28th EWGLAM meeting, Zurich, October 2006 ALARO Physics developments at LACE Neva Pristov LACE Working group for physisc

28th EWGLAM meeting, Zurich, October 2006 ALARO physics package - introduction continous transition from ARPEGE/ALADIN to AROME (continuity + improvements) to treat ‘grey-zone’ 3-7 km mesh size economical computation, numerical efficiency algorithmic flexibility  good basis for further developments

28th EWGLAM meeting, Zurich, October 2006 Main developments topics Radiation Orographic forcing Large scale precipitation Prognostic turbulent scheme Precipitating convection Luc Gerard, J-M Piriou, D. Banciu, I.Stiperski, R. Brožkova, J-F Geleyn J-F Geleyn, G. Hello, N. Pristov, Y. Bouteloup, M. Derkova, J. Mašek, A.Trojakova, R. Fournier B. Carty, F. Bouyssel, R. Brožkova, J-F Geleyn, M. Derkova, R. Mladek, J. Cedilnik, D. Drvar, I. Beau B. Carty, J-F Geleyn, R. Brožkova, J. Cedilnik, D. Drvar F. Vana, J. Cedilnik, M. Tudor, J-F Geleyn, A.Simon

28th EWGLAM meeting, Zurich, October 2006 Radiation Aim: using the current delta-two stream approximation of radiative transfer equation for solar and thermal bands economical computation (a good quality cost ratio) better consideration of clouds New features: new technique for thermal radiative fluxes computation on the basis of Net Exchanged Rate (NER) formalism gaseous transmition functions for computation of optical depth closer to RRTM scheme introduction of the complete aerosol model updating of the cloud optical properties

28th EWGLAM meeting, Zurich, October 2006 Cloud optical properties availability of prognostic cloud water calls for more sophisticated treatment of clouds in radiative transfer static treatment of saturation effect in old scheme (clouds are too opaque in some circumstances) new scheme:  coefficients k_abs, k_scat dependent on cloud water content  dynamic treatment of saturation, taking into account cloud depth and geometry remain cheap, only two bands: solar and thermal

28th EWGLAM meeting, Zurich, October 2006 Cloud optical properties – strategy Dependency of coefficients k_abs, k_scat on cloud water content was fitted using experimental sample of 7 liquid and 16 ice cloud types Evaluation of saturation effect in idealized framework:  multi-layer delta-two stream system  only clouds taken into account, gases and aerosols ignored  cloud geometry with random or maximum overlaps between adjacent layers  atmosphere illuminated from one side by direct flux (solar) or diffuse flux (thermal), reflected and transmitted fluxes evaluated  broadband fluxes diagnosed by summing up monochromatic results computed for several hundred separate wavelengths

28th EWGLAM meeting, Zurich, October 2006 Cloud optical properties red – liquid clouds, blue – ice clouds, black – mixed clouds Saturation factor versus optical depth for homogeneous clouds, solar band k_absorbtionk_scatter

28th EWGLAM meeting, Zurich, October 2006 Cloud optical properties parameterized versus reference solar reflectance, sample of non-homogeneous 3 layer clouds old new

28th EWGLAM meeting, Zurich, October 2006 Cloud optical properties Solar absorbtion new (blue) versus old (red) scheme Problematic peak around model level 20

28th EWGLAM meeting, Zurich, October 2006 Statistical method for the weighting function in NER parameterized versus computed thermal flux

28th EWGLAM meeting, Zurich, October 2006 Pseudo-prognostic turbulent scheme pTKE the turbulent memory of the previous timesteps is kept the advection and diffusion of TKE are added to the current scheme more general computation of mixing length prognostic variable TKE

28th EWGLAM meeting, Zurich, October 2006 TKE vs pseudoTKE = advection + diffusion + mechanical or shear production/destruction + buoyancy production/consumption + viscous dissipation full = advection + diffusion + Newtonian relaxation towards stationary solution pseudo

28th EWGLAM meeting, Zurich, October 2006 Academic test with 1D model: GABLS II experiment

28th EWGLAM meeting, Zurich, October 2006 Mixing length computation - current formulation Empirical formula dependent on the height of the PBL (Ayotte, et al. 1996)  = f (z, h PBL ) -exponential function Increase of the mixing length with the PBL height (h PBL ) Modifications:    1,  2 = f (h PBL )

28th EWGLAM meeting, Zurich, October 2006 Tests with the BL89 parameterization Bougeault-Lacarrère (1989) : “non-local” mixing length dependent on TKE and integral buoyancy (used e.g. in ARPEGE and Mèso-NH) Direct application of BL89 in the pseudo-TKE scheme: numerically stable but not consistent with the original K- theory part (too large mixing length – increase of exchange coefficients and turbulent fluxes) Consequences:  systematic increase of TKE and winds at surface,  too big diffusion in the upper troposphere, danger of tropopause erosion

28th EWGLAM meeting, Zurich, October 2006 Merger with BL89 or TKE/N schemes current mixing length (GC) taken as a first guess additional information about TKE and buoyancy from the BL89 scheme, modulation with k-parameter more suitable for computation of K-coefficients Merger with TKE/N scheme (only extensively tested, 1-D evolution too noisy, not so good properties)

28th EWGLAM meeting, Zurich, October 2006 Academic test with 1D model: GABLS II experiment Vertical profile and time course of mixing length Modified GCGC +BL89 PBL top

28th EWGLAM meeting, Zurich, October D case: strong jet stream 15 December 2005, Northern Germany TKE and  cross-sections Modified GCBL89 AB only small TKE (no CAT) BA impact in jet-stream area higher TKE in the PBL

28th EWGLAM meeting, Zurich, October D case: strong jet stream GC+BL89: more feasible for PBL, TKE signals in jet region (CAT) but not too violent TKE/N: Too much TKE in upper troposphere GC +BL89GC +TKE/N

28th EWGLAM meeting, Zurich, October 2006 Mixing length - conclusion GC+BL89 : reasonable solution for both PBL and upper troposphere rather neutral results for surface parameters (wind, MSL pressure) tuning, more case studies in 3-D, verification (scores)

28th EWGLAM meeting, Zurich, October 2006 Large scale precipitation a simple micro-physics scheme with 5 water species included into precipitation scheme  cloud water, cloud ice, rain, snow - new prognostic variables  fluxes  statistical approach for sedimentation of rain and snow

28th EWGLAM meeting, Zurich, October 2006 ALARO-0 minus 3MT better space distribution of precipitation oper alaro 6h precipitation

28th EWGLAM meeting, Zurich, October 2006 ALARO-0 minus 3MT Vertical profiles of horizontal averaged values cloud water cloud ice

28th EWGLAM meeting, Zurich, October 2006 Plans Evaluation of parameterization developments  Technical and scientific validation  Case studies, verification Training Continuation of work  Convection (3MT)  More complex options