Forty-Year Sea Level Pressure and Sunspots

Abstract

The 40-1/2 years of mean montly sea level pressure maps based on the Historical Map Series have been typed according to numerical indices that indicate to what extent each particular monthly map resembles a typical or normal winter or summer map on one hand, or a typical spring or fall map on the other hand. These indices are easily determined from the average pressure of certain key areas and are quite effective in separating the winter from the summer months and the spring months from the fall months. The persistence in these indices and their relation to the sunspot cycle has been investigated.