Despite years of research and measurement, we still know too little about the mechanisms that cause smog. Today’s air monitoring system fulfils its main tasks: it informs residents of exceedances in the permissible concentrations of particulate matter, provides data for statistical purposes, and the resulting findings have legal consequences. But it does not provide answers to the questions: why is smog still with us? Will we ever be able to get rid of it? Is smog really just a local problem for local authorities? What are the real limits to preventing smog? Specialised modern research instruments are needed to answer these questions. It is therefore necessary to strengthen cooperation between the research and development community and institutions responsible for air monitoring in order to expand existing measurement tools. Then the fight for clean air will be effective and successful.

The phenomenon of smog is by no means new; it has been with humanity for decades. Poland, like the majority of European Union countries, is taking effective measures to minimise it. Despite the occurrence of smog episodes, there has been a downward trend in air pollution over the last decade, recorded as a reduction in the concentration of particulate matter by the State and Provincial Inspectorates for Environmental Protection (the Chief Inspectorate of Environmental Protection/the Provincial Inspectorate of Environmental Protection). 

This is a result of actions taken at national, regional, and above all civic level, thanks to the growing public awareness of the air quality problem. These measures are mainly aimed at reducing low emissions of pollutants at heights of up to 40 metres. In particular, the reduction of low emissions of dust and gases from inefficient combustion of fossil fuels, biomass and waste in domestic heating cookers and local boiler houses, e.g. by replacing boilers with higher class boilers, changing the fuel and the method of combustion, using renewable energy sources, is producing positive results. Less noticeable results are given by the equally important reduction of low emissions from combustion transport. E.g. through improvement of the quality of exhaust gas purification filters, reduction in the use of combustion engine cars in favour of urban and railway transport, increased interest in purchasing electric cars.

An important aspect of counteracting poor air quality is social and educational information activities, the introduction of penalties for exceeding acceptable standards of concentration of pollutants in the air, and mitigation of the risk of health effects of smog.
The fight for even better air quality in Poland requires hard work, but these efforts will not remain idle, as they will contribute to further improvements in the quality of life and health of society.   However,  due to the specific nature of the dangerous smog, its complete elimination does not appear to be realistic.

Faces of smog

By definition, smog is a mixture of heterogeneous particles of smoke dust, gases, and chemical substances in the atmosphere formed under favourable meteorological conditions (temperature inversion and no or little wind, no precipitation, low temperatures and high humidity, or vice versa – high temperatures and strong sunshine). Also local topography (depressions in the land), which is directly associated with human activity as a link providing air pollution to the atmosphere (low emissions mainly over populated and industrialised areas). Figure 1 shows a conceptual scheme of possible smog situations under conditions depending on the type of terrain, the degree of urbanisation,  industrialisation, and the extent of the phenomenon. 

It is important to distinguish between smog observed in winter and in summer. During episodes of winter smog – the characteristic dull fog – mainly associated with increased low-level emissions of particulate and gaseous pollutants from the burning of fossil fuels.  biomass in heating cookers. Smog is just as prevalent in cities located in basins as in villages in inhabited mountain basins. Such smog mainly contains sulphur dioxide, carbon dioxide, soot, and particulate matter also known as atmospheric aerosols. Photochemical smog, observed on hot summer days with strong sunshine as a brown haze, is less common and is mainly associated with motorised transport based on internal combustion engines in larger cities and agglomerations. The main components of photochemical smog are chemically active organic compounds (superoxides, aldehydes) and ozone, carbon monoxide, and nitrogen oxides. Due to the above-mentioned differences between the two phenomena (type and composition, scale and location of occurrence), the health effects of exposure to both smog types are different, but nonetheless harmful.

How to measure air pollution?

Smog measuring methods should be seen from the point of view of the individual, e.g. through the senses and the impact on their psyche and health, of the authorities at different levels of government, e.g. through mandatory pollution monitoring, and of the scientific and research community, e.g. through in-depth studies of the phenomenon at different time and space scales.

