Do you wonder about the facts? 
We can give you deeper insight and an unbiased explanation
on how air pollution affects weather and climate.



  • Air pollution and human health assessments

  • Climate change predictions and assessments 

  • Numerical weather forecasts and model development

  • Solar irradiance and renewable power consumption forecasts

  • Large-scale climate variability predictions and seasonal forecasts

  • Regional dust outbreaks and long-range, transatlantic transport modeling  

  • Blockchain applications & artificial intelligence in the above mentioned fields

We are committed to work for a better future. Everyone benefits from our work.



Novel Concepts & Codes
Air pollution & Climate change assessments
Unique analytical aerosol composition model (EQSAM) 

The key product of our research is a unique computationally efficient gas-liquid-solid aerosol equilibrium partitioning model, EQSAM (Metzger et al., 1999, 2000, 2002, 2006, 2007, 2012, 2016, 2018), which is extended by a generalized aerosol dynamical model (GMXe). GMXe has been introduced with Pringle et al. (2010), but originally developed as part of Metzger et al. (2007). Both codes are widely used by modelers around the globe.

EQSAM, for instance, is used at the core of air quality forecasts on fine particulate matter (PM2.5) of the C-IFS ensemble model (Flemming et al., 2014, 2015). The C-IFS forecast data are provided by the European Centre for Medium-Range Weather Forecasts (ECMWF) as part of the Copernicus atmospheric monitoring service (CAMS). The CAMS air quality forecasts are widely used by various weather applications, such as the leading weather information provider Windy or meteoblue AG.

The CAMS regional forecasting service provides daily 4-day forecasts of the main air quality species and analyses of the day before, from 7 state-of-the-art atmospheric chemistry models and from the ENSEMBLE median calculated from the 7 model forecasts (Flemming et al., 2015). Within the CAMS Ensemble, EQSAM is used to calculate the fine particulate matter (Section 2.5.5), "Gas-aerosol partitioning is calculated using the equilibrium Simplified Aerosol Model (EQSAM, Metzger et al., 2002a, 2002b)".

Our most recent update, EQSAM4clim, has has been successfully applied (Koo et al., 2018) in the Comprehensive Air quality Model with extensions (CAMx). CAMx has been employed extensively by local, state, regional, and federal government agencies, academic and research institutions, and private consultants for regulatory assessments and general research throughout the U.S. and the world. CAMx has been used in more than 20 countries on nearly every continent (CAMx Applications). 

EQSAM4clim is currently implemented in EMEP MSC-W model, which is developed as part of the co-operative programme for monitoring and evaluation of the long-range transmission of air pollutants in Europe (inofficially 'European Monitoring and Evaluation Programme' = EMEP). EMEP is a scientifically based and policy driven programme under the Convention on Long-range Transboundary Air Pollution (CLRTAP) for international co-operation to solve transboundary air pollution problems. The EMEP program was set up 1979 to advise European policy makers. EQSAM has been previously used in the MSC-W model (Tsyro 2005).

EQSAM is also used as the thermodynamic core of many global climate models (e.g., NASA/GISS, Bauer S. et al., 2007a, 2007b). EQSAM has been used for a long time at the German Aerospace Center (DLR) (e.g., Lauer et al., 2005, Kaiser et al., 2014). Further EQSAM applications are listed in Table 1 of Metzger et al. (2018). As shown therein, EQSAM4clim has been successfully evaluated on climate time scales in combination with GMXe. Both aerosol modules are part of the comprehensive chemistry-climate and Earth System model, EMAC, which is developed as a community effort by the MESSy community.

Our EMAC version has been successfully applied to study (I) the dust–air pollution dynamics over the eastern Mediterranean (Abdelkader et al., 2015), and (II) the sensitivity of transatlantic dust transport to chemical aging and related atmospheric processes (Abdelkader et al., 2017) and to (III) evaluate the Metop PMAp2 AOD products (EUMETSAT ITT 15/210839, Final Report, Metzger et al., 2016b). These studies, as well as (IV) our recent long-term evaluation (Metzger et al., 2018) show that our aerosol set-up yields reliable results on various time scales, i.e., short-term, in the order of a satellite overpass (1 hour) and up-to climate time scales (decades).

Our aerosol composition product is characterized by major cations and anions and used to describe various

anthropogenic pollution aerosols, as well as natural aerosols such as sea salt and mineral dust. The cation-anion neutralization products (salt compounds) make up our size-resolved particulate matter (PM), and, together with the associated water uptake of these salt compounds (aerosol water), they determine our aerosol optical depth (AOD), long-term & short-term radiative forcing estimates, air pollution and climate change studies.

