Northern Hemisphere Surface Pressure and Climatic Fluctuations and Vegetation Growth in Northern Finland

Abstract

THE recent article by Dr. I. Hustich¹ and the accompanying note of Dr. E. W. Jones presenting data on vegetation growth and temperature trends in Europe are of considerable interest when viewed in relation to trends in the surface pressure of the northern hemisphere during the period 1899–1939. I have pointed out recently² that there has been a considerable decrease in the total mass of air over the northern hemisphere between 1899 and 1939. The accompanying graph, which is reproduced from that paper², shows the departures of mean annual hemisphere pressure from normal for the 41-year period. These values were obtained from the series of Daily Historical Maps³ prepared in the United States in 1943–44. The smooth curve shown is the cubic regression line fitted to the annual departures by the method of orthogonal polynomials⁴.