Geneviève Jaubert , Ludovic Auger, Nathalie Colombon, Véronique Ducrocq, François Bouttier - PowerPoint PPT Presentation

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Geneviève Jaubert , Ludovic Auger, Nathalie Colombon, Véronique Ducrocq, François Bouttier
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Geneviève Jaubert , Ludovic Auger, Nathalie Colombon, Véronique Ducrocq, François Bouttier

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  1. Meso-γ 3D-Var Assimilation of Surface measurements: Impact on short-range high-resolution simulations Geneviève Jaubert, Ludovic Auger, Nathalie Colombon, Véronique Ducrocq, François Bouttier CNRM/GAME Météo-France and CNRS G.Jaubert Météo-France WSN05 5-9 september 2005 Toulouse France

  2. Introduction • Feasibility study for: • the assimilation part of the next operational NWP high-resolution system of Meteo-France AROME • high-resolution reanalyses of the field phase of cooperative experiments • Validation on the Gard torrential event (8-9 sept.2002) and the MAP IOP08 frontal case (20-21 oct.1999) G.Jaubert Météo-France WSN05 5-9 september 2005 Toulouse France

  3. Hybrid assimilation system Aladin 3D-Var Analysis First guess: large scale analysis (ECMWF or ARPEGE) Two domains: Mesoscale domain mesh 10 km Convective scale domain mesh: 2.5 km 1 analysis or 6-hour assimilation with 1 hour step Guess Increments Assimilation cycle Meso-NH model Meso-NH configuration: Two nested models mesh: 10 and 2.5 km 3 ice types Explicit convection at 2.5 km Meso-NH simulation G.Jaubert Météo-France WSN05 5-9 september 2005 Toulouse France

  4. REF12 12 UTC Large scale analysis ANA 12 UTC mesoscale analysis and 12 UTC convective scale analysis REF06 06 UTC Large scale analysis 06 UTC mesoscale analysis and 06 UTC convective scale analysis ASSIM 07 08 09 10 11 12 Assimilation step 1 hour Experimental design 06 UTC 12 UTC 12 UTC 24 hours Simulation G.Jaubert Météo-France WSN05 5-9 september 2005 Toulouse France

  5. Radiosounding data (60 messages) Temperature, humidity, wind, geopotential 06 UTC and 12 UTC Data used in the analyses MAP IOP8 frontal case Gard torrential event Mesoscale domain Convective scale domain Surface data (3000 observations) surface pressure 2m temperature and humidity, 10m wind hourly measurements G.Jaubert Météo-France WSN05 5-9 september 2005 Toulouse France

  6. Convective scale domain (mesh 2.5 km) ALADIN horizontal length scales reduced Larger variances at low levels 720 km The background error statistics Based on the background errors covariances used for the ALADIN analyses Mesoscale domain (mesh 10 km): ALADIN statistics except at low levels: larger variances except for the rotational wind  geostrophic balance reduced at low levels Vertical profiles of background errors stdev 2800 km G.Jaubert Météo-France WSN05 5-9 september 2005 Toulouse France

  7. METEOSAT IR 20020908 18 UTC Gard torrential rain event 12h precipitation statistics T+0  T+12 DATA REF12 Simulation REF12 ANA ASSIM Bias -3.80 -4.81 -2.31 Correlation 0.20 0.62 0.13 ANA ASSIM 12h accumulated rain Convective scale domain 8 sep 2002 12 UTC  9 sep 2002 00 UTC T+0  T+12 G.Jaubert Météo-France WSN05 5-9 september 2005 Toulouse France

  8. DATA REF12 ANA ASSIM Gard torrential rain event 12h precipitation statistics T+0  T+12 ETS 0.1 mm 20 mm 0.14 0.18 0.16 0.31 0.12 0.19 Simulation REF12 ANA ASSIM Bias -3.80 -4.81 -2.31 Correlation 0.20 0.62 0.13 12h accumulated rain Convective scale domain 8 sep 2002 12 UTC  9 sep 2002 00 UTC T+0  T+12 G.Jaubert Météo-France WSN05 5-9 september 2005 Toulouse France

  9. REF12 DATA METEOSAT WV 991021: 00 UTC ANA ASSIM MAP IOP8 frontal case 12h precipitation statistics T+6  T+18 Simulation REF06 REF12 ANA ASSIM Bias 3.31 4.10 1.98 0.76 Correlation 0.61 0.66 0.68 0.70 12h accumulated rain Convective scale domain 20 oct 18 UTC  21 oct 06 UTC T+6  T+18 G.Jaubert Météo-France WSN05 5-9 september 2005 Toulouse France

  10. REF12 REF12 DATA DATA 12h precipitation statistics T+6  T+18 ETS 0.1 mm 20 mm 0.66 0.30 0.65 0.34 0.65 0.35 0.63 0.36 Simulation REF06 REF12 ANA ASSIM Bias 3.31 4.10 1.98 0.76 Correlation 0.61 0.66 0.68 0.70 METEOSAT WV 991021: 00 UTC ANA ANA ASSIM ASSIM MAP IOP8 frontal case 12h accumulated rain Convective scale domain 20 oct 18 UTC  21 oct 06 UTC T+6  T+18 G.Jaubert Météo-France WSN05 5-9 september 2005 Toulouse France

  11. Stdev Stdev Bias Bias 2 m Humidity Comparaison with the surface measurements(convective scale domain) Gard torrential event MAP IOP8 frontal case --- REF12 --- ANA --- ASSIM --- REF12 --- ANA --- ASSIM Stdev 2 m Temperature Stdev Bias Bias G.Jaubert Météo-France WSN05 5-9 september 2005 Toulouse France

  12. MAP IOP8 frontal case Comparaison with the 13 radiosoundings included in the convective scale domain at 18 UTC (T + 6 hours) Stdev Stdev Bias Bias Temperature (K) Mixing ratio (g/kg) G.Jaubert Météo-France WSN05 5-9 september 2005 Toulouse France

  13. Conclusion • The mesoscale assimilation improved: • the forecast of precipitation • the forecast of temperature in the first 3 km The assimilation of the surface measurements reduces the bias of temperature and humidity at low levels Improvement only if the background error covariance matrice is tuned to limit the contribution of the balanced part of the flow at low levels Better results if both the surface measurements and the altitude data are used G.Jaubert Météo-France WSN05 5-9 september 2005 Toulouse France