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Simulations of thermal circulations over complex terrain during ESCOMPTE using Méso-NH

Simulations of thermal circulations over complex terrain during ESCOMPTE using Méso-NH. Sophie Bastin + and Philippe Drobinski. Institut Pierre Simon Laplace/ Service d’Aéronomie. + : Current affiliation: NCAR, Boulder, CO, USA. What is at stake?.

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Simulations of thermal circulations over complex terrain during ESCOMPTE using Méso-NH

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  1. Simulations of thermal circulations over complex terrain during ESCOMPTE using Méso-NH Sophie Bastin+ and Philippe Drobinski Institut Pierre Simon Laplace/ Service d’Aéronomie +: Current affiliation: NCAR, Boulder, CO, USA

  2. What is at stake? • Better understanding and forecast of pollution episodes in the Marseille area: • numerous and intensive pollution events during summertime that are not well forecasted • Poor understanding of the atmospheric boundary-layer dynamical processes in this region that play a major role in the distribution of pollutants • Improvement of chemistry-transport models • Generalisation at other areas Study of the atmospheric boundary layer dynamics at the scale of the ESCOMPTE area during summertime

  3. Méso-NH simulations • 50 vertical levels from the surface to 18 km: • 12 levels in the first 1000 m • 9 levels with a grid size less than 100 m • 2 simulations with 2 or 3 nested domains: • Resolution of the finest domain: 2 or 3 km • Initialisation and forcing with ECMWF analyses

  4. Triangles: model Solid line: surface stations 25 June 2001 case study: pure sea breeze Bastin and Drobinski, QJRMS, in revision 25 June 2001 case study Very good agreement • Development of the breeze everywhere along the coast • Propagation speed:  10-20 km hr-1 (Bechtold et al., 1991)

  5. coastline 25 June 2001 case study: pure sea breeze WIND observations between 1645 & 1710 UTC MESO-NH simulation at 1700 UTC

  6. Turbulent Kinetic Energy (TKE) e : ui’: turbulent components of the wind 25 June 2001 case study: pure sea breeze Sea breeze front Structure 1200: convection over land where there is no sea breeze flow. 1400: strong upward and mixing at the breeze ‘head’ 1700: decrease of upward and mixing 1900: no more TKE sea land

  7. 25 June 2001 case study: pure sea breeze Sea breeze front Structure TKE budget: Shear production advection Buoyant production Diffusion Dissipation 12 14 17 19

  8. 25 June 2001 case study: pure sea breeze Mass fluxes 14 UTC 0 – 300 m 300 – 1000 m Slope winds Slope winds + breeze detrainment front convergence Intensification of slope winds by the sea breezeBastin and Drobinski, BLM, 2005

  9. Massif Central wake Vallon d’Ol 11 UTC 14 UTC 17 UTC 22 June 2001 case study: combination with Mistral Bastin et al., MWR, in revision

  10. Vallon d’Ol North-westerly wind Westerly wind Bastin et al., GRL, 2005 22 June 2001 case study: combination with Mistral

  11. Publications Bastin S., Drobinski P., Guénard V., Caccia J.L., Campistron B., Dabas A. M., Delville P., Reitebuch O., Werner C.: On the Interaction Between Sea Breeze and Summer Mistral at the Exit of the Rhône Valley. Mon. Wea. Rev., in revision Bastin S., Drobinski P.: Sea Breeze Induced Mass Transport over Complex Terrain in Southeastern France: A Case Study. Quart. J. Roy. Meteorol. Soc., in revision Bastin S., Champollion C., Bock O., Drobinski P., Masson F., 2005: On the Use of GPS Tomography to Investigate Water Vapor Variability During a Mistral/Sea Breeze Event in Southeastern France.Geophys. Res. Let, 32, L05808, doi:10.1029/2004GL021907 Bastin S., Drobinski P., Dabas A.M., Delville P., Reitebuch O., Werner C., 2005: Impact of the Rhône and Durance Valleys on Sea-Breeze Circulation in the Marseille Area. Atmos. Res., 74, 303-328 Bastin S., Drobinski P., 2005: Temperature and Wind Velocity Oscillations along a Gentle Slope during Sea-Breeze Events. Boundary Layer Meteorol., 114, 573-594

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