Marek Półrolniczak

If not NAO then what?—regional circulation patterns governing summer air temperatures in Poland

The correlation between the daily/monthly North Atlantic Oscillation (NAO) index and the daily/monthly anomalies of the summer (JJA) surface air temperatures in Poland is close to 0.00, being positive in most of the country (but hardly exceeding 0.15) and negative in the southeast. Therefore, the regional scale circulation patterns other than NAO were determined using principal component analysis (PCA) to establish the relationship between the air circulation and the daily anomalies of the mean, maximum and minimum air temperatures in Poland. Regression and correlation analysis were applied to define the strengths and spatial distributions of these relationships. The best results were obtained for the mean and maximum daily temperature anomalies, for which the Pearson correlation coefficient (r) between the modelled and observed values exceeded 0.75 in the vast areas of central and southeastern Poland, while, over the rest of the country, it amounted to 0.7. The weaker influence of the circulation on air temperatures is observed in the northwestern part of the country, along the Baltic Sea shore (r < 0.65). The weakest results were obtained for the anomalies of the daily minimum temperatures (r equals 0.5–0.6 over most of the country and drops below 0.4 in the northwest). Furthermore, the influences of each PCA-based regional circulation pattern on the variabilities of the surface temperatures were analysed. The circulation pattern recognized as the second principal component, distinguished in the positive phase by the high-pressure conditions with the anticyclonic centre located right over central and southeastern Poland, revealed the strongest positive relationship with the air temperature.

Evaluation of Thermal Conditions in Jeziory (The Wielkopolski National Park)

Abstract 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. < 2°C, Δtavr. 2.1-4.0°C, Δtavr. 4.1-6.0°C, 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.

Initial Assessment of the Weather Research and Forecasting Model for Forecasting Bioclimatic Conditions During Breeze Circulation – Case Study of the Słowiński National Park

Abstract 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.

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

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.