Impact of the Wintertime NAO on the Summertime Atmospheric Circulation and its Solar Cycle Modulation

The summer high-latitude climate in the Northern Hemisphere is influenced by the NAO of the previous winter. We find this influence in the summertime surface air temperature, the geopotential height, the sea surface temperature (SST), sea-ice/continental snow cover extent fields as well as in the zonal mean geopotential height and zonal wind fields. This summertime NAO signal is annular but its meridional scale is much smaller than the winter annular mode. We suggest that the sea-ice, SST and snow cover anomalies provide the memory allowing the winter NAO to affect the summer climate. In addition, the 11-year solar cycle modulation of the winter-to-summer linkage is examined. During the solar maximum years, the winter NAO has a significant relation with the spring-summer climate, while the linkage is very weak during the solar minimum years. During the solar maximum years, the winter NAO affects spring snow cover over the Eurasian continent and sea ice over the Barents Sea.