Cool Autumns in the 1970's

Abstract

Autumns in the Northern Hemisphere during the 1974?78 pentad were substantially cooler than in the pentad ending in 1938. Zonally averaged surface air temperature in October along latitude 80°N was 4.8°C lower, while summers were 0.6°C warmer. The recent pentad is cooler between 20 and 80°N in all seasons except spring when virtually no change was detected. The largest temperature difference was observed in autumn and winter in the high latitudes, which is a region of negative surface heat balance. In latitudinal bands along 80, 65, 55 and 40°N, the average October temperatures were lower in the recent pentad than during 87% or more of the 1891?1978 period. However, July and August along 80°N were warmer than 91% of the 88-year long interval. Zonal mean temperatures used in the study were obtained from a recent publication of Gruza and Ran'kova (1979). Monthly surface air temperature anomalies during 1974?78 in the latitudinal belt close to the snowline were inversely related to anomalies of the total hemispheric snow and ice extent.