北半球积雪/海冰面积与温度相关性的差异分析

积雪和海冰的时空变化对区域以及全球的气候、水文具有重要影响。基于雪冰数据和NCEP再分析气温数据,利用MK检验、滞后分析等方法,分析了积雪、海冰的时空变化特征及其与温度的相关特征。结果表明：1979-2013年,北半球积雪区、北极圈的年均温度呈显著上升的趋势,而积雪面积和海冰面积呈显著下降的趋势。在大部分地区,积雪覆盖频率随着温度的上升呈显著减少的趋势,但在中国长江中下游、青藏高原等局部地区,积雪覆盖频率随着温度的上升呈显著增加趋势。在大部分的近陆地海域,海冰覆盖频率随着温度的上升呈显著下降趋势。超前时间1~2个月的温度与海冰面积的负相关性最高。超前1~4个月的温度与积雪面积的负相关性最高。温度对海冰的影响时间比对积雪的影响时间长1~2个月。温度变化对海冰和积雪的影响存在一致性,但积雪和海冰对温度的响应时间存在差异,具有空间变异性。

Different influences of temperature on snow cover and sea ice area in the Northern Hemisphere

Snow and sea ice are two of the most important sources of water, which play significant roles in regional and global climate change and hydrological cycle. The MK test and lag analysis methods were employed to study the spatio-temporal characteristics of relationship between temperature and snow cover and relationship between temperature and sea ice based on NCEP reanalysis temperature data and NSIDC weekly snow and ice data. The results indicate that during the period of 1979-2013, the annual average temperature over the Northern Hemisphere and the Arctic showed a significant increasing trend, while the area of snow and sea ice showed a decreasing trend. Snow cover frequency decreased with the increase of temperature in most parts of the Northern Hemisphere, but increased with the increase of temperature in the lower Yangtze River Basin and Tibetan Plateau. In much of the near land sea, sea ice cover frequency significantly decreased with the increase of temperature. The variation of sea ice area was mainly attributed to the temperature change, and the highest negative correlation occurred when temperature change was 1-2 months ahead of the change of sea ice area. For snow cover, the temperature change is also the main reason. When the temperature change was 1-4 months ahead of the change of snow cover, the negative correlation index was the highest. Compared with snow, response of sea ice to the change of temperature is 1-2 months later, which was mainly caused by larger density of sea ice than that of snow. In general, the effect of temperature change on sea ice and snow cover has consistency with different response time to temperature and shows a strong spatial variability.