Impact of Natural and Anthropogenic Factors on Fog Frequency and Variability in Kraków, Poland in the Years 1966–2015

Abstract

The aim of the study was to determine the long term variability of fog occurrence in Kraków in the light of the changeability of fog favoring factors. The annual number of days with several fog characteristics was studied for the period 1966-2015, using data from two meteorological stations located in the city center and in the suburbs. For all these data series on fog, a strong decrease was observed in the study period, i.e., the number of days with fog decreased on average by about 60%, with the tendency being more distinct in the city center. Fog favoring conditions were determined by atmospheric circulation, wind speed, relative humidity, urban heat island (UHI) and air pollution and correlated with data on fog. Results statistically significant at p < 0.01 show that the relationship is the strongest between fog frequency and air pollution. However, as the air pollution levels decreased, especially after the change of political and economic system in 1989, environmental factors became decisive in controlling fog occurrence. Although the role of atmospheric circulation in fog formation is unquestionable, fog favoring circulation types (Sa, SWa, Ca, Ka) show no meaningful tendency and no significant correlation with long-term fog occurrence frequency. Therefore, decreasing trends in days with low wind speed and in days with relative humidity RH ≥ 80% and RH ≥ 95% are considered as additional factors which contributed to the observed fog frequency decrease. UHI showed no impact on fog frequency as in Kraków relief modified UHI (RMUHI) is observed and no significant changes in the part of UHI defined for the lowest part of the city were observed.

Changes in Fog, Ice Fog, and Low Visibility in the Hudson Bay Region: Impacts on Aviation

“…Hanesiak and Wang [1] noted that visibility arose from fog and blowing snow and had an error rate of 10%. Nonetheless, with the exception of Churchill, each of the community studied has very little industry and population due to their remoteness, which allows them to be good study sites to monitoring fog frequency caused by environmental change and anthropogenic climate change while minimizing other anthropogenic factors such as air pollution from vehicle emissions, intense human activities and urban heat island [60][61][62].…”

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

“…A short description of the calendar structure is provided in Bokwa et al (2018), and all the classification schemes can be found in the cited literature (Niedźwiedź, 1981(Niedźwiedź, , 2000(Niedźwiedź, , 2016.…”

“…The rapid development of industry after the Second World War caused dynamic spreading of the city. Because of the city's location and intensive human activity, the bioclimate of Kraków is considered to be rather unfavorable for the inhabitants (the study area has been described in detail in Bokwa et al, 2018).…”

“…), as it is a season more prone to fog occurrence (80% of all fog days) (Bokwa et al, 2018). A day with fog was defined as a day when the phenomenon occurred at least at one of the stations, and at least at one of the observation times (i.e., 06, 12, 18 UTC).…”

“…UHI in Kraków, Poland, is a part of a complicated air temperature spatial pattern which is controlled by both land use/land cover and relief; therefore, the concept of RMUHI (Relief Modified Urban Heat Island) needs to be used (Bokwa et al, 2015). Additionally, the city experienced large changes in both fog frequency and the factors important for fog occurrence after the Second World War (Bokwa et al, 2018).…”