Temporal and Spatial Evolution of Teleconnection in the Troposphere during the Northern Hemisphere Winter at the End of the 1970s

Using the NOAA monthly reanalysis geopotential height on 500 hPa, the sea surface temperature (SST), the Pacific decadal oscillation (PDO) index and the triple mode of North Atlantic SST anomaly (ATM)index from 1950 to 2008, the temporal and spatial evolution of teleconnection in the troposphere during the Northern Hemisphere winter at the end of the 1970s is studied with correlation analysis method, Mann-Kendall analysis method, and coherence wavelet analysis method. The results indicate that the spatial distributions and temporal evolutions of Pacific-North American (PNA), Eurasia-Pacific (EUP), West Pacific (WP), and West Atlantic (WA) teleconnection patterns change significantly at the end of the 1970s. The spatial distribution changes are found in the intensity and range of abnormal centers of these teleconnection patterns. On temporal evolution, the upward tendency of PNA and WP indexes and the downward tendency of EUP and WA indexes are also found. After the end of the 1970s, the key SST areas impacting on the 5 teleconnection patterns during the Northern Hemisphere winter have changed, in which those areas impacting on the EUP, and those areas in the Pacific impacting on WA have significantly decreased; those areas in the middle and southern Atlantic impacting on EA have obviously changed. On the time scale above 16 years, the variation of PDO is the main reason which leads to the variation of PNA, EUP, WP, and WA teleconnection patterns; the variation of ATM is the main reason which leads to the variation of WA and EA teleconnection patterns during the Northern Hemisphere winter.