复杂地形对计算地表太阳短波辐射的影响

The Effects of Complex Terrain on the Computed Surface Solar Short-Wave Radiation

首先利用数字高程数据 (DEM)、大气辐射传输模式 6S以及野外观测资料计算了复杂地形 (青藏高原 )上地表入射太阳辐射 ,然后计算不考虑地形产生的地表辐射的计算误差 ,对误差进行归一化后得到相对辐射误差。结果显示 ,相对辐射误差的标准差 (即相对地表辐射计算误差绝对值的统计平均值 )Se 随太阳天顶角的增加呈指数增长 ,随高度标准差的增加几乎呈线性增长 ,随数字高程数据的分辨率 (或卫星资料的分辨率 )降低而降低。利用分步拟合方法拟合了Se 随太阳天顶角、高度标准差和数字高程分辨率的变化。利用拟合方程可以计算任意地形条件下 ,不同分辨率的卫星 (或数字高程 )资料在不同太阳天顶角情况下 ,不考虑地形复杂性产生的平均地表入射太阳辐射的计算误差 ,结果表明 ,使用中分辨率的卫星 (如MODIS)资料计算地表太阳净辐射时 。

Surface incoming solar radiation over complex terrain is calculated by using topographic data from a girded digital elevation model, field measurements, and atmospheric radiation transfer model 6S. The error caused by not taking into account terrain complexity is calculated, and relative radiation error is estimated by standardizing the error. The results show that the standard deviation of the relative radiation error increases exponentially with solar zenith angle, and almost linearly with the standard deviation of height, but decreases when the resolution of the digital elevation model (or resolution of satellite remotely sensed data) decreases. Using a step by step regression method, the regression equation of the standard deviation of relative radiation error is calculated. The regression equation can describe well the change of standard deviation of relative radiation error with solar zenith angle, standard deviation of height, and resolution of digital elevation model. The result demonstrates that it is necessary to consider terrain complexity when using moderate resolution of remotely sensed data.