1 / 35

The composite Lagrangian cases: LES intercomparison

The composite Lagrangian cases: LES intercomparison. Irina Sandu, Andy Ackerman, Peter Blossey, Chris Bretherton, Johan van der Dussen, Adrian Lock, Stephan de Roode, Bjorn Stevens. Lagrangian analysis of the air mass flow. How?. Trajectories + Re-analysis + Satellite data.

sienna
Download Presentation

The composite Lagrangian cases: LES intercomparison

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. The composite Lagrangian cases:LES intercomparison Irina Sandu, Andy Ackerman, Peter Blossey, Chris Bretherton, Johan van der Dussen, Adrian Lock, Stephan de Roode, Bjorn Stevens

  2. Lagrangian analysis of the air mass flow How? Trajectories + Re-analysis + Satellite data MODIS (Terra, Aqua) AMSR-E HYSPLIT (ERA-INTERIM) ERA-INTERIM 2002-2007 (May to October in NE, July to December SE) Starting time: 11 LT, Duration: 6 days, Height: 200m When? Where? Klein&Hartmann (1993) zones : NE/SE Atlantic, NE/SE Pacific NEP NEA SEA SEP Sandu, Stevens and Pincus, ACP, 2010

  3. An ensemble of composite cases: slow, intermediate and fast transitions CF MODIS ref slow fast Composites NEP JJA 2006-2007 3 days D LTS SST

  4. Our questions • Are the LES able to reproduce: • the observed changes in cloudiness induced by changes in the SST/LTS? • the transition’s pace and its dependence on the inversion strength? • Do they agree in term of : • The decrease in cloud albedo and cloud cover during the 3 days • The time evolution of the cloud fraction • The growth rate of the boundary layer

  5. Outline Simulations : initial conditions, requirements, models First results for the reference case The fast/slow cases Conclusions & Next steps

  6. Composite REF case : NEP - JJA 2006-2007 Initial profiles (10 LT) Forcing qt (g/kg) l (K) SST (K) Calipso Time (days) v (m/s) u (m/s) D (x106 s-1) Time (days)

  7. Initial conditions ql l ref slow fast SST Cts divergence (the same) No advective tendency

  8. Simulations • initial time : 10 LT, duration: 72 hours • initial date: 15 July (but 15 June for UCLA ) • diurnal cycle of solar radiative forcing taken into account • cloud droplet number concentration: 100 cm-3 • resolution : x = 35m, z = 5m (at cloud top) • domain size : 4.48 X 4.48 X 3.2 km (128 x 128 X 428 points)

  9. Models & participants REF FAST SLOW           • UCLA-LES (Irina Sandu) • DALES (Johan van der Dussen, Stephan de Roode) • UKMO (Adrian Lock) • SAM (Peter Blossey, Chris Bretherton) • DHARMA (Andy Ackerman)

  10. Outline Simulations : initial conditions, requirements, models First results for the reference case The fast/slow cases Conclusions & Next steps

  11. Difficult to compare to the observed cloud cover UCLA ( ! Qualitative comparison only)

  12. The simulated SCT (UCLA – big domain) Albedo decreases by 41 %

  13. The simulations capture the major observed features of the SCT, and corroborate the conceptual model proposed by Bretherton (1992) to explain it w’v’ UCLA CF

  14. Do the models agree? (I –time series)

  15. Do the models agree? (I – time series)

  16. Hopefully, it does not matter a lot…

  17. Do the models agree ? (II – decoupling) w’v’ (10-4 m2/s3) UCLA SAM DALES DHARMA

  18. Do the models agree ? (III – cloud fraction) Cloud fraction UCLA SAM DALES DHARMA

  19. Do the models agree ? (IV – entrainment rate)

  20. Do the models agree ? (V – FT state) l qt ql qr CF w’’v LW w’2 SW

  21. Do the models agree ? (V – FT state) l qt ql qr CF w’’v LW w’2 SW

  22. Do the models agree ? (V – FT state) l qt ql qr CF w’’v LW w’2 SW

  23. Is there a drift in time ? (UCLA) 1h 12h 24h 36h 48h 60h 68h

  24. Is there a drift in time ? (SAM) 1h 12h 24h 36h 48h 60h 68h

  25. Is there a drift in time ? (DALES) 1h 12h 24h 36h 48h 60h 68h

  26. Is there a drift in time ? (DHARMA) 1h 12h 24h 36h 48h 60h 68h

  27. Outline Simulations : initial conditions, requirements, models First results for the reference case The fast/slow cases Conclusions & Next steps

  28. Slow against fast SCT (UCLA – big domain)

  29. Slow against fast SCT

  30. Role of the inversion strength

  31. Role of the inversion strength Boundary layer growth rate during the first 24 hours

  32. Conclusions • LES reproduce well not only the main features of the SCT, but also subtle details like differences between slow and fast transitions (UCLA) • The SCT timescale is mostly related to the strength of the temperature inversion capping the Sc topped boundary layer (UCLA) • striking resemblance of the 4 simulations of the reference case (differences well rather understood)

  33. Next steps • fix l,qt at 3km • check why LWD is different in DHARMA (fix LWD) • correct surface fluxes in UCLA-LES • re-run the 3 cases (same domain) - perhaps just the reference case in the beginning

More Related