22 May 2023
 | 22 May 2023
Status: this preprint is open for discussion and under review for Atmospheric Chemistry and Physics (ACP).

Evaluation of modelled climatologies of O3, CO, water vapour and NOy in the upper troposphere – lower stratosphere using regular in situ observations by passenger aircraft

Yann Cohen, Didier Hauglustaine, Bastien Sauvage, Susanne Rohs, Patrick Konjari, Ulrich Bundke, Andreas Petzold, Valérie Thouret, Andreas Zahn, and Helmut Ziereis

Abstract. Evaluating the global chemistry models in the upper troposphere – lower stratosphere (UTLS) is an important step toward a further understanding of its chemical composition. The latter is regularly sampled through in situ measurements based on passenger aircraft, in the framework of the In-service Aircraft for a Global Observing System (IAGOS) research infrastructure. This study focuses on the comparison of the IAGOS measurements in ozone, carbon monoxide (CO), nitrogen reactive species (NOy) and water vapour, with a 25-year simulation output from the LMDZ-OR-INCA chemistry-climate model. For this purpose, we present and apply an extension of the Interpol-IAGOS software that projects the IAGOS data onto any model grid, in order to derive a gridded IAGOS product and a masked model product that are directly comparable to one another. Climatologies are calculated in the upper troposphere (UT) and in the lower stratosphere (LS) separately, but also in the UTLS as a whole, as a demonstration for the models that do not sort out the physical variables necessary to distinguish between the UT and the LS. In the northern extratropics, the comparison in the UTLS layer suggests that the geographical distribution in the tropopause height is well reproduced by the model. In the separated layers, the model simulates well the water vapour climatologies in the UT, and the ozone climatologies in the LS. The opposite biases in CO in both UT and LS suggest that the cross-tropopause transport is overestimated. The NOy observations highlight the difficulty of the model in parameterizing the lightning emissions. In the tropics, the upper-tropospheric climatologies are remarkably well simulated for water vapour, as the observed CO peaks due to biomass burning in the most convective systems, and the ozone latitudinal variations. Ozone is more sensitive to lightning emissions than to biomass burning emissions, whereas the CO sensitivity to biomass burning emissions strongly depends on the location and on the season. Through this evaluation, the present study demonstrates that the Interpol-IAGOS software is a tool facilitating the assessment of the global model simulations in the UTLS, potentially useful for any modelling experiment involving chemistry-climate and chemistry-transport models.

Yann Cohen et al.

Status: open (until 03 Jul 2023)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

Yann Cohen et al.

Data sets

Interpol-IAGOS Yann Cohen, Virginie Marécal, Béatrice Josse, Valérie Thouret

Yann Cohen et al.


Total article views: 160 (including HTML, PDF, and XML)
HTML PDF XML Total Supplement BibTeX EndNote
112 44 4 160 9 2 3
  • HTML: 112
  • PDF: 44
  • XML: 4
  • Total: 160
  • Supplement: 9
  • BibTeX: 2
  • EndNote: 3
Views and downloads (calculated since 22 May 2023)
Cumulative views and downloads (calculated since 22 May 2023)

Viewed (geographical distribution)

Total article views: 190 (including HTML, PDF, and XML) Thereof 190 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
Latest update: 04 Jun 2023
Short summary
The upper troposphere - lower stratosphere (UT-LS) is a key region regarding the lower atmospheric composition. This study consists of a comprehensive evaluation of an up-to-date chemistry-climate model in this layer, using regular in situ measurements based on passenger aircraft. For this purpose, a specific software (Interpol-IAGOS) has been updated and made publicly available. The model reproduces particularly well the carbon monoxide peaks due to biomass burning over the continental tropics.