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Ozone, UV and Aerosol studies

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You are here: Ozone, UV and Aerosol studies Projects Completed projects

Completed projects

TASTE (Technical Assistance To Envisat validation)

2004-2007

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.

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

2006-2007

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.

References

  • 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.

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

2005-2007

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.

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

2000-2005

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)

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

2000-2004

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.

 
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