Ozone, UV and Aerosol studies

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Completed projects

BELATMOS - Monitoring atmospheric composition at the Belgian Antarctic station Princess Elisabeth

BELATMOS has been coordinated by the Royal Meteorological Institute of Belgium, in collaboration with partners BIRA - Belgian Space Aeronomy Institute (Christian Hermans, Michel Van Roozendael) and Ghent University (Willy Maenhaut). BELATMOS has been financed by the Belgian Science Policy Office (Belspo). It started in 2008 and came officially to an end in 2014. Within the AEROCLOUD project, the data of the installed instrumentation will be valorised.

Project PI: Hugo De Backer

Project principal scientist: Alexander Mangold

Royal Meteorological Institute of Belgium
Ringlaan 3, Avenue Circulaire
BE-1180 Brussels, Belgium

Tel: 0032-23730593; email: alexander.mangold at

The scientific activities are continued within the AEROCLOUD project. 

The activities within the BELATMOS project have been described in a blog.

A description of the installed instruments can be found either under Instruments or within the AEROCLOUD project description.


Belgium has a long history of Antarctic exploration and scientific activities, dating back to 1897 and the first expeditions to Antarctica under the lead of Adrien de Gerlache. At the occasion of the 1958 International Geophysical Year, Belgium organised a new expedition to Antarctica and set up the Roi Baudouin base at Princess Ragnhild Kyst. This base remained in activity for more than 10 years and allowed scientists to carry out essential research and observations in climate and geophysical sciences. At the occasion of the International Polar Year 2007, the Belgian government decided to build a new scientific summer station in Antarctica and assigned the International Polar Foundation to design and build this new base. The new Antarctic base was built during the Antarctic summers 2007/2008 and 2008/2009 and the first scientific activities started in January 2009. In the summer season 2009/2010 the station received the finishing works and a powerful satellite dish. The Princess Elisabeth station is situated north of the Sor Rondane Mountains in Dronning Maud Land, East Antarctica, on the small, granite Utsteinen ridge (71º57’S, 23º20’E, 1390 m asl).

Via the Belgian Science Policy (BELSPO), the Belgian federal government has been financing several research programmes at Princess Elisabeth station in Antarctica. The Royal Meteorological Institute, in collaboration with BISA and Ghent University, has proposed to carry out observations on the composition of the atmosphere at the Antarctic base. The project has been formally approved by the Belgian science policy authorities in summer 2008. The BELATMOS partners have been closely collaborating with the HYDRANT project of KU Leuven, which investigated the atmospheric hydrological branch (meteorology, clouds, precipitation) in Antarctica.



The objective of the BELATMOS project planned by RMI, BIRA and Ghent University was, to contribute to the long-term monitoring of the chemical and particle composition of the Antarctic atmosphere and to the quantification of the UV radiation reaching the surface, using a suite of complementary ground-based instruments.

Aerosols play an important role in atmospheric physics and chemistry. They provide surfaces for photochemical reactions and they attenuate, scatter and absorb solar radiation and re-distribute in this way the energy coming from the sun, influencing photochemical reactions, the temperature at the surface and within the atmosphere and exerting a positive or negative radiative forcing. In addition, aerosols influence the formation, the properties and the lifetime of clouds. The Belatmos measurements were important to investigate aerosol-cloud interactions and the aerosol radiative impact in this sensitive region. They delivered important parameters for radiative transfer schemes in global circulation or climate models or satellite retrieval algorithms.

Atmospheric composition measurements at a remote place like Antarctica are important to evaluate changes in background concentrations and to improve our understanding of long-range transport of aerosols. Although being a remote region, Antarctica is influenced by pollution and natural aerosol from lower latitudes or by the research stations themselves. The Antarctic (also as the Arctic) is a very sensitive region for the world’s climate. Atmospheric aerosol particles, ozone and other trace gases are linked to climate change through various complex feedback mechanisms. Analysing and understanding these inter-relations form the basis for decisions to be made with respect to environmental policies.

Ozone is a key atmospheric gas and has a large impact, amplified or compensated by the presence of aerosol particles, on the UV radiation received at the ground. The amount of biological damage to sensitive Antarctic marine organisms, other ecosystems and human health due to increasing UV radiation is therefore directly related to the level of ozone depletion and atmospheric aerosol content. In addition, more and accurate measurements of the ozone column over the Antarctic continent are important to monitor the expected recovery of the ozone layer. The so-called ozone-hole occurs since over 30 years each year over Antarctica during springtime.

