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Ten years of NO2 comparisons between ground-based SAOZ and satellite instruments (Gome, Sciamachy, OMI)

Florence Goutail(1), Dmitry IONOV(1) and Ariane BAZUREAU(1)

(1) CNRS, Route des Gatines, 91370 Verrieres le Buisson, France


SAOZ (Systeme d’Analyse par Observations Zenithales) is a ground-based UV-Visible zenith-sky spectrometer installed between 1988 and 1995 at a number of NDSC stations at various latitudes on the globe. The instrument is providing ozone and NO2 vertical column using the Differential Optical Absorption Spectroscopy in the visible range, during each twilight – at sunrise and sunset.

The ERS-2 Global Ozone Monitoring Experiment (GOME) in 1995 was the first satellite mission to provide a global picture of atmospheric NO2 with reasonable spatial and temporal resolution. It was then followed by SCanning ImAging spectroMeter for Atmospheric CHartographY (SCIAMACHY) onboard ENVISAT in 2002, and Ozone Monitoring Instrument (OMI) onboard EOS-AURA in 2004, with a similar capacity to monitor total NO2. All these instruments are nadir viewing mapping spectrometers, applying DOAS technique to derive NO2 vertical column in UV-Visible range from space.

Here we present the results of NO2 long term comparison between GOME satellite data and SAOZ ground-based measurements, for the whole period of GOME operation since 1995, and at various latitudes – tropics, mid-latitudes and polar regions of both hemispheres. More recently, comparisons are also presented with SCIAMACHY and OMI in 2004-2006. In general, the daytime satellite measurements (around noon) are found in agreement with sunrise ground-based data, with an average smaller difference in southern hemisphere, than in the north. A photochemical box model is used to explain and improve this agreement. However, some seasonal dependence of the difference between ground-based and satellite total NO2 remains, which can be related to the choice of NO2 air mass factor within DOAS processing of both systems.


Full paper

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry