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NRL POST Stratocumulus Cloud Modeling Efforts

NRL POST Stratocumulus Cloud Modeling Efforts. Shouping Wang, William Thompson, Tracy Hack and Yi Jin. Research issues Wind shear impact on the entrainment and cloud structure Stratocumulus diurnal variation in Monterey Bay area

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NRL POST Stratocumulus Cloud Modeling Efforts

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  1. NRL POST Stratocumulus Cloud Modeling Efforts Shouping Wang, William Thompson, Tracy Hack and Yi Jin • Research issues • Wind shear impact on the entrainment and cloud structure • Stratocumulus diurnal variation in Monterey Bay area • Evaluation and improvement of stratocumulus simulation of COAMPS • Evaluation of thermodynamic fluxes in stratocumulus • Approaches • COAMPS-LES and COAMPS mesoscale modeling • Data analysis and comparison with model output • COAMPS real time forecast • Close collaboration with other PIs.

  2. Short wave heating Long wave cooling Subsidence Entrainment zi Turbulence Height Wind Shear Drizzle Sea Spray/aerosols 0 m Surface heat, moisture, and momentum fluxes Stratocumulus-topped Marine Boundary Layer

  3. 1000 900 800 Height (m) 700 C B D 600 500 B D C 400 12 h forecast profiles of buoyancy flux components for point2. 300 200 100 -.050 -.025 0.0 .025 .050 Vertical Profiles of Thermodynamic Fluxes In a Stratocumulus-topped, Entraining Boundary Layer D A B C • A is the total water flux • B is the liquid water flux • C is the liquid water • potential temperature • flux • A, B, and C sum • to D (the buoyancy flux

  4. Cloud Water Temperature Total water mixing ratio The Wind Shear Impact on the Entrainment and Cloud Structure Aircraft observations on 8 July 1999 in Monterey Bay area in DECS (from Qing Wang) • Strong wind shear exists at the top of clouds due to topography and land-sea contrast • What is the effect of the intense wind shear on the entrainment? • How does the wind shear affect the inversion structure? • what is the response of turbulence and cloud structure to the wind shear?

  5. Qt (g kg-1) U (m s-1) V (m s-1) Theta-L (K) Strong Shear Weak Shear No Shear Strong Shear l j k i Radiative Heating (K h-1) Qc (g kg-1) Shear Production (m2 s-3) Buoyancy Production (m2 s-3) The Wind Shear Impact on the Entrainment and Cloud Structure f e g h COAMPS-LES Simulation X=30m; Z=5-20m High-Resolution X=10m; Z=5m • The intense wind shear enhances the TKE buoyancy consumption, decreases the liquid water content, and reduces the radiative cooling near the cloud top.

  6. No Shear Weak Shear Inversion top Inversion base Cloud top Strong Shear Inversion top and base are defined by Cloud-top is defined by the level of the highest cloudy grid point. Wind Shear Impact on the Entrainment and Cloud Structure Wind shear across the inversion significantly change the inversion layer characteristics COAMPS-LES Simulations: • The entrainment mixing is enhanced by the wind shear; • A separation between the cloud top and inversion top is produced; • This separation layer thickness is proportional to the intensity of the wind shear. • Data need: soundings, entrainment zone, surface and cloud layer turbulence and cloud microphysics.

  7. 7:00 AM Jul 29 – 7:00 AM Jul 30, 2007 (PDT) 07Z29-07Z30 Diurnal Variation Monterey Bay Salinas Valley

  8. Diurnal Variation of Stratocumulus in Monterey Bay: COAMPS Simulation Bay Area Averaged Potential Temperature and Liquid Water Bay Area Averaged Vertical Motion Diurnal Variation • The cloud diurnal variation is caused by the diurnal change in mesoscale vertical motion, which is produced by the topography and the land surface diurnal heating. • Data need: Soundings (above and within PBL), surface and cloud layer turbulence and cloud microphysics during day and night if possible.

  9. Evaluation and Improvement of COAMPS Stratocumulus Simulation • Focus •  Entrainment, PBL height, cloud water, mesoscale variability. • Data need: Soundings (above and within PBL), surface and cloud layer turbulence and cloud microphysics • Turbulent fluxes, variances at various levels • Liquid water content, droplet number concentration, drizzle rate, SST, LW and SW fluxes • COAMPS real time forecast (James Doyle) • originally performed for AOSN (Adaptive Ocean Sampling Network) field campaign in the vicinity of Monterey Bay; now supported by CeNCOOS (http://www.cencoos.org) • can be used for POST field program; • has three grids (27, 9, 3km) and 40 levels; • produces 48 hours forecast output presented in a NRL website Diurnal Variation

  10. COAMPS AOSN Real-Time Forecast Liquid water mixing ratio Topography and Vertical Cross Sections 10 m Wind Vectors • http://www.nrlmry.navy.mil/coamps-web/web/mbay • Grid 3 (3km) output are shown • Surface, 3D fields and cross section • Meteograms from 12 locations

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