Estimating High Spatial Resolution Clear-Sky Land Surface Upwelling Longwave Radiation From MODIS Data
Estimating High Spatial Resolution Clear-Sky Land Surface Upwelling Longwave Radiation From MODIS Data
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DOI：
10.1109/tgrs.2008.2005206
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发表时间：
2009-05
影响因子：
8.2
通讯作者：
Wenhui Wang;S. Liang;J. Augustine
中科院分区：
文献类型：
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作者：
Wenhui Wang;S. Liang;J. Augustine
地面上升流长波辐射是地面辐射收支的重要组成部分。现有的卫星获得的LWUP数据集太粗糙，无法支持高分辨率的数值模式，其精度需要提高。在本文中，我们评估了三种方法估计晴空陆地LWUP中分辨率成像光谱仪（MODIS）数据在1公里的空间分辨率。这三种方法是：（1）温度-发射率法;（2）线性模型法;（3）人工神经网络（ANN）模型法。方法2和3是基于广泛的辐射传输模拟和统计分析的新方法。我们明确考虑了表面发射率的影响，将加州大学圣巴巴拉发射率库中的辐射传输模拟。这三种方法进行了评估，使用地面测量的LWUP从六个SURFRAD网站。虽然方法2和方法3是使用中分辨率成像分光仪Terra大气剖面图开发的，但它们适用于Terra和Aqua数据，因为这两种传感器的设计相似。神经网络模型方法的均方根误差（rmses）小于其他两种方法在所有站点。人工神经网络模型方法的平均误差分别为15.89 W/m2（Terra）和14.57 W/m2（Aqua），平均偏差分别为-8.67 W/m2（Terra）和-7.21 W/m2（Aqua）。Aqua的偏差和均方根值比Terra小约1.3 W/m2。人工神经网络模型法的偏差和均方根值比温度-发射率法小~5 W/m2，比线性模型法小~ 2.5W/m2。
Surface upwelling longwave radiation (LWUP) is an important component in the surface radiation budget. Existing satellite-derived LWUP data sets are too coarse to support high-resolution numerical models, and their accuracy needs to be improved. In this paper, we evaluate three methods for estimating clear-sky land LWUP from the Moderate Resolution Imaging Spectroradiometer (MODIS) data at 1-km spatial resolution. The three methods are as follows: (1) the temperature-emissivity method; (2) the linear model method; and (3) the artificial neural network (ANN) model method. Methods 2 and 3 are new methods based on extensive radiative transfer simulations and statistical analysis. We explicitly considered surface emissivity effects by incorporating the University of California Santa Barbara emissivity library in the radiative transfer simulation. The three methods were evaluated using ground-measured LWUP from six SURFRAD sites. Although methods 2 and 3 were developed using MODIS Terra atmospheric profiles, they were applied to both Terra and Aqua data because the designs of the two sensors are similar. The root mean squared errors (rmses) of the ANN model method are smaller than that of the other two methods at all sites. The averaged rmses of the ANN model method are 15.89 W/m2 (Terra) and 14.57 W/m>2 (Aqua); the averaged biases are -8.67 W/m2 (Terra) and -7.21 W/m2 (Aqua). The biases and rmses for Aqua are ~1.3 W/m2 smaller than that of Terra. The biases and rmses of the ANN model method are ~5 W/m2 smaller than that of the temperature-emissivity method and ~2.5 W/m2 smaller than that of the linear model method.