Comparison of OMI ozone and UV irradiance data with ground-based measurements at two French sites

Abstract

Abstract. Ozone Monitoring Instrument (OMI), launched in July 2004, is dedicated to the monitoring of the Earth's ozone, air quality and climate. OMI is the successor of the Total Ozone Mapping Spectrometer (TOMS) instruments and provides among other atmospheric and radiometric quantities the total column of ozone (TOC), the surface ultraviolet (UV) irradiance at several wavelengths, the erythemal dose rates and the erythemal daily doses. The main objective of this work is to compare OMI data with data from ground-based instruments in order to use OMI products (collection 2) for scientific studies. The Laboratoire d'Optique Atmosphérique (LOA) located in Villeneuve d'Ascq (VdA) in the north of France performs solar UV measurements using a spectroradiometer. The site of Briançon in the French Southern Alps is also equipped with a spectroradiometer operated by Interaction Rayonnement Solaire Atmosphère (IRSA). The OMI total ozone column data is obtained from the OMI-TOMS and OMI-DOAS algorithms. The comparison between the TOC retrieved with ground-based measurements and OMI-TOMS data shows good agreement at both sites for all sky conditions with a relative difference for most of points better than 5%. For OMI-DOAS data, the agreement is generally better than 7% and these data show a significant dependence on solar zenith angle. Comparisons of spectral UV on clear sky conditions are also satisfying with relative differences smaller than 10% except at solar zenith angles larger than 65 • . On the contrary, results of comparCorrespondence to: V. Buchard (buchard@loa.univ-lille1.fr) isons of the erythemal dose rates and erythemal daily doses for clear sky show that OMI overestimates surface UV doses at VdA by about 15% and that on cloudy skies, the bias increases. At Briançon, such a bias is observed if data corresponding to snow-covered surface are excluded.

Comparison of UV irradiances from Aura/Ozone Monitoring Instrument (OMI) with Brewer measurements at El Arenosillo (Spain) – Part 2: Analysis of site aerosol influence

“…The set of values with AOD(440 nm) > 0.25 and α ≥ 0.82 is shown as red points. The relationship between OMI-Brewer differences and AOD at 340 nm presents a great variability, depending on the site or aerosol type (e.g., Kazantzidis et al, 2006;Ialongo et al, 2008;Buchard et al, 2008). Antón et al (2007) found a better correlation for binned data, showing clearly that the OMI bias increases as the AOD increase.…”

“…Recent publications on OMI operational UV validation have been carried out by Buchard et al (2008), Ialongo et al (2008) and Weihs et al (2008) at different European locations but no aerosol corrections were made. More recently, the works of Kazadzis et al (2009), Arola et al (2009) and Ialongo et al (2010) have applied the aerosol absorption correction suggested earlier in Krotkov et al (2005) and Arola et al (2005).…”

Validity of satellite measurements used for the monitoring of UV radiation risk on health

“…Intercomparisons were also done with the UV radiation measured in two French sites: Villeneuve d'Ascq and Briançon (Buchard et al, 2008). Comparisons of the erythemal dose rates and erythemal daily doses for clear sky show that OMI overestimates surface UV doses at Villeneuve d'Ascq by about 13 % and that on all sky conditions, the bias slightly increases.…”

Validation of satellite-based noontime UVI with NDACC ground-based instruments: influence of topography, environment and satellite overpass time

“…However, validation exercises are difficult to achieve due to differences in temporal and spatial resolutions of GB and SB data products. Extensive comparison studies between surface UV provided by OMI and GB measurements have been previously made (Tanskanen et al, 2007;Buchard et al, 2008;Ialongo et al, 2008;Weihs et al, 2008). Those studies dealt with version 1.2, which did not account for the influence of absorbing aerosols, implying a positive bias in OMI product.…”