abstract: The next chapter uses the records of mean daily precipitation during the period of 1954-2003 gathered from 7 stations located in the Baltic coast. The annual variability patterns of precipitation and the occurrences of weak and heavy precipitation were analyzed. Using selected characteristics (annual amplitudes of monthly precipitation, irregularity index, precipitation semi period) the following parameters were determined: the level of pluvial continentalism and the season of maximum concentration of precipitation, as well as the dependence of the atmospheric precipitation on regional advection of air masses. Chapter 4 was also devoted to precipitation analysis, it used monthly the results of the atmospheric precipitation measurements conducted in the period of 1951-2005 in 6 meteorological stations located in the middle section of the Oder catchment area. The work examined the variability of precipitation and trends of the changes in different time ranges on the basis of the analysis of 30-year moving sequences. The statistical measurements of precipitation were presented (means, variation coefficient, standard deviation and values of quantiles 10% and 90%), as well as the linear functions illustrating the trends in precipitation changes both during 4 seasons and annually. The results indicate that there is a downward trend in the precipitation but the variability is on the increase; the amount of precipitation and its variability increase in winter, whereas they tend to decrease in spring and autumn. The amount of precipitation influences the amount of water in the environment, its shortage leads to drought which can be described using various indexes. Two of them were used in the following chapter: one is the standard precipitation index SPI, which was estimated on the basis of precipitation during the warm half-year (IV-IX) as well as particular months, and the other is the standardized index of climatic water balance. The research used meteorological data from Wrocław-Swojec station, gathered during the period of 1964-2006. The obtained results indicate heavy precipitation shortage in the region of Wrocław. The biggest negative climatic water balance was observed in 1992 and in the very year both indexes defined drought as extreme. Statistically confirmed increase of air temperature in the years 1964-2004, as well as the downward trend in precipitation, makes the water shortage even worse. The classification of droughts according to two indexes SPI and SCWB gave almost the same quantitative results only the intensity was differently qualified. The next two chapters were devoted to the length of snow cover lingering and snowfall. Chapter 6 examined the data gathered in the period of 1951-2008 from 83 meteorological stations in the area of the whole Poland. The number of days with different thickness of snow cover during two seasons was analyzed: October - May and December - March, as well as the frequency of occurrence of snow cover, length of its lingering, and the medium and maximum thickness of the snow cover. Chapter 7 uses the observations from the meteorological station of the Jagiellonian University gathered in the period of 1951-2008. Long-term changes in the dates of occurring and declining of snow precipitation, the length of the snowy period and also the number of days with snow precipitation and the level of precipitation were analyzed. The trends of changes in the whole winter season and individual months from November to March were studied, both for the 58-year research period and for shorter 30-year periods. The work estimated also the dependence of the number of days and the level of snow precipitation on the index of the regional atmospheric circulation and NAO. It is interesting that, despite noticeable warming, the length of the snowy season in Kraków increases by nearly 4 days every 10 years. A very important scientific task is to determine how the climate changes influence various ecosystems. One of the possible methods of addressing this question are the measurements of the fluxes of mass and energy exchanged between the surface and the atmosphere, particularly the measurements of greenhouse gases such as CO2 and H2O. Unit 8 presented in great detail the Eddy Covariance method used to measure the exchange of the gases between a peat bog and the atmosphere; additionally, the water use efficiency index (WUE) was determined. The measurements were conducted in 2004 in Rzecin. The WUE is a good ecosystem index helpful to estimate the amount of water needed for evapotranspiration and assimilation of CO2 from the atmosphere by a given ecosystem. The presented results show the seasonal variability of this index. In the first quarter of the year, the WUE ranged from 0.8 to about 1.5 g (C-CO2) kg-1(H2O) (a gram of carbon in the form of carbon dioxide per a kilogram of water), while during the full vegetation period, it was 2.8 g (C-CO2) kg-1(H2O). Surprisingly, it turned out that during the autumn-winter period this coefficient continued to grow, which appears to be specific only for wetland environments. The aim of the last chapter of the monograph was to show the capabilities of the Weather Research and Forecasting (WRF) model. The model was used to prepare the weather forecast for countries in the central Europe, especially for the territory of Poland. The paper shows the flowchart for the WRF Modeling System Version 2.2 and the short description of the main blocks. It describes the way of assimilation of the WRF model to Polish climate conditions. It shows the way of preparing climate simulations by means of outputs of ECHAM5 model including different scenarios of CO2 emissions.