The deployed aerosol instruments included an aethalometer, a CIMEL sunphotometer, a Tapered Element Oscillating Microbalance with Filter Dynamic Measurement System (TEOM-FDMS), a nephelometer, a condensation particle counter and a laser aerosol spectrometer. In addition, a Brewer spectrophotometer, and a pyranometer (total solar irradiation) and sensors for UV-A and UV-B irradiation completed the instrument set-up. Most of the instruments have been designed for unattended operation in remote places and measured throughout the year, including the period when there was nobody at Princess Elisabeth station. The sunphotometer and the Brewer spectrophotometer were dismounted at the end of summer season and re-installed with beginning of the next summer season.

The Belatmos project aimed to characterise comprehensively the physical and optical properties of the ambient aerosol at Utsteinen. From the combined measurements, also information on the aerosol type could be derived. Aerosol properties like mean size, number size distribution, presence of particle formation events, spectral dependencies of scattering, absorption and single scattering albedo enabled to classify the aerosol as fresh, locally formed, or aged, longe-range transported aerosol and to determine the presence and importance of dust, sea-salt, light-absorbing aerosols like soot, and rather scattering submicron particles (of which a large part is likely sulphate). With the build-up of long time series, it can be evaluated if there are trends concerning the Antarctic aerosol. Furthermore, the evolution of the total ozone column has been monitored. The data has been made available to the scientific community via international databases. The Cimel sunphotometer is part of the international AErosol RObotic NETwork (AERONET) and the data can be found with the station name 'Utsteinen'. The ozone and UV data of the Brewer spectrophotometer are stored in the international database of the World Ozone and UV Data Centre (WOUDC) under station name 'Princess Elisabeth'.

In autumn 2013, the Royal Meteorological Institute of Belgium (RMI), the Swiss federal research institute for 'Forest, Snow and Landscape' (WSL) and the International Polar Foundation (IPF) started a collaboration in order to launch weather balloons for radio soundings at the Princess Elisabeth station. The first launch of a balloon with a radiosonde took place on 25 January 2014, and daily launches have been made until 20 February 2014. With the radio soundings, vertical profiles up to 20 to 30 km height of temperature, humidity, pressure, wind speed and wind direction are measured. These data are important for interpretation of the larger scale meteorological and atmospheric dynamic conditions. They are also needed to locate temperature inversions and heights of low and high wind speed (low level jets, jet stream,...), and to characterise the conditions around cloud levels. Measurements have been restarted during austral summer 2014-15, and almost daily launches have been done between end of November 2014 to end of February 2015. For the radio soundings, a GRAW GS-E ground station and DFM-09 radiosondes have been used in that period.



The image below shows the vertical profile of the data from a balloon launch on 4 February 2014. The air temperature is the red line, given in Kelvin (273.15 K = 0 deg Celsius); the black line is the wind speed; the blue line gives the dew point temperature, i.e. the temperature when water saturation is reached with respect to liquid water and droplets should form; and the green line gives the frost point temperature, i.e. the temperature when water saturation with respect to ice is reached and ice crystals should form. To be seen is a first strong temperature inversion at around 3500 m altitude and the temperature inversion at the tropopause at around 9500 m. Also, there is a strong wind current between 2500 and 4000 m and another one between 8000 and 10.000 m. In addition, between 3000 and 4000 m, the humidity is around ice saturation, indicating a higher probability of ice formation.

For further results, please refer to the Result-pages within the description of the AEROCLOUD project.


Data of the radio sonde on 4 February 2014


AGACC (Advanced exploitation of Ground-based measurements for Atmospheric Chemistry and Climate applications)

Veerle De Bock, Roeland Van Malderen, Hugo De Backer
Royal Meteorological Institute of Belgium
Ringlaan 3, B-1180 Brussels, Belgium

Contact: Veerle De Bock, Roeland Van Malderen


AGACC - Subject and Objectives

In brief, the subject of the project is an advanced exploitation of existing and current ground-based remote-sensing measurements for the study of a selection of atmospheric species that are related to climate and atmospheric chemistry.

The general scientific objectives of the proposal are to derive new and improved datasets for the target geophysical parameters and to carefully characterize the data products, thereby exploiting possible synergies and complementarities between different instruments operated at the same site. The target parameters are:

  • lower tropospheric aerosols, water vapor (H2O) and its HDO isotopologue in the troposphere and lower stratosphere,
  • methane (CH4) and HCFCs that have a direct impact on climate,
  • carbon monoxide (CO), non-methane hydrocarbons, hydrogen cyanide (HCN), formaldehyde (H2CO), which are source gases that influence the oxidizing capacity of the atmosphere, and therefore indirectly also the climate.

