Atmospheric pressure and anemological conditions in south-western Greenland in the second half of the 18th century

Abstract. Anemological and atmospheric pressure conditions were analysed based on two series (1767/68 and 1784–92) of meteorological observations from Nuuk, the capital of Greenland, located on the south-western coast. The first series is the oldest available long-term series of instrumental measurements for this region. Meteorological observations were conducted using instructions and instruments provided by the Palatinate Meteorological Society. The materials used in this work come from European archives: Moravian Archives in Herrnhut (Germany) and Det Kgl. Bibliotek in Copenhagen (Denmark).

Wind speed had been visually assessed by Moravian observers in a several-degree intensity scale, which was compared to the Beaufort scale and, finally, recalculated to the presently used units (ms^˗1). Atmospheric pressure measurements had been taken using a mercury barometer with Paris inch scales, whereas air temperature had been measured with thermometers in Fahrenheit/Réaumur scales; these were recalculated to hPa and Celsius degrees, respectively. The frequency of occurrence of atmospheric pressure values for different intervals was examined, as were the magnitudes of day-to-day changes that affect the human body. Each year during the historical period, episodes occurred when atmospheric pressure exceeded 1020 hPa. Day-to-day changes were typically below 8 hPa, but changes exceeding 12 hPa occurred in almost every month. Analyses of the frequency of wind from each of eight directions during the year and for the seasons revealed an exceptionally low frequency of wind from the SE direction (3 to 12 %) and that the highest frequency was for winds from the NE (19 to 37 %).

Observations of atmospheric pressure and wind made in the 18th century were compared with those of the modern period (1991–2020). Atmospheric pressure in the historical period was 5.9 hPa lower than the contemporary period, while the average wind speed for both periods was 6.1 m·s^˗1.