Verifying reliability of selected meteorological elements in the GFS and WRF models in Poznań

The article presents the results of a study comparing the reliability of the GFS and WRF numerical models using different spatial resolutions. The study was carried out on the basis of a series of model and observational data for a period of 13 months from January 2015 to January 2016 with computational grid coordinates corresponding to the location of Poznań. Forecast quality was compared for basic meteorological parameters – air temperature, atmospheric pressure and wind speed. The quality of forecasts for the meteorological parameters included in the study decreased systematically in subsequent time steps in the case of both the WRF and the GFS models. It improved in the initial hours of simulation after a higher resolution was applied for the computational grid in the WRF model (1,75 km) as can be seen from the minimal Mean Error values and very high correlation. For forecast time t = 0–60 h, WRF generated better results than GFS, especially when it comes to the quality of forecasting the atmospheric pressure field

Warm winter and cold summer spells in Spitsbergen and their circulation conditions

The objective of the study was to determine multi-annual changes and variability of occurrence of cold spells in summer and warm spells in winter on Spitsbergen in the period 1976–2016, and circulation conditions of their occurrence. Cold days in summer were defined as days with mean daily air temperature lower than temperature corresponding to the 10th percentile from daily temperature, and warm days in winter as days with mean daily air temperature exceeding the 90th percentile from daily air temperature. The research showed a statistically significant increase in mean air temperature, the rate of which in winter was more than four times higher than in summer. The observed warming translated into a decrease in the number of cold days in summer (-2.5 days/10 years in Svalbard Lufthavn and -1.3 days/10 years in Ny-Ålesund) and an increase in the number of warm days in winter (2.7 days/10 years in Svalbard Lufthavn and 2.4 days/10 years in Ny-Ålesund), and warm and cold spells related to the frequency of such days. The rate of the changes was higher in Svalbard Lufthavn than in Ny-Ålesund. The occurrence of cold days and cold spells was particularly related to the advection of air masses from the north-western sector. The occurrence of warm days and warm spells was related to the advection of air masses from the south-west

Točnost prognoza temperature zraka dobivenih odabranim kratko- i dugoročnim numeričkim modelima prognoze vremena iznad Poljske

The article discusses the results of air temperature forecasts from four short-term and two long-term forecasts of numerical weather prediction models. The analysis covered the results of model simulations from January 2015 to January 2016 and compared them at 14 meteorological stations in Poland. The comparison was made based on the most commonly used measures for continuous parameters i.e., ME (mean error), MAE (mean absolute error), RMSE (root mean square error), MSE (mean square error), BIAS and Pearson correlation. In the short time horizon, the best results in the context of the MAE, RMSE, MSE and correlation values were obtained by the Unified Model, although the diagnosed differences between the models are small. All models in the 0–72 h projection horizon reached a correlation of 0.95–0.97 and an MAE in the range of 1.5 °C to 2.1 °C. In the case of long-term forecasts, the HIRLAM model was slightly better than the GFS model. Clearly, in both cases, there is a marked decrease in quality after the fourth and in the following forecast lead days.U članku se razmatraju rezultati prognoze temperature zraka pomoću četiri kratkoročna i dva dugoročna numerička modela prognoze vremena. Analiza je obuhvatila rezultate simulacija modela od siječnja 2015. do siječnja 2016., koji su uspoređeni s podacima 14 meteoroloških postaja u Poljskoj. Usporedba je izrađena na temelju najčešće korištenih mjera za kontinuirane parametre, tj ME (srednja pogreška), MAE (srednja apsolutna pogreška), RMSE (korijen srednje kvadratne pogreške), MSE (srednja kvadratna pogreška), BIAS i Pearsonova korelacija. Za ovako kratak vremenski interval, u kontekstu vrijednosti MAE, RMSE, MSE i korelacije, najbolji rezultati dobiveni su ujedinjenim modelom, iako su utvrđene razlike među modelima male. Svi modeli su u prognostičkom vremenu od 0 do 72 h dostigli korelaciju od 0,95 do 0,97 i MAE u rasponu od 1,5 °C do 2,1 °C. U slučaju dugoročnih prognoza model HIRLAM bio je nešto bolji od GFS modela. Jasno je da u oba slučaja dolazi do znatnog smanjenja kvalitete nakon četvrtog i sljedećih prognostičkih dana

