复杂地形区地表短波辐射估算及时空扩展研究

Land surface shortwave radiation is the dominant factor of the surface radiation and the primary driving force of the earth system’s substance and energy cycles. However, the effects of cloud and complex topography haven’t been thoroughly considered in the current global radiation products. Besides, the spatial resolutions of these products are relatively coarse, therefore, they are difficult to meet the needs of applications in many fields. In order to explore these problems step by step, our project will contain the following parts: 1) On the basis of the previous shortwave radiative transfer model established for flat surface, shortwave radiative transfer models for rugged terrain under all sky conditions will be built by coupling the terrain factors with sun–cloud–surface–satellite geometry. The land surface shortwave radiation components with high spatial resolution will be retrieved over rugged terrain using polar orbit satellite data; 2) The parameterized model will be developed over the region scale by combining the cloud fraction cover and statistical terrain factors. The optimum scale of estimating shortwave radiation using this parameterized model will be analyzed; 3) Land surface shortwave radiation components will be estimated using both of the polar orbit and geostationary satellite data for each hour over the optimal spatial scale. The surface shortwave radiation components will be extrapolated throughout a whole day by analyzing their diurnal variation. The daily averaged surface shortwave radiation will be computed, which is more useful for many land process applications; 4) Finally, the proposed shortwave radiation models and inversion algorithms for rugged terrain will be validated under all sky conditions based on both of the three-dimensional real scene computer simulation and field campaigns.

地表短波辐射是总辐射的主导因素，是整个地球系统物质与能量循环的主要驱动力，但是目前的全球辐射产品未充分考虑云和复杂地形的综合影响，且空间分辨率较粗，难以满足实际应用的需求。本项目在已建立的水平地表全天候短波辐射传输模型的基础上，综合考虑太阳-云-地-观测之间的几何关系，耦合地形因素，建立适合复杂地形区的全天候短波辐射传输模型，利用极轨卫星数据，实现复杂地形区高空间分辨率地表短波辐射分量估算；以此为基础，在区域尺度建立云覆盖度和地形统计因子耦合的参数化模型，寻找区域耦合模型估算短波辐射分量的最优空间尺度；结合极轨和静止卫星数据，在最优空间尺度实现1小时分辨率地表短波辐射分量的估算，提取地表短波辐射的日变化特征并进行时间扩展，得到日平均的复杂地表短波辐射；最后，结合计算机真实场景模拟和野外实验对所提出的复杂地表全天候短波辐射模型和反演算法进行综合验证。

地表短波辐射是地球系统物质与能量循环的主要驱动力，现有的遥感辐射产品未考虑地形起伏的影响，极大制约了对全球辐射分布的准确刻画。地形和云的综合建模、反演与真实性检验是当前遥感辐射收支研究的前沿和难点。.本项目针对复杂地形区有云条件下短波辐射估算，从模型建立与反演、尺度扩展和真实性检验几个方面开展研究，发表SCI论文54篇，其中TOP期刊论文19篇，授权发明专利6项，制订国家标准1项，超额完成既定任务，所取得主要成果如下：.1、综合考虑太阳-坡面-观测之间的几何关系，建立了复杂地形区多尺度方向性反射模型和地表反照率估算模型，全面分析了地形效应对反射率、植被指数以及下行辐射的影响。综合考虑太阳直射遮蔽、天空散射遮蔽及周围地形反射辐射贡献，定量刻画了山区云阴影位置不确定性对高分辨率辐射估算的影响，构建了耦合人工神经网络的山区短波辐射估算模型SWTRM，成功考虑了云和地形的耦合作用，实现了复杂地形区高低两种空间分辨率地表短波辐射建模和分量估算。.2、发展了复杂地形区短波辐射时空尺度转换方法，建立了大尺度云覆盖度和地形统计因子耦合的参数化模型，分析论证了区域耦合模型估算短波辐射分量的最优空间尺度，提取了地表短波辐射的日变化特征并进行时间扩展，得到了日平均的复杂地表短波辐射，研究显示地形导致日均辐射误差可达50w/m2以上。.3、提出了计算机真实场景模拟和野外实验相结合的真实性检验方法体系，在真实性检验方法和计算机真实场景模拟方面取得了全面突破。针对叶面积指数的准确测量，创立了路径长度分布法，将传统的叶面积指数测量精度提高了一倍。针对激光雷达数据的高效处理，提出了布料模拟滤波算法CSF，被多款国际著名数据处理软件集成。针对大场景模拟，建立了三维真实结构模拟模型LESS，相比目前国际上最热门的DART模型，在精度相当情况下，效率提高了20倍，可一次性模拟5*5km的范围。