NAO variations linked to geomagnetic activity

GERARDO L. FLORES IVALDI; ANA G. ELIAS

Cusco

Congreso; X COLAGE; 2014

ALAGE

The North Atlantic Oscillation (NAO) is an internal mode of variability of the atmosphere modulated by external forcings such as aerosols, due to volcanic eruptions, anthropogenic influences on the atmospheric composition, and solar activity variations through the effects of geomagnetic storms over the atmosphere. Several studies show a significant correlation between long-term variations in the NAO and geomagnetic activity suggesting a plausible link between them. In this work we analyze the correlation between the NAO and the geomagnetic aa index in different time scales, ranging from daily to long-term scales. We obtain significant correlations mostly in long-term scales. This correlation vanishes at shorter time scales, although some effects can be detected for intense geomagnetic storms at a daily scale. An explanation of our results is given through the upper atmosphere processes induced by geomagnetic storms followed by coupling mechanisms among the different atmosphere regions, reaching finally the troposphere. Also, the fact that greenhouse gases increase are expected to produce a positive NAO trend, similar to that observed in aa index, is considered. Understanding and interpreting the causes of atmospheric variability, such as the NAO in this case, requires a fundamental understanding of the atmosphere response to solar variations. This is an essential focus of climate science, which is seeking to determine the extent to which human activities are altering the planetary energy balance through the emission of greenhouse gases and pollutants.