1. Eidgenössisches Departement des Innern EDI Bundesamt für Meteorologie und Klimatologie MeteoSchweiz The new multi-layer snow model Guy de Morsier 1, Jean-Marie Bettems 1, Ekaterina Machulskaya 2 1 MeteoSwiss 2 DWD COSMO General Meeting Offenbach, 7 September 2009

2. 2 COSMO General Meeting 2009 | COLOBOC PP Multi-layer snow modelGuy de Morsier et ali Overview Update of the multi-layer snow model Available data for validations Validation experiments Results from the 2 layer snow model Conclusions Outlook

3. 3 COSMO General Meeting 2009 | COLOBOC PP Multi-layer snow modelGuy de Morsier et ali Update of the multi-layer snow model Now in COSMO 4.7 new fields with ke_snow levels T_SNOW_Mmean temperature of the snow layer (K) DH_SNOW_Mlayer thickness between interfaces (m) WL_SNOW_Mliquid water content in the snow (m H2O) WT_SNOW_Mtotal (liquid+solid) water content (m H2O) GRIB details checked with Uli Schättler Start mechanisms: laf* filesread and write all necessary variables re-start filescontinue computing snow model cold-startinitialise snow variables from old 1 layer model Additional CPU cost:less than 1% for 2 layers Scientific documentation available Technical documentation: description of new fields switches, namelists tuning parameters

4. 4 COSMO General Meeting 2009 | COLOBOC PP Multi-layer snow modelGuy de Morsier et ali Available data for validation (i) MSG quality weighted snow mask on COSMO-7 and COSMO-2 grid IMIS measurement at ca. 90 Swiss stations between 1800 and 3000mAMSL from WSL Institute for Snow and Avalanche Research, SLF http://www.slf.ch/lawineninfo/zusatzinfos/Archiv/index_EN. SLF snow height analysis using all IMIS/ENET & NOAA data. Operational snow analysis: COSMO-7, COSMO-2 SNOWPACK finite element model of layered snow structures (including phase change, water transport and snow drifting) at 7 Swiss stations.

5. 5 COSMO General Meeting 2009 | COLOBOC PP Multi-layer snow modelGuy de Morsier et ali Available data for validation (ii) SLF analysis: original 1km resolutionRe-grided with “fieldextra”:

6. 6 COSMO General Meeting 2009 | COLOBOC PP Multi-layer snow modelGuy de Morsier et ali Validation experiments Winter from September 2007 to May 2008 COSMO-7 results are from the operational data assimilation including a daily merge of the snow analysis  snow analysis uses surface observations and the snow mask derived from Meteosat Second Generation SEVIRI (temporal composite) Reference TERRA stand-alone (COSMO SVAT with a single snow layer) driven by hourly atmospheric analysis including precipitation for the whole period without snow analysis New snow model Same as reference but with 2 layer snow model (2LSM)

7. 7 COSMO General Meeting 2009 | COLOBOC PP Multi-layer snow modelGuy de Morsier et ali Validation experiments Bias = 2LSM - REF [m] REF is TERRA stand-alone without snow analysis. Time series of domain mean [m] for 2LSM, COSMO-7 and REF  REF has less snow than COSMO-7  2LSM has more snow on the orography  Spurious precipitation at lateral boundary (qi in IFS, lmixcld=.F.)

8. 8 COSMO General Meeting 2009 | COLOBOC PP Multi-layer snow modelGuy de Morsier et ali Percent Correct Classification (MSG) 6.6km PCC (hits + correct neg.) C-7 PCC (hits + correct neg.) REF MSG Quality Mask SNOW present PCC (hits + correct neg.) 2LSM hits=3.4% fa=2.8% cn=93.2% mis=0.6%hits=4% fa=0.0% cn=96% mis=0% hits=3.4% fa=2.4% cn=93.6% mis=0.6%

9. 9 COSMO General Meeting 2009 | COLOBOC PP Multi-layer snow modelGuy de Morsier et ali Compare with SLF and MSG data at 6.6km PCC (hits+cor.neg.) SLFPCC (hits+cor.neg.) REF MSG Quality Mask SNOW analysed by SLF: 36 cases hits=54.7% fa=41.9% cn=3.4% mis=0%hits=41.4% fa=8.8% cn=46.7% mis=3.1% PCC (hits+cor.neg.) 2LSM hits=41.4% fa=7.9% cn=47.1% mis=3.6%

10. 10 COSMO General Meeting 2009 | COLOBOC PP Multi-layer snow modelGuy de Morsier et ali Validation with SLF data at 6.6km Bias (COSMO-7 – SLF) [m] Period: September 8, 2007 to May 31, 2008 COSMO-7 only 35 cases. REF & 2LSM only 36 cases.  REF has too little snow  2LSM has too much snow Bias (REF – SLF) [m] Bias (2LSM – SLF) [m]

11. 11 COSMO General Meeting 2009 | COLOBOC PP Multi-layer snow modelGuy de Morsier et ali Results with 2 layer snow model (2LSM) Bias (2LSM – SLF) [m] ZOOM_ SNOWPACK stations : OK Period: September 2, 2007 to May 31, 2008 : + : - EVERY day : |  h|>300m Obs!

