Journal cover Journal topic
Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union
Journal topic

Journal metrics

Journal metrics

  • IF value: 3.248 IF 3.248
  • IF 5-year value: 3.650 IF 5-year
  • CiteScore value: 3.37 CiteScore
  • SNIP value: 1.253 SNIP 1.253
  • IPP value: 3.29 IPP 3.29
  • SJR value: 1.869 SJR 1.869
  • Scimago H <br class='hide-on-tablet hide-on-mobile'>index value: 60 Scimago H
    index 60
  • h5-index value: 47 h5-index 47
Volume 6, issue 8 | Copyright

Special issue: Observations and modeling of aerosol and cloud properties...

Atmos. Meas. Tech., 6, 2207-2220, 2013
© Author(s) 2013. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 30 Aug 2013

Research article | 30 Aug 2013

Measurements on pointing error and field of view of Cimel-318 Sun photometers in the scope of AERONET

B. Torres1,2, C. Toledano1, A. Berjón3, D. Fuertes1, V. Molina1, R. Gonzalez1, M. Canini4, V. E. Cachorro1, P. Goloub2, T. Podvin2, L. Blarel2, O. Dubovik2, Y. Bennouna1, and A. M. de Frutos1 B. Torres et al.
  • 1Group of Atmospheric Optics, Valladolid University, Valladolid, Spain
  • 2Laboratoire d'Optique Amosphérique – UMR8518, Université des Sciences et Technologies de Lille, Villeneuve d'Ascq, France
  • 3Izana Atmospheric Research Center, Spanish Meteorological Agency, Tenerife, Spain
  • 4CIMEL Electronique, Paris, France

Abstract. Sensitivity studies indicate that among the diverse error sources of ground-based sky radiometer observations, the pointing error plays an important role in the correct retrieval of aerosol properties. The accurate pointing is specially critical for the characterization of desert dust aerosol. The present work relies on the analysis of two new measurement procedures (cross and matrix) specifically designed for the evaluation of the pointing error in the standard instrument of the Aerosol Robotic Network (AERONET), the Cimel CE-318 Sun photometer. The first part of the analysis contains a preliminary study whose results conclude on the need of a Sun movement correction for an accurate evaluation of the pointing error from both new measurements. Once this correction is applied, both measurements show equivalent results with differences under 0.01° in the pointing error estimations. The second part of the analysis includes the incorporation of the cross procedure in the AERONET routine measurement protocol in order to monitor the pointing error in field instruments. The pointing error was evaluated using the data collected for more than a year, in 7 Sun photometers belonging to AERONET sites. The registered pointing error values were generally smaller than 0.1°, though in some instruments values up to 0.3° have been observed. Moreover, the pointing error analysis shows that this measurement can be useful to detect mechanical problems in the robots or dirtiness in the 4-quadrant detector used to track the Sun. Specifically, these mechanical faults can be detected due to the stable behavior of the values over time and vs. the solar zenith angle. Finally, the matrix procedure can be used to derive the value of the solid view angle of the instruments. The methodology has been implemented and applied for the characterization of 5 Sun photometers. To validate the method, a comparison with solid angles obtained from the vicarious calibration method was developed. The differences between both techniques are below 3%.

Publications Copernicus
Special issue