Regional modelling of tracer transport by tropical convection – Part 2: Sensitivity to model resolutions 1Laboratoire de Physique et Chimie de l'Environnement et de l'Espace, 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 Champagne-Ardenne and CNRS, Faculté des sciences, Moulin de la Housse, B.P. 1039, 51687 Reims Cedex, France
Received: 29 Dec 2008 – Published in Atmos. Chem. Phys. Discuss.: 04 Mar 2009 Abstract. The general objective of this series of two papers is to evaluate long
duration limited-area simulations with idealised tracers as a possible 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. The goal is to study the impact of the
model spatial resolution on convective transport of idealized tracer in the
tropics. 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
with 850 m vertical resolution in the UTLS (CVR). The simulations are run for
one month during the SCOUT-O3 field campaign. Aircraft data, TRMM rainrate
estimates and radiosoundings 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 gives generally
the worst results. The vertical distribution of the tropospheric tracers for
the simulations has a similar shape with a ~15 km altitude maximum for
the 6h-lifetime tracer of 0.4 ppbv for REF, 1.2 for HR and 0.04 for CVR.
These differences are 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. HR simulates more frequent and
stronger convection leading to enhanced fluxes compared to REF and higher
detrainment levels compared to CVR. HR provides also occasional overshoots
over the cold point dynamical barrier. For the stratospheric tracers the
differences between the three simulations are small. The diurnal cycle of
the fluxes of all tracers in the Tropical Tropopause Layer exhibits a
maximum linked to the maximum of convective activity.
Revised: 11 Aug 2009 – Accepted: 28 Aug 2009 – Published: 24 Sep 2009
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., 9, 7101-7114, doi:10.5194/acp-9-7101-2009, 2009.