Research on Fog and Low Clouds at Météo-France / CNRM

Transcription

1 Research on Fog and Low Clouds at Météo-France / CNRM 1) Improved site-specific numerical prediction COBEL-ISBA 1D numerical model CdG field experiment Operational forecast at Paris CdG international airport 2) Numerical prediction at mesoscale CAPITOUL field experiment MesoNH : 3D high resolution numerical model 3) Prospectives Collaboration with the US C&V project

2 Improved site-specific numerical prediction Observations ISBA offline Mesoscale NWP model (3D) Local Assimilation Scheme guess COBEL/ISBA Adjustment requirements / forecast fog and low clouds forecasting

3 CdG field experiment Ground measurements : T / W inside the soil (between ground and 50cm) short- and long-wave radiations Since december 2002 Airport terminal 1: T / H% Radiation fluxes Meteorological tower of 30m : T / Hu%

4 occurrence of LVP conditions at Paris CdG airport LVP : visi<600m and/or ceiling<200ft Forecast time (h) False Alarm Rate Hit Ratio Forecast time (h)

5 Operational forecast at Paris CdG international airport ) winter season Assimilation-forecast cycle : 3h Great improvement of the forecast Cobel-Isba 1D numerical model is very efficient to forecast local parameters (LVP conditions, ) ) Future work for winter season Assimilation-forecast cycle : 1h Frequent update of the forecast in LVP conditions Detailed forecaster interface Estimation of the predictability (sensitivity to input parameters : next talk from Stevie Roquelaure) Application for NY airports (US C&V)

6 International CAPITOUL field experiment airport Toulouse downtown country lake 2 km

7 Toulouse downtown Short- and long wave radiation at 30m sonic anemometer at 30m, 18m and 4m T/Hu% at 6 levels Meteorological tower (30m) mast 2 mast m 20m 250 m

8 Ground measurement (permanent and mobile) 20 permanent ground measurements Radiation fluxes 2 intrumented cars

9 Atmospheric sounding Sounding location : downtown, country, and meteorological center Frequency : 5 soundings / day for each site

10 aerosol measurements GRIMM SMPS CPC Number + granulometric spectra Radiation aspect Chemical aspect CCNC Nephelometre TEOM aethalometre

11 Aircraft measurements North Radiative temperature 11 Juillet 2004, à 10h

12 Instrumented cars IOP 10 : 7-8 January 2005 soundings 20h : fog layer toulouse Next day 14h

13 IOP 11 : January 2005 Voiture instrumentée : T, Hu, IR toulouse

14 Prospective ) Research on fog and low clouds in heterogeneous conditions IOPs from Capitoul field experiment 3D high resolution numerical model mesonh (L.E.S.) IOP from NY field experiment (US C&V) ) Collaboration with the US C&V project Cobel-Isba 1D forecast at NY airports Comparison of 3D high resolution models : mesonh and RUC ) Intercomparison of 1D model : improvement of physical arameterizations Next talk!

15 QUESTIONS!

16 Mesoscale terms : ALADIN Advections Geostrophic wind clouds COBEL Radiative processes (IR+vis) Turbulent processes (stable cases) Microphysical processes (condensation-evaporation, sedimentation) ISBA Exchanges between soil, vegetation and atmosphere

17 (Bergot 1993 ; Bergot and Guedalia 1994 ;Guedalia and Bergot, 1994) First level : 0.5m 20 levels below 200m Physical parameterizations High resolution radiation scheme (232 spectral intervals) Turbulence scheme : turbulent kinetic energy (TKE) Fine mesh vertical grid

18 Assimilation at local scale ) Initialisation of dry atmosphere Methodology : variational assimilation 1D-Var Data : local observations, operational 3D NWP forecast ) Initialisation of fog / low clouds Define the depth of the cloudy area (minimization of the model errors on the radiative fluxes divergence) Correction of the atmospheric profiles below and inside the cloudy area (dry / moist mixed area) ) Initialisation of soil parameters Soil temperature and moisture have a strong influence on the surface cooling (energy budget at the surface : spin-up problem!) Offline version of the ISBA model, driven by observed atmospheric forcings