1. LM-PAFOG: three dimensional fog forecasting with the “Lokal Modell” of the German Weather Service Matthieu Masbou 1,2 & Andreas Bott 1 1 Meteorological Institute, University of Bonn, Germany, mmasbou@uni-bonn.de 2 Laboratoire de Météorologie physique, University Blaise Pascal, Clermont-Ferrand, France COST 722 : Short Range Fog Forecasting, Visibility and low cloud 6th EMS Conference Ljubljana, September 2006

2. Fog Formation cooling Increase in humidity Radiation fogAdvection fog Valley fog Upslope fog Precipitation fog 1D3D (1D)

3. 3D FOG Model = LM + PAFOG Droplets number Concentration Liquid Water Content LM-DynamicsPAFOG-Microphysics Boundary NcNc 2000 m 20 000 m Soil Model NcNc qcqc qcqc Water/Ice CloudPrecipitation Fog/Stratus NcNc

4. PAFOG Microphysics Assumption for droplet spectra : Log-normal D droplet Diameter D c,0 mean value of D σ c Standart deviation of size distribution (σ c =0.2) Supersaturation S Diameter in μmCCN Concentration 0.2 0.25 0.3 0.35

5. PAFOG Microphysics 2b-Time dependent relation between 2a-Detailed Condensation/Evaporation : Parameterized Köhler relation [Chaumerliac et al. (1987) and Sakakibara (1979)] 3-Droplet size dependent Sedimentation Positive Definite Advection Scheme Supersaturation S and Diameter D 1- Activation [Twomey (1954)] : k and C depend on their environment (maritime, rural, urban) [Bott (1989)]

6. Resolution of LM-PAFOG LMLM-PAFOG 68 m 153 m 256 m 0.2 m 1.9 m 4m ….. 40m Ksoil = 2Ksoil = 8 ke = 35 ke = 40 k=35 k=25 0.002m 0.18m 1.2m ks=1 ks=9 k=34 k=33 k=18 k=16 Horizontal Resolution : 100 x 100 pixels Δxy = 2.8 km 25 levels in the lowest 2 000 m Vertical Resolution : Atmosphere - 35 levels ΔZmin = 4m Soil - 8 levels ΔZs,min = 5 mm

7. Surface Fluxes LW in W/m 2 SW in W/m 2 Tsurf in K Initialization: 2005 September 26th 48 hours forecast Time Step: 6 sec.

8. LM-PAFOG Cross Section LWC in kg/kgT in K RH in % 2005 September, 27th 00 UTC

9. LWC in kg/kgT in K RH in % FOG LM-PAFOG Cross Section 2005 September, 27th 01 UTC

10. LWC in kg/kgT in K RH in % FOG LM-PAFOG Cross Section 2005 September, 27th 02 UTC

11. LWC in kg/kgT in K RH in % FOG LM-PAFOG Cross Section 2005 September, 27th 03 UTC

12. LWC in kg/kgT in K RH in % FOG LM-PAFOG Cross Section 2005 September, 27th 04 UTC

13. LWC in kg/kgT in K RH in % FOG LM-PAFOG Cross Section 2005 September, 27th 05 UTC

14. LWC in kg/kgT in K RH in % FOG LM-PAFOG Cross Section 2005 September, 27th 06 UTC

15. LWC in kg/kgT in K RH in % FOG LM-PAFOG Cross Section 2005 September, 27th 07 UTC

16. LWC in kg/kgT in K RH in % LM-PAFOG Cross Section 2005 September, 27th 08 UTC

17. CONCLUSION - 3D Fog models with complex microphysics - Very Promising results/ case studies - Long time verification (Sept-Dec 2005) - Statistics Methods : Comparison Satellite/3D Model Future plans Thanks COST 722

18. REFERENCES Chaumerliac, N., Richard, E. & Pinty, J.-P. (1987), Sulfur scavenging in a mesoscale model with quasi-spectral microphysic : Two dimensional results for continental and maritime clouds, J. Geophys. Res. 92, 3114- 3126. Sakakibara, H. (1979), A scheme for stable numerical computation of the condensation process with large time step, J. Meteorol. Soc. Japan 57, 349-353. Twomey, S. (1959), The nuclei of natural cloud formation. Part ii : The supersaturation in natural clouds and the variation of cloud droplet concentration, Geophys. Pura Appl. 43, 243-249. Berry, E.X & Pranger, M. P. (1974), Equation for calculating the terminal velocities of water drops, J. Appl. Meteor. 13, 108-113. Bott, A. (1989), A positive definite advection schemme obtained by nonlinear renormalization of the advective fluxes, Monthly Weather Review 117, 1006-1015. Bott, A. & Trautmann, T. (2002), PAFOG – a new efficient forecast model of radiation fog and low-level stratiform clouds, Atmospheric Research 64, 191-203.

20. Boundary Condition for Nc Diameter in μm CCN Concentration Height σcσc 1 000m PAFOG TOP 1 000m