The first chapter presents the outline of the history of the meteorological network in the 19^th century in the southern Polish Kingdom which was denominated Galicia by the Austrian invaders. The second half of the 18^th century was characterized by extensive development of new branches of science in Europe. New instruments for measuring weather elements, such as mercury barometers and thermometers appeared. Unfortunately, political events in the Polish Kingdom namely three consecutive partitions impeded the development of science. In spite of the fact the new meteorological stations were founded, first in Warsaw in 1779, and later in Krakow in 1792. Professor Jan Śniadecki - a famous mathematician and astronomer, the first head of the Astronomical Observatory of the Jagiellonian University in Krakow began to gather records of instrumental and visual observations in 1792. The meteorological network in Galicia was founded in 1865 by the Physiographic Committee and its Meteorological Section. The Astronomical Observatory in Krakow was its central institution. The Committee published Materials for the Climatography of Galicia, from 1867 to 1914. They are a very rich assemble of used frequently in meteorological research. Solar radiation is the principal source of energy for atmospheric processes. Therefore, it is one of the key climate forcing agents. Next (II) chapter attempts to outline the history of heliographic and actinometric observations in the area of present-day Poland from their onset until the World War II. The first regular measurements of insolation began in Kraków in 1883. The measurements were also started early in such locations as Wrocław, Warsaw, Kołobrzeg and on Mt. Śnieżka. Before the World War I, and thus before the State Meteorological Institute (PIM) was established, measurements of insolation were also carried out (with frequent breaks) at a number of other stations. A rapid growth of the heliographic network can be observed after the end of the World War I. Systematic actinometric measurements were started in Warsaw in 1900. Besides Warsaw, regular measurements of insolation were carried out in a few other few places, e.g. in Silesia and on the coast. Some short series of measurements were collected for a few locations in the centre of the country as well. Actinometric measurements were also performed in the mountains. Initially, these comprises a short series between a few days and a few months, however longer series are available for Zakopane (1935-1938) and Mt. Kasprowy Wierch (1938-1939). The aim of the third chapter is to show the results of regular temperature and air pressure measurements conducted by David von Grebner in Wrocław from 1710 to 1721. This series is the oldest surviving measurement series available in Poland. They were conducted at various times however the most systematic ones are those taken just after sunrise. The following work presents the results of the analyses using morning temperature records. David von Grebner used Thermometrum Academiae Florentinae for the temperature measurements with its 180 degree scale. The air temperature in Wrocław in the observation period was probably colder than today. The analyses show a very high frequency of temperatures lower than –20.0 in Florentine scale. In the study period the mean annual temperature reveals a growing tendency. Rough comparison of the annual measurement periods of 1710-1720 and 1970 and 1981 showed some similarities between the courses of measurements however, reliable comparison of temperature values between historical and present-day periods is difficult due to conversion problems from the scale used on the Florentine thermometer in Wrocław to the scales used in contemporary thermometers. The next chapter presents the results of a comparison between the ten-day period values of relative air humidity and saturation deficit obtained from standard (manual) station and automatic station in Agro- and Hydrometeorology Wroclaw-Swojec Observatory of Wroclaw University of Environmental and Life Sciences for the period 2000-2009. The data for 2009 were used to verify calculated regression equations. Standard measurement of air humidity was accomplished by August psychrometer which was placed in the meteorological screen, 2 meters above the ground and by means of daily thermohygrograph. Saturation deficit mean daily values were calculated from three terminal measurements (7, 13, 19 CET) and relative air humidity from four terminal measurements (1, 7, 13, 19 CET). Mean daily values of two analyzed humidity indicators according to automatic station Campbell Sci. Ltd. (CR23X) were calculated from all 24 hourly values. In the fifth chapter the following material from the weather station in Ustka gathered during the period from April to September over the years 1986-2005 was used: 24-hour period values of air temperature, relative humidity of air, wind speed and atmospheric