H o m e

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NO₂ concentrations in the stratosphere are mainly determined by photolysis of NO₂ itself and the partitioning between NO_x and the reservoir species, mainly N₂O₅, HNO₃ and ClONO₂. As a result of decreased photolysis, most of the NO₂ is in its reservoirs in polar winter, and therefore NO₂ concentrations are low. In addition to photolysis, temperature also plays an important role, low temperatures leading to decreased NO₂ concentrations.

For stratospheric chemistry, NO₂ is a key species as on one hand it acts as a catalyst in ozone destruction and on the other hand is essential in forming the reservoir species ClONO₂ and BrONO₂. Observation of NO₂ can be used as an indicator of denoxification in the arctic stratosphere, and in combination with other measurements can also yield information on denitrification which is important in determining the duration of chlorine activation.

The University of Bremen in co-operation with the University of Heidelberg has developed and validated an algorithm for the detection of the atmospheric NO₂ absorption from GOME. The level 1 GOME data is transferred from the ESA satellite receiving stations to the University of Bremen where the daily spectral analysis of NO₂ is carried out. The produced GOME NO₂ maps show the so-called vertical column (VC) of NO₂ for each single GOME measurement. The VC is the atmospheric NO₂ concentration integrated from the surface to the top of the atmosphere. It therefore contains not only the stratospheric part, but also tropospheric NO₂, mainly from pollution. The tropospheric contributions can usually be neglected in the polar regions, but are readily visible at mid-latitudes. In these regions, the NO₂ columns shown should only be used in a qualitative sense as the GOME sensitivity to tropospheric absorbers is not fully corrected for in this analysis.

More information on the GOME NO₂ products can be found in the following References

Leue, C., M. Wenig, T. Wagner, U. Platt, and B. Jähne, 2001: Quantitative analysis of  NO_x emissions from GOME satellite image sequences, J. Geophys. Res., 106, 5493–5505, 2001.

Richter, A., Kreher, K., Johnston, P. V., Wittrock, F., and J. P. Burrows, Validation of GOME O₃, NO₂, BrO, and OClO Measurements in Southern High Latitudes, Fifth European Workshop on Stratospheric Ozone, 1999

Richter, A. and J.P. Burrows, Retrieval of Tropospheric NO₂ from GOME Measurements, Adv. Space Res., 29(11) ,1673-1683, 2002 .

Velders, G. J. M.; C. Granier, R. W. Portmann, K. Pfeilsticker, M. Wenig, T. Wagner, U. Platt, A. Richter, and J. P. Burrows, Global tropospheric NO2 column distributions: Comparing 3-D model calculations with GOME measurements, JGR, D 106, 12643-12660, 2001.