GAWPFR WMO reference

New AOD tracking technique by ESA with AERONET and the GAWPFR WMO reference

Keywords : Aerosols, Atmosphere, Sun/Sky/Lunar photometer, Meteorology

The World Meteorological Organization (WMO) has recognised the Word Optical Depth Research and Calibration Center (WORCC) as the primary reference center for Aerosol Optical Depth measurements. The WORCC is a section within the World Radiation Center at the Physikalisch-Meteorologisches Observatorium Davos (PMOD/WRC), located in Davos, Switzerland.

With its new QA4EO project, European Space Agency (ESA) wishes to obtain homogeneous results between the various passive monitoring networks of passive remote sensing of aerosol optical properties, presents in Davos and in France at the Observatoire de Haute Provence (OHP).

Consequently, a precision filter radiometer (PFR) travelling standard was installed at the European calibration site of AERONET to supply continuous traceability of aerosol optical depth measurements to the World reference maintained at Davos through a PFR Triad.

The precision filter radiometer was installed in July 2020 at the Observatoire de Haute Provence (OHP) on a solar tracker provided by the Laboratoire d’Observation Atmosphérique (LOA) next to our 4 sun photometers (CE318-T).

OHP’s platform, with four CIMEL Sun/Sky/Lunar photometers CE318-T and the PFR traveling (at the right of the picture).

The measurements of spectral solar irradiance during clear sky periods are used to retrieve AOD from our photometers with AERONET calibration and the PFR.

You can follow the comparison between these two instruments in real time on this web page. This real-time analysis allows for continuous monitoring and quality control of the measurements provided by these two devices.

Real-time monitoring of the measurement analysis of the two instruments on 24 March 2021 – Source:

After 6 months of comparison (August 2020 to January 2021) between the two networks, results have been very promising with an Aerosol Optical Depth difference of less than 0.01, corresponding perfectly to the WMO criteria for AOD traceability for 3 of its 4 channels. This shows that the results provided by CIMEL CE318-T photometers are in line with the WMO expectations and that CIMEL photometers may be used as an instrument of reference for other research projects.

Other projects are in parallel with this one such as the 19ENV04 project funded by EURAMET and the European Commission to extend the traceability of international unit systems through the characterization and calibration of our Sun/Sky/Lunar photometers from these networks (See more information here).

This collaboration between research institutes and the European metrology community will establish a consistent framework providing calibrations of our Sun/Sky/Lunar photometers with traceability to the SI as well as comprehensive uncertainty budgets that will be a necessary part of the data provided to the users and actors of these networks.

Kazadzis, S., Kouremeti, N., Nyeki, S., Gröbner, J., and Wehrli, C.: The World Optical Depth Research and Calibration Center (WORCC) quality assurance and quality control of GAW-PFR AOD measurements, Geosci. Instrum. Method. Data Syst., 7, 39-53,, 2018.

MAP-IO campaign

Ship-borne CE318-T photometer aboard the Marion Dufresne in the frame of the MAP-IO.

January 11th – March 8th2021

Since the beginning of January 2021, one of our CE318-T photometers is permanently embarked on the Marion Dufresne as part of the MAP-IO (Marion Dufresne Atmospheric Program – Indian Ocean) research programme.

The objective of a permanent installation of our photometer on the Marion Dufresne is to allow the measurement of atmospheric aerosols from mobile platforms, and to extend and automate the coverage of the AERONET network.

CE318-T CIMEL photometer aboard the Marion Dufresne (Credits : LACY/University of la Réunion)

In future campaigns, our photometer will be used mainly in the Southern Hemisphere and the Indian Ocean to measure the aerosol optical depth (AOD). The new campaign that has just started is the result of preparatory campaigns like OCEANET and SEA2CLOUD, during which the system has been tested, improved and validated.

Below, the preliminary results of the campaign obtained thanks to satellite data transmitted to the LOA/CNRS to measure spectral AOD, water vapour content, Ångström exponent, and sky radiance for AERONET.

Map of the first daytime recorded AOD (level 1.5) between 13 and 31 January 2021 (Source: Luc Blarel at LOA/CNRS/U. Lille).


  • To monitor long-term atmospheric changes in the Indian and Austral oceans regions which are very poorly documented (IR ACTRIS and ICOS).
  • To calibrate and validation data from satellites.
  • To understand better the ocean-atmosphere exchanges and regional pollution by improving and adapting and adapting the parametizations used in numerical weather and climate predition models over the Indian and the Austral oceans.

If you want to know more about this campaign click here !

Key words: Aerosols, Atmosphere, sun/sky/lunar photometer, Meteorology



ROSAS – A new BRDF photometer installed in Lamasquère by CESBIO

The Lamasquère site (France) is now equipped with a CIMEL 12 filters photometer (CE318-TU12) which measures direct and diffuse irradiation, and the directional reflectance of the surface (BRDF).

