Zmiany, zmienność i ekstremalne sumy parowania terenowego i ewapotranspiracji potencjalnej w Łodzi w drugiej połowie XX wieku
Changes, changeability and extreme total surface evaporation and potential evapotranspiration in Łódź in 2nd half of the XXth century

Summary/Abstract: The work, which is presented below, is an attempt to keep up with changes and changeabilityof potential evapotranspiration (EVAP) and surface evaporation (PARTER) inperennial and seasonal aspect. Number of 50-years long series (between 1951-2000) of totalmonthly evaporation, obtained by Konstantinov method and potential evapotranspiration,calculated by Thornthwaite's formula were analyzed. The calculations based on the data fromŁódź-Lublinek hydrological observing station.Mean total annual potential evapotranspiration and surface evaporation during particulartime 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 perennialscale the alternate sequences of relatively low and high total annual surface evaporation wereobserved. They appeared rhythmically every 8 years. However, such regularity had not beenobserved for potential evapotranspiration.Total monthly surface evaporation distribution is the most often approximated by Weibull'sfunction. The calculated quantiJes of the probability of exceeding indicated that in July theevaporation of probability exceeding value of l% might be greater than 90 mm, while inNovember might slightly exceed 15 mm. Total evaporation of probability of exceeding equal to99% 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 ofsurface evaporation and potential evapotranspiration the participation of evaporation andevapotranspiration in winter and spring months (in total annual evaporation) systematicallyincreased, while the participation of summer and autumn months decreased. Despite the factthat the difTerent kinds of the observed changes in seasonal structure of evaporation andevapotranspiration in Łódź were ambiguous, they simultaneously indicate that water shortageswould be bigger in the region, as a result of increase of so called balance water loss.

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