pressure and a number of days with precipitation >0.1 mm and >1.0 mm and the state of the sky. Apart from this, a decade of real sunshine over the years 1986-2000 was taken into account. The number of days of the following meteorological conditions was determined: comfort days (tmax 18-23°C), warm days (tmax >25°C), very hot days (tmax >30°C), days with 24-hour period of amplitude of air temperature >8 and >12°C, days with 24-hour period of relative humidity of air >85 and >95%, days with pressure changing every 24 hours within the values of >8 and >12 hPa, days with precipitation >0.1 and >1.0 mm in 24-hour period and with wind speed of >8 and >10 m s^–1. In the second part of the study, the bioclimatic indexes such as subjective temperature index STI, heat load of organism HL, predicted insulation of clothing Iclp and weather evaluation index WEI for the needs of recreation and tourism were taken into consideration. In the region of Ustka the dominating type of weather is warm weather (37% of days of the whole half-year period), then cool weather (31%), comfort days occur in 25%, and days with cold and hot weather – in 4 and 3%, respectively. Throughout the whole warm half-year period, the weather conditions in the region of Ustka are favourable for sunbathing if clothing of suitable insulation is worn, and in May the conditions are even very favourable. However, in this month, a low temperature of air is a limiting factor. In April, the moderately favourable weather occurs every three days on average and sporadically it is unfavourable. Similar weather conditions pervade for sunbathing. The bioclimatic conditions in the region of Ustka make it possible to lengthen the most intensive touristic season which lasts at present from mid-June to August, for about 45 days, i.e. from mid-May to mid-September. Previous research has shown that the thermal heat island in Warsaw is a frequent phenomenon but it does not occur every day. The goal of the sixth chapter was to determine the intensity of the urban heat island and its variability in the course of the day and night in conditions of light and heavy cloudiness. The study used meteorological data from automatic measurement stations made accessible by the Provincial Inspectorate for Environmental Protection (WIOŚ), collected in the period from 01.09.2003 to 31.12.2008 at four urban background stations in Warsaw, one in Piastów and at the regional background station in Legionowo, located beyond the range of influence of the Warsaw agglomeration. Information on a degree of cloudiness comes from observations conducted at the Warsaw University of Life Sciences (SGGW) meteorological station and from daily meteorological bulletins of the Institute of Meteorology and Water Management (IMGW). On the basis of the data, differences in air temperature between particular stations and the station in Legionowo were determined. The differences enabled determination of the intensity and time of the occurrence of the urban heat island. Frequency distributions of the differences were also carried out and the development and disappearance of the island at different times of day and night were graphically presented, taking into consideration seasons of the year. The phenomenon of an urban heat island appears both in the case of assumed cloudless days (N<=2) and cloudy days (N>6). On the analysed days the highest intensity of the urban heat island was recorded in the heart of the city centre (Krucza Street and Niepodległości Avenue). On cloudless days the intensity of the heat island was considerably higher than the intensity on cloudy days. The study presented in the next (VII) chapter involved daily mean air temperatures measured at 200 cm above the ground level, recorded by the meteorological station in the city of Bydgoszcz, Poland, between November and March 1946-2005. An atmospheric thaw event was defined as a period of two or more days with a mean daily temperature above 0°C that followed at least a three-day long period of a mean daily temperature below 0°C. Duration of winter thaws was expressed as a total number of days in the thaw, as well as sequences of up to 5, 6-10, 11-20, and more than 20 consecutive days of thaw, however, only in relation to winter seasons. Thaw intensity was described as mean daily air temperatures during thaw days within the winter thaw periods, as well as the frequency of the following temperature ranges: 0.1-1.5, 1.6-3.0, 3.1-4.5, 4.6-6.0, 6.1-7.5, and >7.6°C. A statistically significant increase in frequency and intensity of thaws in January and March was found for the period 1946-2005. It was demonstrated that both frequency and intensity of thaws, as well as the onset of spring thaw periods, was determined by atmospheric circulation in January, February, and March. In chapter eight the study was based on average and hourly concentrations of suspended particulates (PM10) over the years 2005-2007 recorded by