This paper presents the development of artificial neural network models for the prediction of the daily maximum hourly mean of surface ozone concentration for the next day at rural and urban locations in central Poland. The models were generated with six input variables: forecasted basic meteorological parameters and the maximum O₃ concentration recorded on the previous day and number of the month. The training data set covered the period from April 2015 to September 2015. An analogous data set of input variables, for the 2014 year, not used during the process of training the networks, was used as test data to examine the quality of these models. From the results of simulations for the year 2014, the average relative error values were equal to 15.3% and 15.7% for Belsk and Warsaw stations, respectively. The mean error (ME) value indicates a tendency to overestimate the predicted values by 4.8 µg/m³ for Belsk station and to underestimate the predicted values by 0.9 µg/m³ for Warsaw station. The analysis of days when the relative error value was >50% revealed that all predictions with extremely high relative error value were associated with relatively low daily maximum surface ozone concentration values that occurred suddenly due to a sharp drop in day-to-day ozone concentration values.

Surface ozone (O₃) and nitrogen oxides (NO_x = NO + NO₂) measured at the rural station in Belsk (51.83° N, 20.79° E), Poland, over the period of 1995–2023, were examined for long-term variability of O₃ and its relationship to changes in the air temperature and NO_x. Negative and positive trends were found for the 95th and 5th percentile, respectively, in the O₃ data. A weak positive correlation (statistically significant) of 0.33 was calculated between O₃ and the temperature averaged from sunrise to sunset during the photoactive part of the year (April–September). Recently, O₃ maxima have become less sensitive to temperature changes, reducing the incidence of photochemical smog. The ozone–climate penalty factor decreased from 4.4 µg/m³/°C in the 1995–2004 period to 3.9 µg/m³/°C in the 2015–2023 period. The relationship between O_x (O₃ + NO₂) and NO_x concentrations averaged from sunrise to sunset determined the local and regional contribution to O_x variability. The seasonal local and regional contributions remained unchanged in the period of 1995–2023, stabilizing the average O₃ level at Belsk. “NO_x-limited” and “VOC-limited” photochemical regimes prevailed in the summer and autumn, respectively. For many winter and spring seasons between 1995 and 2023, the type of photochemical regime could not be accurately determined, making it difficult to build an effective O₃ mitigation policy.

A long-term series of exposures to solar ultraviolet radiation (UVR) is required to assess the risks and benefits of radiation for different human biological processes. However, homogenisation of the amount of biologically effective solar energy (i.e. energy-weighted according to the sensitivity of the selected biological process to solar radiation) reaching the Earth's surface over long periods is challenging due to changes in measurement methods and instruments. This paper presents the world's longest homogenised time series of biologically effective daily radiant exposures (DRE) from regular monitoring with different erythemal broadband radiometers (EBRs) operated at the Central Geophysical Laboratory of the Institute of Geophysics, Polish Academy of Sciences (IG PAS), Belsk (20.79° E, 51.84° N), from 1 January 1976 to 31 December 2023. The following biological effects were considered: erythema, cutaneous synthesis of previtamin D₃, and clearing of psoriatic lesions. The data for the latter two biological effects are estimated based on the proposed method of using EBR measurements to calculate other non-erythemal DRE. The following EBRs were used in the monitoring: Robertson–Berger meter (1975–1992), Solar Light model 501 (1993–1994 with #927, 1995–2013 with #2011), and Kipp & Zonen UV-AE-T #30616 from 5 August 2013 to the present. From 1976 to 2013, the homogenisation procedure consisted of comparing the measured erythemal DRE and daily maximum of UV index (UVI_MAX) with the corresponding modelled values from simulations using a radiation transfer model for cloudless conditions. Between 2014 and 2023, the EBR data were compared with data from a collocated reference instrument, the Brewer Mark II #64 spectrophotometer. Such comparisons resulted in a set of multipliers that were applied to the EBR measurements. Two different versions of the homogenisation method were applied, analysing modelled and observed values for erythemal DRE and UVI_MAX assuming different criteria for cloudless days. Three regression models of the erythemal data on common UVR proxy data (total column ozone, aerosol optical depth, and global clear-sky irradiance index) were used to reconstruct the UVR data from the beginning of the Belsk observations, allowing further validation of the homogenised UVR data. Linear trends calculated showed a statistically significant increase in erythemal annual and summer (June to August) radiant exposures of about 6 % per decade over the period 1976–2005. Thereafter, no trend was observed. Similar trend estimates were found for all biological effects considered. The data are made freely available via the following repository: https://doi.org/10.1594/PANGAEA.972139 (Krzyścin et al., 2024). An additional version of the re-evaluated data, together with the corresponding clear-sky and proxy data used in the UVR data reconstruction, is archived at https://doi.org/10.25171/InstGeoph_PAS_IGData_Biologically_Effective_Solar_Radiation_Belsk_1976_2023 (Krzyścin, 2024).

