Saharan dust and photovoltaic energy in Hungary

In our article, we examined four years (2020–2023) of PV production and forecasting in Hungary, with a special focus on the day-ahead forecast errors experienced during Saharan dust storm events.

Varga, Gy., Gresina, F., Gelencsér, A., Csávics, A., Rostási, Á. (2025). Desert dust and photovoltaic energy forecasts: Lessons from 46 Saharan dust events in Hungary (Central Europe). Renewable and Sustainable Energy Reviews 212. 115446

The main lessons we have highlighted in this article are:

• The impact of atmospheric particulate matter is significant, both on PV production and on generation forecasting. This effect is likely to be more pronounced in the case of meridional (south-north) dust transport due to the steeper thermal gradient, which results in a greater impact on cloud formation processes due to both warm advection and increased fine-grained atmospheric particulate mass.
• PV production projections cannot be sufficiently accurate if coarse resolution aerosol climatology data are used without considering aerosol-cloud interactions, instead calculations need to incorporate up-to-date dust loading data and appropriate cloud physics relationships.
• The amount of atmospheric dust, the transport dynamics and the mineralogical and physical properties (grain size, grain shape) of the dust material are not well understood and these factors have a diverse impact on cloud formation processes. A better understanding is needed in the future.
• Also, due to climate change and the natural variability of the climate system, forecasts are made in an unsteady hydrometeorological and atmospheric regime, which always carries uncertainties. These errors are likely to become more significant with increasing installed PV capacity, so managing them will require expanding electricity storage capacity alongside increasingly accurate forecasts.

Record number of Saharan dust events in Hungary - effects on solar energy forecast

Researchers from the HUN-REN Research Centre for Astronomy and Earth Sciences (HUN-REN CSFK), Pannon University and Eötvös Loránd University (ELTE) have investigated the impact of mineral dust carried by Saharan dust storms on domestic photovoltaic energy production and electricity generation schedules. The paper, published in the prestigious scientific journal "Renewable and Sustainable Energy Reviews," provides answers regarding when, from where, and how much mineral dust with specific properties from the Sahara arrives over Hungary. According to the researchers, scheduling should take into account these episodic dust storms, which can lead to reduced irradiance, resulting in less electricity production than initially anticipated by the planners.

Photovoltaic energy production and weather-dependent renewable energy sources, in general, are unpredictable. Unlike gas, for example, electrical energy cannot currently be effectively stored, and there is a continuous need for a balance between production and consumption, with no buffer in the system. The composition of fossil and renewable energy sources in the electricity mix varies from day to day. However, due to the necessity of maintaining a forced balance between production and consumption, it is crucial to know the proportion of weather-dependent renewables in the system for the next day. If the schedule is not accurate, it may require the rapid activation of expensive and fossil fuel backup capacities, primarily gas power plants.

The system operator, therefore, needs to know in advance how much the solar power plants will produce. Models are running for this purpose, and historical climatic data are also available. However, these models often do not take into account many parameters or misparameterise certain processes, and the historical data are essentially unusable due to the ongoing climate change.

Researchers from HUN-REN CSFK, Pannon University and ELTE have expanded their previous basic research on atmospheric dust and Saharan dust storm events in a direction that is also socially and economically significant. Specifically, they have focused on the impact of mineral dust on photovoltaic energy production and schedules.

In their recently published scientific paper, György Varga, a senior scientist at HUN-REN CSFK's Geographical Institute, along with his colleagues, examined the significantly flawed 24-hour schedules for photovoltaic energy production during the 2022 record-breaking 16 Saharan dust storm events in Hungary. They shed light on the significant role of mineral particles in cloud formation during dust storm events, leading to increased cloud cover and extended cloud lifetimes. This results in lower irradiance, causing less electrical energy production than anticipated by the schedulers.

Among the methods applied by the researchers were satellite measurements, numerical simulations, calculations of air mass trajectories, and synoptic meteorological analyses. In addition, laboratory analyses of dust particles washed out with precipitation during Saharan dust storm events were also included. During individual episodes, researchers detected periodical deficits of up to 500 MW between actual and forecasted performance, necessitating the use of expensive and polluting backup capacity to cover the shortfall.

The main problem is that the role of atmospheric dust in the overall radiation balance is difficult to quantify in advance. Within individual dust clouds, various materials such as quartz, calcite, gypsum, clay minerals and mica, as well as variously shaped individual mineral particles and aggregates can be found, each with different optical properties. Darker-coloured particles, like hematite and goethite, absorb more radiation and have a local heating effect, whereas in the case of lighter particles, dominant effects include reflection (e.g., salt crystals) and scattering (e.g., quartz), which result in temperature decrease. The mineral composition is primarily dependent on the geological composition of the source area, but it constantly changes during atmospheric transport since larger and/or heavier particles can fall out of the dust cloud earlier, thereby modifying radiative properties.

