1 / 50

Jason Milbrandt Recherche en Pr é vision Num é rique [RPN]

A New Multi-Moment Cloud Microphysics Package for the GEM-LAM. Jason Milbrandt Recherche en Pr é vision Num é rique [RPN] Meteorological Research Division, Environment Canada GEM Workshop, June 12, 2007. Why develop a new cloud scheme for GEM? Computer resources increasing

bairn
Download Presentation

Jason Milbrandt Recherche en Pr é vision Num é rique [RPN]

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. A NewMulti-Moment Cloud Microphysics Packagefor the GEM-LAM Jason Milbrandt Recherche en Prévision Numérique [RPN] Meteorological Research Division, Environment Canada GEM Workshop, June 12, 2007

  2. Why develop a new cloud scheme for GEM? • Computer resources increasing • High-resolution NWP grids are becoming mainstream • Important to predict cloud processes as well as possible • GEM-LAM-2.5 has systematic problems with the precipitation forecasts

  3. OUTLINE • Background on bulk schemes • Description of the new microphysics package • Some advantages of the multi-moment approach

  4. One of the goals of NWP model: Predict the effects of the clouds

  5. MODEL GRID: (hypothetical NWP model) CPS CLOUDY (RH = 100%) EXPLICIT SCHEME CLOUD- FREE PARTLY CLOUDY (RH < 100%)

  6. Single cloudy grid element: CLOUDY (RH = 100%) EXPLICIT SCHEME

  7. Single cloudy grid element – interaction with NWP model: INPUT: w, T, p, qv

  8. MICROPHYSICAL PROCESSES in thecloudy grid element

  9. Single cloudy grid element – interaction with NWP model: MICROPHYSICAL PROCESSES • OUTPUT: • Latent heating • Hydrometeors • (cloud, rain, ice,…) •  qc, qr, qi, ... qc, qr, qi, ... Changes to w, T, p, qv and qc, qr, qi, ... Advection and Turbulent Mixing INPUT: w, T, p, qv

  10. Single cloudy grid element: Slight magnification = cloudy (saturated) air

  11. Single cloudy grid element: Extreme magnification

  12. Single cloudy grid element: Extreme magnification

  13. 1 m3 (unit volume) [e.g. Cloud droplets] (not to scale)

  14. 101 N(D) 100 [m-3 m-1] 10-1 10-2 0 40 20 80 60 100 D [ m] 1 m3 (unit volume) [e.g. Cloud droplets] (not to scale)

  15. 101 N(D) 100 [m-3 m-1] 10-1 10-2 0 40 20 80 60 100 D [ m] 1 m3 (unit volume) (Example of observed cloud droplet spectrum) [e.g. Cloud droplets] (not to scale)

  16. 101 N(D) 100 [m-3 m-1] 10-1 10-2 0 40 20 80 60 100 D [ m] Representing the size spectrum DISCRETE SIZE BINS 1 m3 (unit volume) SPECTRAL METHOD [e.g. Cloud droplets] (not to scale)

  17. 101 N(D) 100 [m-3m-1] 10-1 10-2 0 40 20 80 60 100 D [ m] Representing the size spectrum ANAYLTICAL FUNCTION 1 m3 (unit volume) BULK METHOD [e.g. Cloud droplets] (not to scale)

  18. Varying l: (N0 and a constant) Varying N0: (l and a constant) Varying a: (Q* and N0 constant) log N(D) log N(D) log N(D) D [mm] D [mm] D [mm] INCREASING VALUES (of l, N0 and a) Gamma Distribution Function: * Q = r q (mass content)

  19. BULK METHOD Total number concentration, NTx 101 N(D) 100 Hydrometeor Category x 10-1 10-2 Mass mixing ratio, qx 0 40 20 80 60 100 D Radar reflectivity factor, Zx Size Distribution Function: Example of Moments: pth moment:

  20. BULK METHOD Total number concentration, NTx Mass mixing ratio, qx Radar reflectivity factor, Zx Size Distribution Function: Example of Moments: Predict changes to specific moment(s) e.g. qx, NTx, ... Implies changes to values of parameters i.e. N0x, lx, ... pth moment:

  21. T < 0C * * (May contain traces of supercooled water)

  22. T < 0C = ICE CRYSTAL (May contain traces of supercooled water)

  23. T < 0C        = ICE CRYSTAL  = SNOW CRYSTAL / AGGRETATE (May contain traces of supercooled water)

  24. T < 0C            = ICE CRYSTAL  = SNOW CRYSTAL / AGGREGATE  = GRAUPEL (May contain traces of supercooled water)

  25.          T < 0C = ICE CRYSTAL  = SNOW CRYSTAL / AGGREGATE  = GRAUPEL = HAIL (May contain traces of supercooled water)

  26.          T < 0C = ICE CRYSTAL  = SNOW CRYSTAL / AGGREGATE  = GRAUPEL = HAIL = LIQUID WATER

  27.          PARTITIONING THE HYDROMETEOR SPECTRUM SNOW LIQUID WATER ICE HAIL GRAUPEL

  28.          PARTITIONING THE HYDROMETEOR SPECTRUM SNOW CLOUD ICE HAIL GRAUPEL RAIN

  29. BULK METHOD           PARTITIONING THE HYDROMETEOR SPECTRUM SNOW CLOUD ICE HAIL GRAUPEL RAIN

  30. Milbrandt-Yau CloudScheme* Full TRIPLE-MOMENT Version: • Six hydrometeor categories: • 2 liquid: cloud and rain • 4 frozen: ice, snow, graupel and hail • ~50 distinct microphysical processes • Warm-rain scheme based on Cohard and Pinty (2000a) • Ice-phase based on Murakami (1990), Ferrier (1994), Meyers et al. (1997), Reisner et al. (1998), etc. • Predictive equations forZx added for triple-moment* *Milbrandt and Yau (2005a,b) [J. Atmos. Sci.]