The key for the individual is the sensory input that allows for direct and immediate experience of the smog - the grey/brown colour of the sky, the pungent suffocating smell, the unpleasant viscosity, and the irritation of the eyes. In addition, there is concern about a number of health threats. The first being broadly defined respiratory diseases, including cancer, followed by diseases of the circulatory, nervous, reproductive, immune and digestive systems.

From the point of view of the authorities, smog is primarily perceived through high concentrations of particulate matter (PM10 and PM2.5 with particle sizes below 10 and 2.5µm) and gases (sulphur dioxide, carbon monoxide, nitrogen dioxide, ozone and benzene) measured close to the ground, which are monitored in Poland by ground-based stations of the Chief Inspectorate of Environmental Protection (, including 16 provincial inspectorates. In some locations, measuring stations are also financed by municipalities. Modelling of dust concentrations and their forecasting is an important aspect of activities in this respect, especially if it takes into account measurements from existing ground stations of the Chief Inspectorate of Environmental Protection (

Scientific studies on the phenomenon in Poland are interesting mainly from the point of view of the poorly recognised vertical structure of smog and photo-smog, in particular from the aspect of the association – pollution vs. water vapour. In this respect, monitoring measurements and modelling are not sufficient,  particularly because measurements at ground level do not give a representation of the vertical distribution of dusts with height and make it difficult to interpret the origin of pollution (i.e. only local dusts or dusts with admixtures of pollutants in higher layers of the atmosphere).

The strengths of the existing air quality monitoring in the country (the Chief Inspectorate of Environmental Protection/the Provincial Inspectorate of Environmental Protection) covers that – with minor exceptions – a representative area of Poland as a whole , records and assesses the quality of measured data, archives and makes measurement data available free of charge. Thisincludes providing on-line, near real-time, and non-confidential information on possible exceedances of threshold values regulated by Polish standards and EU directives.
The weakness of the Chief Inspectorate of Environmental Protection’s monitoring is not only the lack of a clear connection of the above-mentioned activities with the sector of observations and scientific research on atmospheric aerosols. This includes dusts of anthropogenic pollution conducted at universities and research institutes with the sector of satellite observations of the same. The lack of strong cooperation with the Institute of Meteorology and Water Management – National Research Institute (IMWM-NRI) seems incomprehensible, in particular e.g. expensive access to ECMWF (European Centre for Medium-Range Weather Forecasts) data, useful for modelling and forecasting weather and air quality could be considered as a joint investment of both institutions.

Smog under the magnifying glass of researchers

Research on phenomena such as smog is carried out among other things through Research Infrastructures, which derive from long-standing activities within national and then international research networks giving initiatives in the field of atmospheric observation. Research networks tend to specialise in a fairly narrow field, e.g. lidar measurements of aerosol structure in the atmosphere within EARLINET (European Aerosol Research Lidar Network). By consolidating such measurements in distributed Research Infrastructures such as ACTRIS (Pan-European Aerosols, Clouds and Trace Gases Research Infrastructure), the expertise of top specialists in the respective fields of research has been put to the test and a new research direction has been taken by exploiting measurement synergies and their complementarity. E.g. synergistic use of in situ devices measuring near the ground, lidars profiling the atmosphere, or passive sensors such as photometers providing information in the atmospheric column.

The access of broad users, including those from science, government, the economy, etc., to the research infrastructure and the high quality measurement data products generated within it is non-trivial. And this in terms of both building the infrastructure itself in Poland, which requires large amounts of money and specialised staff (technicians, engineers, analysts, researchers), and the costs of accessing specific data products and scaling them up for local and national needs, particularly when they are not sourced in Poland.

