Trends and Inter-Decadal Variations of the Surface and Lower-Tropospheric Temperature in the Northern Hemisphere from 1964 to 93

[摘要] In this study, we demonstrate remarkable warming trends in northern winter and spring not only at the surface but also in the lower troposphere during a recent 30 year period (1964-93). In winter, major warming has happened over central Siberia and the northwestern Canada/Alaska region. The vertical structure of the warming tendency is somewhat different between these two regions. In spring, tropospheric warming is most noticeable over the northern part of North America. A three-dimensional rotated EOF analysis of the temperature anomaly field in these seasons confirmed the warming trends as the most dominant mode at the surface and in the lower troposphere.The rotated EOF analysis also shows that an interdecadal-scale fluctuation with abrupt changes in the periods of 1976/77 and 1988/89 is another dominant mode in the temperature field in winter. The spatial structure of this mode shows a wavenumber-three spatial pattern with positive factorloadings over North America, Northern Europe and the eastern part of Eurasia. In spring, a fluctuation of 10-13 year period is noticed in the second largest mode, which suggests a possible relation with the solar cyle of the same period. Possible forcing factors of these tropospheric temperature trends and fluctuations are briefly discussed.

[学科分类] 大气科学