Toward operational shortwave radiation modeling and retrieval over rugged terrain
Toward operational shortwave radiation modeling and retrieval over rugged terrain
复制标题
崎岖地形上的可操作短波辐射建模和检索
DOI：
10.1016/j.rse.2017.11.006
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发表时间：
2018
影响因子：
13.5
通讯作者：
Chu Qing
中科院分区：
文献类型：
--
作者：
Wang Tianxing;Yan Guangjian;Mu Xihan;Jiao Zhonghu;Chen Ling;Chu Qing
短波辐射(0.3-3.0μm)是地表全波辐射收支的主要组成部分。对全球短波辐射的可靠估计对于深入了解全球变化尤为重要。不幸的是，现有的大量基于空间的算法忽略了地形的影响，简单地假设表面是理想的平坦的。正如许多研究指出的那样，这种对地形影响的忽视导致了导出辐射的显著误差。通过量化太阳直接辐射屏蔽、天空辐射遮挡、附近地形反射辐射和某些目标的不可见性，提出了一种短波地形辐射模型(SWTRM)。为了驱动SWTRM，采用了人工神经网络(ANN)方法来生成短波辐射预算的多个分量。新模型在青藏高原地区运行，并使用MODIS产品和数字高程数据(DEM)相结合。通过耦合SWTRM和ANN输出，得到地形校正的短波通量。结果表明：(1)基于人工神经网络的短波辐射模型在山区的应用效果良好；(2)基于人工神经网络的短波模型具有较高的反演精度(所有短波辐射分量的均方根误差为60 W/m2，偏置误差为13 W/m2)。更重要的是，ANN模型可以同时提供驱动SWTRM所必需的所有辐射分量；(3)在山区，短波净通量的诱导误差可以超过600W/m2。因此，地形的影响是不可忽视的；(4)地形和太阳照度角是空间短波辐射的关键调制因子，控制着山区短波辐射的大小和空间分布。
Shortwave radiation (0.3–3.0 μm) is a dominant component of land surface all-wave radiation budget. Reliable estimation of shortwave radiation throughout the globe is particularly important for an in-depth understanding of global changes. Unfortunately, a large number of existing space-based algorithms ignore the effects of topography by simply assuming that the surface is ideally flat. As pointed out by many studies, such neglect toward topographic effects leads to significant errors in derived radiation. This study proposes a shortwave topographic radiation model (SWTRM) by quantifying solar direct radiation shielding, occlusion of sky radiation, reflected radiation from nearby terrain, and invisibility of certain targets. To drive the SWTRM, an artificial neural network (ANN) approach was employed to generate multiple components of the shortwave radiation budget. The new model was run over the Tibetan Plateau region and used MODIS products coupled with digital elevation data (DEM). Topographically corrected shortwave fluxes were derived by coupling SWTRM and ANN outputs. The results show that: (1) the proposed SWTRM works well over mountainous regions; (2) the ANN-based shortwave model provides reasonable retrieval accuracy (RMSE < 60 W/m2, bias < 13 W/m2for all shortwave radiation components). More importantly, the ANN model can simultaneously provide all radiation components that are indispensable for driving the SWTRM; (3) over mountainous areas, the induced error can exceed 600 W/m2for shortwave net flux. Hence, topographic effects cannot be neglected; and (4) topography and solar illumination angle are key modulators in deriving shortwave radiation from space, which control the magnitude and spatial distribution of shortwave radiation over mountainous regions.