欧亚北部冬季增雪“影响”我国夏季气候异常的机理研究——陆面季节演变异常的“纽带”作用

本文主要利用美国冰雪资料中心 (The National Snow and Ice Data Center) 提供的卫星反演积雪资料和ERA40土壤温度再分析资料, 采用相关分析, 对欧亚北部冬季新增雪盖面积 (冬季TFSE) 与我国夏季气候异常关系的可能物理途径进行了初步研究。结果表明, 春夏季陆面季节演变异常是上述“隔季相关” 的重要纽带: 当冬季TFSE偏大时, 欧亚北部大范围积雪—冻土自西向东、 由南向北的融化进程明显减慢, 受其影响, 至夏季, 东亚中高纬区积雪和地表冻土的融化异常强烈, 土壤温度明显偏低, 这种夏季陆面异常可能通过自身的冷却作用, 通过加强东亚中高纬异常北风对东亚中纬区夏季变冷产生直接影响, 进而与西太平洋副热带高压, 乃至与我国江南夏季降水异常产生关联; 冬季TFSE偏小时相反。分析表明, 冬季TFSE信号在东亚中高纬局地的春季积雪—冻土融化过程中被加强, 并在夏季达到显著。

Mechanism for the Correlation of Winter Fresh Snow Extent over Northern Eurasia and Summer Climate Anomalies in China: Anomalous Seasonal Transition of Land as a Bond

Using the National Snow and Ice Data Center (NSIDC) snow cover and snow water equivalent data, monthly four-layer soil temperature from ERA40 reanalysis dataset, the mechanisms of the linkage between the Winter Northern Eurasian Fresh Snow Extent (winter TFSE) and subsequent summer climate anomalies in China are investigated. Correlation analysis shows that, the consistent seasonal evolvements of land anomalies act as a bridge for the lag correlation. A large winter TFSE is followed by a slower northeastward retreating progress of snow and frozen soil over northern Eurasia. Consequently, in summer, snow and frozen soil over East Asian middle and high latitudes melt more intensively, the soil temperature correspondingly gets lower than normal, which influences local temperature by cooling and by influencing local meridional wind, and through enhancing East Asian jet, is related to the subtropical high in the western Pacific, even climate anomalies in China, and vice versa. As well as local variations of land factors over East Asian middle and high latitudes are concerned, the signal of winter TFSE is significantly strengthened during snow-and-frozen-soil melting process.