Instrumental pressure observations and atmospheric circulation from the 17th and 18th centuries: London and Paris

Abstract

Daily pressure observations recorded by William Derham (1657Derham ( -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.

A daily series of mean sea‐level pressure for Paris, 1670–2007

“…Since this time, a good deal of use has been made of the data contained in the journals Le Goff, 1987, 1992;Pfister and Bareiss, 1994;Slonosky, 1999;Slonosky et al, 2001). The barometer measurements for the period March 1670-December 1712, as used in the Paris Daily Pressure Series, have previously been transformed into the units of mmHg and reduced to standard temperature, gravity, and sea level by Legrand and Le Goff (1992).…”

“…In Paris, the physician, Louis Morin, began to record daily barometer observations in 1670, not long after the original experiments, and continued likewise until 1712 (Legrand and Le Goff, 1992;Pfister and Bareiss, 1994;Slonosky et al, 2001). The astronomical observatories also recorded meteorological observations from an early date, with the influential Paris Observatory recording barometer observations sporadically from 1669 (Cotte, 1774;Legrand and Le Goff, 1987).…”

Instrumental pressure observations from the end of the 17th century: Leiden (The Netherlands)

“…Note that in the calculation the barometric term in Equation (2) is really needed, as the response of thermometer B to 1°C temperature rise is the same as a drop of 5 hPa. Table III shows Senguerd's 17th century pressures for Leiden, together with those of London (Slonosky et al, 2001) and Paris (Legrand and Le Goff, 1992). The Leiden values are much lower than modern climatology.…”

“…An adjustment of 16.7 hPa is needed to bring the mean of barometer A to the 1971-2000 normal value of 1015.3 hPa of Valkenburg. This adjustment is large, but not unrealistic: the bias correction required for 17th century London data (9.5 hPa) is of comparable magnitude (Slonosky et al, 2001). The most likely cause is trapped air in the barometer originating from outgassing of the mercury, which had been neither boiled nor distilled before its use.…”

Reconstructing The Trajectory of The August 1680 Hurricane From Contemporary Records

“…Morin was a Paris-based scientist whose daily observations have already been of service (Slonosky et al 2001). Figure 2 shows Morin's corrected daily sea level pressure data for August 1680.…”