Therefore, the participation of Polish universities and scientific institutions in the projects of European research programmes, e.g. Horizon 2020, such as ACTRIS-IMP (implementation project of the Research Infrastructures consolidating studies of aerosols, trace gases and clouds by ground-based in situ and remote sensingmeasurements) or ATMO-ACCESS (pilot project of access to Research Infrastructures such as already mentioned ACTRIS, ICOS – Integrated Carbon Observation System, IAGOS – In-service Aircraft for a Global Observing System) is particularly valuable. Polish participation in projects aimed at standardising the formal and legal existence, extension and long-term support by member states of research infrastructures on the Polish Research Infrastructure Map ( and the European Roadmap for ESFRI (

The strength of the existing ACTRIS scientific research stations in Poland is that they cover a diverse environment – the urban observation station in Warsaw ( of the Faculty of Physics of the University of Warsaw and the rural station in Belsk ( near Warsaw of the Institute of Geophysics of the Polish Academy of Sciences. As part of the work of ACTRIS-Poland, several more observation stations are planned to be retrofitted and put into operation, in Wielkopolskie (University of Life Sciences in Poznań and Warsaw University), Śląskie (Institute of Fundamentals of Environmental Engineering of the Polish Academy of Sciences, University of Silesia in Katowice and Institute of Geophysics of the Polish Academy of Sciences), Dolnośląskie (University of Wrocław) and Podkarpackie (University of Warsaw), including an experimental mobile platform and a specialised physico-chemical laboratory for in situ sample analysis.

From the measured data at the ACTRIS stations in Warsaw and Belsk, operating among others within the framework of the aforementioned European LIDAR network EARLINET, as well as the global photometric network AERONET (Aerosol Robotic Network) on the basis of cooperation contracts with the National Aeronautics and Space Administration (NASA). Specific physical quantities are calculated after undergoing quality control, are publicly available through the ACTRIS Data Centre and the AERONET Web-Portal, respectively. In addition, atmospheric observations on satellites, including those of the NASA mentioned above, as well as those of the European Space Agency (ESA) and the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT), are actively used in research, and ACTRIS measurements contribute to the quality assessment of satellite measurements through participation in calibration and validation missions.

A weakness of current scientific research is the relatively low involvement in joint activities with the air quality monitoring sector, including its modelling, which is mainly due to the the Chief Inspectorate of Environmental Protection limiting itself to using only its measurement data. The situation is similar with regard to the relatively low intensity of cooperation with the Institute of Meteorology and Water Management – National Research Institute (IMWM-NRI).

Increasing cooperation between areas in a closed cycle: monitoring – research – synoptics, is inevitable in the near future, from the point of view of improving air quality, including the smog situation in the country. Figure 2 shows an instinctively imposing pattern of complementary pathways for obtaining comprehensive smog information in which different institutions should be involved.

How high does smog go?

Intuitively, it seems, unfortunately erroneously, that the Chief Inspectorate of Environmental Protection’s ground monitoring alone is sufficient. This is based on the correct assumption that there must be a direct link between concentrations measured at ground level and the local air pollution that covers the urban, municipal or industrial area where the smog phenomenon is observed. However, what is no longer so intuitive is that pollutants measured near the ground surface can be mixtures of local aerosol particles and inflow particles! The latter can be both dust and aerosol particles of anthropogenic origin (e.g. industrial pollution) and natural origin (e.g. forest fires, mineral dust from desert areas) transported long distances over smog areas. Information on the dynamics of atmospheric state changes on at least a synoptic scale is crucial, along with locally measured profiles of temperature, relative humidity,  vertical, and horizontal movements of air masses. Also, information on the local vertical distribution structure of atmospheric aerosol dusts, water vapour content changes, and changes in the optical and microphysical properties of aerosol particles, especially if recovered on a high time scale (at least half an hour) will play a very important role in determining the contribution of aerosol dusts from non-local sources. Information extracted from satellite data in turn provides the horizontal spatial coverage of an episode.

To quantify the composition of the atmosphere measured at the ground surface or in the lowest layers of the atmosphere, source apportionment techniques can be applied to both gaseous atmospheric pollutants and aerosols containing suspended particulate matter. This uses a combination of modelling of the advection of air masses over the area from a source area and chemical analyses of in situ samples taken during ground-based measurements in the smog area. Complementary to such analyses is the use of measurements taken with top-class atmospheric lidars (EARLINET), which allows to determine the spatio-temporal variability of optical (e.g. vertical profiles of scattering and extinction coefficients, degree of depolarisation, hydration) and microphysical (size distribution, complex refractive index, single-scattering albedo) properties of particles measured simultaneously in the boundary layer of the atmosphere (local sources) and in the free troposphere (sources of advection from distant areas), as well as their possible mixing. The image is complemented by photometric measurements (AERONET), which gives similar informationthroughout the atmosphere column. Measurements using combinations of such devices can determine to what extent concentrations of particulate matter measured at ground level are indeed local, and to what extent they are caused by the transport of aerosols and particulates from other, often very distant transboundary sources.