seven measurement stations functioning within the range of the system monitoring the air quality (National Inspectorate of Environmental Protection). It was stated that during the years 2005-2007, the average concentrations of suspended PM10 particulates, recorded in series of hours and days with precipitation, were by 10 to 35% lower, depending on the season of the year and the day, than the concentrations recorded before the phenomenon occurred. However, a slight statistically significant effect was proved only in reference to the amount of precipitation, taking into account the concentration of PM10 particulates before precipitation. The lowest effectiveness was characteristic for the precipitation in summer, but contrary to the remaining seasons of the year, its positive effect in reducing the immission of particulates was still observed the next day after precipitation. The example of Częstochowa demonstrated that an analysis of hourly values of both variables gives definitely larger possibilities to evaluate the washing out role of precipitation, not only in respect if its amount, but also its intensity. Next chapter presents selected characteristics concerning precipitation conditions of the north-eastern Poland. The study is based on twenty-four-hour data originating from 14 stations and posts of the Institute of Meteorology and Water Management between 1951-2000. The research included analysis of the frequency of vegetation periods (IV-IX) with deficiencies or excess of precipitation according to Kaczorowska's criterion. The frequency of precipitation-free periods (lasting >=10, >=15 and >=20 days) was calculated for individual months of the vegetation period from April to September, and for the entire vegetation period, as well as the average number of days with precipitation >=0.0 mm, >=1.0 mm, >=5.0 mm, >=10.0 mm, >=20.0 mm and >=30.0 mm in the vegetation period (IV-IX). Additionally, a spatial diversification of selected precipitation indicators in the vegetation period in the examined area is presented. It was found that precipitation-free sequences of all analysed categories (>=10, >=15 and >=20 days) most frequently appeared in the areas of the lowest number of days with low precipitation (>=1.0 and >=5.0 mm) and at the same time of the most frequent occurrence of dry vegetation periods (selected according to the classification presented by Kaczorowska), i.e. in the western and the south-western parts of the region. The study in the tenth chapter presents the comparison between two methods (objective and subjective) of atmospheric circulation classification. The comparison of the two methods indicated some discrepancies stemming from the differences in typological procedure, the quality of data sources and various layouts of baric systems. The objective method is partly based on Jenkinson and Collison method. The degree of adaptation of the objective method to subjective method of classification of atmospheric circulation were checked by means of a comparison of daily circulation types in both methods on a given day and analyses of synoptic situations. Moreover, selected meteorological parameters during particular circulation types in both methods were also analyzed. The comparisons show that both methods in many cases give different results of classification of synoptic situations. This discrepancy results from different methodologies of determination of atmospheric circulation types in both methods. The purpose of the eleventh chapter is to examine the relative impact of North Atlantic Oscilation (NAO) on the atmospheric instability over Europe and to compare it with the influence of other circulation patterns such as: East Atlantic Pattern (EA) and Scandinavia Pattern (SCAND). The investigation is based on selected instability indices such as: Vertical Total (VT), Total Totals (TTI), KI index (KI) and Convective Available Potential Energy (CAPE) using the radio sounding measurement from 41 European stations taken at 00UTC over 1993-2007. To examine the influence of different circulation patterns on the instability is based on correlation coefficient calculated for monthly average from May to August. Results show positive values of correlation coefficient between TTI and KI indices and NAO circulation type over southern Europe in July and August, and negative correlation over the Scandinavian Peninsula and over the zone from Ireland to Poland. The strongest relationship is observed between selected instability indices and SCAND index over northern and central Europe. Four instability indices: CAPE, LIFT, KI, TTI are described and the potential of these indices in storm prediction is examined for the area of Northern Poland. The analysis in the next (XII) chapter is based on upper air sounding data from Łeba, Legionowo, and Greifswald and storm data from meteorological stations in Szczecin and Suwałki regions for the period 1981-2000. The analysis