Solar influence on North Atlantic mean sea level pressure

Abstract

A PRINCIPAL component analysis (PCA) of mean sea level (MSL) pressure data for the North Atlantic–European sector of the Northern Hemisphere has revealed evidence of a solar-terrestrial relationship. The principal components represent independent atmospheric circulation anomaly patterns and the coefficients give the variation in time of the contribution of each anomaly pattern^1,2. The data set described here comprises 101 winter MSL pressure anomalies (relative to the 1874 to 1974 winter average) on a 25-point, 20° longitude by 10° latitude grid covering the area 40°W–40°E, 30°N–70°N. Winters (December–February) are dated by the year of the January. The suitability of this grid for calibrating proxy data for the European sector is being investigated as a preliminary stage to the derivation of Holocene climatic information³. The data were obtained from the UK Meteorological Office, and are likely to contain in homogeneities due to different analysis techniques⁴ and so on. Some errors have become apparent in the course of the analysis and in general are confined to negligible low variance principal components. Missing data were replaced by the 101-yr mean for the grid point. Similar principal components were obtained by repeating the analysis for 30-yr sub-intervals. A slight latitudinal shift in the patterns occurred and there was some change in the relative importance of the principal components. Detailed results of the PCA are to be published elsewhere.