A more detailed description of the project is available on the AGACC-website.
The project is funded by the Belgian Federal Public Planning Service for Science Policy under the theme "Climate and Atmosphere" of the "Science for a Sustainable Development (SSD)" Research Program. AGACC is a collaboration between the Belgian Institute for Space Aeronomy (BIRA-IASB), the RMIB, the Université Libre de Bruxelles (ULB) - Service de Chimie Quantique et Photophysique, and the Institute of Astrophysics and Geophysics of the University of Liège (ULg) - Groupe Infra-Rouge de Physique Atmosphérique et Solaire (GIRPAS).

AGACC - Water Vapor

The abundance and vertical distribution of water vapor in the atmosphere influences very strongly convection and cloudiness, therefore the albedo of the planet as well as the infrared opacity of the atmosphere.

Of particular interest is the upper troposphere - lower stratosphere (UTLS) layer, because of the dynamical coupling existing between these two regions of the atmosphere. The humidity field in the UTLS is of fundamental importance for all aspects of the chemistry and physics, in particular with respect to radiation, cloud dynamics, energy transport or aerosol processing. Thus, it is directly linked to a sound assessment of the future climate. A recent increase in stratospheric water abundance has been demonstrated, and possible effects on ozone and climate have been emphasized. The exact cause of this trend is still poorly understood.

AGACC - Aerosols

Much of the current research in the field of atmospheric aerosols arises because of the interrelations between aerosols, clouds, radiation, and climate. The influence of aerosols on atmospheric chemistry and physics, and in particular on the Earth's radiation budget, is complex as it depends on the composition, number and size distribution, and shape of the aerosol particles. Aerosols influence the Earth's radiation budget via the so-called direct effect (scattering, absorbance, and emittance of solar and thermal radiation). Additionally, aerosols have also an indirect impact on the Earth's radiation budget. As they act as cloud condensation nuclei, an increased levels of aerosols can enlarge the amount and reduce the size of water cloud droplets, increase the reflectance for solar radiation, increase the absorption of UV-B radiation, reduce precipitation, and change the cloud's lifetime. Clouds in turn are an important regulator of the Earth's radiation budget.

Overall there exists a great lack of detailed and comprehensive knowledge on the optical properties of aerosols and the respective feedback mechanisms on clouds and the radiative budget. This causes one of the largest uncertainties in radiative forcing and climate change assessments.

AGACC - RMIB contribution

  • Water Vapor: At Ukkel, the RMIB has measured Vaisala radiosonde profiles of atmospheric relative humidity since January 1990. These humidity profiles have not been exploited up to now, because radiosondes are known to yield no reliable results at low temperatures and low absolute humidity. Recently, two groups have independently developed correction methods to retrieve unbiased and improved relative humidity data from the soundings. These correction algorithms will be applied to both new and old radiosonde data. Nevertheless, also a careful assessment of the used Vaisala radiosondes (RS80-A, RS90-H, and RS92-H) is required, as the types changed over the years and the corrections have to be adapted accordingly. An intercomparison of radiosondes and Fourier Transform Infrared (FTIR) spectrometer measurements of water vapor is also planned for validation purposes and improvement of the data products during simultaneous measurements at the Ukkel Plateau. As water vapor is highly variable in the upper troposphere and tropopause region, the high temporal and vertical resolution of the radiosondes (one measurement every 10 seconds, i.e. ~100 m resolution) up to altitudes of 30-35 km, will be ideal for assessing the UTLS relative humidity field. The long duration of over 15 years of radiosonde data at Ukkel constitutes a unique data set, which will also allow for trend and climatological analyses.
  • Aerosols and UV: During the project, an intercomparison campaign is set up at Ukkel between three instruments:
    • an UV/visible spectrometer using the Multi-Axis Differential Optical Absorption Spectroscopy method (MAXDOAS), which will be used to infer vertically resolved information on aerosol properties in the 0-3 km altitude range,
    • the Brewer ozone spectrophotometer of the RMIB, which measures the total Aerosol Optical Depth (AOD) in the UV-B range,
    • a CIMEL sun photometer, which yields very precise (1%) values for AOD, and information on the scattering phase function.

    This unique combination of instruments will provide an unprecedented data set for a more comprehensive characterization of the tropospheric aerosol optical properties (AOD, single scattering albedo, aerosol type, size, refractive index). Additionally, this intercomparison provides a unique opportunity to assess the performance of the individual instruments, and in particular of the Brewer AOD retrieval. Using the AOD and aerosol type information determined during the project, it will be possible to investigate the impact of aerosols on the UV index and to improve the operational UV index prediction at the RMIB. This will in turn provide better information to the general public on the risk of being exposed to solar UV-B radiation (e.g. development of skin cancer).


