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Daily pressure observations recorded by William Derham (1657–1735) at Upminster, Essex (near London), from 1697 to 1706 and 1708 have been corrected, converted to modern units and the Gregorian calendar, and adjusted for homogeneity. These pressure readings have been compared with previously published contemporary observations from Paris, and the two sets of early instrumental data used to calculate a daily series of the pressure difference between Paris and London. Frequency analysis of the daily series reveals that reversals of the south–north pressure gradient and easterly winds were more common from 1697 to 1708 than during the 1990s. Monthly mean values of Paris–London pressure differences have been compared with previously published monthly mean reconstructed surface pressure maps and to a reconstructed North Atlantic Oscillation (NAO) index. There is a good agreement between the strength and direction of monthly mean flow between London and Paris estimated from the circulation maps and the sign and magnitude of the Paris–London westerly flow index, but the correlation between the Paris–London index, known to be a good proxy for European zonal circulation, and the reconstructed NAO index, is low (0.2). Correlations between the monthly mean Paris–London zonal circulation index and central England temperatures suggest a strong relationship during winter and late summer from 1697 to 1708. The meticulous daily instrumental observations and the monthly and seasonal climate descriptions of Derham, his collection of instrumental observations and climatic descriptions from contemporary observers throughout Europe, and his early theories on the causes of climate change make his publications a valuable source of information for studies on climate during the early instrumental period. It is hoped that more of Derham's papers related to weather and climate may eventually come to light. Copyright © 2001 Royal Meteorological Society. [ABSTRACT FROM AUTHOR]

The relationship between surface atmospheric circulation and temperature in Europe from the 1770s to 1995 is examined using correlation analysis. The atmospheric circulation is represented by six indices: the three leading principal components (PCs) of an empirical orthogonal function (EOF) analysis of 20 European pressure series from 1822 to 1995, which represent the central tendency of European pressure (EOF 1), a zonal circulation pattern (EOF 2) and a meridional pattern (EOF 3), a North Atlantic zonal index constructed from Gibraltar and Reykjavik pressure series for 1821–1995; a Western European zonal index constructed from Madrid, Barcelona, Lund and Trondheim for 1786–1995; and an index constructed from Paris and London, 1774–1995. Eight long temperature series from northwestern and central Europe were correlated with these circulation indices. European temperatures in general had the highest correlations with the zonal circulation indices in winter, with almost 70% of the variability in the temperature records explained by variations in the zonal index. The correlation coefficients between PC 3 (representing meridional circulation) and temperatures were highest in spring and autumn, particularly for Scandinavia. Running correlation series calculated over 25-year windows reveal significant non-stationarities in the relationship between surface temperature and atmospheric circulation on decadal time scales, suggesting caution must be used in extrapolating current relationships between circulation and temperature for future climate predictions based on downscaling or past palaeoclimatic reconstructions. Copyright © 2001 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

Long series of monthly surface pressure observations are analysed from the 1770s to 1995, using empirical orthogonal function (EOF) analysis and circulation indices. Analyses of the associated principal components show that the variability of surface atmospheric circulation over Europe (35°–70°N and 30°W–40°E) is well captured, using only 20 stations. The first three EOF patterns of the study are the central tendency of European pressure (EOF 1), a zonal flow pattern over Europe (EOF 2), and a blocking/cyclonic pattern in the eastern North Atlantic (EOF 3). EOF analyses on sub-periods of the station records suggest episodes of more intense meridional circulation (EOF 3) from 1822 to 1870, and stronger zonal westerlies from 1947 to 1995. Simple zonal circulation indices were also constructed for a North Atlantic Oscillation (NAO) index using Gibraltar and Reykjavik (1821–1995), a western European zonal index using Madrid, Barcelona, Trondheim and Lund (1786–1995), and a Paris–London index (1774–1995). Correlation analysis suggests that the NAO may be a better indicator of eastern North Atlantic blocking or cyclonicity (EOF 3) than of European zonal flow, especially outside the winter months. Both the western European and Paris–London zonal indices were highly correlated with the time series principal components (PCs) of EOF 2, extending the construction of a reliable monthly index of European surface westerlies to 1774. The zonal flow indicated by these circulation indices appears to have been considerably more variable, with more extreme values, in the late 18th and early 19th centuries than in the 20th century. From the 200-year perspective presented here, the recent positive trend in the NAO does not appear unusual. Copyright © 2000 Royal Meteorological Society [ABSTRACT FROM AUTHOR]