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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
© Author(s) 2017. This work is distributed under
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Research article
06 Dec 2017
Review status
This discussion paper is a preprint. A revision of this manuscript was accepted for the journal Atmospheric Chemistry and Physics (ACP) and is expected to appear here in due course.
Results from the 4th WMO Filter Radiometer Comparison for aerosol optical depth measurements
Stelios Kazadzis1,11, Natalia Kouremeti1, Henri Diémoz2, Julian Gröbner1, Bruce W. Forgan3, Monica Campanelli4, Victor Estellés5, Kathleen Lantz6, Joseph Michalsky6, Thomas Carlund7, Emilio Cuevas8, Carlos Toledano9, Ralf Becker10, Stephan Nyeki1, Panagiotis G. Kosmopoulos11, Viktar Tatsiankou12, Laurent Vuilleumier13, Frederick M. Denn14, Nozomu Ohkawara15, Osamu Ijima15, Philippe Goloub16, Panagiotis I. Raptis11,1, Michael Milner3, Klaus Behrens10, Africa Barreto8,9,17, Giovanni Martucci13, Emiel Hall6, James Wendell6, Bryan E. Fabbri14, and Christoph Wehrli1 1Physikalisch-Meteorologisches Observatorium Davos, World Radiation Center, Switzerland
2Aria e Atmosfera – Radiazione solare e atmosfera ARPA Valle, Saint-Christophe, 11020, Italy
3Standards & Metrology, Bureau of Meteorology, Docklands Vic, 3008, Australia
4SACI-CNR, Via Fosso del Cavaliere 100, 00133 Rome, Italy
5Department of Earth Physics and Thermodynamics, Solar Radiation and Research Unit, Univ. de València, Valencia, Spain
6Cooperative Institute for Research in Environmental Studies, NOAA/ESRL/GMD, Boulder, CO 80305, USA
7Swedish Meteorological and Hydrological Institute, 601 76 Norrköping, Sweden
8Izaña Atmospheric Research Centre, State Meteorological Agency (AEMET), Santa Cruz de Tenerife, Spain
9Atmospheric Optics Group (GOA), University of Valladolid, 47011 Valladolid, Spain
10Deutscher Wetterdienst Meteorologisches Observatorium Lindenberg, D-15848 Tauche, Germany
11Institute of Environmental Research and Sustainable Development, National Observatory of Athens, Greece
12COFOVO Energy Inc. 800 King Edward Avenue, Suite 3014 Ottawa, ON, K1N 6N5, Canada
13Federal Office of Meteorology and Climatology MeteoSwiss, Payerne, Switzerland
14Science Systems & Applications Inc NASA Langley Science Directorate, Hampton, VA 23666, USA
15Japan Meteorological Agency 1-3-4 Otemachi, Chiyoda-ku, 100-8122 Tokyo, Japan
16Laboratoire d'Optique Atmosphérique, Univ. des Sciences et Technologies de Lille, 159655 Villeneuve d'Ascq, France
17Cimel Electronique, 75011 Paris, France
Abstract. This study presents the results of the 4th Filter Radiometer Comparison that was held in Davos, Switzerland, between September 28 and October 16, 2015. Thirty filter radiometers and spectroradiometers from 12 countries participated including reference instruments from global aerosol networks. The absolute differences of all instruments compared to the reference have been based on the WMO criterion defined as 95 % of the measured data has to be within 0.005 ± 0.001/m (where m is the air mass). At least 24 out of 29 instruments achieved this goal at both 500 and 865 nm, while 12 out of 17 and 13 out of 21 achieved this at 368 and 412 nm, respectively. While searching for sources of differences among different instruments, it was found that all individual differences linked to Rayleigh, NO2, ozone, water vapor calculations and related optical depths and air mass calculations were smaller than 0.01 in AOD at 500 and 865 nm. Different cloud detecting algorithms used have been compared. Ångström exponent calculations showed relatively large differences among different instruments partly because of the sensitivity of this parameter at low AOD conditions. The overall low deviations of these AOD results and the high accuracy of reference aerosol network instruments demonstrated a promising framework to achieve homogeneity, compatibility and harmonization among the different spectral AOD networks in the near-future.

Citation: Kazadzis, S., Kouremeti, N., Diémoz, H., Gröbner, J., Forgan, B. W., Campanelli, M., Estellés, V., Lantz, K., Michalsky, J., Carlund, T., Cuevas, E., Toledano, C., Becker, R., Nyeki, S., Kosmopoulos, P. G., Tatsiankou, V., Vuilleumier, L., Denn, F. M., Ohkawara, N., Ijima, O., Goloub, P., Raptis, P. I., Milner, M., Behrens, K., Barreto, A., Martucci, G., Hall, E., Wendell, J., Fabbri, B. E., and Wehrli, C.: Results from the 4th WMO Filter Radiometer Comparison for aerosol optical depth measurements, Atmos. Chem. Phys. Discuss.,, in review, 2017.
Stelios Kazadzis et al.
Stelios Kazadzis et al.


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Publications Copernicus
Short summary
Aerosol optical depth measured from ground based sun-photometers is the most important parameter for studying the changes in the earth's radiation balance due to aerosols. Various sun-photometer types belonging to individual institutions or broader aerosol networks are gathering every five years, for three weeks in Davos Switzerland in order to compare their Aeorosl Optical Depth retrievals. This work presents the results of the latest (4th) filter radiometer intercomparison.
Aerosol optical depth measured from ground based sun-photometers is the most important parameter...