Long-term tendencies in variations of hydro-meteorological characteristics in Kaliningrad Oblast

Abstract

The variability (1901–2018) of the average annual values of air temperature, precipitation and sea level with climate averaging (within 30-year climatic periods with a shift of the 30- year “window” in 10-year increments) was analyzed for the coastal zone of the Kaliningrad Oblast (the territory of Russia in the southeastern part of the Baltic Sea). It was found that their synchronous increase was identified in the second half of the twentieth century (from the 1950s), intensified in 1961–1990 and, especially, in 1991–2018. This increase provides an apparently high correlation coefficients between the time variations of the 30-year average of these parameters (r = 0.70÷0.95), although in fact this synchronous increase is a response to external (for the region) impact. Considering the link between the variations of 30-year averages around the lines of their positive trends, it was found that this link (a) is extremely weak for precipitation and air temperature (r = 0.10); (b) is weak for sea level and precipitation (r = 0.48); and is rather high for sea level and air temperature (r = 0.85). Analysis of changes in average annual values of these parameters within 30-years periods showed that trends for the air temperature and sea level were extreme in the last period (1991–2018). A more detailed consideration of changes in the average annual temperature, precipitation and sea level over 15-year half-periods within time of growth (1961–2018) showed that the main increase occurred in the first half of this interval, and this increase was slightly slowed down in the second half. The increase in average annual air temperature is mainly due to an increase in temperature in winter and spring, which is associated with a decrease in contrast between seasons. The ambiguity of the contribution of extreme levels to the growth of the average annual level (4.5 cm/decade) was shown for 1961–2018: the positive trends of the minimum level was 3.4 cm/decade, and for the maximum level – 1.2 cm/decade. It was noted that the main increase in the average annual level was due to the growth of the level in the winter period. The reason may be an increase in the number of warm and humid winters due to general climate warming.