Climatic and bioclimatic conditions on the Labrador coast at the turn of the 20th century

Abstract

Meteorological sub-daily measurements (three to five times per day) conducted by Moravian missionaries at the turn of the 20th century provide a reliable description of the climatic and bioclimatic conditions of the Labrador coast. The observations were carried out on behalf of the Deutsche Seewarte and are available in the archives of Deutscher Wetterdienst (Germany). For the climate analysis, long, continuous sub-daily temperature series (7–36 years) for six stations—Rama (1882–1890), Hebron (1882–1918), Okak (1883–1889), Nain (1882–1913), Zoar (1882–1894), and Hoffenthal (1882–1898)—were used.

For the estimation of bioclimatic conditions, midday temperature and wind speed data were applied. Wind force was estimated using the Beaufort scale and converted to m s⁻¹ at a height of 1.2 m above ground. Mean daily air temperatures, calculated as the average of sub-daily measurements, were adjusted to true mean daily air temperatures. These corrected data were used to calculate standard climatic characteristics, including monthly, seasonal, and annual means; day-to-day temperature variability; thermal seasons; Growing Degree Days; Air Thawing Index; Positive Degree Days; and Air Freezing Index. To describe the bioclimatic conditions, two indices were utilized: Wind Chill Temperature (WCT) and Insulation Predicted (Iclp).

Mean annual air temperatures during the historical period were approximately 1.5–2.3°C lower than today, while wind speeds were lower by about 0.8 m s⁻¹. Spatial differences in climate and bioclimate conditions between stations in both periods were generally small. In the contemporary period, more favorable bioclimatic conditions occurred on the Labrador coast than in the historical period. Mean annual WCT and Iclp were smaller in the historical period by 1.8°C and 0.1, respectively, compared with the present. The results reveal both greater climate continentality and day-to-day variability in the historical period than today