1. Radiation fogs: WRF and LES numerical experiments
C. Román-Cascón, G-J. Steeneveld, C. Yagüe, M. Sastre, G. Maqueda
European Meteorological Society
14th EMS / 10th ECAC
09 October 2014, Prague (CZ)

2. MOTIVATION & RESEARCH QUESTION
WHAT IS HAPPENING HERE?

3. 1. OBSERVATIONS 2. SIMULATIONS - WRF - LES
OUTLINE
1. OBSERVATIONS SIMULATIONS WRF LES
CABAUW
TOWER
WRF-ARW v
Dutch Atmospheric Large
Eddy Simulation (DALES) v. 3.1

4. OBSERVATIONS
CABAUW
TOWER

5. General overview  (from visibility meas.)
OBSERVATIONS
General overview  (from visibility meas.)
CABAUW
TOWER
FOG
6 hours
PERSISTENT FOG - MORE THAN 2 DAYS
UTC
MS2G SEVIRI Ch1. EUMETSAT

6. OBSERVATIONS
Wind speed
FOG
Height
(m)
Time (dec day)
m/s

7. OBSERVATIONS
TKE
FOG
Height
(m)
Time (dec day)
m2/s2

8. OBSERVATIONS
TKE
Height
(m)
Time (dec day)
Time (dec day)

9. WRF-ARW V3.5.1 CONFIGURATION
Domain
1 domain (300 x 300 grid points)
Horizontal resolution
2.5 km
Vertical resolution
51 levels (8 levels <100 m)
Boundary conditions
ECMWF (pressure levels)
Radiation
Dudhia 1998 (SW), RRTM (LW)
Microphysics
WDM6-class
PBL
MYNN 2.5
Surface layer
Monin-Obukhov scheme
Land-surface
Unified Noah
Land use dataset
USGS

10. LWC (g/kg) from VIS measurements (Kunkel, 1984)
OBS - WRF
LIQUID WATER CONTENT
Height
(m)
LWC (g/kg) from VIS measurements (Kunkel, 1984)
OBS
g/kg
Time (dec day)
Height
(m)
WRF
g/kg
Time (dec day)

11. SW, T2, r2 OBS - WRF SW down (W/m2) Temp 2m (ºC) Specific Humidity 2m
(g/kg)
Time (dec day)

12. Friction velocity (m/s)
OBS - WRF
FRICTION VELOCITY
(surface)
Friction velocity (m/s)
Time (dec day)

13. LES
LES MATURE
LES ONSET
LES DISSIPATION

14. LWC LES OBS OBS- LES FOG – MATURE STAGE Height (m) Height (m)
g/kg
OBS
Height
(m)
g/kg
Time (UTC)

15. TKE OBS - LES FOG – MATURE STAGE LES Height (m) OBS Height (m)
m2 / s2
OBS
Height
(m)
Time (UTC)
m2 / s2

16. CONCLUSIONS OBSERVATIONS
- Fog thickness directly related with wind, u* or TKE.
- Good mixing inside fog (TKE from 0.1 – 0.3 m2/s2)
WRF
- Good simulation of fog, BUT:
- Not able to correctly reproduce the mixing events
LES
- INFRAESTIMATION of LWC (specially at the top)
- LWC spread in the vertical  OVERESTIMATION of thickness
- Able to reproduce mixing events as seen in observations (but too aggressive)
- OVERESTIMATION of LWC  INFRAESTIMATION SW
- OVERESTIMATION of U*  OVERESTIMATION of thickness

17. Thanks !! Děkuji !! carlosromancascon@ucm.es
...
Radiation fogs: WRF & LES numerical experiments.