NOAA IMS雪冰产品在青藏高原积雪监测中的适用性分析

在系统评估青藏高原积雪观测典型气象站历史定位坐标精度基础上，利用站点雪深资料对NOAA IMS 4 km和1 km分辨率雪冰产品在青藏高原的精度和适用性进行了验证和评估，定量分析了IMS 4 km到1 km空间分辨率提高和气象站历史定位与GPS定位坐标之间的差异对青藏高原IMS积雪监测精度的影响。结果表明：青藏高原个别气象站历史坐标与当前GPS接收机定位之间存在较大的差异，如安多气象站经度偏小0.6°，纬度偏大0.08°。IMS 4 km雪冰产品在青藏高原的总精度介于76.4%~83.2%，平均为80.1%，积雪分类精度介于35.8%~60.7%，平均为47.2%，平均误判率为17.1%，平均漏判率为45.5%，总体上呈现地面观测的积雪日数越多、平均雪深越大，其总体监测精度越低，而积雪分类精度越高的特点。IMS分辨率从4 km到1 km总体精度平均提高了2.9%，积雪分类精度平均提高了0.9%，主要是由于个别站点的精度提升较大引起的，对高原多数台站积雪监测精度的改进和提升很小。除个别台站外，目前气象站历史坐标和GPS定位坐标之间的差异，对IMS 4 km积雪监测精度验证结果没有影响。然而，今后随着卫星遥感技术的发展，更高时空分辨率的遥感积雪产品将用于积雪监测和研究，精确的地面观测站坐标信息是对这些遥感数据开展精度验证与实际应用的前提。

Analysis on applicability of NOAA IMS snow and ice products in snow cover monitoring over the Tibetan Plateau

Snow on the Tibetan Plateau （TP） is a vital fresh water source in western China and Himalayan regions， and snow cover variation is also a significant indicator of climate condition in the TP and its surroundings. As a snow cover product based on blended approaches， including active and passive satellite sensors， ground observation and other auxiliary information， NOAA IMS （Interactive Multisensor Snow and Ice Mapping System） is most widely used for large-scale snow cover detection and relevant climate research. In this study， the evaluation of the historical positioning coordinate accuracy of representativemeteorological stations for snow observation in the TP is systematically made for the first time， and then the accuracy and applicability of NOAA IMS 4 km and 1 km products over the TP are verified and evaluated using snow depth data from these stations， and the effect of IMS spatial resolution improvement from 4 km to 1 km on the snow detection accuracy over the TP， and the influence of the difference between the historical and GPS positioning coordinates of meteorological stations on the accuracy of IMS snow detection over the TP are quantitatively analyzed in this study. The results show that： There are great differences between the historical coordinates and current GPS positioning information for some meteorological stations in the TP， such as the longitude of Amdo （Anduo） Meteorological Station recorded by historical positioning is 0.6° smaller than GPS positioning and the latitude is 0.08° greater than GPS positioning information. Overall accuracy of IMS 4 km product on the TP ranges 76.4%~83.2% with an average of 80.1%. The accuracy of snow detection is 35.8%~60.7% with an average of 47.2%， and average commission error rate is 17.1% while average omission error rate is 45.5%， which generally features that the more snow-covered days and the higher average snow depth are observed on the ground， the lower the overall monitoring accuracy and the higher the snow detection accuracy. Compared with IMS 4 km product， overall accuracy of IMS 1 km increased by 2.9% on average， the accuracy of snow detection increased by 0.9%， average commission error rate reduced by 5.1% and omission error rate increased by 4.1%， which is mainly caused by the greater accuracy improvement of several stations while there is little impact on the overall accuracy improvement of snow detection for most of stations on the TP. Except for some meteorological stations， the impact of differences between the historical and GPS positioning coordinates of meteorological stations on IMS 4 km product accuracy over the TP is limited at present. However， with the development of satellite remote sensing technology， remote sensing snow products with higher spatial-temporal resolution will be used for snow monitoring and study in the future. Accurate coordinate information of ground observation station is essential for accuracy validation and practical application of these remote sensing data.