AIR TEMPERATURE VARIABILITY IN THE COASTAL ZONE OF THE KALININGRAD REGION FOR THE PERIOD 1848–2024

Abstract

The article presents an analysis of time series of air temperatures that determine the behavior of the natural environment in the coastal zone of the Southeastern Baltic Sea. The analysis is based on historical monthly data on the average air temperature for the weather station in Kaliningrad (Königsberg) (1848–2024). A comparison is made with the surface air temperature according to the ERA5 reanalysis data for the Southeastern Baltic for the period 1950–2024. The obtained statistical characteristics and calculated linear trends made it possible to distinguish three periods in the region that characterize the temperature regime: 1) a decrease in temperature in the second half of the 19th century; 2) “secular” stagnation throughout the 20th century; and 3) a steady increase (trend 0.35 ºC/decade), starting from 1988, which was especially pronounced at the end of the first quarter of the 21st century. This indicates temporal heterogeneity due to seasonal trends. A comparison of seasonal temperatures with those during the standard climate period (1961–1990) revealed that during the period of intensive growth, only three winters were recorded with temperatures below the standard period, while the average summer temperature exceeded standard values, with maximum anomalies of up to +2.7 °C characteristic of the final years of the study period. Changes in seasonal air temperature variability include an extension of the growing season, a reduction in the number of frost days, and a decrease in winter severity. The intensity of the climate process has increased, resulting in an increased frequency of extreme events (e.g., heat waves). Over a shorter period (1940–2024), the average annual temperature over the southeastern Baltic Sea is 0.4°C higher than over the adjacent land. The intra-annual variation in average monthly air temperatures is smoother over the sea. This is evidenced by the range of fluctuations of 20.4 °C over land and 17.6 °C over the sea, as well as the monthly shift in the maximum average monthly temperature: July (17.8 °C) over land and August (17.7 °C) over the sea. The decadal trend (°C/10-year trend) over this period over the sea exceeded the trend over land by 1.7 times, driven by the maximum trend increase in Kaliningrad in winter (4.7 °C/February/period), and over the sea – 4.4 °C/period in summer. In the coastal zone of the Southeastern Baltic Sea, an increase in the duration of the summer climatic season and the frequency of heat waves, particularly in May–June, were observed, as well as a decrease in the severity and duration of winters.