Solar wind signal in the wintertime North Atlantic oscillation and Northern Hemispheric circulation

The impact of the solar wind on sea level pressure (SLP), sea surface temperature (SST), zonal mean zonal wind (U) and air temperature (T) was examined using multiple linear regression analysis. Our analysis of the December–January–February (DJF) mean fields indicates that significant links between the solar wind speed (SWS) and the North Atlantic oscillation (NAO), SST tripolar structure and polar stratospheric temperature. The monthly reanalysis data (November to March) show that high SWS is associated with a poleward- and downward- propagating solar wind signal from December to February. The response of the Eliassen-Palmer (EP) flux shows that more planetary wave activity is refracted equatorward in the upper stratosphere under higher SWS conditions, corresponding to an enhanced EP flux convergence in early winter. Enhanced EP flux divergence occurs in the stratosphere starting in January and propagates poleward and downward from January to February. For the coupling mechanism between the stratosphere and troposphere, in addition to chemical-dynamical processes, cloud microphysical processes associated with the global electric circuit (GEC) might play a role in the downward propagation of the solar wind signal and the modulation of the NAO.