Atmos. Chem. Phys. Discuss., 9, 5929-5965, 2009
© Author(s) 2009. This work is distributed
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Regional modelling of tracer transport by tropical convection – Part 2: Sensitivity to model resolutions
J. Arteta1, V. Marécal1, and E. D. Rivière2
1Laboratoire de Physique et Chimie de l'Environnement, CNRS and Université d'Orléans, 3A avenue de la recherche scientifique, 45071 Orléans cedex 2, France
2Groupe de Spectroscopie Moléculaire et Atmosphérique, Université de Reims, Moulin de la Housse, B.P. 1039, 51687 Reims Cedex, France

Abstract. The general objective of this series of two papers is to evaluate long duration limited-area simulations with idealised tracers as a tool to assess the tracer transport in chemistry-transport models (CTMs). In this second paper we analyse the results of three simulations using different horizontal and vertical resolutions against meteorological observations and their impact on idealized tracer transport. The reference simulation (REF) uses a 60 km horizontal resolution and 300 m vertically in the upper troposphere/lower stratosphere (UTLS). A 20 km horizontal resolution simulation (HR) is run as well as a simulation (CVR) with 850 m vertical resolution in the UTLS. The simulations are run for one month during the SCOUT-O3 field campaign. The Falcon and Geophysica aircraft data and the TRMM rainrate estimates have been used to evaluate the simulations. They show that the HR configuration gives generally a better agreement with the measurements than the REF simulation, the CVR simulation giving generally the worst results. The vertical distribution of the tropospheric tracers for the simulations has a similar shape with a 15 km altitude maximum of 0.4 ppbv for REF, 1.2 for HR and 0.04 for CVR. This is related to the dynamics produced by the three simulations that leads to larger values of the upward velocities on average for HR and lower for CVR compared to REF. The HR provides more frequent overshoots over the cold point dynamical barrier than REF and CVR. For the stratospheric tracers the differences between the three simulations are small. The diurnal cycle of the fluxes of all tracers in the TTL (Tropical Tropopause Layer) exhibits a maximum linked to the maximum of convective activity that is particularly well marked in the HR simulation. The largest integrated fluxes are found for tropospheric tracers in HR.

Citation: Arteta, J., Marécal, V., and Rivière, E. D.: Regional modelling of tracer transport by tropical convection – Part 2: Sensitivity to model resolutions, Atmos. Chem. Phys. Discuss., 9, 5929-5965, doi:10.5194/acpd-9-5929-2009, 2009.
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