Porównanie przebiegu temperatury powietrza i wilgotności względnej w Petuniabukta i Svalbard-Lufthavn (Spitsbergen) w sezonie letnim 2016

This work presents the values of air temperature and relative humidity measured in the period 7th July 2016 – 31th August 2016 in Petuniabukta and Svalbard-Lufthavn. The course of air temperature and humidity was compared. These values depend primarily on the type of atmospheric circulation. In the article, basic statistical methods were used (arithmetic mean, standard deviation, correlation Pearson coefficient). The research revealed that Petuniabukta point is colder by 0.2°C and has higher average relative humidity of about 3%. Higher temperatures cause smaller differences of air temperature and relative humidity at the tested points. Also in this case, a lower value for relative humidity was observed.68193

WARUNKI SYNOPTYCZNE PODCZAS WYSTĘPOWANIA WYSOKICH KONCENTRACJI PM10 W POZNANIU W LATACH 2010–2017

The article presents examples of synoptic situations when the permissible concentration of PM10 was severely exceeded in 2010–2017 in Poznań. In many Polish cities, there are deviations from the norms for a number of days during the year. The scale of concentration of PM10 in the air is largely affected by the prevailing meteorological conditions such as low temperature and low wind speed. First, periods of the highest daily concentrations of pollutants were selected. Subsequently, synoptic maps for selected days were analysed. The most common cause of the pollution was a large boom which brought Arctic air to Poland. In this case, the highest concentration was accompanied by very low air temperatures and the resulting more intensive heating of buildings

Thermal conditions in the summer season on the Polish coast of the Baltic Sea in 1966-2015

―The Baltic Sea coast is characterized by a large frequency of days with biometeorologically adverse effects. In many Polish and foreign studies there are issues related to the increase in the frequency of warm days, hot days, and heat waves. The present study introduces the characteristics of thermal conditions on the Polish coast in the 1966– 2015 multiyear period, as well as the identification of circulation conditions favoring the occurrence of extremely warm periods. The analysis included the maximum temperature data (obtained from five measurement stations), on the basis of which the characteristics such as: average maximum air temperature, sum of maximum air temperatures occurring in summer, warm days (Tmax >25 °C), hot days and heat waves (Tmax >30 °C) were determined. The existing thermal classification proposed by Lorenc (2000) was also used in relation to the maximum daily temperature. In addition, there appeared a topic of atmospheric circulation regarding the determination of conditions for the occurrence of exceptionally warm months (mean Tmax >Ts+1.5σ). The research results indicate an increase in the average maximum temperature (Tmax) in the summer season in 1966–2015. The changes are particularly visible in the western part of the research area (0.43 °C/10 years). Furthermore, the observed warming was translated into a higher occurrence of warm and hot days, which was discussed by other authors in the context of the whole of Poland. The occurrence of exceptionally warm months has reached the maximum frequency in the last 15 years, which is associated with positive anomalies of the sea level pressure and the 500 hPa isobaric surface. Periods of occurrence of the above mentioned anomalies were related to the presence of high pressure systems and the advection of air masses from the eastern sector (according to the presented T850 maps)

Influence of Atmospheric Circulation on Cloudiness and Cloud Types in Petuniabukta and Svalbard-Lufthavn in Summer 2016

The paper analyzes the influence of atmospheric circulation on cloudiness and cloud types during July and August of 2016 in Petuniabukta and Svalbard-Lufthavn. For the meteorological parameters, basic statistical measures were calculated and the average diurnal cloud patterns were analyzed. Taking the data from meteorological reanalysis (NCEP/NCAR-The National Centers for Atmospheric Prediction/The National Center for Atmospheric Research) regarding the mean sea-level pressure (SLP), 500 hPa geopotential height, and air temperature at 850 hPa (T850), composite maps of the synoptic situation for the studied area were constructed. For the observed types of clouds, the frequency of their occurrence in particular types of atmospheric circulation was then determined according to the Niedźwiedź classification. Differences in the amount of cloudiness in the examined measuring points were ascertained. The occurrence of cloud types is associated with both the direction of air mass advection and type of circulation. The results may also indicate the possibility of influence from specific, local environmental features on cloudiness