Aerosol water is crucial for the aerosol-emission-chemistry-cloud-radiation coupling at saturated and subsaturated atmospheric conditions. Especially the latter, i.e., conditions with fog, haze and optical thin clouds, can, on a global scale, largely control the Earth's radiation budget, while being highly sensitive to man-made influences on climate change through the various direct and indirect aerosol and pollution effects.

The aerosol water uptake of aged (polluted natural) aerosols, e.g., mineral dust coated by hydrochloric acid through the interaction of ship exhaust (e.g., sulphuric acid) with sea salt or mineral dust aerosols, can become important for the forecasting of the Earth’s radiation budget and the locally ever changing weather phenomena.

Noteworthy, the chemical aging of natural aerosols through air pollution largely controls the aerosol water mass, which in turn causes changes in the aerosol wet diameter and hence largely determines the light scattering, adsorption and absorption ability of atmospheric aerosols. This effect can thus have an important impact on the short-term AOD and the radiative forcing signals, due to significant changes in the gas-liquid-solid partitioning, which controls the associated water uptake and the aerosol radius on a time-scales of hours (or less).

To solve the underlying complex multiphase and multicomponent processes, comprehensive thermodynamic schemes are required, which are, however, 1.) computationally too expensive for operational applications, and/or are 2.) numerically not sufficiently stable, mostly due to the iterative nature of the numerical solver that are internally required to solve the complex aerosol thermodynamic systems.

The advantage of our EQSAM concept is twofold:

1) unique computational efficiency 

2) and unique ACD complexity

Air-pollution & climate-change feedback?

Air-pollution & climate-change feedback?

Contrails from aviation

Air-pollution & climate-change feedback?

Air-pollution & climate-change feedback?

Rhine-Main Valley 1 of 3

Air-pollution & climate-change feedback?

Air-pollution & climate-change feedback?

Rhine-Main Valley 2 of 3

Air-pollution & climate-change feedback?

Air-pollution & climate-change feedback?

Rhine-Main Valley 3 of 3

Frequently asked questions

  • Man made climate change - a hoax ?

  • Air pollution & climate change - feedbacks possible ?

  • Aerosol associated water - a modulator for weather & climate? 
  • Aerosol-cloud coupling -  important and which factor is determinant ?

  • Importance of ultra-fine particles for air pollution effects on human health ?
  • Studies that only rely on PM2.5 mass measurements to assess air pollution & health effects ?

  • How important is the particle number distribution to accurately assess pollution-health effects ?

  • Air pollution - nitrogen oxides (NOx) - Diesel internal combustion engines (ICE) the only source ?

  • How dangerous ist the exhaust of gasoline ICE cars - really negligible for NOx limits as assumed? 

  • What are the major side-effects of the gas-to-particle conversion on air pollution & climate ?

  • How to improve solar irradiance forecasts to maximise the renewable energy yield ?

  • How does transatlantic dust transport interact with air pollution (ships & planes) ?

  • Can air pollution impact natural variability - El Niño Southern Oscillation (ENSO) ? 

  • How climate change can impact global stock markets and individual sectors?

Our concepts & models give the answers & show why !

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Mass consistent treatment of water in all its phases. From salt molecules to clouds.



➥ Browse 25 years of disruptive research in a nutshell ...

  • New water modeling concept 

  • New aerosol water uptake concept

  • Analytical solver, free of numerical noise

  • New modeling concept of chemical aging 

  • Thermodynamic gas-liquid-solid partitioning code

  • Cloud cover routine, water mass conserving in all its phases

  • Numerical efficient air-pollution and climate change modelling

  • Improved modeling of mineral dust outbreaks and forecasts

  • Improved modeling of transatlantic dust transport

  • El Niño Southern Oscillation (ENSO) forecasting

RC Application 1

RC Application 1

Improving the development of satellite algorithms that monitor the Earth’s radiative budget and its atmospheric composition such as applied in our PMAp2 Evaluation study (EUMETSAT ITT 15/210839).

RC Application 2

RC Application 2

Improving the development of global climate models and climate change assessments through a more consistent process coupling.

RC Application 3

RC Application 3

Improving air pollution assessments in the Eastern Mediterranean and the Middle East (EMME) through more explicit size-resolved aerosol composition data.

RC Application 4

RC Application 4

Improving regional climate change modelling assessments in the Eastern Mediterranean and the Middle East (EMME) through more explicit hygroscopic growth calculations.