AGACC-II (Advanced exploitation of Ground-based measurements for Atmospheric Chemistry and Climate applications)

Veerle De Bock, Hugo De Backer
Royal Meteorological Institute of Belgium
Ringlaan 3, B-1180 Brussels, Belgium
For more information, please contact: Veerle De Bock


AGACC-II: Subject and objectives

This project (funded by the Belgian Federal Public Planning Service for Science Policy under the “Science for Sustainable Development (SSD)” Research Program) is the successor of a previous project (AGACC – see completed projects) in which RMIB was also involved. The complementary expertise and instrumentation of four partners (BISA, RMIB,ULB, ULg) are brought together within the project to further advance ground-based atmospheric remote sensing techniques.

The subject of AGACC-II is the development of advanced data products from ground-based remote sensing techniques, for supporting chemistry-climate applications. The project focusses on 4 observatories:

  • Uccle (50.5°N, 4°E)
  • Jungfraujoch (46.5°N, 8°E)
  • Ile de la Réunion (21°S, 55°E)
  • Bujumbura (3°S, 29°E).

It involves various remote sensing instruments with which the partners have already acquired a long-lasting expertise: Brewer spectrometers, CIMEL sunphotometers, Fourier-transform infrared spectrometers and MAXDOAS spectrometers. New in the project is the addition of a lidar ceilometer for measuring aerosol backscatter vertical profiles and an aethalometer and nephelometer for the in-situ characterisation of aerosol optical properties.

The major objectives of the project are the following:

  1. Derive new information about important greenhouse gases
  2. Enlarge the range of atmospheric trace gases that can be detected from the ground
  3. Advance our expertise in the field of aerosol remote sensing above Uccle
  4. Study African emissions
  5. Interact with satellite, modelling communities and spectroscopists
  6. Integrate our data in regional and global assessment reports

AGACC-II: Contribution of RMI

RMIB contributed to the study of aerosols and their properties at Uccle. More specifically, we were responsible for the following tasks:

  • Developing and/or improving algorithms for the retrieval or modelling of aerosol properties (such as the Aerosol Optical Depth or Single Scattering Albedo) from ground-based spectral measurements (of our Brewer spectrophotometers). For example, a better cloud screening method was developed for deriving Aerosol Optical Depth from the Brewer measurements.
  • Continuous operation of ground-based remote sensing instruments (such as the Brewer spectrophotometers) for aerosol characterisation at Uccle. A new instrument within AGACC-II is the lidar (ceilometer), which can be used to derive the aerosol backscatter ratio profiles and additional parameters (mixing layer height, cloud information). It allows the monitoring of the boundary layer height and the detection of denser particle plumes in the free troposphere like volcanic ash, Saharan dust or fire smoke. The instrument has an operating range of up to 15 kilometers.
  • Interpretation of aerosol data at Uccle. To this end observations from several ground-based remote sensing instruments operated by BISA and RMIB at Uccle were combined to get a more comprehensive data set of aerosol properties. The RMIB instruments involved are two Brewer spectrophotometers, a lidar ceilometer, an aethalometer and a nephelometer. The nephelometer is designed to measure the scattering and backscattering coefficients of particles, which are important in all assessments of the direct radiative aerosol forcing. The aethalometer measures the aerosol absorption coefficients at 7 wavelengths (370, 450, 570, 615, 880 and 950nm) and the mass concentration of black carbon particles (also indicative of pollution). Next to measuring different aerosol properties, we also tried to model them. To achieve this a chemical transport model (CHIMERE) was combined with the OPAC software package in order to generate the expected AOD and SSA in the UVB. Both parameters were validated by comparing them to the AOD time series from the Brewer instrument and the SSA values from AERONET sunphotometer measurements.
    The correlation between observed optical properties, source regions (determined with backtrajectory analysis) and meteorological parameters was also investigated.
    Finally, we are constantly looking for ways to improve the UV index forecast. Currently, the UV index forecast model uses a constant SSA value and climatological monthly means for the AOD. We examined whether the UV index forecast could be improved using modeled AOD and SSA values.

GEMS (Global Earth-system Monitoring using Satellite and in-situ data)

Alexander Mangold, Bart De Paepe, Hugo De Backer, Steven Dewitte
Royal Meteorological Institute of Belgium
3, Avenue Circulaire
1180 Uccle

Contact: Alexander Mangold


GEMS - Objectives

The GEMS project has been started in May 2005, was funded by the European Commission within FP 6 and has come to a successful end in May 2009. GEMS is led by the European Centre for Medium-Range Weather Forecast (ECMWF), comprises 17 European research institutes, 10 regional modelling centres, 2 environmental protection agencies, and has been established to develop a real-time operational assimilation and forecast capability of aerosols, greenhouse gases and reactive gases. This new European operational system will be an extension of current data assimilation and forecast capabilities for Numerical Weather Prediction. It will also provide the initial and boundary conditions for operational regional air-quality and ‘chemical weather’ forecast systems across Europe. Satellite data will be a major source of information for assimilation. Ground-based observations and other satellite data will be used for validation and evaluation. As such, GEMS will be a major contribution to the GMES initiative (Global Monitoring for Environment and Security) launched a few years ago by the European Union and the European Space Agency.

