中国西部积雪类型划分

利用中国105°E以西地区189个地面气象台站1960-2004年积雪日资料和1981-2004年SMMR、SSM/Ⅰ反演的逐日雪深资料,使用积雪年际变率方法划分中国西部积雪类型,并与积雪日数方法的划分结果进行比较.在此基础上,尝试建立了结合以上两种要素的综合分类指标.利用积雪年际变率方法和台站资料,将中国西部积雪划分为3类.其中,稳定积雪区主要包括北疆、天山和青藏高原东部高海拔山区；年周期性不稳定积雪区包括南疆和东疆盆地周边、河西走廊、青海北部、青藏高原中西部、藏南谷地以及青藏高原东南缘；其他积雪区均为非年周期性不稳定积雪区.气候突变后,积雪日数方法划分的积雪类型变化反映出沙漠和低纬度地区积雪变幅增大,在积雪年际变率方法的结果中体现出青藏高原东部地区趋于稳定的积雪面积在增加.在没有台站记录地区,卫星遥感资料很大程度上弥补了台站观测的缺陷,使用这种资料划分积雪类型时,积雪年际变率方法比积雪日数方法的结果更符合西部积雪的分布特点,反映出积雪分布与地形的密切关系.利用综合分类指标划分西部积雪类型的结果表明,台站资料的划分结果很大程度上受积雪持续时间的影响,而在卫星遥感结果中,积雪年际变率则是影响类型划分的主要因素.

On the classification of the snow cover in western China

Using the daily snow cover data from 189 meteorological stations to the west of 105°E in China for the period 1960-2004, and the daily snow depth data retrieved from the passive microwave remote sensing data (SMMR and SSM/I) in 1981-2004, types of the snow cover are classified by the interannual variability of snow cover days (IVSCD) and by snow cover days (SCD), and the differences between the two methods of dividing snow cover types have been analyzed. Furthermore, a new comprehensive indicator combining the above two elements (IVSCD and SCD) has been established. The results show that, based on the observational data, 3 types of snow covered areas (including stable snow-covered areas, annual and non-annual periodic unstable snow-covered areas) are classified by IVSCD in western China. Stable snow-covered areas include northern Xinjiang, the Tianshan Mountains, and the high-altitude mountains in the eastern Tibetan Plateau, and, annual periodic unstable snow-covered areas are mainly located at the periphery of the southern and eastern Xinjiang Basin, the Hexi Corridor, northern Qinghai, the central and western Tibetan Plateau, the southern Tibet Valley, and the southeastern fringe of the Tibetan Plateau. In addition to the above mentioned, there are non-annual periodic unstable snow-covered areas. After abrupt change of climate, changes of snow cover types, as classified by IVSCD and by SCD, reflect increases in the stable snow-covered area in the eastern Tibetan Plateau and the amplitude of variations of snow cover in the desert and the low-latitude areas, respectively. In a large extent, satellite remote sensing data can compensate for data that is missing due to the scarcity of stations, and the types of snow cover classified by IVSCD are better in determining the characteristics of snow cover in western China, implying that there exists a close relationship with the topography as shown by these data. As classified by the comprehensive indicator, the distribution of snow cover types in western China has been more significantly influenced by the snow cover duration based on the observational data, and for the one based on the satellite remote sensing data the IVSCD is the major influencing factor.