多源卫星遥感积雪资料在青藏高原的验证与应用研究

Based on the spatial and temporal distribution of snow cover and snow disasters on the Tibetan Plateau(TP), 2 typical meteorological stations among the current stations will be selected to carry out the intensive snow observations(snow depth, snow water equivalent and weather condition etc.) when MODIS and FY3 satellites are crossing over the observation sites to obtain simultaneous snow observation data from the ground and the satellites, and 1 automatic snow depth observation instruments will be deployed in key snow cover zones on the TP along with annual field snow observation to build simultaneous snow observation database for the TP. Using these observation data, the comprehensive accuracy evaluation of daily snow cover products derived from MODIS and FY3 will be systematically carried out and the comparison will be tested with snow cover extent from Landsat TM in typical areas, which will be used to adjust and improve snow cover mapping methods and to enhance accuracy of operational snow cover monitoring algorithm in the TP (mainly for Tibet Autonomous Region). Meanwhile, IMS snow/ice products will be introduced to the TP snow cover monitoring through validating and applicability evaluation to make up for the limitations of optical snow remote sensing. Final purpose of this study will contribute to rapidly and effectively monitoring snow cover extent and related snow disaster distribution on the TP in order to provide more accurate, timely snow information for snow disaster prevention and mitigation and to play an important role of satellite remote sensing in the social and economic development.

根据青藏高原积雪和雪灾的时空分布特点，从现有台站中选取2个代表性气象站开展加密积雪观测(观测要素包括雪深、雪水当量和天气现象等)，获取MODIS和FY3卫星过顶测站的同步地面积雪观测数据，并在重点区域架设1套自动雪深观测系统，结合降雪之后重点区域的野外积雪观测，建立较为完善的青藏高原星地同步地面积雪观测数据，在此基础上，对MODIS和FY3逐日积雪产品在青藏高原的精度进行系统评估与验证，并在典型区域与Landsat等高分辨率资源卫星积雪制图对比试验，进一步调整和改进目前青藏高原(西藏为主)遥感积雪监测业务中的积雪制图阈值和判识条件，有效提高积雪监测精度，同时，通过验证IMS雪冰产品在青藏高原的适用性，弥补光学遥感的局限性，进而更加快速、有效地监测青藏高原积雪范围和雪灾分布特点，为防灾减灾提供更为准确、及时的信息，发挥卫星遥感在社会经济建设中的作用。

根据项目计划任务书完成了各项研究内容，购置了 2套Campell SR-50A型超声自动雪深观测仪，委托当地气象站开展了星地同步的加密积雪观测，利用地面观测数据对MODIS逐日积雪产品和IMS 1km/4km分辨率的雪冰产品在青藏高原的精度进行系统评估与验证，并与Landsat-8卫星积雪制图结果进行了对比分析。作为项目主要成果，出版了2部专著，发表论文12篇，其中SCI论文2篇，国内核心期刊论文10篇。作为项目主要成果之一，2018年7月由气象出版社出版了项目主持人专著《青藏高原积雪图集》一书。利用青藏高原典型气象站雪深观测资料对Terra/MODIS逐日积雪产品MOD10A1产品精度进行了评价，结果表明总体精度在37.1~ 99.1%，平均80.5%，平均误判率4.7%，平均漏判率84.5%。Terra卫星过境青藏高原时平均云覆盖率为38.7%，且不同月份之间云覆盖率差异很大。IMS 4km雪冰产品总精度在76.4~ 83.2%，平均总精度为80.1%，平均积雪分类精度为47.8%，误判率为17.1%，漏判率平均45.5%。相比同期IMS 4km产品，IMS 1km总体精度平均提高了2.9%，积雪分类精度提升了0.9%，平均误判率减少了5.1%，漏判率反而有所增加，增加了4.1%。但是除个别台站积雪判识精度提升较大之外，IMS空间分辨率的提高对其积雪监测总体精度的提升和改进程度很小。基于Landsat-8 OLI晴空图像的IMS 1km精度评价结果表明，IMS 1km的总精度达到81.6%，积雪漏判率为5.1%，误判率29.2%，积雪分类精度72.4%，无雪分类精度为94.4%。两幅图像的Kappa系数为0.64，IMS雪冰产品与Landsat-8 OLI参考图像之间存在高度一致性，表明IMS 1km雪冰产品在青藏高原具有较高的精度，可以用于青藏高原大范围积雪覆盖的监测。