revealed that the best upper air station for storm forecast in Suwałki region is Legionowo whereas for Szczecin it is Greifswald or Łeba. 12.00 UTC atmospheric soundings represent convective phenomena better than 00.00 UTC soundings. Threshold values for each analyzed instability index differ according to a month and K Index seems to be the best instability predictor, especially when it comes to storm forecast. Thirteenth chapter presents results of research concerning the analysis of the Arctic Oscillation (AO) variability in the period of 1971-2006. AO daily data allowed the recognition of the period of distinct features in AO course. The usage of daily AO values enabled the analysis of other statistical characteristics, namely extremes. The selected sub-periods in the AO course serve as a point of reference for the analysis of relative vorticity field evolution in the Euro-Atlantic region. The analysis revealed major differences in the course of AO and its characteristics as well as substantial shifts in the relative vorticity field. Eddy covariance method is currently the main tool used to measure mass and energy flux exchange between various ecosystems and the atmosphere. The XIV chapter presents the principles of the method as well as the strategy of data management in the case of the data obtained from the measuring system used by the Meteorology Department of the University of Life sciences in Poznań. Subsequent steps of the procedure were described in detail and their influence on the obtained results was presented in the charts. The fifteenth chapter presents the results of climatological elaboration of pluvial conditions in Beskid Śląski Mts. The data come from measurements from the years 1957-2008 which were collected at 26 meteorological stations and posts situated in Beskid Śląski region. The aim of this study was evaluation of the rainfall changeability on spruce stand stability in Beskid Śląski lower subalpine forest zone. The multiannual average rainfall indices showed no significant change. Total precipitation has decreased in the warm part of the year, this decrease is mainly observed in June and July. Total precipitation in May several times evolved the standard deviation, both positive and negative, in the last two decades. In June there were significantly more likely to decline relative to the average of many years, most often highlighted as one of the decade from 1988 to 1997. In this respect July is unique, because through 20 consecutive years, with one exception that is 1980, the yearly sum of precipitation was lower than climate pluvial norm for this month. Complementing this disadvantage was the fact that during the period from 1990 to 1996, indicators of rainfall in three consecutive months: May June and July were lower than the multiannual average Field studies presented in the next (XVI) chapter were carried out on marshland areas in the Promotion Forest Complex Rychtalskie Forest. Marshland areas are characterized by very large water storage capacities. Weather conditions in the study period were evaluated on the basis of data from the Siemianice Station, where measurements have been taken since 1975. The analysis involved the hydrological year of 2004/2005, which in terms of total precipitation (514.5 mm) and mean annual temperature (8.6°C) may be considered as average, since deviations of the above values do not exceed 10% from the respective means. The trend of mean annual air temperatures is positive (+0.027oC year^-1). The trend of total annual precipitation is negative (-1.573 mm year^-1). Total annual outflow is relatively small – about 4% of the total annual precipitation and it occurs only in winter half-year and in May. Ground water levels lie shallow, about 1 m under the surface area. The forecast of water condition change in the investigated areas, expressed by ground water changes, was based on negative trend of precipitation. It has been assumed that, essential changes on marshland area ecosystems will occur, when average ground water levels come down by about 50% of the present state. It has been estimated that it will happen after around 100 years. Chapter seventeen discusses the principles of data quality monitoring for the meteorological data obtained from automatic measurement stations. The analyses used the data from the years 2005-2007 which were obtained in four automatic measurement stations located in Wielkopolska region. WMO guidelines applied to conduct their qualitative analysis were adopted to the climatic conditions of the site in which the monitored meteorological station operates. The results indicate that even regularly serviced measurement stations are not capable of maintaining absolute continuity and reliability of measurements. Thus, independently of the method of measurement there are some information gaps in the collected data which should be filled applying proper methods also described in this chapter.