T. Bergot - Météo-France CNRM/GMME 1) Methodology 2) Results for Paris-CdG airport Improved site-specific numerical model of fog and low clouds -dedicated observations -Cobel-Isba 1D model -adaptative local assimilation scheme -results for 2002-2003, 2003-2004 and 2004- 2005 winter seasons -applications / limits 3) Conclusions / prospectives
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T. Bergot - Météo-France CNRM/GMME 1) Methodology 2) Results for Paris-CdG airport Improved site-specific numerical model of fog and low clouds -dedicated.
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T. Bergot - Météo-France CNRM/GMME
1) Methodology
2) Results for Paris-CdG airport
Improved site-specific numerical model of fog and low clouds
-dedicated observations-Cobel-Isba 1D model-adaptative local assimilation scheme
-results for 2002-2003, 2003-2004 and 2004-2005 winter seasons-applications / limits
3) Conclusions / prospectives
Introduction
1) LVP conditions at Paris CdGvisi<600m or ceiling <200ft (LVP conditions) : the capacity of landing / take-off is reduced by a factor 2Current operational NWP models are not able to provide valuable information to forecast LVP conditions
2) Why?Physical processes associated to fog (e.g. turbulence in stable layer) : see Bergot et al. WSN05 –1.04Vertical resolution : see Bergot et al. WSN05 – 1.04Sensibility to initial conditions : high density observing network + adaptive mesoscale assimilation scheme
“local” integrated forecast system : •High resolution Cobel-Isba model•Dedicated observations + local assimilation scheme
2) Accurate forecast requires : integrated approach
Accurate high resolution modelDedicated measurements inside surface boundary layer (nocturnal inversion)Adaptive assimilation scheme at local scale
1) Forecast quality
1D model can be an alternative tool to forecast local parametersForecast is helpful during the first 6h
Conclusions / perspectives
1) Operational forecast : Paris CdG
2) Other sites in France : Paris-Orly, Lyon-St Exupery
Operational since 2004-2005 winter season : improvement of the forecast of LVP conditionsFuture : 1h assimilation – forecast cycle (frequent update of the forecast in LVP conditions)Future : predictability - local ensemble forecast system (Roquelaure et al. WSN05 2.30)
Conclusions / Prospective
1) Collaboration : US C&V(http://www.ll.mit.edu/AviationWeather/cvp.html)
2) Collaboration : Morocco – Casablanca airport
dedicated observations = sounding + SYNOP/METAR Optimization of local assimilation schemeTest of Cobel-Isba assimilation / forecast system
San Francisco : Cobel-Isba model operational in a consensus forecast systemNew-York : tests on Brookhaven site dedicated to observation of fog and low clouds (http://www.rap.ucar.edu/staff/tardif/fog/BNLsensors.html)
QUESTIONS!
Fine mesh vertical gridFine mesh vertical gridFirst level : 0.5m
20 levels below 200m
(Bergot 1993 ; Bergot and Guedalia 1994 ;Guedalia and Bergot, 1994)
1) Local 1D-VarAdaptive variational assimilation schemededicated observations
2) Initialisation of fog / low clouds
3) Initialisation of soil parameters
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)
Soil temperature and moisture : linear interpolation of measurements
Guess = previous COBEL-ISBA forecast (3h)Altitude « observations » = 3D NWP Aladin forecastSurface observations = local data (30m tower, 2m obs.)
2002-2003 WinterBias = 0.0°CStd. Dev. = 0.3°C
Temperature at 1m (observation)
Tem
pera
ture
at 1
m (
CI
Cob
el-I
sba)
1D-Var : T / q surface boundary layer
Temperature at 1m(initial conditions)
Results for the 2002-2003 winter season:2m temperature
Results for the 2002-2003 winter season :IR radiative fluxes
IR fluxes when low clouds are detected
Low clouds from Aladinbias=-41.9W/m2
low clouds from local assimilationbias=-1.0W/m2
3D operational NWP models are not able to give realistic forecasts of low clouds!