1D shallow convective case studies and comparisons with LES

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Derek Simpson
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1 1D shallow convective case studies and comparisons with CNRM/GMME/Méso-NH 24 novembre / 17

2 Contents 1 5h-6h time average vertical profils 2 2 / 17

3 Case description 5h-6h time average vertical profils Météorological situation : stationnary cumuli Non-precipitating cumuli which were the only type of cumulus convection that was observed during the undisturbed BOMEX period of phase 3 from 22 to 26 June 1969 over the ocean near Barbados. Prescribed forcings Large scale subsidence Radiative cooling Large scale horizontal advection of moisture Geostrophic wind 3 / 17

undisturbed BOMEX period of phase 3 from 22 to 26 June 1969 over the ocean near Barbados.

4 A new closure 5h-6h time average vertical profils Convective vertical velocity w Instead of the CAPE iterative closure, we directly compute the cloud bottom mass flux with a convective vertical velocity proportionnal to the shallow convective activity in the boundary layer (for exemple, Grant et al, 1999) M u (LCL) = ρ w S with w computed in the turbulence scheme as a function of the surface fluxes and the depth of the boundary layer. 4 / 17

the shallow convective activity in the boundary layer (for exemple, Grant et al, 1999) M u (LCL) = ρ w S with w

5 θ l vertical flux 5h-6h time average vertical profils τ = 1h 5 / 17

6 r t vertical flux 5h-6h time average vertical profils τ = 1h 6 / 17

7 θ l vertical flux 5h-6h time average vertical profils τ = 1h 7 / 17

8 r t vertical flux 5h-6h time average vertical profils τ = 1h 8 / 17

9 5h-6h time average vertical profils Cloud mixing ratio r c τ = 1h 9 / 17

10 Case description Meteorological situation : diurnal cycle of cumuli This case is based on observations at the ARM site on the Southern Great Plains (USA) on 21st june During that day, Cumulus clouds developed at the top of an initially clear convective boundary layer. Prescibed forcings Prescibed surface fluxes Large-scale forcings and radiation Geostrophic wind 10 / 17

During that day, Cumulus clouds developed at the top of an initially clear convective boundary

11 θ l vertical flux τ = 1/2h 11 / 17

12 r t vertical flux τ = 1/2h 12 / 17

13 θ l vertical flux τ = 1/2h 13 / 17

14 r t vertical flux τ = 1/2h 14 / 17

15 Cloud mixing ratio r c τ = 1/2h 15 / 17

16 Summary of «cloud physics for subgrid motions» In Arome/Méso-NH, the microphysics is the cloud/precipitation physics of grid scale motions. In Arome/Méso-NH, the turbulence scheme and the shallow convection scheme are quite well tuned for the subgrid transport of conservative variables (good pronostic evolution of conservative variables), but the «projection» of these variables on the cloud variables and θ is not yet well tuned. And it is an important problem for the interaction with radiation and with the surface. we are still working to improve the current schemes (see Christine s presentation) we cooparate with other communities (P.Soares/KNMI, Hirlam) 16 / 17

evolution of conservative variables), but the «projection» of these variables on the cloud variables and θ is not yet well tuned.

17 Summary of «cloud physics for subgrid motions» Everybody is welcome to help for the objective of a pre-operational model in 2006 or for a longer term evolution of Arome 17 / 17

Using Cloud-Resolving Model Simulations of Deep Convection to Inform Cloud Parameterizations in Large-Scale Models

Using Cloud-Resolving Model Simulations of Deep Convection to Inform Cloud Parameterizations in Large-Scale Models S. A. Klein National Oceanic and Atmospheric Administration Geophysical Fluid Dynamics