When fine particles of atmospheric dust enter the atmosphere, they can also act as condensation nuclei necessary for cloud formation, without which cloud droplets would not form. An increase in the number of condensation nuclei, at a given water vapor content, leads to the formation of more but smaller cloud droplets. As a result, the cloud appears brighter and reflects more radiation. Another characteristic of smaller droplets is that they have a relatively long atmospheric residence time, thereby exerting their radiative effects for a longer duration. Additionally, the probability of precipitation decreases, which means that it is less likely to wash the panels.

The researchers provided answers to several open questions in the paper. For instance, they addressed when, from where, and how much Saharan dust arrives over Hungary, the mineral properties of the dust particles, and the size and shape of the dust grains. They emphasised that in addition to applying general aerosol climatology, episodic dust storms should also be considered in scheduling. Thus far, the microphysical processes related to clouds, specifically the relationships between dust and cloud formation, have not been factored into the calculations.

Publication:

Varga et al., 2024. Effect of Saharan dust episodes on the accuracy of photovoltaic energy production forecast in Hungary (Central Europe). Renewable and Sustainable Energy Reviews https://doi.org/10.1016/j.rser.2024.114289

Desert dust in Finland

Hungarian, Icelandic, and Finnish researchers led by Dr. György Varga, a senior research fellow at the Geographical Institute of the HUN-REN Research Centre for Astronomy and Earth Sciences (HUN-REN CSFK FTI), analysed dust storm events that reached the Finnish atmosphere from long distances between 1980 and 2022. They also identified signs of ongoing climate change, including the growing occurrence of south-north meridional atmospheric flows, attributed to the increased warming of higher geographical latitudes. The study presenting the results was published in the prestigious journal Environment International.

Through the investigations, researchers uncovered dust storm events during which particulate matter from the Sahara, the Aral-Caspian region, and the deserts of the Middle East reached the Finnish atmosphere. Based on model calculations, satellite measurements and images, as well as data from surface monitoring stations, among the episodes identified as potential dusty situations, events confirmed through calculations of air mass trajectories and traceable back to desert and semi-desert regions were added to the database. Thus, during the examined 43 years, a total of 86 long-distance dust storm events were identified in the atmosphere of Northern European countries, including 59 originating from Sahara areas, 22 from the dried-up bed of the Aral Sea and the desert and semi-desert regions of the Caspian Sea area, and 5 from the deserts of the Middle East.

While the emissions from these source areas, excluding the 'dried-up' Aral Sea, are not directly linked to human activity, researchers still emphasize that the effects of ongoing anthropogenic climate change can be identified in the time series and through synoptic meteorological backgrounds of individual episodes. The number of relatively scarce winter events has doubled since 2010, making these studies particularly significant, as local meteorologists have reported freezing rain during every identified winter occasion. Behind this phenomenon are warm upper-level inflows associated with dust storm events, similar to the Saharan dust influx, which was also one of the causes of the 2014 Normafa disaster.

These seasonal changes have evolved similarly in many other regions of Europe, including Hungary. It was, in fact, the frequency and intensity variations of Saharan dust transport observed in Hungary that initially drew the attention of researchers to Northern Europe. The underlying cause of these changes is the increased warming of the Arctic region and, consequently, the decreasing temperature difference between lower and higher latitudes. As a result, high-altitude jet streams lose their strength and become more meandering, adopting a wavier pattern. This, in turn, increases the likelihood of situations where south-north airflow predominates for extended periods, thereby raising the chances of dust reaching northern areas. These changes have also been detected in the case of Iceland.

Systematic, long-term research into these phenomena had not previously been conducted in the region of Finland. News and occasional case studies had only appeared in connection with specific events. Beyond its extended investigation period, the recent study was innovative because it focused not only on episodes originating from the dominant Saharan source areas. The Aral Sea region serves as an outstanding example of harmful human impacts. The waters of the Amu and Syr Darya rivers, once feeding the Earth's fourth-largest lake, were diverted for cotton irrigation, thus, the former lakebed is now occupied by one of the planet's most recent deserts, the Aralkum. A quarter of the identified dust storm events originated from this area. What surprised researchers even more was that on five occasions, dust from the Middle East – Syria, Saudi Arabia, and Iraq – also reached Finland.

Through the investigations, it has once again been confirmed that atmospheric processes changing due to climate change increasingly contribute to the occurrence of extreme weather events. However, the particulate matter reaching long distances is not just one symptom of it all. For example, when deposited on the snow and ice-covered regions of northern areas, it can also contribute to faster melting as the darker surface absorbs more heat, further amplifying the increased warming of higher latitudes. Since the start of the research, there have been two significant Saharan dust depositions in Finland. Consequently, the Finnish Meteorological Institute requested assistance from the public. In their call, they suggested that people melt the snow in saunas and then submit the samples, allowing the researchers to analyse as many dust samples as possible.

The research was carried out with the support of the NKFIH FK138692 and RRF-2.3.1-21-2021 projects, with the involvement of Hungarian, Finnish, and Icelandic researchers.

Publication:

Varga et al. Saharan, Aral-Caspian and Middle East dust travels to Finland (1980-2022). Environment International.

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 https://drive.google.com/file/d/11dFYEsPp5rU7S-jviyZlmEkXOGCAY4nl/view?usp=sharing

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Varga et al.