12. 12 COSMO General Meeting 2009 | COLOBOC PP Multi-layer snow modelGuy de Morsier et ali Results with 2 layer snow model (2LSM) OK Period: September 2, 2007 to May 31, 2008 EVERY day Station at 2240m in the Western Alps Model at 2097m  h = -143m

13. 13 COSMO General Meeting 2009 | COLOBOC PP Multi-layer snow modelGuy de Morsier et ali Results with 2 layer snow model (2LSM) Too little! Period: September 2, 2007 to May 31, 2008 EVERY day Station at 1510m on the North Western slope of the Alps Model at 1462m  h = -48m

14. 14 COSMO General Meeting 2009 | COLOBOC PP Multi-layer snow modelGuy de Morsier et ali Results with 2 layer snow model (2LSM) Too little but Period: September 2, 2007 to May 31, 2008 good ablation EVERY day Station at 1650m on the North Western slope of the Alps Model at 1654m  h = 4m

15. 15 COSMO General Meeting 2009 | COLOBOC PP Multi-layer snow modelGuy de Morsier et ali Results with 2 layer snow model (2LSM) OK Period: September 2, 2007 to May 31, 2008 EVERY day Station at 2230m Next grid point South Model at 2177m  h = -53m

16. 16 COSMO General Meeting 2009 | COLOBOC PP Multi-layer snow modelGuy de Morsier et ali Results with 2 layer snow model (2LSM) : OK Period: September 2, 2007 to May 31, 2008 : + : - EVERY day : |  h|<300m Obs! Bias (2LSM – SLF) [m] ZOOM_ SNOWPACK stations

17. 17 COSMO General Meeting 2009 | COLOBOC PP Multi-layer snow modelGuy de Morsier et ali Results with 2 layer snow model (2LSM) Too much Period: September 2, 2007 to May 31, 2008 Station at 2430m In the Alps Model at 2479m  h = 49m

18. 18 COSMO General Meeting 2009 | COLOBOC PP Multi-layer snow modelGuy de Morsier et ali Results with 2 layer snow model (2LSM) OK Period: September 2, 2007 to May 31, 2008 Station at 2450m 2 grid points to the East Model at 2350m  h = -100m

19. 19 COSMO General Meeting 2009 | COLOBOC PP Multi-layer snow modelGuy de Morsier et ali Results with 2 layer snow model (2LSM) Obs! Period: September 2, 2007 to May 31, 2008 Station at 2195m Within the Alps Model at 2192m  h = -3m  dubious observations!  possible wind ablation

20. 20 COSMO General Meeting 2009 | COLOBOC PP Multi-layer snow modelGuy de Morsier et ali Results with 2 layer snow model (2LSM) SNOWPACK Period: September 2, 2007 to May 31, 2008 stations! Height difference 9m -47m North slope of the Alps 2 neighbor grid points: North South  dubious observations?  or possible accumulation

21. 21 COSMO General Meeting 2009 | COLOBOC PP Multi-layer snow modelGuy de Morsier et ali Results with 2 layer snow model (2LSM) OK but… Period: September 2, 2007 to May 31, 2008 Station at 1340m North slope of the Alps Model at 1331m  h = -9m  Problem when merging the analysis (red) with the new model

22. 22 COSMO General Meeting 2009 | COLOBOC PP Multi-layer snow modelGuy de Morsier et ali Conclusions Slightly better snow/no snow with multi layer snow model over Northern Europe In Eastern Europe and over orography the new snow model produces larger snow depth The systematic underestimation of the snow height by the original snow model is largely removed by using the 2 layer snow model The multi layer snow model works well at different altitudes in complex topography but might overestimate the snow height in some areas Findings:  better representation of the ablation period (Spring) with the 2 layer snow model

23. 23 COSMO General Meeting 2009 | COLOBOC PP Multi-layer snow modelGuy de Morsier et ali Outlook Snow model: check other snow model variables (SNOWPACK): snow water content (liquid and total), snow temperature look at wet and dry periods and spatial distribution of precip. evaluate temporal evolution also outside of the Alps re-compute winter 2007-2008 with full 3D model with COSMO-7 and COSMO-2 in particular evaluate effect of higher resolution Snow analysis: Adapt to better use the good information provided by the new snow model

24. 24 COSMO General Meeting 2009 | COLOBOC PP Multi-layer snow modelGuy de Morsier et ali Results with 2 layer snow model (2LSM) SNOWPACK Period: September 2, 2007 to May 31, 2008 station! Height difference 214m Eastern CH Alps