Since 2013, such studies of atmospheric aerosols (including measurements during smog episodes) have been carried out as part of the extensive activities of the Remote Sensing Laboratory (RS-Lab) led by Iwona Stachlewska[i2]  at the Institute of Geophysics, Faculty of Physics, University of Warsaw (FUW). Research and development and organizational activities  are conducted in dynamic cooperation with national and foreign partners (scientific units, international agencies, private sector) and cover both long-term measurements at the station in Warsaw and dedicated measurement campaigns within scientific projects and statutory research in other locations.

The long-term research was made possible thanks to intensive and fruitful bilateral cooperation abroad, within the framework of a research and development project for the construction of an innovative lidar device, funded by the now defunct Foundation for Polish Science and Technology. Thanks to the support of the Foundation for Polish Science,Technology, and the subsequent operational support of the acquired infrastructure by the Directorate of the Institute of Geophysics and the Dean’s Office of the Faculty of Physics, Poland has one of the most modern operational lidars in the world. In the framework of the above mentioned grant of the FUW and TROPOS (Leibniz Institute for Tropospheric Research e.V., Leipzig, Germany) built in 2012-2013 a multi-channel, transportable PollyXT lidar, of the Raman-Mie type, equipping it with a unique set of 8 channels allowing remote quasi-continuous measurements of the vertical backscattering structure and of the extinction and depolarization rates of radiation at representative wavelengths in the near infrared (1064nm), visible light (532nm) and ultraviolet (355nm). In addition, lidar profiles the mixing ratio of water vapour in the atmosphere. In a similar collaboration between the FUW and TROPOS, an independent but PollyXT-compatible Near-Range Aerosol Raman lidar (NARLa) was developed in 2014-2015, which efficiently enhanced the measurement regime at the lowest atmospheric altitudes, making measurements of smog, among other things, more meaningful.

It is worth mentioning that the NARLa lidar was used during several aerosol field campaigns in the country organised by the FUW (2015-2018), as well as in the collaboration of the FUW with the Alfred Wegener Institute for Polar and Marine Research (AWI) during the Arctic measurement campaign in 2015. At the German-French AWI-PEV polar station in Spitsbergen under funding from the Polish-Norwegian iAREA grant, and in the collaboration of the FUW with the National Observartory of Athens (NOA) during the 2016 smog campaign in Athens under the joint research activity JRA1 of the ACTRIS infrastructure.

LidarPollyXT and NARLa were used with respect to research on the closure effect on air traffic (COVID-19 lockdown) of most airports in Europe at the turn of February-May 2020. Preliminary results showed a negligible effect at ACTRIS stations located in northern and eastern Europe (Poland), compared to central and south-eastern Europe, where the effect of reducing aerosol in the low troposphere was found to be significant, as well as compared to south-western Europe, where conversely an increase in aerosol in the low and high troposphere was observed. The results of these studies are currently undergoing in-depth analysis.

Another breakthrough in the activities of RS-Lab (the FUW) was the acquisition of funds from the European Space Agency (ESA). This made it possible to conduct dedicated measurement campaigns using the mobile lidar built under the POLIMOS contract. The EMORAL (ESA Mobile Raman Aerosol Lidar) lidar prototype was reconstructed from scratch into a Raman-Mie lidar in 2017-2018 in close collaboration between ESA, the FUW, NOA, Ludwig Maximilians University Munich (LMU, Germany) and Raymetrics S.A. (Athens, Greece). It has been enhanced with features that place it at the reference level for validation and calibration of ESA satellite missions as a mobile laboratory installed on board a research vehicle ready for 24/7 operational activity. Lidar performed regular measurements at the station of the University of Life Sciences in Poznań (UPP) during two dedicated measurement campaigns in the periods March-October 2018 and June-August 2019, aiming to study ecosystem-atmosphere relationships as part of the interdisciplinary POLIMOS activity. Figure 4 shows images of the EMORAL lidar during one of these campaigns at the PolWET UPP peat station in Rzecin.

