Homogenization Techniques for European Monthly Mean Surface Pressure Series

Abstract

The quality of 51 series of surface pressure (extending back to between 1780 and 1871) over Europe is assessed using three different homogenization techniques. A new technique introduced here based on an iteration of multiple qualitative comparisons and adjustments (MCAs), and the Caussinus and Mestre technique, based on multiple decision rules and Bayesian statistics, are two methods that do not require a homogeneous reference series for the detection and adjustment of inhomogeneities. The third technique, the standard normal homogeneity test, does require a homogeneous reference series for the homogenization procedure, and has been used only on the last 100 yr of each station series. The results of the three methods, as well as the original, unadjusted data, are compared for differences in the variance of the individual series and in their interstation correlations. Empirical orthogonal function analysis is also used to assess differences in the results of the adjustment methods. The comparisons suggest that surface pressure in this geographical domain may be considered as being stationary over periods ranging from decades to centuries, and thus homogeneous parts of a surface pressure record can be used to adjust for inhomogeneities, as is done using MCA. It is also seen that EOF analysis can be an effective tool to assess the homogeneity of a dataset. The results of the EOF analysis show that inhomogeneities and poorly adjusted series can have undue influence on subsequent analyses.