A Closer Look at the Effect of the 11-Year Solar Cycle and the Quasi-biennial Oscillation on Northern Hemisphere 700 mb Height and Extratropical North American Surface Temperature

A recently discovered association between the 11-year solar cycle and the Northern Hemispheric low-frequency atmospheric circulation structure, which is most easily delectable when the two phases of the Quasi-biennial Oscillation (QBO) are considered individually, is described and subjected to global statistical significance tests. Highly significant relationships are found during the January–February period. This is especially true for the west QBO phase, in which the solar flux is positively correlated with 700 mb heights and surface temperatures over central and northern Canada, and negatively correlated with heights in the western Atlantic along 30°N and with temperature in the southern and much of the eastern portions of the United States. The pattern of the flux-height correlation field resembles primarily the Tropical/Northern Hemisphere (TNH) long-wave circulation pattern and secondarily the North Atlantic Oscillation (NAO) pattern. For east QBO phase years a different structure is found, and for all years pooled a weaker but quite Characterizable pattern emerges. January–February correlations are studied for sensitivity to lead time in the QBO phase definition and for shorter period means for the west QBO phase. The latter inquiry reveals a concentration of the west phase relationship during the latter half of January. The climate of the October–November period also appears to participate, to a lesser but significant degree, in a solar–QBO relationship for west phase QBO years. For the west QBO phase, the January–February solar flux versus 700 mb height (and United States–Canada surface temperature) correlation pattern contains sufficient amplitude and field significance to be exploited for operational forecasting purposes at the Climate Analysis Center. However, in the absence of a verifiable physical basis of the solar–QBO–atmosphere association, and because the 45 mb stratospheric winds were selected to characterize the QBO in an a posteriors manner, the relationships are accepted with caution and will be regularly reevaluated.