高分五号卫星多角度偏振探测仪(DPC)是国内首台具备业务化多光谱多角度偏振探测能力的星载遥感器。发展了一套针对DPC观测数据的处理算法,可获取观测区域上空云检测结果、相态分布和云光学厚度。利用670 nm、865 nm反射率、490 nm几何归一化偏振辐亮度和865 nm线偏振度进行云检测;利用865 nm归一化偏振辐亮度进行相态识别;利用670 nm、865 nm反射率以及相态识别结果反演云光学厚度。由于尚未获取可反演的DPC L1级观测数据,仅将算法应用于地球反射率多角度偏振观测仪(POLDER)数据,以验证算法有效性。对比POLDER云产品,得到判云一致性和判晴一致性分别为93.3%和92.9%;水云、冰云和混合相态判别一致性分别为87.4%,76.6%和22.8%;云光学厚度的相关系数为0.89,故该算法可行有效。该算法为DPC发展业务化云产品提供参考。

The directional polarimetric camera (DPC) aboard the GF-5 satellite is the first domestic space-born instrument with operational multi-spectral, multi-directional, and polarimetric observations. A series of algorithms used for DPC measurements were formulated to acquire cloud detection results, cloud thermodynamic phase distribution, and cloud optical thickness of the observed zones. The cloud detection results were derived from the reflectance at 670 and 865 nm, the geometric normalized polarized radiance was obtained at 490 nm, and the linear degree of polarization was obtained at 865 nm. The cloud thermodynamic phase was derived from the normalized polarized radiance at 865 nm; the cloud optical thickness was obtained from the reflectance at 670 and 865 nm and results of cloud thermodynamic phase. Because of the lack of L1 data of DPC, the algorithms were applied to POLDER data to validate their feasibility. Results indicated that the consistency of “cloudy judgment” and “clear judgment” was 93.3% and 92.9%, respectively. Further, the consistency of “water clouds,” “ice clouds,” and “mixed-phase clouds” was 87.4%, 76.6% and 22.8%, respectively. The correlation coefficient of the optical thickness was 0.89, which demonstrates the feasibility of the proposed algorithms. The proposed algorithms can develop the operational cloud production of DPC.