ELKH: Hungarian researchers identify giant Saharan dust particles as far away as Iceland

Saharan dust storms traveling as far as Iceland have been identified in an international collaboration led by Hungarian researchers from the Geographical Institute of the ELKH Research Centre for Astronomy and Earth Sciences (CSFK FTI). Due to changing atmospheric transport mechanisms associated with climate change, similar events are increasingly being observed at higher latitudes. Of particular significance is the fact the Hungarian researchers also found large quantities of giant mineral dust particles (more than a tenth of a millimetre in diameter), which play the opposite role in the Earth’s energy balance to the cooling effect of fine-grained dust, causing net warming of the atmosphere. The results of the research on long-distance transport of Saharan dust were published in the journal Scientific Reports  a member of the Nature family of journals.

In the recently published paper “Saharan dust and giant quartz particle transport towards Iceland”, György Varga, Senior Research Fellow at CSFK FTI, Fruzsina Holman-Gresina (Research Assistant at CSFK; ELTE PhD student) and their Czech and Icelandic co-authors describe Saharan dust storm events identified in the Icelandic region over the past decade and a half, their meteorological background, dust transport routes, possible source areas and general characteristics of the dust particles. The 15 dust storm events identified by remote sensing methods and computer models clearly show that fine-grained mineral dust can travel thousands of kilometres from the Saharan source areas. In fact, particle size and shape analyses of dust collected during two intense events in the Reykjavík area showed that it is not just fine-grained dust of, up to a few tens of microns in diameter that can reach such distances as previously thought, but also large numbers of very large mineral particles of up to 100 microns in size. The researchers carried out the tests using a granulometric characterization instrument based on automated image processing in the Laboratory for Sediment and Soil Analysis of the CSFK FTI .

Climate change: more dust?

The research addresses several aspects of the ongoing climate change issue. Through this study, the researchers have provided new results on the relationship between increased atmospheric meridionality – i.e. the increased dominance of south-north flow systems – and the increased warming of the Arctic, as well as the resulting decrease in the temperature difference between higher and lower latitudes and changing atmospheric flow systems. Reliable instrumental measurements have been available since the 1880s. Since then, the global average temperature has risen by almost 1 degree Celsius. The vast majority of this warming has occurred in the last 10-15 years and its spatial distribution is not uniform: warming in polar regions is several times greater than the temperature change at lower latitudes (a process known as Arctic amplification). The evolution of Rossby waves, which are responsible for cyclonic activity in the temperate zone, varies with the meridional temperature difference: the smaller the difference, the slower the formation of high atmospheric waves with larger amplitudes. Because of these large-amplitude swings, choppy flows from the desert areas of North Africa can carry large amounts of dust northwards (like blowing the dust off a table with a strong wave motion of the tablecloth). This can sometimes be seen across Europe, and a link has been found in Hungary between the meandering jet stream and the increasing amounts of Saharan dust being transported into the Carpathian Basin. What is particularly interesting, however, is that Saharan dust can travel as far as Iceland on so many occasions.

Giant Saharan dust particles in the Arctic atmosphere

The significance of the research is further enhanced by the fact that the analysis of hundreds of thousands of individual mineral particle sizes and fractions has shown that many more large particles are being released into the atmosphere than previously thought. Because of their size, these dust particles – unlike fine-grained dust – absorb rather than reflect radiation from the Sun, so they have a heating rather than a cooling effect. For this reason, the parameterization of their role in the Earth’s energy balance in global climate models needs to be modified. As Iceland is itself the largest dust-emitting region in Europe, with 44,000 km2 of desert area and an average of 135 dust storm days per year, samples collected from the Icelandic source areas were analyzed in the laboratory to separate Saharan and local dust and to exclude possible local ‘contamination’ of the samples thought to be from the Sahara. Like the samples from settled particulate matter, these were analyzed using automated static image processing. This method allows researchers to obtain direct particle size and shape data from small samples. The granulometric data from hundreds of thousands of individual particles are complemented by data from the Malvern Morphologi G3-IDSE Raman spectroscope, which also provides mineral phase information. The researchers found that the size and shape properties of the dust material from local source areas can be effectively distinguished from each other using this method. Particles of similar size had different shapes and particles of similar shape had different sizes. These tests could not have been carried out with any other instrument. For recurrent dust storm events, this method is used only by the CSFK FTI research team worldwide.

The research was carried out with the support of CSFK, project No. KH130337 (“Granulometric analysis of recent Saharan dust”), project No. K120620 (“Paleoenvironmental reconstruction based on particle size and shape of aeolian dust deposits “) of the National Research, Development and Innovation Office (NKFIH), and the Excellence Cooperation Program (KEP-08/2018) of the Hungarian Academy of Sciences, and in cooperation with the COST Action in Dust program with the participation of Hungarian, Czech and Icelandic researchers.

Publication:

Varga, Gy.; Dagsson-Walhauserová; Gresina, F.; Helgadottir, A. (2021). Saharan dust and giant quartz particle transport towards Iceland. Scientific Reports