Atmos. Chem. Phys. Discuss., 7, 15067-15103, 2007
www.atmos-chem-phys-discuss.net/7/15067/2007/
doi:10.5194/acpd-7-15067-2007
© Author(s) 2007. This work is licensed under the
Creative Commons Attribution-NonCommercial-ShareAlike 2.5 License.
Review Status
This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
NO2 climatology in the northern subtropical region: diurnal, seasonal and interannual variability
M. Gil1, M. Yela1, L. N. Gunn2, A. Richter3, I. Alonso1, M. P. Chipperfield2, E. Cuevas4, J. Iglesias1, M. Navarro1, O. Puentedura1, and S. Rodríguez1
1Area de Investigación e Instrumentación Atmosférica, INTA, Torrejón de Ardoz, Spain
2Inst. for Atmospheric Science, School of Earth and Environment, Univ. of Leeds, Leeds, UK
3Institute of Environmental Physics, University of Bremen, Bremen, Germany
4Centro de Investigación Atmosférica de Izaña, INM, Sta. Cruz de Tenerife, Spain

Abstract. Daily NO2 vertical column density (VCD) has been routinely measured by zenith sky spectroscopy at the subtropical station of Izaña (28° N, 16° W) since 1993 in the framework of the Network for the Detection of Atmospheric Composition Change (NDACC). Based on 14 years of data the first low latitudes NO2 VCD climatology has been established and the main characteristics from short scales of one day to inter-annual variability are presented. Instrumental descriptions and different source of errors are described in detail. The observed diurnal cycle follows that expected by gas-phase NOx chemistry, as can be shown by the good agreement with a vertically integrated chemical box model, and is modulated by solar radiation. The seasonal evolution departs from the phase of the hours of daylight, showing the signature of upper stratospheric temperature changes. From the data record no significant long-term trends in NO2 VCD can be inferred. Comparison of the ground-based data sets with nadir looking satellite spectrometers shows excellent agreement for SCIAMACHY with differences between both datasets of 1.1%. GOME displays unrealistic features with largest discrepancies during summer. The ground-based data are compared with long-term output of the SLIMCAT 3-D chemical transport model (CTM). The basic model, forced by ECMWF (ERA-40) analyses, captures the observed NO2 annual cycle but significantly underestimates the spring/summer maximum. In a model run which uses assimilation of satellite CH4 profiles to constrain the model long-lived tracers the agreement is significantly improved. This improvement in modelled column NO2 is due to better modelled NOy profiles and points to transport errors in the ECMWF ERA-40 reanalyses.

Citation: Gil, M., Yela, M., Gunn, L. N., Richter, A., Alonso, I., Chipperfield, M. P., Cuevas, E., Iglesias, J., Navarro, M., Puentedura, O., and Rodríguez, S.: NO2 climatology in the northern subtropical region: diurnal, seasonal and interannual variability, Atmos. Chem. Phys. Discuss., 7, 15067-15103, doi:10.5194/acpd-7-15067-2007, 2007.
 
Search ACPD
Discussion Paper
    XML
    Citation
    Final Revised Paper
    Share