Principal component analysis of the Lamb catalogue of daily weather types: Part 1, annual frequencies

Principal component analysis is applied to annual weather type frequencies for the British Isles. The results objectively define characteristic relationships between the different types, and are used to determine changes in the atmospheric circulation in the region of the British Isles over the period 1861 to 1980. It is shown that, as far as annual frequencies are concerned, only six (of the 27) weather types are needed to define and monitor changes in the atmospheric circulation.