基于多层土壤温度的地表冻融变化被动微波遥感验证分析

Verification and Analysis of Land Surface Freeze-Thaw Change by Passive Microwave Remote Sensing Technique Based on Multi-layer Soil Temperature

目前基于被动微波遥感技术的地表冻融变化监测对垂直剖面内表层土壤温度的差异考虑较少。该文从判别算法和多层土壤温度差异性两方面进行分析,结果显示:1)基于准发射率和基于亮温标准差的冻融判别算法的判别结果均与1 cm表层土壤地面监测结果吻合率最高,表明被动微波冻融产品的验证应尽可能使用最靠近地面的土壤层温度,两种算法在1~5 cm不同深度表层土壤的验证中均显示出较大差异;2)土壤表层温度在0 cm和5 cm深度处的相关性极好,但在冻融判别阈值0℃附近存在较大差异,该差异是导致判别误差的重要来源。研究结果对于地表冻融参量的定量化、精细化遥感监测研究具有理论意义和应用价值。

In previous studies about land surface freeze-thaw monitoring based on the passive microwave remote sensing technique,little consideration has been given to the difference in the inner surface soil temperature on the vertical profile.In this paper,the analysis was done from the perspective of discriminant algorithm and the validation data of multi-layer soil temperature,respectively.From the perspective of discriminant algorithm,it was found that the discrimination results of the freeze-thaw discriminant algorithm based on quasi-emissivity and that based on the standard deviation of bright temperature were most consistent with the observation results of surface soil temperature at 1 cm depth.This suggested that the top layer of surface soil(with the depth of 1 cm)should be selected when doing the test of passive microwave freeze-thaw products.Nonetheless,the two algorithms showed large difference when tested using multi-layer soil temperatures in the range of 1 cm to 5 cm.From the perspective of validation data,it was found that there is a very good correlation between the soil temperature at the surface layer depth of 0 cm and the depth of 5 cm,but there is a big difference near the freeze-thaw discrimination threshold of 0℃,which is an important source of discrimination error.This study has important theoretical significance and applications for the quantification and refinement of the remote sensing monitoring of surface freeze-thaw parameters.