RC Application 5

RC Application 5

Improving solar irradiance forecasts for more reliable predictions of the renewable energy yield through augmented irradiance calculations.

RC Application 6

RC Application 6

Improving modeling of mineral dust outbreaks and forecasts through chemical ageing and water uptake.

RC Application 7

RC Application 7

Improving modeling of transatlantic dust transport through consideration of chemical ageing and water uptake.

RC Application 8

RC Application 8

Improving air-pollution modelling assessments in the U.S. through our stable thermodynamical solver that avoids numerical noise.

RC Application 9

RC Application 9

Improving numerical weather predictions (NWP) through a consistent feedback of air-pollution with weather and climate.

RC Application 10

RC Application 10

Improving El Niño Southern Oscillation (ENSO) forecasting through augmented radiative forcing calculations.

RC Application 11

RC Application 11

Analysing the variability of global stock markets and estimating potential future developments, by using, e.g., the S&P 500 - an American stock market index based on the market capitalizations of 500 large companies having common stock listed on the NYSE, NASDAQ, or the Cboe BZX Exchange.

RC Application 12

RC Application 12

Flow chart of our evaluation toolkit that we have used to validate our model and observational data such as the PMAp2 AOD products of EUMETSAT.

RC Application 13

RC Application 13

Aerosol composition data (ACD): Example, modal aerosol concentrations time series of EMAC at the AERONET station Sede Boker. This type of ACD has been appeared to be most useful for our PMAp2 evaluation study. The aerosol species include the total particulate matter (PM), the particle number concentration (AERNUMB), aerosol water (H2O), bulk sea salt (SS), bulk mineral dust (DU), and the lumped (liquid+solid) aerosol compounds sulphate (SO2--), calcium (Ca2+), bi-sulphate (HSO-), ammonium (NH+), nitrate (NO-), chloride (Cl-), and the aerosol optical depth (AOD), besides the major cations sodium (Na+), potassium (K+), and magnesium (Mg2+), bulk organic (OC) and black carbon (BC), the aerosol precursor gases ammonia (NH3), hydrochloric acid (HCl), nitric acid (HNO3), sulphuric acid (H2SO4) that are shown in our Results section (click the Button below).


Our technology is fundamental and applicable to a wide range of topics.

Some Examples

  • Air-pollution loadings, particularly the hygroscopic growth of natural and anthropogenic aerosols,
    due to the feedback on long-range transport and the interaction with clouds and solar irradiation.

  • Improved numerical weather predictions that consider the feedback of air-pollution and weather.

  • Predictions of weather extremes, dust storms, hurricanes, thunderstorms, flooding, hail and snow.

  • Air-pollution and climate change modelling assessments on both the regional and global scale.

  • Improved solar irradiance forecasts for more reliable predictions of the renewable energy yield.

  • Optimal operation of flow/fuel cells due to a better understanding of degradation processes.

  • Enhanced energy storage, longer life-time and cost saving of redox flow cells / batteries.

  • Optimizing material coating processes with nano-particles, colloid & gel like substance.

  • Degradation of historical buildings and modern houses due to diffusive water transport.

  • Food conservation, pharmaceutical and medical applications (e.g., inhalation sprays).

  • Big data analysis of, e.g., the variability of stock markets, by using, e.g., the S&P 500.



1) Satellite AOD Evaluation 

Short Summary: The European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) has released in January 2016 the Polar Multi-sensor Aerosol product version 2.1 (PMAp2).

The PMAp2 inversion algorithm retrieves the aerosol optical depth (AOD), aerosol type (e.g., volcanic ash, dust) and cloud properties over the ocean and land using a multi-sensor approach. The algorithm uses the Polarization Monitoring Devices (PMD) from the instrument of the Global Ozone Monitoring Experiment-2 (GOME-2) in combination with data from other instruments of the Meteorological Operational (MetOp) satellites, in particular of the Advanced Very High Resolution Radiometer (AVHRR) and of the Infrared Atmospheric Sounding Interferometer (IASI). Compared to the pre-operational PMAp product, PMAp2 provides an extended set of aerosol and cloud properties, which include AOD over land and an improved volcanic ash retrieval combining AVHRR and IASI. PMAp has been first delivered in January 2014 for GOME-2. GOME is an optical spectrometer on the MetOp satellites GOME-2 Newsletter(38).

