山区地形效应对微波辐射特征与土壤水分反演的影响——以青藏高原地区为例

Relief effects of mountain areas on soil moisture retrieval using passive C-band:A case study in Qinghai-Tibet Plateau

采用星载微波辐射计AMSR-E的低频C波段(6.925GHz),改进了山区微波辐射传输方程,以中国青藏高原地区为例,研究山区可能产生的多种地形效应对微波辐射特征以及土壤水分反演的影响。结果表明,地形效应使得垂直极化亮温最多衰减达到16K,水平极化的亮温最大增强了18K,土壤水分在地形的影响下将被高估超过最大允许误差4%。最后,利用地形效应模拟模型计算的山区地表有效发射率,为山区土壤水分的反演提出了可行的地形校正方法。

Topography affects the distribution of land surface microwave radiation and soil moisture. Therefore, it is one of significant factors for passive microwave remote sensing. Using the spaceborne radiometer AMSR-E at C-band, a simplified mi- crowave radiative transfer model for mountain areas was developed. Its implement for the relief effect estimations over Qinghai- Tibet Plateau shows due to topography brightness temperatures at vertical polarization are attenuated about 16 K, conversely, horizontal brightness temperatures are enhanced 18 K, and soil moisture is overestimated and even exceeds the maximum al- lowed retrieval error （4%）. Finally, the potential approach of the topographic correction is provided by the computation of the surface effective emissivity.