。从而为提高模式的模拟精度、深入理解高原能量和水分循环过程及高原的天气气候影响做出贡献。

青藏高原地表辐射收支是高原地气系统物质和能量交换过程的源动力，对地表辐射平衡、能量平衡和天气气候的形成和变化具有重要影响。但长期以来，地表辐射平衡各分量的精度难以满足实际运用的需求，尤其是缺乏全天空条件下的地表辐射各分量的时间序列资料，这也进一步限制了对青藏高原地表热源作用的定量理解。为此，利用高空间分辨率极轨卫星（Landsat ETM+）、高时间分辨率静止卫星（FY-4A AGRI）以及SPOT和MODIS数据，结合青藏高原综合立体观测网络数据和气象驱动资料（CLDAS-V2.0、ERA5等），发展了针对青藏高原非均一下垫面类型的地表特征参数和地表湍流通量的估算方法，建立了青藏高原全域高时空分辨率的地表特征参数和地表热通量产品，将青藏高原地表特征参数空间分辨率升至30 m，将地表热通量时间分辨率提升至小时尺度。在此基础上，进一步利用时间序列谐波处理算法对地表特征参数进行去云与重建处理，建立了青藏高原无云影响的植被指数数据集。发现高原在增温的同时，伴随着生态好转，高原总体呈现植被指数增加的趋势。发展了适用于青藏高原的全天空下行短波辐射通量和长波辐射通量的卫星遥感估算方案，新方法不需要考虑复杂的辐射传输过程，输入参数少，计算简便而且精度较高。全天空下行短波辐射和下行长波辐射的均方根误差分别为77.34W⋅m^-2 和19.19W⋅m^-2，平均百分比误差分别为-4.75%和0.11%，其时空变化和下垫面状况吻合。通过和已有主流辐射产品的对比表明，新产品的空间分辨率和精度均较高。项目以上研究成果可为深入理解高原能量和水分循环过程及高原的天气气候影响做出贡献，进而为高原自然灾害风险评估和风险防范服务，促进第三极地区的防灾减灾和可持续发展。