The average influence of decadal solar forcing on the atmosphere in the South Pacific region

Abstract

Composite mean difference analyses are applied to historical sea level pressure (SLP) and sea surface temperature (SST) data to investigate the spatial dependence of the Pacific climate system response to 11-year solar forcing. Previous work has found that the SST and SLP responses are most clearly detected near the times of sunspot maxima, which occur as much as two years prior to the centers of the broad decadal solar cycle maxima. In January-February, the SLP response at sunspot maximum is nearly the same on either side of the equator, although the amplitude is larger in the winter hemisphere. The solar influence is seen as above normal SLP in the sub-Arctic Pacific, as found previously, and as corresponding positive SLP anomalies in the sub-Antarctic Pacific, as shown here for the first time. These SLP anomalies are associated with previously documented signals at sunspot maxima of greater ocean upwelling and cooling along the Pacific equator, and a poleward extension of the tropical convergence zones in both hemispheres. Previous studies using multiple linear regression methods show the broad decadal solar maxima being associated with the lagged warm response in equatorial Pacific SSTs seen in the composites, which is not inconsistent with the present results. In the South Pacific Ocean, the solar effect is visible in the southern summer in the year before the sunspot number peak. The SST and SLP anomalies in the South Pacific in the solar peaks differ markedly from those in Cold Events (La Nia events) of the Southern Oscillation. Copyright 2011 by the American Geophysical Union.