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

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 Development of the breeze everywhere along the coast Propagation speed:  10-20 km hr -1 (Bechtold et al., 1991) 25 June 2001 case study Very good agreement Bastin and Drobinski, QJRMS, in revision

5. coastline WIND observations between 1645 & 1710 UTC MESO-NH simulation at 1700 UTC References H / v relationship H / v at 43.5°N Rotunno (1983)N/(f 2 -  2 ) 1/2 146 Dalu and Pielke (1989)N/(f 2 +k  2 ) 1/2 75 Niino (1987); Steyn (1998)N/  138 Bastin et al. (AR, 2005)observations200 25 June 2001 case study: pure sea breeze

6. Sea breeze frontStructure Turbulent Kinetic Energy (TKE) e : u i ’ : turbulent components of the wind 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 sealand 25 June 2001 case study: pure sea breeze

7. Sea breeze front advectionBuoyant production Shear production DiffusionDissipation TKE budget: Structure 1214 1719 25 June 2001 case study: pure sea breeze

8. Mass fluxes 14 UTC 0 – 300 m300 – 1000 m front Slope winds convergence Slope winds + breeze detrainment Intensification of slope winds by the sea breeze Bastin and Drobinski, BLM, 2005 25 June 2001 case study: pure sea breeze

9. 14 UTC17 UTC11 UTC Massif Central wake Vallon d’Ol 22 June 2001 case study: combination with Mistral Bastin et al., MWR, in revision

10. Bastin et al., GRL, 2005 Vallon d’Ol Westerly wind North-westerly wind 22 June 2001 case study: combination with Mistral Flow regimeOnset Maximum depth DirectionIntensity Inland penetration Pure sea breeze08-10 UTC~ 1500 mS  5 m s -1 100 km Mistral/breeze11-17 UTC< 1000 mO/SO  5 m s -1 < 50 km

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