Sensible temperature at the Łeba Sandbar (Słowiński National Park) on selected days of the 2010 summer season

The analysis was performed on the basis of weather measurements conducted in the Słowiński National Park at the Łeba Sandbar in the period from 8th July to 6th August 2010. Two biometeorological indices were calculated: the effective temperature (ET) and the radiative-effective temperature (RET). The daily course of RET was used to select the typical days, which were then subjected to a detailed analysis. This consisted in assessing the influence of individual meteorological elements and the synoptic situation on the development of the values of the RET and ET indices. A considerable diversity of sensible conditions was determined, as well as the considerable variability thereof during the day, in particular during the movement of atmospheric fronts. The sensible conditions were also influenced by factors connected with local circulation and the presence of the sea. Finally, a considerable decrease in the values of RET and ET was observed during changes in wind direction, namely when the wind was blowing from the northern sector

Evaluation of thermal conditions in Jeziory (the Wielkopolski National Park)

The purpose of this paper is to present selected methods of evaluation of thermal conditions in the Wielkopolski National Park and their initial characterization. The analysis was based on data from the automatic meteorological station in Jeziory measured during the period 2001–2010. The calendar of thermal classes graphically shows the variation in thermal conditions for each month and deviation from the standard adopted for the period concerned (Table 2). A good complement to the calendar seems the graphs of mean daily air temperature for months above and below the standards that enable their connection with the peculiarities of weather occurring in the area of Central Europe (Fig. 1). In addition to complete characterization of thermal conditions, specific number of days according to the average daily temperature ranges (Tavr): tavr. < 10°C, tavr. 10.1–15.0°C, tavr. 15.1–20.0°C, tavr. 20.1–25.0°C, tavr. 25.1–30.0°C and interdiurnal changes of average daily temperature (ΔTavr): Δtavr. 6.0°C were calculated (Table 3, 4). They were the basis for separating the year into thermal seasons (Table 5, Fig. 2). Ward’s method was used giving the best results in the case while both Tavr and ΔTavr were taken into consideration. The results obtained allow concluding that different methods of evaluation of thermal conditions applied separately do not give a full picture of thermal conditions of the area. Only a combination of results obtained using the Ward’s and calendar methods can give a complete thermal conditions characterization

Atmospheric circulation conditions during winter warm spells in Central Europe

The objective of the paper was to characterise the temporal and spatial variability of winter warm spells in Central Europe in the years 1966/1967-2015/2016 and to determine the circulation conditions of their occurrence. The applied data were obtained from the Polish Institute of Meteorology and Water Management, Deutscher Wetterdienst and the National Centre for Environmental Prediction/National Centre for Atmospheric Research. A warm spell was defined as a sequence of at least three warm days, i.e. when the maximum air temperature is higher than the 95th percentile of the probability density function designated from observation. The research has proven that over the study period the air temperature increased in the winter season in Central Europe and this translated into an increase in the number of warm days. An average of 3-5 warm spells was recorded per 10 years. The most numerous warm spells occurred during three winter seasons, i.e. 1989/1990, 2006/2007 and 2015/2016. The occurrence of warm spells was related to positive anomalies of geopotential heights over the study area in the cross section of the entire troposphere. Maximum anomalies appeared at 250 hPa geopotential height, and they developed on average 9 days before the commencement of warm spells over the study area

Synoptic conditions governing upwelling along the Polish Baltic coast

The study analyses atmospheric feedback to the occurrence of upwelling along the Polish Baltic coast. Upwelling events were identified on the basis of daily mean sea surface temperature (SST) maps from the period 1982–2010 derived from the NOAA OI SST V2 High Resolution Dataset. Synoptic conditions favourable to the occurrence of upwelling were determined on the basis of the NCEP/NCAR reanalysis data. On average, there are approximately 23 days with upwelling each year along the Polish Baltic coast, which account for approximately 13

Initial assessment of the Weather Research and Forecasting model for forecasting bioclimatic conditions during breeze circulation – case study of the Słowiński National Park

Land-sea interaction at the Polish Baltic Coast impacts the specific local climate conditions. Thermally driven circulation, observed mainly in the summer season, causes the advection of the cool sea air over land and influences the local atmospheric environment, including bioclimatic conditions. The aim of this paper is to present the evaluation of the WRF model for forecasting sensitive bioclimatic conditions on a selected day with sea breeze in the vicinity of the Łeba Sandbar (the Słowiński National Park). The results obtained from a numerical weather prediction model were post-processed to calculate the daily variability of two biothermal indices: the Effective Temperature (ET) and the Dry Cooling Power (H). To evaluate the thermal comfort of a person wearing typical clothes, the Michajlow’s, Petrovič and Kacvińsky’s scales were adopted. A detailed analysis performed for 31st July 2010 shows in most cases a satisfactory level of agreement between the simulated data and the in-situ measurements for nested domains with horizontal grid resolution less than 2 km. However, the simulation results tend to underestimate the thermal comfort, especially in the middle part of the Łeba Sandbar due to terrain data misrepresentations, which results in the overestimation of wind speed