The MetOp program launched a series of three satellites sequentially over an observational period of 14 years. MetOp-A is Europe's first polar, low Earth orbit (LEO) spacecraft launched on 19 October 2006, while Metop-B was launched on 17 September 2012. Recently, Metop-C was launched on 7 November 2018 in an even lower polar orbit at an altitude of 817 kilometres, to provide more detailed observations of the global atmosphere, oceans and continents. The three satellites will operate in unison for as long as Metop-A's available capacities bring benefits to users. 

With EUMETSAT ITT 15/210839, we have evaluated the Polar Multi-sensor Aerosol product version 2 (PMAp2) of the Meterological Operational Satellites (MetOp) A and B on global scale using MISR-Terra, MODIS-Aqua/Terra, AERONET, CASTNET, EMEP and EMAC data. Our cross-platform analysis comparison based on a 0.5 hour temporal collocation window and a 30~km radius for the spatial collocation relative to AERONET station observations, and a fairly high spatial (0.1° by 0.1°) and high temporal model resolution (hourly output globally), reveals best the differences and similarities between the various AOD products, which are most likely caused by various cloud masking assumptions. For PMAp2.1, AERONET and EMAC, the best agreement is found for the Caribbean, NE America, European and Asian stations, while generally, the PMAp2 AOD time-series are supported by our model result, which are mostly in good agreement with independent AOD (AERONET, MODIS, MISR), and aerosol composition (CASTNET, EMEP) observations.

  • Metzger, S., Abdelkader, M., Klingmueller, K., Steil, B., and Lelieveld, J.: Comparison of Metop PMAp Version 2 AOD Products using Model Data, Final Report EUMETSAT ITT 15/210839, EUMETSAT, Max Planck Institute for Chemistry, Department of Atmospheric Chemistry,, 2016. 

  • Metzger, S., Abdelkader, M., Demetroullas, C., Klingmüller, K., Steil, B., Cacciari, A., Grzegorski, M., Lang, R., Munro, R., Navarro, V.M., Fougnie, B.: Evaluation of the Metop PMAp version 2 AOD products using EMAC model data, AERONET ground station and reference satellite observations (MISR and MODIS-Aqua/Terra), in preparation, 2020.

2) Solar Irradiance Forecasting 

Topic: Day-ahead forecasts of the Direct Normal Irradiance (DNI) and Global Horizontal Irradiance (GHI) for the Concentrated Solar Power (CSP) Plant Facility of the Cyprus Institute, Pentakomo (Cyprus). Our coupled EMAC — WRF-solar results show a considerable sensitivity to the AOD values provided by EMAC, and can help to improve the DNI forecasting for certain conditions, i.e., when aerosol loadings become dominant. 

A contribution to the H2020-EINFRA-2015-1 project “Energy oriented Centre of Excellence (EoCoE)” ⪼ Optimal operation of Concentrated Solar Power under Weather Uncertainty ⪻.

First results have been highlighted in the ECHOES, Vol. 1, Issue 1, 10th February 2017 - The Newsletter of the Energy oriented Centre of Excellence (EoCoE), phase-I project.

The EoCoE Project Deliverable

⪼ Formulation for optimization under uncertainty ⪻
Cumpston, J.; Metzger, S.; Mitsos, A., is available from OpenAire:

3) Air pollution modeling

Short Summary: A computationally efficient thermodynamic equilibrium model, EQSAM (Metzger et al., 1999, 2000, 2002, 2006, 2007, 2012, 2016, 2018) was implemented in CAMx and compared with ISORROPIA. Both models’ results are sufficiently similar that either could reasonably be selected. Advantages of using EQSAM are that it runs faster (in our test, EQSAMclim reduced the overall CAMx runtime by 4% (January) to 7% (July)) relative to the overall CPU usage of CAMx. Noteworthy, EQSAM4clim is free of numerical artifacts.

Koo, B.[1], Metzger, S.[2], Emery, C.[1], Wilson, G.[1], and Yarwood, G.[1]: Comparing the ISORROPIA and EQSAM Aerosol Thermodynamic Options in CAMx - ITM 2018 - 36 TH INTERNATIONAL TECHNICAL MEETING ON AIR POLLUTION MODELLING AND ITS APPLICATION, 14 - 18 MAY 2018, THE LORD ELGIN HOTEL, OTTAWA, CANADA, (IN CONJUNCTION WITH THE ANNUAL WMO-GURME MEETING),, [1] Ramboll, 773 San Marin Dr., Suite 2115, Novato, CA 94945, USA, [2] ResearchConcepts io GmbH, Freiburg im Breisgau, Germany,

Download Presentation: ITM_Presentation, 2018.

To have a quick look at our key modelling results, see: Results.html