Figure 3 shows images of the PollyXT and NARLa lidars performing complementary measurements as one of the ACTRIS observation stations. Lidars at the Warsaw station have only been operational in ACTRIS since March 2015, but thanks to it’s uniqueness, great commitment, and skills of the team, the Warsaw station is highly valued and recognised as one of the stations providing the best and complete lidar measurement data in ACTRIS/EARLINET.

Several other dedicated measurements were carried out with EMORAL during the field campaigns, including two campaigns in Warsaw in order to obtain recommendations for the validity of the EMORAL lidar in direct comparison of the operationally measured data to the PollyXT-NARLa lidar (the FUW) and the ACTRIS reference lidars, i.e. POLIS (LMU) and RALi (National Institute for R&D in Optoelectronics – INOE, Bucharest, Romania).

Positive passing of the required measurement and data quality tests resulted in further time. Scientific measurement campaigns and intensive cooperation between the FUW and AGH University of Science and Technology (AGH; Smog Campaign in Kraków, 2019), cooperation between the FUW, UPP and INOE (Campaign under the joint ESA initiative of POLIMOS and RAMOS activities, 2019), cooperation between the FUW, AGH and German Space Agency (DLR; CoMet aerial measurement campaign in Silesia, 2018).

At present, research and development work is underway in collaboration between ESA, Raymetrics S.A. and the FUW to design a fluorescence channel for the EMORAL lidar, which will greatly extend the range of measured parameters, in particular towards improving the detection of biogenic aerosols, including such important ones as allergenic pollen.

It is worth noting that RS-Lab (the FUW) is also participating in the ESA-funded MULTIPLY international R&D project, coordinated by Romanian partner INOE, which is building a unique High Spectral Resolution (HSRL) aircraft lidar with parameters far beyond those offered by NASA's existing HSRL. The MULTIPLY lidar uses a unique technique of multiple signal filtering with sequential Fabry-Pérot Interferometers (FPI) at 355 nm, 1064 nm, and classical detection at 532 nm using an iodine absorption cell. This also measures polarisation at these three wavelengths. As an airborne lidar, MULTIPLY must be characterised by very high operational stability and ease of alignment and calibration, so a honeycomb methodology is used in its construction, whereby key elements of the optical system are duplicated several times, and modern refractive technology in combination with optical fibres are used. The MULTIPLY lidar is currently in the testing phase and, once completed, will eventually be installed on one of the National Institute of Aerospace Research’s “ELIE CARAFOLI” instrumented research aircraft (INCAS, Bucharest, Romania) offered for international atmospheric research as part of the EUFAR (European Facility for Airborne Research) fleet of research aircraft. Poland’s (the FUW) unique contribution to this project is the development of a technology for simultaneous adjustment of sensitive optics for channels at wavelengths filtered by sequential FPIs. After the ground tests, operational tests and research measurements are foreseen on board the aircraft over Romania and Poland in zones of highest air pollution by anthropogenic dust and natural atmospheric aerosols.

From the point of view of the research carried out so far within the RS-Lab at the FUW, i.e. having in mind broadly understood air pollution, not limited only to the phenomenon of smog in winter and summer, it is important to understand the dynamics, the range of this phenomenon in terms of vertical movements of air masses and its horizontal displacements. This means in practice using available tools for modelling air mass trajectories (e.g. HySPLIT being developed at NOAA, USA; FLEXPART being developed by ZAMG and NILU), synoptic analyses (e.g. ECMWF and IMWM-NRI models), and air quality (e.g. NAAPS Air Quality Model being developed at NAVY, USA).

