A micrometeorological fog experiment was carried out in Budapest, Hungary during the winter half year of 2020–2021. The field observation involved (i) standard meteorological and radiosonde measurements; (ii) surface radiation balance and energy budget components, and (iii) ceilometer measurements. 23 fog events occurred during the whole campaign. Foggy events were categorized based on two different methods suggested by Tardif and Rasmussen (2007) and Lin et al. (2022). Using the Present Weather Detector and Visibility sensor (PWD12), duration of foggy periods are approximately shorter (~ 9%) compared to ceilometer measurements. The categorization of fog based on two different methods suggests that duration of radiation fogs is lower compared to that of cloud base lowering (CBL) fogs. The results of analysis of observed data about the longest fog event suggest that (i) it was a radiation fog that developed from the surface upwards with condition of a near neutral temperature profile. Near the surface the turbulent kinetic energy and turbulent momentum fluxes remained smaller than 0.4 m² s^–2 and 0.06 kg m^–1 s^–2, respectively. In the surface layer the vertical profile of the sensible heat flux was near constant (it changes with height ~ 10%), and during the evolution of the fog, its maximum value was smaller than 25 W m^–2, (ii) the dissipation of the fog occurred due to increase of turbulence, (iii) longwave energy budget was close to zero during fog, and a significant increase of virtual potential temperature with height was observed before fog onset. The complete dataset gives an opportunity to quantify local effects, such as tracking the effect of strengthening of wind for modification of stability, surface layer profiles and visibility. Fog formation, development and dissipation are quantified based on the micrometeorological observations performed in suburb area of Budapest, providing a processing algorithm for investigating various fog events for synoptic analysis and for optimization of numerical model parameterizations.

The study introduces the current situation of electric vehicle technologies, the possibilities and possible directions of their market, as well as the economic and environmental aspects in the eastern region of the EU, with special regard to Hungary. Our calculations show that despite the higher costs of ownership, in the case of 7 years of use (among Hungarian conditions), the total cost of the Battery Electric Vehicles (BEV) is lower than that of the Internal Combustion Engine Vehicles (ICEV) in each of the four segments analysed. The purchasing power of the population in the eastern regions of the EU is clearly lower compared to the western regions, yet people in this region spend beyond their financial means on motorization. Despite its unfavourable position, Hungary is in a particularly advantageous position compared to other countries in the region per vehicle and per capita in terms of the spread of BEVs. In the long run, even taking higher prices into account, the use of electric cars, in general, has significant advantages from an economic point of view; lower maintenance costs and fuel prices (especially with increased use) make EVs more cost-effective overall.

The effect of decreased mobility on air quality due to the COVID-19 period was analysed from 2018 to 2022 in Debrecen city, Hungary. The PM₁₀ concentrations were analysed at three sampling sites. We compared PM₁₀ concentrations from 2018 to 2022 during three periods: pre-pandemic, pandemic, and post-pandemic. We also studied the effect of lockdowns on the PM₁₀ concentrations during the pandemic period. Over the 2018–2022 period, the concentration of PM₁₀ decreased across all sites, suggesting improved air quality. Significant differences were found in PM₁₀ levels among the pre-pandemic (before February of 2020), pandemic (from March of 2020 to February 2022), and post-pandemic period (after March of 2022) in the case of all stations. Significant differences were also found among years and stations during the lockdown periods. Drastically significant decreases were found only in January of 2021 in the case of all stations. Our results also demonstrated that the reduction in emissions took place simultaneously, as exceptional weather conditions such as wind direction and wind speed were observed in the year 2020, which have been highlighted by an unusually warm pre-lockdown February and springtime drought. PM₁₀ levels indicated heterogeneous patterns characterized by variations including decreases, slight increases, or stability, contingent upon the specific sampling sites under consideration. These findings emphasize the complex dynamics of air pollutants and stress the necessity for ongoing monitoring and targeted interventions to alleviate detrimental effects on air quality and public health.

Characteristic phenomena in the Pannonian basin during the winter half year are the mist (500-1000 hours/year), the fog (150-300 hours/year) and the cold air pool with high air pollution concentrations. Formation, development and dissipation of fog events are complex processes that are impacted by short- and longwave radiation, condensation and evaporation, turbulent exchange, furthermore fog chemistry. The research presented here aims at exploring the interaction of these processes using field observations. To this end, complex field campaigns were conducted in Budapest (WMO code: 12843) and in the Sió Valley, 6 km away from Siófok (12935) during 1 to 3-month periods in the last three winter half years.Besides air chemistry and standard meteorological variables, the leaf wetness, surface and soil temperature, soil moisture, soil heat flux (Huskeflux), radiation budget components (CNR1) and turbulent fluxes based on eddy covariance (CSAT3, EC150) and gradient methods were measured above the grassland. Time resolutions of measurements for slow sensors were 10 sec or rather 1 minute and for eddy covariance system 10 Hz. The mist and fog periods were detected using a cloud camera (in Sió Valley) and by synoptic observations in Budapest and Siófok.Additional measurements in Budapest were i) the wind speed (U), air temperature (T) and relative humidity (RH) profiles together with Gill sonic anemometer at the top of a 30 m high tower, ii) LUFT CHM 15k ceilometer. SODAR and aviation meteorological measurements were also available from the Budapest Ferenc Liszt International Airport (LHBP) at 8 km distance. Other field experiments were done in the wet leeward Sió Valley in 2018-19 and 2019-20. Vaisala WXT530 sensor, LUFT CHM 15k ceilometer, tethered balloon measurements with GRAW radiosondes and METEK SODAR measurements were also provided as additional information behind the energy budget measurements.Our results confirmed that according to the expectations, we have recorded more foggy situations in the Sió Valley than in Budapest (12843) and Siófok (12935). Radiation and advection type fog events were formed in most cases. The measured RH was above 95 and gradually increased during the onset period of fog. RH was around 100%, fluctuations could be measured less accurately.  Dissipation of the fog is usually characterized by wind intensification and rise in the incoming solar radiation. The data of two field campaigns will be analyzed i) a cold pool situation in Sió Valley in January 2020 and ii) the foggy season 2020-21 in Budapest. The developed complex (micrometeorological, furthermore air and liquid chemistry) database gives opportunity to validate numerical model results (WRF, CHIMERE and detailed box model) and to improve parameterizations of the numerical models.