Droughts in Poland, 1951-90

One of the negative features of Poland’s climate is the periodic occurrence of atmospheric droughts. The most frequent source of this phenomenon is the occurrence of long-term (sometimes lasting several weeks) rainless periods. The occurrence of these periods is connected with the persistence of a stationary east European high that joins with the Azores anticyclone via central Europe. In such situations, with the accompanying lack or insufficiency of atmospheric precipitation, a drought begins to develop gradually. First, a soil drought appears, followed by hydrologic drought. During a hydrologic drought, a decrease in the ground water flow into surface waters is observed, among other phenomena. This results in the reduction of water flow in rivers. During such periods, a significant drop in the level of underground waters, as well as drying of some springs and small water courses, is observed. In its initial phase of development, a drought exerts its first negative effects on crops. Intensification of this phenomenon also causes disturbances in other sectors of the national economy. Droughts and their negative results do not pose the same threat to all areas of Poland, although in general the influence of droughts is stronger here than in the majority of central European countries. This situation is the result of a combination of natural and historic factors. One of the areas of interest of the Institute of Meteorology and Water Management (IMGW) is continuous monitoring and assessment of the course of meteorological and hydrological phenomena occurring in all areas of Poland. When preparing an analysis of the course of successive periods of drought spells, specialists from the IMGW branch in Poznan noticed the absence of similar studies of this phenomenon in Polish literature. In an attempt to fill this gap, they catalogued all droughts that occurred in Poland from 1951 to 1990. The research methods adopted in this study, and also the general characteristics of droughts in Poland, are summarized in this article

Wieloletnia zmienność temperatury powietrza i opadów atmosferycznych w zlewni rzeki Warty

The variability of the mean annual air temperature and precipitation totals in three periods: 1848–2010, 1951–2010 and 1981–2010 was investigated in the large Warta River basin, being the area with lowest rainfall in Poland. For the purposes of research, nine meteorological stations with the longest measurement series were selected. Air temperature increase in this river basin was similar than in neighbouring countries. In the last 30 years this trend kept increasing. The precipitation in the whole studied period was slightly increasing in the northern part of the Warta River basin, but decreasing in the southern part. The mean annual precipitation totals in the catchment area did not change visible. In the period 1981–2010, the precipitation totals show a small increase in the winter and spring and a decrease in summer. A negative influence of this climate change was not visible in the Warta River discharge. The main objectives of this study were the collection long-term records of air temperature and precipitation in the Warta River basin, and the statistical analysis of climate variability.W zlewni rzeki Warty, położonej w rejonie o najniższych w Polsce opadach atmosferycznych, analizowano zmienność średnich rocznych wartości temperatury i sum opadów w latach 1848–2010, 1951–2010 i 1981–2010. W tym celu wykorzystano dane z dziewięciu stacji meteorologicznych dysponujących najdłuższymi seriami pomiarowymi. Głównym celem tych badań było zebranie wieloletnich danych dotyczących temperatury powietrza i sumy opadów atmosferycznych w zlewni Warty i statystyczna analiza ich zmienności. Temperatura powietrza wzrastała w tej zlewni w podobny sposób, jak w sąsiednich krajach. W ostatnich 30 latach zaobserwowano nasilenie się tego trendu. Opady atmosferyczne w całym badanym okresie nieco wzrosły w północnej i zmalały w południowej części zlewni, ale średnia roczna suma opadów w całej zlewni nie zmieniła się istotnie. W latach 1981–2010 roczna suma opadów nieco wzrastała zimą i wiosną oraz malała latem. W średnich rocznych przepływach Warty negatywny wpływ tych zmian nie był widoczny