Sezony bioklimatyczne międzydobowych zmian ciśnienia atmosferycznego w Poznaniu w drugiej połowie XX wieku

The article analyses the interdiurnal changes of atmospheric pressure as biometeorological mechanical stimulus that exerts influence on the human organism. It is based in the study of the daily values of the atmospheric pressure recorded in the years 1951–2000 in the area of Poznań. The following classification of inter-diurnal pressure changes is used in the research: type a, when the change is lower than 1 hPa and is not felt by the human organism; type b, when the range of the change is 1–4 hPa and is felt by the human organism only to an insignificant degree; type c, the average; type d, significant (Kozłowska-Szczęsna et al. 1997). The area of study is the mutability of pressure change throughout the period of many years and finding out the patterns in these changes and the annual cycle of the average interdiurnal pressure changes and the particular stimuli. As far as the annual cycle of the interdiurnal pressure changes characterised by the occurrence of the greater changes in the colder part of the year and the smaller ones in the warmer part of the year is concerned, it has been studied by other authors, who point out that it constitutes the permanent feature of this meteorological element (Kozłowska-Szczęsna 1991; Fortuniak et al. 2000). The annual cycle has been an incentive to searching for bioclimatic seasons of the interdiunal pressure changes, which are marked out by the application of Ward procedure. The method has made it possible to take into account all types of pressure changes at a time. The average frequency of their occurrence in the period of five days, therefore a matrix of data embracing 73 pentads, each of which has four features (corresponding to the four types of pressure changes. The pentads, which have been properly grouped, create dendrite, on the basis of which the image of the annual structure of bioclimatic diurnal seasons of pressure change is made. The study shows that in the area of Poznań there are four bioclimatic seasons during the entire year and that they differ in terms of the influence on the human organism. The most significant influence in terms of the frequency of occurrence is the season D, which takes places in the coldest time of the year. The least influential is season A due the infrequency of days when significant pressure changes take place. Between these two seasons, two transition seasons, B and C, happen twice a year.A617389Badania Fizjograficzn

Thermal Conditions in the City of Poznań (Poland) during Selected Heat Waves

The aim of the study was to characterise the occurrence of hot days and heat waves in Poznań in the 1966–2015 period, as well as to describe the thermal conditions in the city during selected heat waves between 2008 and 2015. The basis of the study was the daily maximum and minimum air temperature values for Poznań–Ławica station from 1966–2015 and the daily values of air temperature from eight measuring points located in the city in various land types from 2008 to 2015. A hot day was defined as a day with Tmax above the 95th annual percentile (from 1966 to 2015), while a heat wave was assumed to be at least five consecutive hot days. The research study conducted shows the increase of Tmax, number of hot days and frequency of heat waves in Poznań over the last 50 years. Across the area of the city (differentiation of urban area types according to Urban Atlas 2012), there was a great diversity of thermal conditions during the heat waves analysed

Międzydobowe zmiany ciśnienia atmosferycznego w Poznaniu na tle cyrkulacji atmosferycznej

Relying on data concerning atmospheric pressure noted between 1951-2000 in Poznań, interdiurnal changes of the average atmospheric pressure has been addressed. In accordance with biometeorological literature, the following ranges of atmospheric pressure felt by the human organism are assumed: weak (the change of 1-4 hPa), moderate (5-8 hPa) and strong (> 8 hPa). Furthermore, an additional range of change was adopted for a situation when the change does not take place or is less than 1 hPa. This situation is considered imperceptible to human organism. In the present article the ranges of pressure change are treated as types of change and marked as: a (< 1 hPa), b (1-4 hPa), с (5-8 hPa), d (8 hPa). The adopted pressure change ranges are here studied in terms of the occurrence of various types of atmospheric circulation as well as in terms of the direction of air mass influx. The analysis that has been conducted demonstrates that the average values of diurnal air pressure changes, as well as of the frequency of days the changes, occur in a specific cycle within the period of the whole year. The largest interdiurnal changes, as well as the greatest number of days with significant fluctuations, take place in the colder seasons of the year. In contrast, the slightest changes and the highest frequency of days when the changes are insignificant or none occur in the warmer seasons of the year. The average annual value of interdiurnal pressure changes in Poznań is 4.4 hPa, which means that the average bioclimatic conditions occur within the scope of weak stimuli. During the entire year 27 days with a scope of imperceptible stimuli may be expected (type a), 196 days with the stimuli that are hardly perceptible (type b) and 92 days with the stimuli of average perceptibility (type c) and 49 with the stimuli of strong perceptibility (type d). The attempt to associate the diurnal changes of atmospheric pressure with types of atmospheric circulation and the direction of air mass influx have proved a vivid relationship between the cyclic types and influxes from the west and the frequency of day with high fluctuations of atmospheric pressure changes. The days with large interdiurnal pressure changes often coincide with cyclonal circulations: the north-west circulation of the type CB (more than 20%) and south-west of type D (about 10%). The days with no or little pressure changes coincide the following anti-cyclonal types: north-east E (21%), south-east and east Ei (10%) and west C2D (about 10%)