GEMS-AER - Aerosol Sub-Project

RMIB contributes within GEMS to the Aerosol Sub-Project. The figure above illustrates schematically the links and the flow of data and information between the main elements of the GEMS system: Global Reactive Gases (GRG), Greenhouse Gases (GHG), Global Aerosol (AER), Regional Air Quality (RAQ), and the global atmospheric assimilation system at ECMWF.

GEMS-AER will provide operational aerosol products for a variety of end-users (e.g. modeling radiative transfer, air-quality). An improved and explicit representation of aerosols in forecasting models will have several positive impacts. The reduction of the uncertainty of the direct and indirect aerosol radiative effects is considered as a priority in climate change assessments. It will also provide key informations relevant to the UN Convention on Long-Range Trans-boundary Air Pollution.

RMIB Contribution

The ground observations group of RMIB will contribute with the determination of the total aerosol optical depth (AOD) in the UV-B (320 nm) from direct sun observations with Brewer spectrophotometers, two of them located at RMIB, Uccle. An algorithm to retrieve AOD from Brewer instruments has recently been developed at RMIB (Cheymol & De Backer, 2003). It is the aim to collect data from as many stations as possible from the global network of Brewer instruments. The above-mentioned algorithm can then be applied to create AOD time series at the specific wavelengths in the UV. These aerosol data will be exploited for the validation of aerosol optical depth products from the assimilation runs of the ECMWF Numerical Weather Prediction model.

The satellite group of RMIB will contribute with the detection of aerosols from SEVIRI (Spinning Enhanced Visible and InfraRed Imager) images. Due to the combination of its different spectral channels, the SEVIRI instrument on board the MSG-1 (Meteosat Second Generation) satellite allows for the distinction between clouds and aerosols. The RMIB-SEVIRI aerosol product includes AOD at 630, 830, and 1610 nm, with a spatial resolution of 9 x 9 km and a time resolution of 15 min. The SEVIRI aerosol product is available over ocean only, for the SEVIRI disk and from February 2004 onwards.


GEMS came to a successful end in May 2009 and is succeeded by the MACC project. Within GEMS, multi-year re-analyses for the individual GHG-, GRG-, AER-models were achieved, there is a common integrated re-analysis for the period 2003-2007, and a near real-time integrated analysis and forecast model for GHG, GRG and AER. In addition, the analysis is used as boundary condition for 10 European regional air quality models, which in return produce ensemble and individual predictions of air quality indicators. All these data and maps are online available via the GEMS web page. The model results were comprehensively evaluated, validated and compared to observations.


TASTE (Technical Assistance To Envisat validation)


Hugo De Backer, Rene Lemoine
Royal Meteorological Institute of Belgium
Av. Circulaire 3,
1180 Uccle


The TASTE project was introduced in response to an ESA invitation to tender RFQ/3-10885/03/NL/MM and proposes a long-term validation for the ENVISAT satellite.

The goal of the project is to ensure the availability of correlative data records for long-term validation of the three atmospheric science instruments with regard to the measurement of the vertical profiles of ozone, temperature and water vapour and to the measurement of the total ozone column.

The Royal Meteorological Insitute of Belgium (RMI) will deliver observations on the total ozone column and ozone profile measurements. These data will be used for the validation of ozone measurements performed by ENVISAT.
For this validation study, two types of ground-based measurements will be used :

  • ozone soundings launched at Uccle. These will allow for the validation of the vertical profiles of ozone. They are always combined with a radio sounding.
  • Brewer and Dobson spectrophotometers located at Uccle. These will allow for the validation of the total column of atmospheric ozone above Uccle.

At the present time, the routine soundings amount to and 3/week (at noon) for the ozone soundings. Brewer and Dobson measurements are performed throughout the day but are subject to the meteorological conditions. It should also be noted that the data available at the Meteorological Institute date back to 1969 and are subject to a continuous quality control which showed its usefulness in various validation studies like e.g. validation of GOME and SAGE II data.

The satellite ENVISAT has been succesfully launched on the first of march 2002. More information about the ENVISAT satellite and its playload can be found on the ENVISAT website.


