Role of Fog in Urban Heat Island Modification in Kraków, Poland

Abstract

The impact of fog on relief modified urban heat island (RMUHI) in Kraków has been presented using fog observations at 06 UTC from two meteorological stations: a rural one (Balice, B) and an urban one (Botanical Garden, BG) from the period 2006-2015. Daily UHI magnitude for the valley floor for the same period was estimated as T min BG-T min B, while for the period 2010-2015, eight daily courses of UHI were available, for the urban areas in the valley floor and 50 m above it, together with air temperature inversion data. UHI data for days with various combinations of fog occurrence and weather conditions were compared using non-parametric statistical tests: Wald-Wolfowitz test, Kolmogorov-Smirnov test and U Mann-Whitney test. Data of 2010-2015 were also the subject of cluster analysis (k-means method). Fog is an important factor decreasing UHI magnitude by about 1 K but mainly during weather conditions with little or no cloudiness and small wind speed or atmospheric calm, during anticyclonic synoptic situations, and only in the valley floor areas. With an increase in cloudiness and wind speed, the role of fog decreases and is similar in all parts of the city.

Assessment of the Effect of Meteorological Conditions on the Concentration of Suspended PM2.5 Particulate Matter in Central Europe

“…The location of the city of Krakow in the Vistula River valley determines certain features of its natural climate, including the formation of cold air pools, frequent temperature inversions, and increased frequency of freezing temperatures, calm or light wind, and fog. These circumstances favour the accumulation of pollutants near the ground and the formation of smog, causing values to exceed the acceptable and target levels [31,43,[52][53][54][55][56][57][58]. This explains the substantial differences in the PM 2.5 concentrations between calendar seasons (spring, summer, autumn, and winter).…”

“…Air pollution levels are influenced not only by current emissions associated with the municipal and housing sector, transport, and industry, but also by meteorological conditions (air temperature, precipitation, and wind speed) and the type of atmospheric circulation [25][26][27][28][29][30]. Atmospheric circulation is one of the most important factors determining weather conditions, due to the temperature inversion occurring during anticyclonic circulation [31], when pollutant concentrations increase. This study focused on the concentrations of PM 2.5 particulate matter in Krakow, the capital and largest city of the Lesser Poland Voivodeship.…”

Temperature and urban heat island effect in Lublin city in Poland under changing climate

“…The influence of topography on the diversity of the city's thermal field in Krakow led to the development of the concept "relief-modified UHI effect" (Bokwa 2010;Bokwa et al, 2015). Bokwa et al (2018) studied the impact of fog on UHI intensity in Kraków, Poland, and found that fog can decrease the UHI effect by about 1 K under specific weather conditions. Półrolniczak et al (2017) analyzed the UHI effect in Poznań, Poland, and concluded that the UHI effect is more pronounced, particularly in the evening and nighttime.…”

Evaluation of a WRF-LCZ system in simulating urban effects under non-ideal synoptic patterns

“…The elevated number of cloud condensation nuclei from anthropogenic activities leads to higher probability of cloud (and fog) formation and precipitation in urban areas (Oke 1987, Bokwa et al 2018.The typical annual days of fog in Szeged is around 50-55, which is the consequence of the geographic location and the relatively high frequency of high-pressure synoptic patterns in autumn and winter months. Due to the projected effects of climate change, the frequency of high precipitation events will likely be increased in the forthcoming decades (Kis et al 2017) over the Carpathian Basin.…”