Low Altitude Atmospheric Circulation Characteristics of Arctic Oscillation and Its Relation to Solar Activity

A comparative analysis is made to the monthly average geopotential height, geopotential height anomaly, and temperature anomaly of the Northern Hemisphere at the place with an air pressure of 1000 hPa during the positive and negative phases of arctic oscillation (AO). The result shows that the abnormal warming period in the Arctic region corresponds to the negative phase of AO, while the anomalous cold period corresponds to its positive phase. It means that the abnormal change in the Arctic region is an important factor deciding the anomalies of AO. The AO phenomena occurring in January have a clear quasi-110-year centurial cycle and quasi-22-year decadal cycle, which are closely related to solar activities. The specific expressions are as follows: (1) The AO phenomena occurring in January have a clear quasi-110-year centurial cycle closely related to solar activities. The variance contribution rate of this cycle for AO indexes reaches 44.4%, which is the most significant centurial change characteristic of the AO phenomena in January. (2) The spectral analysis results show that the AO indexes in January after filtering out the 110-year centurial variation have a significant 22-year cycle, and their variance contribution rates reach 18.5%, which is the second important characteristics of the interdecadal changes of AO indexes after the quasi-110-year centurial cycle. The comparative analysis results show that there is a close inverse relationship between the solar activities (especially the solar magnetic field index changes) and the changes in the 22-year cycle of the AO in January, and that the two trends are basically opposite to each other. That is to say, in most cases after the solar magnetic index MI rises from the lowest value, the solar magnetic field turns from north to south, and the high-energy particle flow entering the Earth's magnetosphere increases to heat the polar atmosphere, thus causing the AO to drop from the highest value. After the solar magnetic index MI drops from the highest value, the solar magnetic field turns from south to north, and the solar high-energy particle flow passes through the top of the Earth's magnetosphere rather than entering it to heat the polar atmosphere. And thus the polar temperature drops, causing the AO to rise from the lowest value. In summary, the variance contribution rate of the changes in the Quasi-110-year centurial cycle and Quasi-22-year decadal cycle to the AO is up to 62.9%, indicating that solar activity is an important driving factor of the AO.