CHIMERE (Assimilation of vertical ozone profile data in the chemical transport model Chimere coupled to weather prediction models at RMI)


ir. Andy Delcloo, Dr. Hugo De Backer
Royal Meteorological Institute of Belgium
Ringlaan 3
1180 Uccle


The combination of the presence of air pollutants and specific meteorological conditions during summer sometimes causes high ozone concentrations in the troposphere. These high concentrations can be detrimental to different forms of life on Earth. For the protection of human health, a warning threshold of 180 g/m3 has been defined. At the European level, long-term objectives for the reduction of ozone concentrations have been defined in the Directive 96/62/EC. In 2002, a new Directive 2002/3/EC relating to ozone in ambient air strengthened the EU's policy. This Directive sets long-term objectives, target values, an alert threshold and an information threshold for ozone. The current Directive 92/72/EEC states that Member States have to comply with Directive 2002/3/EC, from 9 September 2003. The Directive foresees that governments prepare action plans when the alert level of 240 µg/m3 is exceeded. When ozone concentrations are expected to exceed these levels warning messages are issued to help people to limit the health risks. Since meteorology plays a crucial role for the formation of tropospheric ozone, at least part of this task fits naturally in the mission of the RMI.

Different models to predict ozone concentrations in the troposphere have been developed during last years. These ranges from statistical regression models over neural networks to Chemistry Transport Models (CTM) in different dimensions, fed by meteorological input from General Circulation Models (GCM) or numerical weather prediction models (NWP). However, it seems that, especially during high ozone events (e.g. summer of 2003), the forecasting models tend to underestimate the real ozone concentrations in Belgium (Brasseur, 2004). It is well known that high ozone concentrations may be transported over long ranges (e.g. Stohl et al., 2003). At the same time Chemistry Transport Models (CTMs) suffer from the limited knowledge of emissions, and from incomplete description of the chemistry and the dynamics (McHenry et al., 2004).

For this project we will make use of the Chemical Transport Model (CTM) Chimere, developed by the Institut Pierre-Simon Laplace (IPSL-Paris). An example of an output with the Chimere-model for the heatwave of July 2006 is presented here:

10 days simulation of maximum ozone concentrations with CHIMERE


10 days simulation of maximum ozone concentrations with CHIMERE

An attempt to improve the performance of such models is proposed in the current project by the combined use of information from a model and observational data. To achieve this goal data-assimilation techniques will be used. Not only ground observations of ozone will be assimilated, but also special attention will be drawn to vertical ozone profiles measured at Uccle. A long-term database of ozone profiles from balloon soundings since 1969 exist at Uccle. This time series has been homogenised and the quality has been checked by comparisons (Lemoine and De Backer, 2001). Normally the time series consists of three soundings per week. During June, July and August 1997 there has been and intensive measurement campaign, with daily ozone soundings during these three months. This unique set of data will be exploited to investigate the influence of the assimilation of vertical profile ozone data on the ozone levels at the ground in the analysed fields. It has to be stressed that the measurements for certain ground stations of ozone are only representative for a very local area, and not for a large region. Therefore, it is important to address the region of the representativity of the ground stations (Blond et al, 2004). Delcloo and De Backer (2005) have illustrated that from ozone profiles data can be extracted that are representative for a larger region. An objective method has been applied to extract planetary boundary layer ozone (PBL ozone) out of the ozone profile data. By using these high-resolution vertical ozone profiles we can also extend our knowledge about the influence of the free tropospheric ozone on ozone concentrations at the ground. Finally, this assimilation of ozone soundings will be implemented in an operational context in order to improve the forecast.


  • Blond, N., L. Bel, and R. Vautard, Three-dimensional ozone data analysis with an air quality model over the Paris area, J. Geophys. Res., bf 108, 4744, doi:10.1029/2003JD003679, 2003.
  • Brasseur, O., Etude descriptive du modèle de chimie atmosphérique "Chimère", rapport final de la convention IRM - Région wallonne intitulée " Traitement et modélisation des données en matière de pollution atmosphérique. Seconde phase ", 2004.
  • Delcloo, Andy and H. De Backer, Modelling planetary boundary layer ozone, using meteorological parameters at Uccle and Payerne, Atmospheric environment, submitted, 2005.
  • Lemoine, René and H. De Backer, Assessment of the Uccle ozone sounding time series quality using SAGE II data, J. Geophys. Res., 106, 14515-14523, 2001.
  • McHenry, J.N, W.F. Ryan, N.L. Seaman, C.J. Coats, J. Pudykiiewicz, S. Arunachalam, J.M. Vukovich, A real-time Eulerian Photochemical model forecast system, Bulletin of the American Meteorological Society, vol 85, nr 4, pp 525-548, april 2004.
  • Stohl A., C. Forster, S. Eckhardt, N. Spichtinger, H. Huntrieser, J. Heland, H. Schlager, S. Wilhelm, F. Arnold, O. Cooper, A backward modeling study of intercontinental pollution transport using aircraft measurements, J. Geophys. Res., 108 (D12), 4370, doi:10.1029/2002JD002862, 2003.