The atmospheric potential gradient (PG) has been measured at ground level with a radioactive collector method in the Stanisław Kalinowski Geophysical Observatory in Świder (52.12° N, 21.23° E), Poland, for several decades. The long-term Świder measurements analysed previously revealed rather typical behaviour in the diurnal and seasonal variations of the PG of a land station, assumed to be controlled by pollution. Observations of the PG at such a station usually show a maximum at local winter months which are affected by anthropogenic pollution the most. A recently digitised series of 1965–2005 hourly data has been newly analysed to describe the Świder PG variations in greater detail, also in connection with an analysis of simultaneous measurements of condensation nuclei (CN) measured at 06:00, 12:00, and 18:00 UT. An attempt is made to calculate the diurnal and seasonal variations at the CN number concentrations below 10 000 cm⁻³. There is a decrease in the PG in the diurnal variation by up to 11 % in the winter and no significant change in the summer. The reduction in the annual variation is 11 %–26 %, with the biggest difference in February. In the summer months this difference is negligible. Despite the efforts to minimise the aerosol effect on the PG in the measured CN range, the character of the seasonal and annual variation of PG preserves its character with a maximum in the Northern Hemisphere winter and the minimum in the summer as observed at other mid-latitude stations in this part of the globe. When investigating the effect of reduced CN concentrations on the measured positive conductivity (PC), an increase of 7 %–17 % is found. In addition to an additional mechanism affecting the PG in the summer, there may be another aerosol fraction outside of the range of the condensation nuclei like dust, which affects the conductivity and indirectly the annual variation of the PG.

The continuous two-year monitoring of a set of air pollutants, as well as gases directly related to shale gas exploration processes (methane, non-methane hydrocarbons, carbon dioxide), was carried out at Stary Wiec village in the vicinity (1100 m) of the shale gas wells area in Wysin (Pomeranian voivodeship, north of Poland), covering the stages of preparation, drilling, hydrofracturing and closing of wells. The results of analysis of air pollution data from Stary Wiec and nearby urban and rural stations, over the period 2012–2017 (starting three years before preparations for hydraulic fracturing) indicated that Stary Wiec represents a clean rural environment with an average concentration of nitrogen oxides, carbon monoxide and particulate matter that is one of the lowest in the Pomeranian region. The aim of this study was to explore the range of potential impact of shale gas exploration on local ambient air quality. Analysis of dependence of the concentration level of pollutants on the wind direction indicated that during the drilling period, when the air was coming directly from the area of the wells, nitrogen oxide concentration increased by 13%. Increases of concentration during the hydro-fracturing period, recorded at the Stary Wiec station, were equal to 108%, 21%, 18%, 12%, 7%, 4%, 1% for nitrogen oxide, non-methane hydrocarbons, carbon monoxide, nitrogen dioxide, particulate matter, carbon dioxide and methane. The results of one-minute concentration values for the period 1–4 September 2016 showed a series of short peaks up to 7.45 ppm for methane and up to 3.03 ppm for non-methane hydrocarbons, being probably the result of operations carried out at the area of the wells.

A long-term series of exposures to solar ultraviolet (UV) radiation is required to assess the risks and benefits of radiation on different human biological processes. However, homogenisation of the amount of biologically effective solar energy reaching the Earth's surface over long periods (i.e. energy weighted according to the sensitivity of the selected biological process to solar radiation) is challenging due to changes in measurement methods and instruments. This paper presents the world's longest homogenised time series of biologically effective daily radiant exposures (DRE) from regular monitoring with different erythemal biometers (EB) operated at the Central Geophysical Laboratory of the Institute of Geophysics, Polish Academy of Sciences (IG PAS), Belsk (20.79° E, 51.84° N) from 1 January 1976 to 31 December 2023. The following biological effects were considered: the appearance of erythema, cutaneous synthesis of previtamin D₃, and clearing of psoriatic lesions. The data for the latter two biological effects are estimated based on the proposed method of using EB measurements to calculate other non-erythemal DRE. The following broadband erythemal radiometers were used in the monitoring: Robertson-Berger (1975−1992), Solar Light model 501 (1993−1994 with #927, 1995−2013 with #2011) and Kipp-Zonen UV-AE-T #30616 from 5 August 2013 to the present. From 1976 to 2013, the homogenisation procedure consisted of comparing the measured erythemal DRE and UV index (erythemal irradiance at noon) with the corresponding synthetic values from simulations using a radiation transfer model. Between 2014 and 2023, the raw data were compared with data from a collocated reference instrument, the Brewer Mark II #64 spectrometer. Such comparisons resulted in a set of multipliers that were applied to the raw EB measurements. Two different versions of the homogenisation method were applied (for erythemal DRE and UV index with different selection of cloudless days), and three regression models were constructed for the erythemal data based on total column ozone, aerosol optical depth and global irradiance clearness index. Linear trends calculated from reevaluated and reconstructed time series (a total of seven time series were considered) showed a statistically significant increase in erythemal annual and summer (June to August) radiant exposures of about 6 % per decade over the period 1976−2005. Thereafter, no trend was observed. The same trend estimates were found for all biological effects considered. The raw and reevaluated data are made freely available via the following repository: https://doi.org/10.1594/PANGAEA.972139 (Krzyścin et al., 2024). An additional version of the reevaluated data, together with the corresponding clear sky and proxy data used in the UV data reconstruction, is archived in the IG PAS Data Portal: https://doi.org/10.25171/InstGeoph_PAS_IGData_Biologically_Effective_Solar_Radiation_Belsk_1976_2023 (Krzyścin, 2024).