Climate conditions of the coastal part of Labrador in the late 18th century

This study focuses on the analysis of air temperature, pressure and wind conditions of Labrador's coastal region in the period 1771-1787.To reconstruct the climatic conditions of this historical era, we draw upon invaluable instrumental meteorological observations made by the Moravian missionaries. All data were taken from three primary archival collections: the Moravian Archives in Herrnhut (Germany), the Moravian Archives at Muswell Hill in London, and the Archives of the Royal Society in London (Great Britain).

The eighteenth-century Moravian missionary observations offer a unique perspective on the climate of the Labrador coast, providing essential data on air temperature, atmospheric pressure, wind force and direction, and short descriptions of the weather, observed two, three, or four times a day. By examining records in a detailed and systematic manner, we aim to better understand the region's climate variability and trends during the early instrumental period. For this study, we utilized sub-daily air temperature, atmospheric pressure, and wind force and direction measurements from three sites: Nain (1771-1786), Okak (1776-1787), and Hoffenthal (1782-1786). All available historical data were quality controlled and converted to present units (°C, hPa, ms^˗1 ). The necessary corrections to all studied variables were introduced. For example, the original daily air temperature means (calculated from different measurement times) were corrected to real means calculated from 24 hourly measurements. Corrections for each month were calculated based on contemporary data (1991–2010). The corrected data have been used to calculate monthly, seasonal and yearly means and other statistics. For example, we calculated a number of different categories of cold/warm days, growing degree days sum (GDD), air thawing index degree-days sums (ATI), positive degree-days sum (PDD) and air freezing index degree-days sum (AFI). The last four indices were calculated using definitions proposed by Nordli et al. (2020). The climate conditions of the study period in the coastal part of Labrador are compared to present-day ones.

The work was supported by the National Science Centre, Poland project No. 2020/39/B/ST10/00653.

References:

Nordli, Ø., Wyszyński, P., Gjelten, H. M., Isaksen, K., Łupikasza, E., Niedźwiedź, T., and Przybylak, R., 2020, Revisiting the extended Svalbard Airport monthly temperature series, and the compiled corresponding daily series 1898–2018, Polar Res., 39, 3614, http://dx.doi.org/10.33265/polar.v39.3614.