This project is funded by the Federal Office for Scientific, Technical and Cultural Affairs.


AERO (Aerosol optical depth derived from ground based spectral observations of solar radiation)


Anne Cheymol, Hugo De Backer
Royal Meteorological Institute of Belgium (RMIB)
Av. Circulaire 3,
B-1180 Bruxelles, Belgium


At Uccle, the Brewer spectrophotometer measures the solar radiation in th UV-B. Within the last project (ESAC II), a method was developed to retrieve Aerosol Optical Depth (AOD). For more details, see Cheymol and De Backer 2003. The aims of this new project financed by the Belgian Federal Public Services for Science Policy are:

  • Comparison of the AOD from the 2 Brewer spectrophotometers at Uccle in order to have an idea of the accuracy of AOD values
  • Determination of the AOD's origin with a back trajectory model already used at the RMIB
  • Determination of the AOD from 300nm to 1000 nm in order to improve the characterization of the AOD

If you have any questions on aerosol, article..., please contact me to my e-mail address.


ESAC-II (Experimental Studies of Atmospheric Composition, phase II)


Anne Cheymol, Hugo De Backer
Royal Meteorological Institute
Av. Circulaire 3,
B-1180 Bruxelles, Belgium


The aim of the ESAC II (Experimental Studies of Atmospheric Changes) project  is based on three topics:

  • Extend the belgian contribution in the atmospheric research.
  • Investigate the evolution of the chemical processes in the atmosphere mainly with experimental means.
  • Help the politicians to take decisions about the environment.

At Uccle, the ozone column and the UV radiation from the sun is measured every day with a BREWER spectrophotometer. In recent years, the solar radiation scattering and infrared radiation absorption by the aerosols is recognized to be an important parameter affecting the climate system and to have some impact on Humans and on the biosphere. The 2 photos from Camnet web site below shows the impact of the aerosols due to pollution, humidity on the visibility of the air.


Clear day at Boston.

Hazy day at Boston

Now the quantity of aerosol can be inferred from the Brewer ozone measurements. More precisely, the Aerosol Optical Depth (AOD) which is directly linked to the quantity of aerosol in the atmosphere is calculated. AOD represents the extinction of solar radiation along the path through the whole atmosphere. Thus, more aerosol there is, more absorbed is the solar light. As the Brewer spectrophotometer measures every 30 minutes, the AOD can be calculated at Uccle several time per day. Thus, it is possible to see the diurnal variation of the quantity of aerosol in the air. Details of the method are explained in in a paper by Cheymol and De Backer (2003). A second way to our work is to determine the impact of AOD on the quantity of UV-B received at the ground (see pdf: 344 kb) within the COST726.
If you have any questions on aerosol, article..., please contact me to my e-mail address.

The Meteorological Institute participates in ESAC II which is sponsored by the Federal Office for Scientific, Technical and Cultural Affairs (OSTC)


TROPO (Study of free tropospheric ozone at Uccle, in relation with meteorological parameters)


Andy Delcloo, Hugo De Backer
Royal Meteorological Institute of Belgium
Ringlaan 3
1180 Uccle


The goal of this project is to explore the balloon sounding database at Uccle, particularly for the troposphere. During this project we want to do research on the following topics:

  • The quantification of the ozone exchange between the planetary boundary layer (PBL) and the free troposphere and the study of the stratosphere-troposphere exchange
  • The determination of tropospheric ozone trends as a function of different meteorological parameters
  • The quantification of the causes for the seasonal variations in the tropospheric ozone concentration, with special attention for the spring ozone maximum

Atmospheric ozone has different effects, depending on the altitude the ozone is situated. In the stratosphere (between 10 and 40 km), ozone absorbs the UV-C- and partly the UV-B radiation, which otherwise could reach the earth's surface. Such ultraviolet radiation is destructive for genetic cellular material in plants and animals, as well as human beings. In the free troposphere (between 2 and 10 km) it is an important oxidising element in the removal of atmospheric pollutants. On the other hand, in the boundary layer, high concentrations of ozone are harmful for human health, crop production and are able to damage several materials.

Photochemical processes in the boundary layer and the free troposphere play a key role in the formation of ozone out of pollutants like nitrogenoxides and volatile organic compounds (VOC's). The equilibrium between this ozone production and ozone destruction at the surface determines the ozone concentrations in the boundary layer. To make the correct decisions in policy to prevent episodes of high ozone concentrations near the surface, it is necessary to understand all the mechanisms which lead to such high ozone events.