  31. Milbrandt-Yau CloudScheme* Diagnostic-Dispersion DOUBLE-MOMENT Version: Identical to full version except: • Diagnostic-ax relations added for double-moment* Recall: Size Distribution Function:

  32. Milbrandt-Yau CloudScheme CURRENT VERSIONS AVAILABLE FOR GEM: GEM_v3.2.2 / PHY_4.4 available upon request** GEM_v3.3.0 / PHY_4.5 part of official RPN/CMC library Single-moment version • Six hydrometeor categories • Single-moment (Qx) for each Double-moment version • Six hydrometeor categories • double-moment (Qx,, Nx) for each • fixed-ax **(also available for MC2_v4.9.8)

  33. Milbrandt-Yau CloudScheme UPCOMING VERSION AVAILABLE FOR GEM: Prototype cloud scheme for the 2010 Winter Olympics “Olympic” version * CLOUD double-moment (Qc, Nc) RAIN double-moment (Qr, Nr) [diagnostic-ar] ICE/SNOW double-moment (Qi, Ni) [hybrid category] GRAUPEL single-moment (Qg) HAIL double-moment (Qh, Nh) [diagnostic-ah] * To be implemented in GEM-LAM 2.5 km AUTUMN 2007

  34. Advantages of multi-moment approach: Prognostic Nc Double-Moment “CLOUD” Category: • Condensation rate based on saturation adjustment • Nc initialization is air-mass (CCN) dependent

  35. Advantages of multi-moment approach: CCN-dependent Nc nucleation: 103 CONTINENTAL 102 MARITIME NCCN (cm-3) 101 100 10-1 10.0 0.1 1.00 0.01 SUPERSATURATION (%)

  36. Qc (Cloud Mixing Ratio)

  37. Nc (Cloud Number Concentration)

  38. Dc (Cloud Mean-Mass Diameter)

  39. DRIZZLE Advantages of multi-moment approach: The warm-rain coalescence process RAIN CLOUD Mass Density [g m-3 (lnr)-1] Time [min] Radius [cm] Bin-resolving coalescence modelSOURCE: Berry and Reinhardt (1974)

  40. Advantages of multi-moment approach: DRIZZLE vs. RAIN Qr Mass Content [g m-3] RAIN 0.1–1 mm STRATIFORM RAIN Dr Mean Diameter [mm] DRIZZLE

  41. Advantages of multi-moment approach: SEDIMENTATION Analytic bin model calculation:(1D column) Mass Content Total Number Concentration Equivalent Reflectivity Mean-Mass Diameter INITIAL 5 min z [km] 10 min 15 min 20 min Dm[mm] Q[g m-3] NT[m-3] Ze[dBZ] Contours every 5 min

  42. SEDIMENTATION: Bulk scheme DM = mass-weighted fall velocity = number-weighted fall velocity TM = reflectivity-weighted fall velocity SM

  43. SINGLE-moment scheme (SM): z [km] Dm [mm] Q [g m-3] NT [m-3] Ze [dBZ] ANALYTIC BIN model (ANA): INITIAL 5 min z [km] 10 min 15 min 20 min Dm [mm] Q [g m-3] NT [m-3] Ze [dBZ]

  44. DOUBLE-moment scheme, FIXED DISPERSION (a = 0): z [km] Dm [mm] Q [g m-3] NT [m-3] Ze [dBZ] ANALYTIC BIN model (ANA): INITIAL 5 min z [km] 10 min 15 min 20 min Dm [mm] Q [g m-3] NT [m-3] Ze [dBZ]

  45. DOUBLE-moment scheme, DIAGNOSTIC DISPERSION, a = f (Dm): z [km] Dm [mm] Q [g m-3] NT [m-3] Ze [dBZ] ANALYTIC BIN model (ANA): INITIAL 5 min z [km] 10 min 15 min 20 min Dm [mm] Q [g m-3] NT [m-3] Ze [dBZ]

  46. TRIPLE-moment scheme: z [km] Dm [mm] Q [g m-3] NT [m-3] Ze [dBZ] ANALYTIC BIN model (ANA): INITIAL 5 min z [km] 10 min 15 min 20 min Dm [mm] Q [g m-3] NT [m-3] Ze [dBZ]

  47. INITIAL 5 min 10 min z [km] 15 min 20 min Q [g m-3] z [km] DOUBLE- MOMENT Fixed a = 0 DOUBLE- MOMENT Diagnosed a TRIPLE- MOMENT Prognosed a SINGLE- MOMENT Q [g m-3] Q [g m-3] Q [g m-3] Q [g m-3] Advantages of multi-moment approach: SEDIMENTATION Analytic model: Mass Content Bulk schemes:

  48. Advantages of multi-moment approach: MASS ≠ SIZE SNOW (large crystals / aggregates) Qs Mass Content [g m-3] 0.1 - 4 mm Ds Mean Diameter [mm] (equivalent sphere)

  49. SUMMARY • Efficient single-moment and double-moment versions of the Milbrandt-Yau scheme are available for GEM-LAM • Single-moment version will be proposed as the operational scheme for GEM-LAM_2.5 by fall 2007 • New version (“semi-double-moment”) will be developed and tested for implementation by spring 2007 • Large-scale version (diagostic cloud-fraction; fewer prognostic variables) to be developed soon • For code, support, bug reports, or question: • Jason.Milbrandt@ec.gc.ca

  50. MERCI

More Related