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Ann. Geophys., 26, 401-412, 2008
www.ann-geophys.net/26/401/2008/
© European Geosciences Union 2008
Comparison of GOME total ozone data with ground data from the Spanish Brewer spectroradiometers
M. Antón1,*, D. Loyola2, B. Navascúes1, and P. Valks2
1Área de Proyectos, Instituto Nacional de Meteorología (INM), C. Leonardo Prieto Castro, n°8, CP: 28071, Madrid, Spain
2Remote Sensing Technology Institute, German Aerospace Center (DLR), Oberpfaffenhofen, 82234 Wessling, Germany
*now at: Departamento de Física, Universidad de Extremadura, Avd. de Elvas, s/n, CP: 06071, Badajoz, Spain
Abstract. This paper compares total ozone measurements from five Brewer
spectroradiometers located at the Iberian Peninsula with satellite
observations given by the GOME (Global Ozone Monitoring Experiment) sensor.
The analyzed period covers simultaneous ozone values from July 1995 until
December 2004. The regression analysis shows an excellent agreement between
Brewer-GOME values in the five locations; the coefficient of correlation is
always higher than 0.92 and the root mean square error is about 3%.
Moreover, the comparison shows that the satellite retrieval accuracy is
within the uncertainty of current ground-based instruments. In addition, the
effects of several variables, such as cloudiness, solar zenith angle (SZA),
effective temperature and total ozone values in Brewer-GOME differences are
analyzed. The results indicate that clouds induce a minor dependence of GOME
values on the SZA. For example, during heavy cloudy conditions in Madrid
station, GOME observations overestimate ground-based Brewer data for low AMF
(low SZA values) by 2% while for high AMF (high SZA values) the satellite
underestimates ground-based ozone values by 1%. Moreover, the dependence
of Brewer-GOME differences with respect to SZA for cloud-free conditions may
be due to the variability of effective temperature. This fact could indicate
that the effective temperature estimated by GOME does not fully reflect the
actual atmospheric temperature variability. Finally, GOME ozone observations
slightly underestimate the highest values measured by the Brewer
spectrophotometers and overestimates the lowest ground-based measurements.
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