北半球及典型区雪深时空分布与变化特征

基于欧空局的GlobSnow雪水当量数据集和国家青藏高原科学数据中心的北半球长时间序列雪深数据集NHSD研究了北半球及9个典型区的雪深时空分布与变化特征。结果表明：北半球1988~2018年平均雪深总体呈显著下降趋势（p<0.01），年际变化幅度为-0.55 cm·（10 a）^-1。在高纬度地区，加拿大北部和阿拉斯加年平均雪深下降明显（p<0.01），下降速率分别为3.48 cm·（10 a）^-1和3 cm·（10 a）^-1，两地区月平均雪深在冬季显著下降。西西伯利亚平原和东欧平原年平均雪深呈下降趋势，其中东欧平原雪深下降较为明显（p<0.01），变化速率为-2.3 cm·（10 a）^-1，两地区的月平均雪深在春季显著下降，其中5月份最为明显。东西伯利亚山地的雪深年际变化呈增加趋势，除堪察加半岛外，其月平均雪深在冬季呈显著增加趋势。对于高山区，阿尔卑斯山脉和落基山脉的年平均雪深呈缓慢增长趋势，而青藏高原地区雪深呈缓慢下降趋势。阿尔卑斯山脉的月平均雪深在冬季呈显著增加趋势，5月份显著减小。落基山脉和青藏高原雪深变化呈现出空间异质性：在整个研究时段，落基山脉北部月平均雪深呈下降趋势，中部和南部呈上升趋势；青藏高原的北部边缘山脉雪深呈显著上升趋势，中部大多数地区呈下降趋势。喜马拉雅山脉的北坡雪深增加，南坡雪深减小，但其变化率绝对值小于0.5 cm·a^-1。东南部雪深较大的念青唐古拉山脉冬季雪深呈显著下降趋势。对9个典型区雪深的年内分析（2001~2010年平均值）结果显示：高山区雪深峰值远低于高纬度地区雪深峰值。除青藏高原外，高山区的积雪融化起始日期明显早于高纬度地区。

Temporal and Spatial Distribution and Variation Characteristics of Snow Depth in the Northern Hemisphere and Typical Areas

The temporal and spatial variation characteristics of snow depth over the Northern Hemisphere and nine typical areas were analyzed based on the GlobSnow snow water equivalent datasets of European Space Agency and the NHSD sow depth datasets of the National Qinghai-Tibet Plateau Scientific Data Center. The results showed that： the Average Annual Snow Depth （AASD） over the Northern Hemisphere generally decreased significantly （p<0.01） during 1988 to 2018， with a change slope of -0.55 cm·（10 a）^-1. For high latitudes， the AASD in the northern Canada and Alaska decreased significantly （p<0.01）， with a rate of 3.48 cm·（10 a）^-1 and 3 cm·（10 a）^-1， respectively； and the Average Monthly Snow Depth（AMSD） decreased significantly in winner. The AASD decreased in the West Siberian Plain and Eastern European Plain with a significant change rate of -2.3 cm·（10 a）^-1 in the latter （p<0.01）， and the AMSD decreased significantly in spring， especially in May. The AASD in the Eastern Siberia showed an increased trend， except in Kamchatka Peninsula， and the AMSD increased significantly in winner. For high mountainous areas， the AASD showed a slow increase rate in the Alps and Rockies， and slight decrease change in the Qinghai-Tibet Plateau （QTP）. The AMSD in Alps increased significantly in winner and decreased significantly in May. The variation of snow depth in the Rockies and the QTP presented spatial heterogeneity. During the whole study period， the AMSD decreased in the north of the Rockies and most areas of central region of QTP， while increased in the central and south of Rockies and the mountains on the northern edge of the QTP. The snow depth increased on the north slope of The Himalayas， while decreased on the south slope， with the absolute change rates of less than 0.5 cm·a^-1. The AMSD of Nianqing Dangla Mountains which has deep snow showed a significant downward trend in winner. The seasonal variation analysis of snow depth （average snow depth from 2001 to 2010） in 9 typical areas showed that the peak values of snow depth in high mountainous areas are much smaller than those in high latitudes. The snow melting dates in high mountainous areas are obviously earlier than those in high latitudes except for the QTP.