Ozone, UV and Aerosol studies

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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

Project website:


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 RMIB

RMIB will contribute to the study of aerosols and their properties at Uccle. More specifically, we are 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 is 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 will be 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 will also try to model them. To achieve this a chemical transport model (CHIMERE) will be combined with the OPAC software package in order to generate the expected AOD and SSA in the UVB. Both parameters can be 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 will also be 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 will examine whether the UV index forecast could be improved using modeled AOD and SSA values.