Abstract
The objective of the paper consisted in determining the effect of macroscale types of NAO, AO, EA, EAWR, SCAND, and AMO atmospheric circulation on changes in water temperature in Polish rivers. The study has made use of a broad body of hydrometeorological materials covering daily water temperature values for 96 water gauge stations located on 53 rivers and air temperature values for 43 meteorological stations. Percentage shares of positive and negative coefficients of correlation of annual, seasonal, and monthly circulation type indices with air and river water temperature were determined, demonstrating the character of teleconnection. Determinations were made of water temperature deviations in positive and negative phases of the analyzed indices from average values from the years 1971–2015, and their statistical significance ascertained. Research has shown that relations between the temperature of river waters in Poland and macroscale circulation types are not strong, however they are noticeable, sometimes even statistically significant, and both temporally and spatially diverse. NAO, AO, EA, and AMO indices are characterized by a generally positive correlation with temperature, whereas SCAND and EWAR indices are characterized by a negative correlation. Research showed a varying impact of types of atmospheric circulation, with their effectiveness increasing in the winter season. The strongest impact on temperature was observed for the positive and negative NAO and AO phases, when deviations of water temperature from average values are correspondingly higher (up to 1.0 °C) and lower (by a maximum of 1.5 °C), and also for the positive and negative SCAND phases, when water temperature are correspondingly lower (by a maximum of 0.8 °C) and higher (by 1.2 °C) than average values. The strongest impact on water temperature in summer, mainly in July, was observed for AMO. The results point to the complexity of processes determining the thermal regime of rivers and to the possibility of additional factors—both regional and local—exerting an influence on their temporal and spatial variability.
Highlights
The temperature of river water constitutes an important element of the hydrological regime, being subjected to daily, seasonal, annual, and multi-annual change [1]
An analysis of annual variables shows that positive correlations with temperature values were typical of the North Atlantic Oscillation (NAO), Arctic Oscillation (AO), East Atlantic (EA), and Atlantic Multidecadal Oscillation (AMO) indices, whereas negative correlations were predominant for the two remaining indices (EAWR and SCAND)
The analysis showed that the correlational relations of macroscale circulation types with the average water temperature of rivers in Poland are similar to those of air temperature, with the difference being that the strength of the former is weaker (Figure 3B)
Summary
The temperature of river water constitutes an important element of the hydrological regime, being subjected to daily, seasonal, annual, and multi-annual change [1]. The thermal characteristics of river waters are impacted first and foremost by air temperature, the variability of which points to a considerable dependence on macroscale types of atmospheric circulation [6,7,8,9,10]. Żelazny et al [13] have recognized the following as being the main factors controlling the variability of water temperature in mountain rivers (Tatry Mountains—Poland), which are characterized among others by a low degree of anthropogenic interference: height relations (48.5% of variability) and the thermal and hydrological regime of individual water-courses (22.5% of variability)
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