A poster (pdf: 113 kb) has been presented at the Eurotrac-2 Symposium, which took place at Garmisch-Partenkirchen, Germany, 11-15 March, 2002 in the framework of the subproject TOR-2 (Tropospheric Ozone Research). It contains results about tropospheric ozone trends since 1988 and seasonal cycles at Uccle.
At EGS XXVII General Assembly, France, Nice, 21-26 April, 2002, also a poster has been presented with the following title: "Seasonal ozone trends at Uccle in the upper troposphere and lower stratosphere" (pdf: 89 kb).

This project is funded by the Federal Office for Scientific, Technical and Cultural Affairs.


PARHEALTH (Health effects of particulate matter in relation to physical-chemical characteristics and meteorology)

Andy Delcloo, Hugo De Backer
Royal Meteorological Institute of Belgium
3, Avenue Circulaire
1180 Uccle

Contact: Andy Delcloo


Numerous studies have shown a strong association between daily mortality and fine particulate air pollution. However, component-specific toxicity has not been characterized well. In this regard the research unit of lung toxicology (KULeuven) collected unique data for Belgium on the association between fine particulate air pollution and mortality (total, cardiovascular and respiratory mortality) showing that the effects of air pollution are much stronger in summer than in winter, even in our temperate climate. Until now, we can only speculate about the mechanisms underlying the much stronger association between mortality and particulates during warmer periods, even though particulate levels reach higher values in the winter.

This project aims at reducing the health risks and health costs attributable to particulate pollution, through the identification of components that are responsible for the adverse health effects. In a cohort of children and a cohort of elderly, we will measure cardiovascular and respiratory parameters in the same person within the day and across seasons and evaluate their relationship with both physical properties and specific inorganic and organic components associated with particulates. This specific experimental design will allow us to study the particulate induced effects, in association with ozone peaks, independently of the direct meteorological effects.

Elucidating the component specific toxicity and the pathophysiology of the association between cardiopulmonary effects of particulate exposure may open an important new avenue for the prevention of cardiopulmonary complications and the environmental regulations of particulate air pollution. An improved knowledge on which chemical compounds are associated with the adverse health effects will achieve cost-effective reductions in health risks to populations. In view of the high prevalence of cardiopulmonary illness, even a small benefit in terms of preventable cases, will lead to an appreciable decrease in morbidity, an increase in longevity, and in turn, to a decrease in health care costs. This project will also advise the National and Regional Governments on environmental regulations, permissible levels of particulate exposure with characterisation of specific compounds, and strategies to identify at an early stage subjects at an increased cardiopulmonary risk.

This project is funded by the Belgian Federal Public Planning Service for Science Policy under the theme "health and environment" of the "Science for a Sustainable Development (SSD)" Research Program [].
PARHEALTH is a collaboration between the Katholieke Universiteit Leuven (KULeuven) - Eenheid voor Longtoxicologie, the Université Catholique de Louvain (UCL) - Unité de toxicologie industrielle et de
médecine du travail, the Universiteit Gent (UGent) - EnVOC, the Universteit Antwerpen (UA) - Milieuchemie and the Institut Royal Météorologique de Belgique (IRM)


PAMIR (A Portal to Atmospheric and Marine Information Resources)

Roeland Van Malderen
Royal Meteorological Institute
Ringlaan 3,
B-1180 Brussels, Belgium



PAMIR is is a BRAIN-be (Belgian Research Action through Interdisciplinary Networks) 2-year project (2014-2015), funded by the Belgian Science Policy Office (BELSPO). The project is coordinated by the Belgian Institute for Space Aeronomy (BISA, Anne De Rudder, Jean-Christopher Lambert). The other partners are the Royal Belgian Institute of Natural Sciences (RBINS, Serge Scory) and the Royal Meteorological Institute of Belgium (Roeland Van Malderen, Laurent Delobbe, Christian Tricot). The homepage of the project can be found here.


The objective of the project is to explore and develop generic concepts related to the description, documentation, classification and quality assurance of atmospheric and oceanographic data of the federal portfolio, in compliance with international standards and practice, including the INSPIRE Directive (Infrastructure for Spatial Information in the European Community). Or, in other words: with ocean and atmosphere, let INSPIRE gain depth and altitude!


  • Design of a generic validation, evaluation and quality control protocol, virtually applicable to any data of the federal portfolio of atmospheric and oceanographic information, and including aspects specific to each scientific domain.
  • Design of a generic validation report template to support data validation reporting.
  • Design of a common metadata model suited to the documented scientific datasets and compatible with the latest INSPIRE Metadata and Interoperability Regulations.
  • Design and development of a metadata editor based on the previous.
  • Set up of a centralized portal prototype offering a dataset catalogue (underpinned by the above metadata model) as well as online information on data validation and model evaluation.