The winter NAO pattern changes in association with solar and geomagnetic activity

The North Atlantic Oscillation (NAO) is considered to be a very robust phenomenon. The analysis of tropospheric pressure deviations, temperature deviations and prevailing wind deviations from their long-term averages, carried out on the data set of winter (January-March) periods of 1963-2001. however, indicates a close association between high geomagnetic activity and the positive NAO phase. The composite maps of the North Hemisphere winter troposphere pressure and temperature deviations.. plotted at geopotential heights of 1000 and 100 mb. together with the composite maps of vertical sections along the profiles Atlantic-polar region-eastern Asia and Europe-polar region-Pacific indicate a distinct relation between the spatial distribution of the pressure and temperature deviations and the geomagnetic as well as the solar activity level. An attempt was made to explain these phenomena by the mechanisms based both on the propagation of planetary and gravity waves and on the changes in the global electric circuit. (C) 2004 Elsevier Ltd. All rights reserved.