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The November event of the Madden-Julian oscillation (MJO) during the Dynamics of North Atlantic Models (DYNAMO) field campaign was simulated using the global compressible nonhydrostatic Model for Prediction Across Scales with global coarse (60 and 15 km) and regional (the Indian Ocean) cloud-permitting (3 km) meshes. The purpose of this study is to compare roles of parameterized deep and shallow cumulus and microphysics in MJO simulations. Two cumulus schemes were used: Tiedtke and Grell-Freitas. The deep and shallow components of Tiedtke scheme can be turned on and off individually. The results reveal that microphysics alone (without cumulus parameterization) is able to produce strong signals of the MJO in precipitation with 3 km mesh and weak MJO signals with 15 km mesh. A shallow scheme (Tiedtke) along with microphysics strengthens the MJO signals but makes them less well organized on large scales. A deep cumulus scheme can either improve the large-scale organization of MJO precipitation produced by microphysics and shallow convection (Tiedtke) or impair them (Grell-Freitas). The deep scheme of Tiedtke cannot reproduce the MJO well without its shallow counterpart. The main role of shallow convection in the model is to transport moisture upward to the lower to middle troposphere. By doing so, it removes dry biases in the lower to middle troposphere, a distinct feature in simulations with weak or no MJO signals, and enhances total precipitation and diabatic heating produced by microphysics and deep cumulus schemes. Changing model grid spacing from 60 to 15 km makes a little difference in the model fidelity of reproducing the MJO. All roles of shallow convection in 15 km simulations with parameterized deep convection cannot be reproduced in 3 km simulations without parameterized deep convection. Results from this study suggest that we should pay more attention to the treatment of shallow convection and its connection to other parameterized processes for improving MJO simulations. In other words, a holistic approach should be taken that consider parameterization of shallow cumulus, microphysics, boundary layer, and deep cumulus as a whole for model improvement.Many studies of modeling comparisons have attempted to identity causes of model infidelity in simulating the MJO [Lin et al., 2006;Zhang et al., 2006;Kim et al., 2009]. None of them has led to any definitive answer. Recent studies diagnosed reproduction of the MJO in three types of global model runs: 20 year climate simulations [Jiang et al., 2015], 20 day hindcast [Klingaman et al., 2015a], and 2 day hindcast [Xavier et al., 2015]. Their finding is intriguing: There is no one-to-one correspondence between model success or failure in producing MJO statistics in 20 year runs and MJO hindcast of 20 and 2 days, there is no clear indication of what biases in the mean state might be responsible for model failure of reproducing the MJO, and there is PILON ET AL. DEEP AND SHALLOW CONVECTION IN THE MJO 10,575

In the Tropics, cumulus convection has a major influence on precipitation and vertical transport of atmospheric particles, which are subject to scavenging by precipitation. A new parametrization of transport and scavenging of trace particles by convective clouds and precipitation has been developed and introduced in the Laboratoire de Météorologie Dynamique general circulation model (LMDz). This model uses the deep convection scheme of Emanuel, which is particularly suited for the Tropics. Our parametrization of transport and scavenging is closely linked to this scheme and our developments follow step-by-step the building of this convection representation. The purpose of this study is to understand better the influence of convection on the tracer vertical distribution and to assess the role of the convection parametrization.Short-term and long-term simulations have been performed focusing on the concentrations of the natural radionuclide 7 Be, which is produced mainly in the stratosphere and upper troposphere and attaches to available aerosols. Single-column simulations forced by data from the Tropical Ocean-Global Atmosphere-Coupled Ocean-Atmosphere Response Experiment (TOGA-COARE) show the high efficiency of in-cloud scavenging by convective and large-scale processes in the removal of the tracer. These simulations show that, in the LMDz model, convection does not affect radionuclide concentrations as much as stratiform clouds and associated precipitation. In the free troposphere and in the boundary layer, below-cloud evaporation of rain has a major effect on tracer distribution, unlike impaction, which has a negligible effect. Three-dimensional model simulation results are compared with surface data of a station belonging to the worldwide network of the Comprehensive Nuclear Test Ban Treaty Organization (CTBTO). We show that this new parametrization is able to reproduce the observed yearly averaged concentrations of 7 Be at the surface and decrease by a third the overestimation of radionuclides formerly simulated without convective scavenging. LMDz simulations have been also performed over the year 2007 on a global scale using the terragenic 210 Pb and cosmogenic 7 Be radionuclides.

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