全球变暖减缓背景下欧亚秋冬温度变化特征和原因

采用气候序列变化趋势诊断和一元线性回归等分析法,研究和讨论了2000-2012年和1976-1999年两种年代际背景下全球陆地不同区域的年平均地表温度的变化特征。发现欧亚大陆中高纬度地区是对全球变暖减缓贡献最大的区域。且该地区在2000年以来秋季年代际增温,而冬季年代际降温。从同期大气环流的配置来看,在对流层低层,秋季西伯利亚高气压年代际减弱,而冬季西伯利亚高气压年代际增强。在对流层中高层,秋季从西欧至东北亚为"高-低-高"的高度场异常分布,纬向环流加强,经向环流减弱,而冬季极地与贝加尔湖地区的高度场呈偶极型分布,东亚大槽加深,经向环流加强。进一步研究发现,超前一个季节的喀拉海附近的海冰与欧亚中高纬度秋冬两季温度的年代际变率有着密切的联系。一方面,夏季(秋季)海冰减少影响秋季(冬季)中高纬度大气环流;另一方面,夏季(秋季)海冰减少,使得秋季(冬季)从北极至中高纬度大陆的对流层低层水汽含量增加(减少),大气逆辐射增强(减弱)导致秋季(冬季)增温(降温)。

Temperature characteristics of Eurasia in autumn and winter and its causes under global warming mitigation

By using climate sequence variation trend diagnosis and unitary linear regression methods, the variation characteristics of annual mean surface temperature in different areas under two decadal time scales: 2000-2012 and 1976-1999, were analyzed. Results show that the mid-high latitude of Eurasia is the region that contributes the largest to global warming mitigation, and the temperature in autumn and winter presented inverse variation trend since 2000, which showed interdecadal warming in autumn but cooling in winter. Judging from configuration of the corresponding atmospheric circulation, in lower troposphere, the intensity of Siberian High weakens interdecadally in autumn while enhances in winter. In mid-high troposphere, the geopotential height in autumn presents a "high-low-high" anomaly distribution from western Europe to Northeast Asia with strengthening zonal circulation and weakening meridional circulation, while in winter, the geopotential height presents a dipole pattern between the polar and Lake Baikal region with deepening East Asian trough and strengthening meridional circulation. Further study suggests that a close relation exists between the sea ice near Kara sea and the decadal variability of temperature in autumn and winter at mid-high latitudes of Eurasia. On one hand, the reducing sea ice in summer(autumn) influences the atmospheric circulation at mid-high altitudes in autumn(winter), on the other hand, the reducing sea ice in summer(autumn) causes the water vapor content of lower troposphere to increase(decrease) in autumn(winter) from arctic to the mid-high latitudes in Eurasia and the downward long-wave radiation to strengthen(weaken), which results in the warming(cooling) in autumn(winter).