AGH UST Scientists Research Smog-Free Altitudes

Sightseeing balloon at Wołyński Boulevard, where the AGH UST physicists installed the measuring equipment, photo by Professor Mirosław Zimnoch, the Faculty of Physics and Applied Computer Science

Krakow panorama from the sightseeing balloon, photo by Łukasz Chmura, DSc, from the Faculty of Physics and Applied Computer Science

Thanks to putting the measuring equipment on a sightseeing balloon, the scientists from the Faculty of Physics and Applied Computer Science have already gathered thousands of vertical profiles of the atmosphere. Their research supplements the knowledge on how air movements influence the particulate matter concentration in Krakow.

When the heating season starts in Krakow, the instruments showing the levels of air pollution with particulate matter, harmful to human organisms, light up in red. They continue to flicker for a considerable amount of days in the autumn and winter seasons, which translates to an increased rate of pulmonary and cardiovascular diseases. Data on the ‘smoging’ of the capital city of Małopolska Province are currently being collected by 8 Voivodship Inspectorate for Environmental Protection stations and an increasingly denser network of private sensors and measuring devices. Thanks to such stations, we can monitor the condition of air we breathe near the ground. However, it does not offer a full picture concerning processes that influence the changes in the atmosphere. ‘If we want to establish where the pollution comes from – whether it is our city that produces it, or the towns and villages around Krakow – it is worth examining it in vertical profiles. We are dealing with an entirely different situation when smog lingers 20 metres high above the ground than when it floats 100 metres up’, explains Jakub Bartyzel, DSc from Environmental Physics Group of the Faculty of Physics and Applied Computer Science.

To answer such questions, physicists from the AGH UST have been conducting research on air quality in vertical distribution using drones for quite some time. However, the machines require human involvement. They also have their limits as far as both the possibility to install indispensable equipmen, as well as existing regulations are concerned. The latter prohibit drones from reaching altitudes higher than 100 metres. Which is why the AGH UST scientists were overjoyed when, two years ago, the owner of the sightseeing balloon located at Wołyński Boulevard suggested that they could put their measuring equipment on the balloon. It allowed the researchers to increase the scope of their research, simultaneously limiting the necessary means to conduct it. Dr Bartyzel, who coordinated the project on behalf of the Faculty of Physics and Applied Computer Science, says: ‘Measurements carried out in this way are practically costless. Both in terms of finance, as well as time and people’s involvement. The balloon flies regardless of us, and we receive the data after each flight’.

Vertical profiles of the atmosphere

Due to such endeavours, the physicists have already been able to obtain thousands of vertical profiles of the atmosphere, measured from the ground up to approximately 280 metres, which is the maximum altitude for the balloon. Interestingly, the measurements are not only locally significant. Earlier research of this kind was conducted only in cities like Paris or Shanghai, which are located either on terrains which are less topographically diverse, or at the seaside. Whereas Krakow is situated in a vast valley surrounded by hills at its three sides. As a result, phenomena, such as katabatic winds, which are winds carrying high-density air from a higher elevation down a slope under the force of gravity are frequently observed here. Temperature inversions also occur often. Perhaps the analysis of the acquired data will allow the scientists to come to general conclusions which will expand the knowledge on the influence of atmospheric movements on the levels of air pollutions in similar agglomerations.

First research articles and reports have already been published. In one of such reports, which was developed in collaboration with the researchers from the Faculty of Physics and Applied Computer Science and the Institute of Meteorology and Water Management, the Jagiellonian University, and the Max Planck Institute for Biogeochemistry in Germany, the authors analyse the maximum vertical range of a cloud of pollution above Krakow. The scientists show that in days with favourable meteorological conditions smog lingered up to 100 metres up.

Why this much?

This is, more or less, the depth of the valley in which the capital city of Małopolska Province is situated. Below that altitude a phenomenon called a wind shear happens, which is a sudden decrease of wind speed. ‘As a result, the wind ventilates towns situated higher but has practically no chance of interfering in the situation below, in Krakow. If we wanted to build something where, on the highest floor, we would be able to breathe fresh air, irrespectively of the conditions, the building would have to have more than 100 metres’, comments the physicist from the Faculty of Physics and Applied Computer Science.