This system, installed in March 2021, is called RObotic Station for Atmosphere and Surface (ROSAS) and operates mounted on top of a 10 m high mast in a field on the agricultural area of Lamothe farm in Lamasquère (France). The CESBIO ROSAS station is thus the 3rd site of this type worldwide after the CNES station in La Crau (France) and the CNES/ESA station in Gobabeb (Namibia), and the first to characterize an agricultural vegetated surface, with seasonal and inter-annual variations of the cover.

The spatial and temporal heterogeneity of the surface of this new site makes it more suitable for the validation of surface reflectance (after atmospheric correction), than for the absolute calibration of satellite sensors, as it is the case for La Crau and Gobabeb. When the Lamasquère field crops become very green and dense, the surfaces are dark and the atmospheric correction errors have a strong impact on the reflectance estimates, and when the crops are mature or the plot is bare ground, the adjacency effects due to the nearby forest become strong. Such in situ measurements are thus of primary interest to CESBIO, CNES and the broader scientific community.

The data are automatically transmitted to CESBIO and CNES every hour via the mobile phone network (GPRS), and processed periodically to derive the filtered bi-directional reflectance distribution function (BRDF).

Here below, you can find the first BRDF measurements acquired a few days after the validation of the station:

Polar diagrams of surface reflectances measured by the ROSAS station in Lamasquère. The 0° azimut corresponds to observations towards the South. The top left image was taken in the morning, the top right around noon, bottom left in the afternoon, and bottom right later on after the arrival of clouds. The yellow dots indicate the position of the sun . The radius of the graph corresponds to the zenith angle, and the other dimension is the azimuth with regard to the North.


More information on :

The plume of the Icelandic volcano Bardarbunga pollutes the air in the Nord – Pas de Calais

The plume of the Icelandic volcano Bardarbunga pollutes the air in the Nord – Pas de Calais

At the end of September 2014, the Nord – Pas de Calais region suffered an episode of heavy air pollution due to the eruption of the Icelandic volcano Bardarbunga, which has already been going on for more than a month.

The analysis of observations of the volcanic plume, obtained from the ground, thanks to CIMEL photometers and LiDAR, and by satellite, by a team of researchers, engineers and technicians from the Laboratoire d’optique atmosphérique (LOA, CNRS / Université Lille 1) in collaboration with the association for monitoring air quality atmo Nord – Pas de Calais, allowed them to describe the journey, from Iceland, of the volcanic plume and its arrival in the lowest layers of the French atmosphere.

BSC Dust Daily Forecast – AAMS platform


BSC Dust Daily Forecast – AAMS platform

Aerosol particles are important and highly variable components of the terrestrial atmosphere, and they affect both air quality and climate. In order to evaluate their multiple impacts, the most important requirement is to precisely measure their characteristics.

Remote sensing technologies such as lidar (light detection and ranging) and sun/sky photometers are powerful tools for determining aerosol optical and microphysical properties. In our work, we applied several methods to joint or separate lidar and sun/sky-photometer data to retrieve aerosol properties. The Raman technique and inversion with regularization use only lidar data. The LIRIC (LIdar-Radiometer Inversion Code) and recently developed GARRLiC (Generalized Aerosol Retrieval from Radiometer and Lidar Combined data) inversion methods use joint lidar and sun/sky-photometer data.

Link to the article: click here

Mobile Automatic Aerosol Monitoring Solution project (M-AAMS)

Mobile Automatic Aerosol Monitoring Solution project (M-AAMS)

Mobile Automatic Aerosol Monitoring Solution project (M-AAMS)

The team of scientists left Lille on Monday morning, direction the « Observatoire de Haute Provence » located in Aix-en-Provence.

Along its trip, the car takes continuous measurements of the atmosphere.

Scientists on board follow them and make sure that all the instruments work properly. The car is not only equipped with a wide range of instruments, but also with a camera and an internet connexion: all needed to document the trip of the car in real time!

Follow the adventure of the #CaPPA_Mobile on twitter.

If the system has already been used locally, this time the route extends from Lille to Aix-en-Provence, nearly 1000 km. This experience is part of Ioana Popovici’s thesis work: “Measurement of aerosol variability at high spatial and temporal resolution, in connection with air quality, using an innovative mobile system. »

This time, the vehicle is equipped with a Cimel CE370 LiDAR (532 nm), the mobile PLASMA photometer (340-1600 nm), a granulometer (GRIMM) and a weather station.

The data collected by the mobile system is being analysed and validated. An inter-comparison of the data will be made with the data collected by the fixed measurement stations of the Haute Provence Observatory and the ATMO stations located along the route. Access to online data of the instrumented car.

The science team relied on good weather to collect as much data as possible. Although the sky cleared several times, clear, cloudless sky conditions were not frequently encountered. Under these circumstances it is difficult to carry out solar photometry measurements and to obtain additional information by combining LIDAR with a solar photometer. However, LIDAR has observed the vertical and spatial variability of the atmosphere. The observation was limited to about 2-3 km altitude by the presence of clouds over most of the trip.

A camera fixed on the roof of the car “confirms” the LIDAR measurements, as follows:

Spatio-temporal series LIDAR obtained between Lille and Valence on 28/03/2016