Abstract
The average latitude, longitude and central pressure of the four centers of action (Icelandic low, Aleutian low, Azores high, Pacific high) have been estimated for each of the 80 years of the Northern Hemisphere Historical Weather Map Series (1899–1978), and compared with year-average values of Northern Hemisphere surface temperature (NHST) and sea surface temperature (SST) in the region 0–10°S, 180–90°W of the equatorial eastern Pacific. Inasmuch as NHST and SST have been positively correlated during the 80-year period, their relations with the centers of action have been estimated using partial correlation coefficients. While there has been a tendency for northward displacement of all four centers of action at time of hemispheric warming, none of the partial correlations is significant at the 95% level, taking into account the serial correlation of the data. However, the correlation (r) of 0.31 in the case of the Aleutian low is on the verge of significance, and the correlation of 0.33 in the case of the Pacific high is appreciable. Hemispheric warming has, however, been associated with a significant lowering of pressure in the Icelandic low (r = −0.31) and Aleutian low (r = −0.45), the latter correlation being significant at the 99% level. A warm equatorial sea surface temperature has been associated with a significant southward displacement (r = −0.31) and higher pressure (r = −0.35) of the Icelandic low, as well as a significantly lower pressure of the Azores high (r = −0.36) and the Pacific high (r = −0.45), the latter correlation being significant at the 99% level.