The composition of aerosol, including dusts from anthropogenic pollution, is also of great importance, as it is the information on what kind and type of particles we are dealing with and what their properties are, e.g. dust whose particles have strong absorption properties (they absorb solar radiation) may cause lowering of the boundary layer and stronger smog effect.

Figure 5 shows the composition of aerosols observed in the boundary layer during the summer in Warsaw in two periods. The summer composition of aerosol in the boundary layer of the Warsaw atmosphere, estimated on the basis of analyses of air mass dynamics and optical properties of aerosol particles derived from lidar measurements in this altitude range, shows a slight predominance of particles associated with urban pollution over other aerosol sources (Wang et al. Atmospheric Chemistry and Physics, 2019). Between 2017 and 2020, the boundary layer shows a significant change in composition particularly at the expense of emerging aerosols classified as mineral dust (the classification does not differentiate between agricultural dust and desert sand).

In addition to smog...

Suspended particulate matter recorded by the Chief Inspectorate of Environmental Protection’s ground monitoring in Poland, may originate from other EU and non-EU countries, and this is by no means an isolated situation, as documented by publications committed at RS-Lab. The Remote Sensing 2017 and 2018 studies prepared by Stachlewska et al , discuss respectively, inflows to the boundary layer of the atmosphere in Warsaw of anthropogenic pollutants brought with air masses from industrialised areas in Germany and aerosols from biomass burning during the burning of meadows, grasses and peat bogs in Ukraine. The results of the studies documented therein have shown that high concentrations of particulate matter monitored by the Chief Inspectorate of Environmental Protection at several point stations in situ at the ground surface, under atmospheric conditions favourable for the occurrence of smog episodes, are positively correlated with the optical thickness of aerosol measured remotely both in the boundary layer measured with lidar and in the column of the atmosphere measured with a solar photometer and in the spatial representation from the acquired SEVIRI satellite data for the area covering the area of Warsaw. However, the positive correlation is not apparent in statistical analyses of the relationship between particulate matter concentrations and optical thickness if a breakdown into episodes dependent on the specificity of weather phenomena is not used (Zawdzka et al. Atmospheric Environment, 2013).

The key value of using synergies of different types of measurement is to show that it is the type and optical and microphysical properties of the aerosol/dust coming in with the air mass and entering the boundary layer of the atmosphere that are very important, not just their size. By implication, this is also relevant in assessments of the harmfulness and health effects of dust. So clearly focusing only on particle size – measurements of PM10, PM2.5, or more recently the increasingly popular PM1 – is not sufficient.

Particularly, a rapid influx of dust with strong solar absorption properties (e.g. with soot content) from over Ukraine, injected into the boundary layer of the atmosphere and accumulated under the layer of temperature inversion, may cause lowering of the boundary layer and quite intuitively stronger pollution of the atmosphere (Stachlewska et al. Atmospheric Research 2017; Stachlewska et al. Remote Sensing 2018).

The influx of pollutants with a negligible absorption coefficient from over Germany caused an increase in the boundary layer, but despite the expected lower sensitivity, i.e. dilution of dust with increasing boundary layer height, it was associated with an increase in pollutant concentration and aerosol optical thickness (Stachlewska et al. Remote Sensing et al. 2017).

These studies clearly show that transboundary transport of air masses into Poland, containing anthropogenic and natural aerosol dusts, can influence concentrations of particulate matter even in central Poland, and not only in border zones. This is an important factor in addition to the undeniable influence of transboundary aerosols in increasing the number of particles in the high troposphere or column of the atmosphere, e.g. through the influx of dust particles and fumes from forest fires in North America, or transports of mineral sand particles and dust from the Sahara (Janicka et al. Atmospheric Environment et al. 2017).

The question remains as to the significance of the effect of such transboundary aerosols on dust concentrations monitored by the Chief Inspectorate of Environmental Protection on a national scale, in particular in large urban agglomerations and highly urbanised and industrialised areas, e.g. in the Silesian Region. At the moment, air quality modelling results sporadically show this effect, mainly because they do not assimilate any lidar results in operational mode. This problem is addressed by one of the ECMWF initiatives of the Copernicus programme within the ACTRIS aerosol profiles for CAMS project (CAMS21b) in which 9 pilot stations (including FUW station in Warsaw) provide high quality Near real time (NRT) profiles of atmospheric aerosol optical properties for CAMS modelling.

