An evaluation of the performance of chemistry transport models - Part 2: Detailed comparison with two selected campaigns

Abstract

Abstract. This is the second part of a rigorous model evaluation study involving five global Chemistry-Transport and two Chemistry-Climate Models operated by different groups in Europe. Simulated trace gas fields were interpolated to the exact times and positions of the observations to account for the actual weather conditions and hence for the specific histories of the sampled air masses. In this part of the study we focus on a detailed comparison with two selected campaigns, PEM-Tropics A and SONEX, contrasting the clean environment of the tropical Pacific with the more polluted North Atlantic region. The study highlights the different strengths and weaknesses of the models in accurately simulating key processes in the UT/LS region including stratosphere-troposphere-exchange, rapid convective transport, lightning emissions, radical chemistry and ozone production. Model simulated Radon, which was used as an idealized tracer for continental influence, was occasionally much better correlated with measured CO than simulated CO pointing towards deficiencies in the used biomass burning emission fields. The abundance and variability of HO x radicals is in general well represented in the models as inferred directly from the comparison with measured OH and HO 2 and indirectly from the comparison with hydrogen peroxide concentrations. Components of the NO y family such as PAN, HNO 3 and NO were found to compare less favorably. Interestingly, models showing good agreement with observations in the case of PEM-Tropics A often failed in the case Correspondence to: D. Brunner (dominik.brunner@env.ethz.ch) of SONEX and vice versa. A better description of NO x and NO y emissions, chemistry and sinks is thought to be key to future model improvements with respect to the representation of chemistry in the UT/LS region.

Regional modelling of tracer transport by tropical convection – Part 2: Sensitivity to model resolutions

“…In CVR which has less vertical levels, the mixing is done over larger depths than in REF and HR leading to a deeper mixing layer. This is consistent with Brunner et al (2005) who showed that sharp tracer gradients across the tropopause are usually not well represented in the models with an excessive mixing between tropospheric and stratospheric air.…”

Estimates of lightning NO<sub>x</sub> production from GOME satellite observations

“…For instance, we note that various studies (Emmonds et al, 1997;Wauben et al, 1997;Meijer et al, 2000) have indicated that TM3 is capable of reproducing aircraft-and surface-observed NO x concentrations for a range of different meteorological and chemical situations. Also, recent studies by Brunner et al (2003Brunner et al ( , 2005 showed that TM3 is well capable of reproducing observed NO x and NO x -related species.…”

“…The model simulations are performed with a spatial resolution of 144×72 grid cells (2.5 • ×2.5 • ) and 31 σ hybrid-pressure levels from the surface up to 10 hPa. Recently the performance of TM3 was evaluated by comparing model simulations with aircraft observations from various aircraft campaigns (Meijer et al, 2000;Brunner et al, 2003Brunner et al, , 2005.…”

Changes in Nitrogen Dioxide and Ozone over Southeast and East Asia between Year 2000 and 2030 with Fixed Meteorology

“…The model has been tested and evaluated recently by Berglen et al (2004), Brunner et al (2005), and Isaksen et al (2005). Results from the CTM2 calculations used in this paper have been evaluated against ozone sondes in , see the "Auxiliary Material" of that paper) and in .…”