Zmiany, zmienność i ekstremalne sumy parowania terenowego i ewapotranspiracji potencjalnej w Łodzi w drugiej połowie XX wieku

Abstract

The work, which is presented below, is an attempt to keep up with changes and changeability of potential evapotranspiration (EVAP) and surface evaporation (PARTER) in perennial and seasonal aspect. Number of 50-years long series (between 1951-2000) of total monthly evaporation, obtained by Konstantinov method and potential evapotranspiration, calculated by Thornthwaite's formula were analyzed. The calculations based on the data from Łódź-Lublinek hydrological observing station. Mean total annual potential evapotranspiration and surface evaporation during particular time were equal to 632.9 mm and 452.5 mm, while variation coefficients were the following: 3.7% and 6.3%. Both characteristics had positive significant trends (Ol: = 0.05). In perennial scale the alternate sequences of relatively low and high total annual surface evaporation were observed. They appeared rhythmically every 8 years. However, such regularity had not been observed for potential evapotranspiration. Total monthly surface evaporation distribution is the most often approximated by Weibull's function. The calculated quantiJes of the probability of exceeding indicated that in July the evaporation of probability exceeding value of l% might be greater than 90 mm, while in November might slightly exceed 15 mm. Total evaporation of probability of exceeding equal to 99% in winter months were higher than 3 mm, while in summer exceeded 50 mm. The results of investigation seemed to prove that in the studied seasonal structure of surface evaporation and potential evapotranspiration the participation of evaporation and evapotranspiration in winter and spring months (in total annual evaporation) systematically increased, while the participation of summer and autumn months decreased. Despite the fact that the difTerent kinds of the observed changes in seasonal structure of evaporation and evapotranspiration in Łódź were ambiguous, they simultaneously indicate that water shortages would be bigger in the region, as a result of increase of so called balance water loss.