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Update on model developments: Meteo-France NWP model / clouds and turbulence

Jean-Marcel Piriou Centre National de Recherches Météorologiques Groupe de Modélisation pour l’Assimilation et la Prévision. Update on model developments: Meteo-France NWP model / clouds and turbulence. CLOUDNET workshop / Paris 27-28/05/2002. Summary.

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Update on model developments: Meteo-France NWP model / clouds and turbulence

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  1. Jean-Marcel Piriou Centre National de Recherches Météorologiques Groupe de Modélisation pour l’Assimilation et la Prévision Update on model developments: Meteo-France NWP model / clouds and turbulence CLOUDNET workshop / Paris 27-28/05/2002

  2. Summary • How may 1D studies improve 3D models? Example of the EUROCS project, links with CLOUDNET • Clouds and turbulence: present developments and perspectives of the ARPEGE/ALADIN NWP model

  3. Global ARPEGE Aquaplanet mode SCM ARPEGE (EUROCS, GATE, TOGA,BOMEX, ARM, …) Global regular ARPEGE / 4DVAR-ass./ 100 km PHYSICS LAM ALADIN / coupled/ 10 km Global stretched ARPEGE / 4DVAR-ass./ 20 to 200 km

  4. Diurnal cycleof convection / JJA Observations Yang and Slingo MWR 2001 ARPEGE NWP Model J.M. Piriou 2002 IFS NWP Model Beljaars 2002 Unified Climate Model Yang and Slingo MWR 2001

  5. Concentrates on 4 major well identified deficiencies of climate models: • stratocumulus over ocean • diurnal cycle of shallow cumulus • sensitivity of deep convection to mid-atmosphere humidity • diurnal cycle of deep convection over land • Bring together a community of modelers : hierarchy of scales • LES & CRMs --- SCMs --- RCMs & GCMs obs obs clouds GCM picture from Colostate web page D z=70m to 600m LES: Large Eddy Simulation CRM: Cloud Resolving Model SCM: Single Column Model RCM: Regional Climate Model GCM: General Circulation Model D x= D y= 1km EUROCS : EUROpean Cloud Systems 3-year project funded by the European Union (Mar 2000 – Feb2003) Final aims: to improve the treatment of cloud systems in global and regional climate models Links with GCSS (GEWEX Cloud System Study) for more infos: www.cnrm.meteo.fr/gcss/EUROCS/EUROCS.html & J.-L. Redelsperger

  6. Diurnal cycle of deep convection(Françoise Guichard, Météo-France)

  7. COMMON CRMs/SCMs CASE STUDY 1 : an « observed case » to assess our models over land (GCSS/ARM) Southern Great Plains • GCSS WG4 Case3a • 4-day runs with deep convection occuring • large-scale advections prescribed from observations • fixed surface heat fluxes • wind nudged towards observed • cyclic lateral boundary conditions • case part of the GCSS intercomparaison exercise for • CRMs Xu et al. (2002) & SCMs (Xie et al. 2002) 2 : building an « idealized case » to address the diurnal cycle of deep convection over land and its representation in models ARM : Atmospheric Radiation measurement

  8. THE IDEALIZED CASE • same framework of previous case except: • 27 Mai 1997 of GCSS case 3 repeated twice large-scale vert. adv. (relatively weak) & prescribed surf. fluxes • 48 h run, begins in the morning instead of the evening results still preliminary, work in progress • rainfall events tend to occurs earlier in SCMs than CRMs (2 SCMs missing) • + similar findings (e.g., noise & no or weak downdraughts)

  9. MAX CLOUD TOP HEIGHT SCM CRM runs (m) THE IDEALIZED CASE: transition regimes transition phase: not represented in several SCMs snapshots of cloud + rain water content in CRM run a « shallow » non-precipitating transition period which last a few hours in CRMs before the development of deep convection 15 km Lx: 300 km

  10. THE IDEALIZED CASE : CIN • almost no CIN in SCM runs during daytime (true for at least 4 SCMs) ! • apparently not simply a resolution problem • challenging for CRMs too • strongly modulated by convective activity • in CRMs runs, deep convection increases the CIN • possibly related to convective downdraughts (?)

  11. CONCLUSIONS from diurnal cycle of deep convection case • deep convection often occurs earlier than observed in SCMs runs too • no succession of dry-shallow-deep regimes in SCMs, dry to deep directly • complex sensitivity to triggering criteria & downdraughts formulation • no CIN during daytime & weak downdraughts ( a link?)

  12. Diurnal cycle of shallow cumulus (Geert Lenderink, KNMI)

  13. EUROCS: Marine stratocumulus case(Peter Duynkerke, IMAU)

  14. EUROCS marine stratocumulus case

  15. Perspectives for the ARPEGE/ALADIN physics • March towards new prognostic cloud and turbulence variables: ql/i, qr/s, TKE, w_ud, w_dd • EUROCS: 4 validation cases (next 12 months) • CLOUDNET: colocated ql/i, qr/s, PBL depth, cloudiness, close TEMP data to provide in-situ validation of new microphysics / turbulence (in some months?)

  16. Conclusions / perspectives • During the last years 1D studies have become more and more important to develop and validate 3D models physical packages • Both EUROCS (well posed lateral conditions) and CLOUDNET (long time series) will be used as a test-bed for the new cloud physics and turbulence

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