1. Atmospheric Boundary Layer evening transitions: a comparison between two experimental sites (CIBA-Spain and BLLAST-France) M. Sastre (1), C. Yagüe (1), C. Román-Cascón (1), G. Maqueda (2). (1) Dept. Geofísica y Meteorología. University Complutense of Madrid, Spain. (msastrem@fis.ucm.es) (2) Dept. Astrofísica y Ciencias de la Atmósfera. University Complutense of Madrid, Spain. 12th EMS Annual Meeting & 9th European Conference on Applied Climatology (ECAC) EUROPEAN METEOROLOGICAL SOCIETY 11 th September 2012

2. Contents 1.- Introduction 2.- Methodology 3.- Experimental data 4.- WRF model 5.- Results 6.- Summary and conclusions

3. 1.- Introduction Evening transition processes in the ABL: from convection to stability Comparison at two experimental sites Simulations: differences between sites?

4. 2.- Methodology Data from two experimental sites: CIBA site (Spain) and the BLLAST campaign site (France). x x

5. 2.- Methodology 1 P BLLAST campaign site: land-use Forest pines moor crops Forest deciduous village industrial town meadow corn meadow

6. 2.- Methodology Data from two experimental sites: CIBA site (Spain) and the BLLAST campaign site (France). Days studied from two summer periods: 2009 (CIBA) and 2011 (BLLAST). Times related to sunset for every site and day (t=0 => t sunset ). Simulations using WRF model. MRFD technique employed. x x

7. 3.- Experimental data Sonic anemometer (CIBA and BLLAST) BLLAST 60m-tower instruments (2, 15, 30, 45, 60 m) CIBA 10m-mast instruments (1.5, 3, 5, 7.5, 10 m) Focus on: Wind speed and direction Temperature Turbulent parameters Friction velocity:

8. 4.- WRF model  Initial and boundary conditions from NCEP-NCAR (1º resolution; data every 6 hours).  4 nested domains whose grids are: 27, 9, 3 and 1km.  Time step: 81 seconds.  50 eta vertical levels.  Spin up: 12 h.  SW radiation: Dudhia (1998).  LW radiation RRTM.  Microphysics package: WSM3. Weather Research and Forecast (WRF) mesoscale model. Test three PBL parameterizations: MYJ, MYNN, QNSE. More about model configuration:

9. 5.- Results Days selected: 28-29-30 August 2009 (CIBA) and 24-25-26 June 2011 (BLLAST). Similar synoptic situations: stability and weak pressure gradient. 30/August/2009 – 00:00 UTC Geopotential at 500 hPa (gpdm) and surface pressure reduced to sea level (reanalysis taken from: www.wetterzentrale.de)www.wetterzentrale.de

10. 5.- Results Comparison of MRFD Friction velocity (U * ) 29 Aug 2009 (CIBA)24 Jun 2011 (BLLAST) m s -1 t=0 => t sunset

11. 5.- Results Comparison of MRFD Friction velocity (U * ) 29 Aug 2009 (CIBA)24 Jun 2011 (BLLAST) m s -1 t=0 => t sunset

12. 5.- Results Comparison of temperature and friction velocity U*U* T CIBA BLLAST

13. 5.- Results Katabatic event - CIBA wind speedwind direction

14. 5.- Results WRF simulations Friction velocity (U * ) 26 Jun 2011 28 Aug 2009 30 Aug 2009 CIBA BLLAST 24 Jun 2011

15. 5.- Results WRF simulations Temperature 25 Jun 2011 (BLLAST)30 Aug 2009 (CIBA)

16. 5.- Results WRF simulations Wind speed 26 Jun 2011 (BLLAST) 28 Aug 2009 (CIBA)

17. 6.- Summary and conclusions  Evening transition processes have been evaluated at two different experimental sites.  MRFD timescales: similar evolution, but with some differences.  Radiative cooling: seems to be influenced by soil moisture.  Simulations: tend to overestimate the turbulence after sunset at one of the sites (the less dried).

18. THANK YOU FOR YOUR ATTENTION Acknowledgements:  Spanish Ministry of Science and Innovation projects CGL2006-12474-C03-03, CGL2009- 12797-C03-03 and CGL2011-13477-E.  UCM fellowship (reference BE45/10).  BLLAST project, especially M. Lothon and F. Saïd for the 60m-tower data.  EMS Young Scientist Travel Award (YSTA).