1. EURO4M 4th GA, Norrköping, 17-19 April 2013 Overview of the new MESCAN precipitation analysis system C. Soci, E. Bazile, J-F. Mahfouf with contributions from F. Besson and M. Lafaysse

2. EURO4M 4th GA, Norrköping, 17-19 April 2013 Analysis of precipitation Validation Issues Further plans Outline

3. EURO4M 4th GA, Norrköping, 17-19 April 2013 Principle: -Based on the OI code used also for the analysis of T2m and RH2m -Background field: accumulated precipitation forecasted by a numerical model (ARPEGE, AROME, ALADIN, HIRLAM). -Observations: cumulated precipitation from raingauge measurements (at this stage) -Possibility of producing 24-h, 12-h, 6-h, 3-h or 1-h accumulated precipitation analysis, the only limiting factor is that the background and the observations must span the same period. -The analysis is performed at the background horizontal resolution Analysis of accumulated precipitation in MESCAN

4. EURO4M 4th GA, Norrköping, 17-19 April 2013 Correlation function: Analysis of accumulated precipitation in MESCAN (2) Two options are available: 1.MESCAN-Log: analysis in log-space on a transformed variable ln(RR+1) RR ~ LN (0, 1 2 ) ln(RR) ~ N (0, 2 2 ) Preliminary error statistics: o =0.6 et b =0.71, L=43km [ after Mahfouf et al., 2007 for CAnadian Precipitation Analysis Project (CAPA)] 2.MESCAN-RR: analysis in physical space on RR ~ N (0, 2 ) Preliminary error statistics: o =5 et b =13, L=35km (as in SAFRAN)

5. EURO4M 4th GA, Norrköping, 17-19 April 2013 Test period : October 2009 – June 2010 First guess: ALADIN operational downscaled with fullpos Indirect validation of the MESCAN analysis system by forcing with its output (analyses of T2m, RH2m, RR24) the surface scheme ISBA and the hydrological module MODCOU. Evaluation of the impact of changing the surface forcing variables (T2m, RH2m, RR24, 10-m wind speed, downward SW and LW radiation) on: River flow, and Snow Depth The reference system used for validation is the operational system called SIM (SAFRAN-ISBA-MODCOU) Preliminary validation over France at 5.5 km grid

6. EURO4M 4th GA, Norrköping, 17-19 April 2013 Validation of MESCAN precipitation analysis vs SAFRAN over France ~ 4200 obs for computing scores ~ 1700 obs for analyses Heidke Skill Score Mar 2010 Jun 2010 Heidke Skill Score Nov 2009 Jun 2010 MESCAN-RR compared to SAFRAN and MESCAN-Log for spring (Mar-Jun): - improves the HSS for RR > 5mm/day, but - deteriorates HSS for RR < 2mm/day Heidke Skill Score Nov 2009 Feb 2010 BiasAbsolute error FG 0.401.87 MESCAN-RR -0.080.87 MESCAN-Log -0.270.96 SAFRAN -0.060.93

7. EURO4M 4th GA, Norrköping, 17-19 April 2013 OBS MAX=397mm ALADIN RR24 MAX=77mm SAFRAN MAX=309mm MESCAN-Log MAX=277mm Validation on extreme event: Var, 2010 (Grid 0.1°, RR24h)

8. EURO4M 4th GA, Norrköping, 17-19 April 2013 OBS MAX=397mm MESCAN-RR MAX=265mm SAFRAN MAX=309mm MESCAN-Log MAX=277mm Validation on extreme event: Var, 2010 (Grid 0.1°, RR24h)

9. EURO4M 4th GA, Norrköping, 17-19 April 2013 Validation of MESCAN precipitation analysis vs SAFRAN over France Accumulated daily RR for 1/10/2009 to 31/07/2010 over France [mm] ~50mm Bias correction needed for MESCAN-log Obs (~4200) MESCAN-RR MESCAN-Log SAFRAN

10. EURO4M 4th GA, Norrköping, 17-19 April 2013 2D Analysis at ~5 km: T2m, Rh2m, RR SURFEX (V7): Surface Externalized (www.cnrm.meteo.fr/surfex) with a sophisticated snowwww.cnrm.meteo.fr/surfex scheme (Vionet et al. submitted) and the lake model: Flake (Mironov, 2008) SH, LH, snow depth, snow cover, soil moisture, Ts_lake Forecast model: SW, LW, Wind, Ps Hydrological Model Coupling the 2D surface analysis and a Surface Scheme for Indirect Validation and Hydrological purposes

11. EURO4M 4th GA, Norrköping, 17-19 April 2013 MESCAN-RR (physical space) and SAFRAN are of equal quality with regard to Nash criterion. SAFRAN is better over the western part of France, i.e. flat terrain! Map based on Nash scores Indirect validation of MESCAN precipitation analysis using the MODCOU hydrological model (F. Besson)

12. EURO4M 4th GA, Norrköping, 17-19 April 2013 Forcing by ALADIN precipitation The forcing provided by the MESCAN-RR precipitation analysis is significantly improved in comparison to the one generated by the ALADIN precipitation. Impact of different types of forcing on the river flow (Oct09-Jun10) Forcing by MESCAN-RR Daily river discharge for the Seine river at Paris Plots provided by F. Besson

13. EURO4M 4th GA, Norrköping, 17-19 April 2013 Impact of precipitation on the river flow (Oct09-Jun10) - in June, the different behaviour of the river flow forced by MESCAN-RR is probably due to a lower accumulation of snowfall during the winter throughout the Rhone watershed. - Compared with SAFRAN, this underestimation is very likely due to the misleading information provided by the non-heated rain gauges in the mountains during the winter season. Daily river discharge for the Rhone river at Beaucaire Provided by F. Besson

14. EURO4M 4th GA, Norrköping, 17-19 April 2013 – Observations – SAFRAN – ALADIN-forecast – MESCAN v0 – MESCAN v1 – MESCAN v2 Validation of snow depth at observation location (M. Lafaysse) Bellecote Nivose (3000 m)FLAINE (1640m) Generally, the underestimation of the snow depth forcing by MESCAN RR is probably due to the misleading information provided by the non-heated rain gauges or to the under catch due to wind.

15. EURO4M 4th GA, Norrköping, 17-19 April 2013 Issues Observations: – high level of uncertainty in using precipitation data particularly in winter (heated/ non-heated rain gauges, Zero precip reports when it snows etc) – rain gauge measurements not corrected for the wind Background (downscaled HIRLAM fields from 22km to 5.5km): – What guess to use: fc 00+30 -fc 00+06, fc 06+24, fc 00+18 -fc 00+06 + fc 12+18 - fc 12+06 ? The quality of the background fields is still under investigation. revised statistics for background and observation errors

16. EURO4M 4th GA, Norrköping, 17-19 April 2013 Further plans At ECMWF for the 2007-2010 (2011 ??) period: – running and monitoring the production of the background files for both the precipitation and screen-level (T2m/RH2m) analyses; – running and monitoring the production of the reanalysis: T2m/RH2m every 6 hours (4 analysis per day) RR24 (one analysis per day) Validation of re-analyses – monthly mean, RMSE of 6-hourly T2m – computation of some categorical scores for RR24

17. EURO4M 4th GA, Norrköping, 17-19 April 2013 Thank you for your attention! Acknowledgements The research leading to these results has received funding from the European Union, Seventh Framework Programme (FP/2007-2013) under grant agreement n o 242093. EURO4M - reanalysis domain