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The ASTEX Lagrangian model intercomparison case

The ASTEX Lagrangian model intercomparison case. Stephan de Roode and Johan van der Dussen TU Delft, Netherlands. The ASTEX First Lagrangian (June 1992). Flight 1. Flight 2. Flight 3. Flight 4. Flight 5.  Lagrangian evolution of cloudy boundary layer observed

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The ASTEX Lagrangian model intercomparison case

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  1. The ASTEX Lagrangian model intercomparison case Stephan de Roode and Johan van der Dussen TU Delft, Netherlands

  2. The ASTEX First Lagrangian (June 1992) Flight 1 Flight 2 Flight 3 Flight 4 Flight 5  Lagrangian evolution of cloudy boundary layer observed  Five aircraft flights  Duration: two days

  3. ASTEX observed stratocumulus to cumulus transition Bretherton and Pincus, 1995 Bretherton et al, 1995 Duynkerke et al, 1995 De Roode and Duynkerke, 1997 GCSS case, 1995 EUCREM/GCSS, Duynkerke et al, 1999 like GCSS ATEX case, Stevens et al, 2001 Study of ASTEX First Lagrangianwtih SCM and 2D models byBretherton et al, 1999: "there are substantialquantitativedifferences in the cloud cover and liquid water pathbetween models."

  4. Satellite images Flights 1 and 5 latitude longitude preciseposition air massduring last flightuncertain

  5. Observations

  6. Contents Motivation  LES results Cloudlayerdepthevolutionanalysis  SCM results Conclusions/outlook

  7. ASTEX case: motivation stratocumulus to cumulus transitioncontroledby - SST, large-scaledivergence, inversionstability -> sensitivity tests Use ASTEX observations to validate LES & SCM results of a transition additionaldiagnosticsfrom LES -eddydiffusivity, PDFs of heat and moisture, mass flux statistics, 3D fields

  8. Motivationfor a revised ASTEX case current LES: Detailedmicrophysics Multibandradiation Longersimulation time GCSS ASTEX A209 case, 1995 EUCREM/GCSS, Duynkerke et al, 1999 Only 3~4 hourssimulation time

  9. Model initialization Model set up and large-scaleforcing Large-scaleforcing (SST & large-scalesubsidence) fromBretherton et al. (1995, 1999)  Model initializationfromFlight 2 (A209) - Identical to first GCSS ASTEX "A209" modelingintercomparison case Microphysics: drizzle and cloud droplet sedimentation Shortwave and longwaveradiation Bretherton ERA-40 mean in ASTEX triangle ERA-Interim ERA-Interim

  10. LES participants

  11. Use SCM version that is identical to the operational GCM

  12. Contents Motivation  LES results Cloudlayerdepthevolutionanalysis SCM results Conclusions/outlook

  13. Cloud boundaries: all LES models give cumulus under stratocumulus inversionheight DALES: large domain are shown meancloud base height lowestcloud base height DHARMA UKMOSAM UCLADALES Boundarylayertoodeepcompared to observations Last 10 hours of simulations are lessreliable (spongelayer, coarserverticalresolution)

  14. Cloud liquid water path DHARMA UKMOSAM UCLADALES Largedifference in LWP!

  15. Cloud cover DHARMA UKMOSAM UCLADALES

  16. Surface precipitation 180 W/m2 DHARMA UKMOSAM UCLADALES More heavy and intermittentprecipitationon a larger domain

  17. Entrainment rates in previous LES intercomparison runs too large? Heus et al. (2010)

  18. Entrainment DHARMA UKMOSAM UCLADALES Entrainmentratedoublesduring the secondnight Entrainmentrate smaller thanduringprevious ASTEX intercomparison case. According to Ackerman and Brethertonthis is due to cloud droplet sedimentationleading to a reduction of evaporativecooling at cloud top.

  19. Liquid water potential temperature DHARMA UKMOSAM UCLADALES Slightdifferences in the upper part of domain: - DALES & UCLA used ASTEX A209 specswith constant lapserate - ASTEX Lagrangian:blend of observations and ERA 40 (neededforradiation and single-column models)

  20. Total water content DHARMA UKMOSAM UCLADALES Mean state duringfirst part of ASTEX Lagrangian is wellrepresented

  21. Liquid water content DHARMA UKMOSAM UCLADALES last part of simulation: wrong cloudheight

  22. East-west wind component DHARMA UKMOSAM UCLADALES Change in geostrophicforcingwellimplemented

  23. North-south wind component DHARMA UKMOSAM UCLADALES Do we need a largerweakening of the geostrophicforcing?

  24. Vertical wind velocity variance DHARMA UKMOSAM UCLADALES

  25. Horizontal wind velocity variance DHARMA UKMOSAM UCLADALES More variance at a larger horizontal domain

  26. Horizontal wind velocity variance DHARMA UKMOSAM UCLADALES More variance at a larger horizontal domain

  27. Total water variance DHARMA UKMOSAM UCLADALES Larger horizontal domain cancontain more variance

  28. Precipitation DHARMA UKMOSAM UCLADALES

  29. Jump in downward longwaverad smaller in observations

  30. Longwave down Obst=36h DHARMA UKMOSAM UCLADALES Presence of high cloudsduringlatter part of transition. A largerlongwaveradiativecoolingratewillcause a largerentrainmentrate and deeperboundarylayers

  31. Shortwave down DHARMA UKMOSAM UCLADALES UCLA: Solarzenithangle DALES: Error in radiationstatistics of ASTEX version of the model

  32. Estimate large-scale divergence from LES radiation in free atmosphere Bretherton and Pincus (1995) Estimateddivergence = 2~3 10-6 s-1duringLagrangian

  33. In constant divergence run stratocumulusvanishes, and longwaveradiativecooling at cloud top becomesverysmall we (cm/s) Large-scaledivergence, entrainment (we) and liquid water path (LWP) LWP (g/m2)

  34. Cloud cover (cc) and cloud boundaries average cloud top average cloud base lowest cloud base  Divergence decreasing: deep solid stratocumulus  Divergence constant: shallow cumulus

  35. Contents Motivation  LES results Cloudlayerdepthevolution  SCM results Conclusions/outlook

  36. Cloud base height evolution qsat qT z (m) cloud base (g/kg)

  37. Cloud base height evolution qsat qT z (m) cloud base (g/kg)

  38. Cloud base height evolution qsat qT cloud base z (m) (g/kg)

  39. Tendencies in mixed layer drizzle

  40. Cloud base height evolution

  41. Cloud base and top height evolution if rad cooling Positivew ("upsidence") deepenscloudlayer!

  42. Cloud base and top height evolution increasewith time of: - cloud top height - cloudlayerdepth rcpwq_zbase= 11.3 W/m2 rLvwq_zbase = 60.0 W/m2 DLW= 74.0 W/m2 Div = 5.0 10-6 s-1 zbase = 300 m, zi= 600 m DqL =5K, DqT = -1.1 g/kg

  43. Example:Dycoms rcpwq_zbase= 11.3 W/m2 rLvwq_zbase = 60.0 W/m2 DLW= 74.0 W/m2 Div = 5.0 10-6 s-1 zbase = 500 m, zi= 800 m DqL =12K, DqT = -9.1 g/kg

  44. Contents Motivation  LES results Cloudlayerdepthevolution  SCM results Conclusions/outlook

  45. SCM cloud boundaries Deepening of boundarylayer is wellrepresented

  46. SCM LWP Liquid water pathvariation is large

  47. SCM total cloud cover

  48. SCM surface precipitation Similardiffusivitiesformoisture and heat?

  49. East-west wind velocity

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