What is hanging over Kraków?

A case study of intrusion of aerosol particles from distant sources into the boundary layer of the atmosphere above Krakow may serve as an example demonstrating the issue in such a clear way that it can be treated as borderline scientific and popularising. The measurements were made with the EMORAL mobile lidar as part of the ten-day “Kraków smog” field campaign carried out in collaboration between FUW, AGH and UPP at the Jagiellonian University (UJ) Campus in February 2019, when continuous observations in smoggy conditions were expected. Figure 6 shows the lidar measurement and air mass trajectories for a period of 2 measurement days, the lidar data shows the variation of aerosol quantity (top) and its polarizing capacity (bottom) with altitude (X axis) over time (Y axis).

Initially, the boundary layer and troposphere above were free of aerosols. The exceptionally low level of weakly polarising aerosol in the lowest atmosphere was partly due to the influx of clean sub-Arctic air masses from over North America, as simulated by the five-day back trajectories of the HySPLIT model (green area). Over time, the intrusion of a significant aerosol mass was observed to be highly polarised, indicative of the non-spherical shape of the dust particles making up the aerosol (yellow area), and the trajectories show the influx of air masses from over North Africa. There is a clear upward trend in the trajectory, so it is likely that this air mass may have contained mineral dust from over the Sahara, the particles of which are indeed non-spherical. Then, another change in the trajectories can be seen, which indicate an influx of air masses from over western Europe, and the lidar measurement shows that the aerosol mass in the boundary layer is significant, and as it depolarises, albeit more weakly, the admixture of mineral dust from over the Sahara to the mainly incoming pollution must be significant (purple area). It is worth mentioning that for the analysed period the ground measurements of particulate matter recorded a significant and gradual increase only in the second half of the measurement (purple area) and without the synergistic information obtained from the lidar and the model the explanation of the observed values of the ground measurements would be difficult, if not incorrect. An interesting research problem would be to carry out analyses on a long-term scale to see how exceedances of concentration thresholds relate to their complex interpretation. It may be that this effect will be negligible or small in smog situations, but for the time being, as long as such studies have not been carried out, it is not legitimate to deny such an effect.

What can we do together?

In conclusion, it is worth noting once again the need to improve real links between the environment focused on air quality monitoring within the Chief Inspectorate of Environmental Protection and the Provincial Inspectorate of Environmental Protection and the scientific environment dealing with weather forecasting and atmospheric research within the Research Infrastructures of the atmospheric domain. Such cooperation should include issues of common air quality modelling and forecasting, with a view to improve alert systems for the public. However, such works should be carried out in close cooperation with IMWM-NRI, using the access to ECMWF measurement data in order to significantly improve results of modelling forecasts available e.g. on the Chief Inspectorate of Environmental Protection portals.

In addition, it is necessary to strengthen the efforts made to build from scratch or extend and retrofit at least one urban research station in Poland with a set of measuring instruments which will make it part of the European Commission’s Green Deal programme, so that it serves as a prototype of a modern observational station with appropriate parameters for conducting scientific research within the framework of air quality monitoring. Thus, such a station will demonstrate a potential worthy of strategic replication at other stations in sensitive areas in the country. A natural choice in this respect would be the Polish stations of the pan-European Distributed Research Infrastructure ACTRIS for coordinated measurements of aerosols, clouds and gases in the atmosphere by remote and/or in-situ techniques.

The use of these measurements perfectly complements the measurements of atmospheric Earth observation satellite missions. It is crucial to strengthen scientific cooperation with the Polish Space Agency, in particular by promoting and making effective use of the Earth Observations sector for atmospheric research (aerosols, clouds, trace gases), in addition to the current use of hard Earth observation data and within the rapidly developing astronomy sector.

Author: Iwona Stachlewska, Faculty of Physics, University of Warsaw

Title, subtitles and lead have been developed by the TOGETAIR editorial team