Thermal Inversion and Particulate Matter Concentration in Wrocław in Winter Season

Abstract

Studies on air quality frequently adopt clustering, in particular the k-means technique, owing to its simplicity, ease of implementation and efficiency. The aim of the present paper was the assessment of air quality in a winter season (December–February) in the conditions of temperature inversion using the k-means method, representing a non-hierarchical algorithm of cluster analysis. The air quality was assessed on the basis of the concentrations of particulate matter (PM10, PM2.5). The studies were conducted in four winter seasons (2015/16, 2016/17, 2017/18, 2019/20) in Wrocław (Poland). As a result of the application of the v-fold cross test, six clusters for each fraction of PM were identified. Even though the analysis covers only four winter seasons, the applied method has unequivocally revealed that the characteristics of surface-based (SBI) and elevated inversions (ELI) affect the concentration level of both fractions of particulate matter. In the case of PM10, the average lowest daily concentration (15.5 µg·m−3) was recorded in the conditions of approx. 205 m in thickness, 0.5 °C intensity of the SBI and at the height of the base of the ELI at approx. 1700 m a.g.l., a thickness of 148 m and an intensity of 1.2 °C. In turn, the average highest concentration (136 µg·m−3) was recorded at a thickness of SBI of approx. 400 m and an intensity of 1.4 °C. Such high concentration occurred when the lowest location of ELI formed at 764 m a.g.l. with a thickness of 308 m and an intensity of 0.96 °C. A marked role of the thickness of the SBI and ELI as well as the height of the base of the lowest location of ELI was also manifested with respect to PM2.5 concentrations.

Effects of Rain and Snow on the Air Quality Index, PM2.5 Levels, and Dry Deposition Flux of PCDD/Fs

“…This is because in cold winter, the wind speed is low, the atmosphere become more stable, resulting in both poor both atmospheric vertical convection and horizontal dispersion, so the AQI were elevated. At the same time, at a certain event of snowstorm, both automobile exhaust and stationary source emission increased and then result in an increase of AQI (Nidzgorska-Lencewicz et al, 2020).…”

Impact of Different Air Pollutants (PM10, PM2.5, NO2, and Bacterial Aerosols) on COVID-19 Cases in Gliwice, Southern Poland

“…In Poland, just as in many other countries in Central and Eastern Europe, high levels of two PM fractions (PM 10 and PM 2.5 ) are observed every winter season. This is due to the high share of solid fuels in the primary energy source structure and the large share of low communal emissions [ 43 , 44 ]. However, what interested us and became an inspiration for further research was that we observed that the relationship between PM and DNCs had been weakening since March (spring season, end of the heating season), despite the continuous increase in the number of cases of SARS-CoV-2.…”

Relationships between Vertical Temperature Gradients and PM10 Concentrations during Selected Weather Conditions in Upper Silesia (Southern Poland)

“…Surface-based air temperature inversions are of great importance to enhance air pollutant concentrations, particularly in winter [5,10,29,35,50,[56][57][58][59][60]. Air pollution similarly to SBI, reveals a close relationship with weather conditions, including air temperature, relative humidity, wind speed, solar radiation, and pressure [50,[61][62][63].…”

“…According to radiosounding in Wrocław (SW Poland) during the period 2001-2020, the average depth of the SBI layer at night is 207 m, changing from 186 m in spring to 249 m in winter. Most often (81%), the SBI thickness ranges from 50 to 300 m [47,60].…”