Regular measurements of the particulate matter concentration in air is not the only benefit that the scientists gain by installing the measuring devices on the balloon. The equipment also collects basic meteorological data, such as temperature, humidity, or air pressure. It allows them to verify the correctness of mathematical weather models, which, in turn, are taken into account in developing models of pollution propagation. The AHG UST researchers once a month for 24 hours measure the concentration of carbon dioxide and methane in the atmosphere. The results of such measurements are then used in the EU project “CoCO2” to verify satellite measurements from the “Copernicus” system.

How are the measurements done?

Initially, the only measuring device that the scientists had at their disposal was a simple dust counter. Currently, they use professional equipment supplied by a French manufacturer. The purchase was funded by the balloon’s owner. It provides data on the fractional composition of the analysed dust particles. Physicists learn not only about the percentage of particles of a given diameter (PM10, PM2.5, etc.), they also gain insight into the origins of the dust particles, whether they are mineral in nature or are a result of combustion. ‘It allows us to draw conclusions on the source of the pollution’, says Dr Bartyzel.

The AGH UST scientists collaborate scientifically with the creators of the device. The features of the dust particles in Krakow are different than of those in Paris, where similar equipment was also installed on a balloon. Sharing information on the results may help to better calibrate our respective devices and increase the preciseness of the measurements.

During monthly measurements of the greenhouse gases, the researchers use a laser spectrometer, similar to the one which they use daily in measurements conducted in KASLAB (a high-mountain greenhouse gas laboratory). In the case of measurements during the flights of the balloon, the scientists cannot afford to be so regular because the device requires huge batteries which have to be installed on the balloon; unfortunately, they use up a considerable amount of space on the observation deck. The scientists cannot use a power generating unit to power the device despite the fact that the infrastructure of the aircraft allows it. This would disrupt the results of the measurements: ‘A power generating unit emits both dust particles and greenhouse gases. Which is why we always have to use our own power source’, explains the physicist.

The researcher adds that the choice of place to install the inlet of air is equally important: ‘It should be placed high above the balloon’s observation deck because during most flights, there are people on board, who naturally produce carbon dioxide’, describes Dr Bartyzel. ‘We can sometimes see subtle differences in our vertical profiles of atmosphere, which is why it is worth to take care of this, so that those differences stem from the situation outside the balloon and not from what the people breath out into the inlet’.

To analyse the data collected during the flights the scientists use tailored computer algorithms. They can, among other things, isolate particular moments of ascending and descending of the balloon or create visualisations based on the collected data. As befits the second part of the faculty’s name “Applied Computer Science”, the physicists developed the algorithms themselves.

The pandemic and a balloon crash

The research into the atmosphere conducted with the help of the balloon were thwarted last year by two events which resulted in putting the flights on hold. The first one was global in nature and the second one – local. The former was the outbreak of the COVID-19 pandemic and the lockdown connected thereto, which grounded the balloon from March to May. In mid-June, in turn, the balloon envelope burst during a storm. All flights were cancelled until the beginning of September.

However, the project coordinator from the Faculty of Physics and Applied Computer Sciences explains that the events had not influenced the realisation of the project significantly: ‘Every cloud has a silver lining – from the point of view of measuring the concentration of PM in air, we were lucky that the bursting occurred in the summer. The situation is then the least interesting and dynamic for scientists. Additionally, we always have the support of our drones. However, during lockdown all projects stopped. Whether we wanted to fly the drones or the balloon, it did not matter. We simply had to stay inside’.

Normally, balloon flights are limited by weather conditions and the regulations of air law. The scientists received heavy criticism from some media that the balloon does not ascend when there is heavy smog. However, Dr Bartyzel warns us against the simplistic putting of those two together:

‘Atmospheric conditions, which cause the accumulation of dense fogs, correlate with high concentration of dust particles in air. However, it is not the dust that reduces visibility, but the lingering of both smog and fog has the same cause. Nevertheless, the fact is that below a certain visibility range, the balloon cannot fly’, says the physicist.

For students and Krakow citizens

When the flights do take place unrestrainedly, the AGH UST scientists conduct classes with students on board of the balloon. Apart from that, their fellow researchers from the Jagiellonian University also use it for educational purposes. The results of the measurements, supplemented with meticulous comments of the faculty physicists, can be found online on the website of the sightseeing balloon. The researchers’ dream is to share their results to an even greater extent and in a more automated way.

‘A meteorological station, which we had installed on the roof of our faculty, enjoys a considerable amount of interest. People search for meaningful and authentic information on the weather outside their windows. In this case, they could also find it interesting to know how high they had to soar above Krakow to be able to breathe fresh air’, says Dr Bartyzel.