Radiative-convective equilibrium simulations with a 2 km horizontal resolution are conducted to investigate the impact on convective organization of different parameterizations for horizonal and vertical sub-grid turbulence mixing. Three standard approaches for representing horizontal diffusion produce starkly differing mixing rates, particularly for the entrainment mixing into updrafts, which differ by more than an order of magnitude between the schemes. The simulations demonstrate that the horizontal sub-grid mixing of water vapor is key, with high mixing rates a necessary condition for organization of convection to occur, since entrainment of dry air into updrafts suppresses convection. It is argued that diabatic budgets, while demonstrating the role of spatially heterogeneous radiative heating rates in driving organization, can overlook the role of physical processes such as updraft entrainment. These results may partially explain previous studies that showed that organization is more likely to occur at coarser resolutions, when entrainment is solely represented by subgrid-scale turbulence schemes, highlighting the need for benchmark simulations of higher horizontal resolution. The recommendation is for the use of larger ensembles to ensure robustness of conclusions to subgrid-scale parameterization assumptions when numerically investigating convective organization, possibly through a coordinated community model intercomparison effort.

NETCDF 3D output fields stored every 24 hours from the main experiments. All variables plotted in the paper are stored. For details of the experiment set up and the simulation names, please refer to the open access publication.Selected variables and the publications plots: Fig. 1 - QVAPOR and total pressure of the main experiments(smag3dpbl, smag3d, smag2dpbl, tke3dpbl) Fig. 2 - OLR of the main experiments Fig. 3 - QVAPOR and total pressure of the main experiments Fig. 4 - QVAPOR and total pressure of the main experiments Fig. 5 - W of the main experiments Fig. 6 - W of the main experiments Fig. 7 - QVAPOR and total pressure of the main experiments Fig. 8 - QVAPOR and total pressure of the main experiments Fig. 9 - ACLWTTEN, ACSWTTEN for simulation smag3dpbl only Fig. 10 - XKMH of the main experiments Fig. 11 - XKMH of the main experiments All the variables, Qvapor, OLR, W, XKMH and total pressure are stored in their corresponding experiment name, smag3dpb has additional sw and lw tendency variables.Fig. 12 - W of experiment UV-smag3dpbl and TQ-smag3dpblFig. 13 and Fig. 14 - xkmh and W values using various mixing strength of tke3dpbl experiments Fig. 15 - vertical velocity W is selected and their values are stored in hysteresis directory

Supplement to: Tompkins, Adrian Mark; Semie, Addisu G (2017): Organization of tropical convection in low vertical wind shears: role of updraft entrainment. Journal of Advances in Modeling Earth Systems