PP COLOBOC 9.2008-9.2011 : Different aspects of snow parameterization

1. General Meeting 2011, COLOBOC Workshop PP COLOBOC 9.2008-9.2011: Different aspects of snow parameterization Developments at Roshydromet, with an emphasis on snow density, partial snow cover and T2m forecasting errors 2010-2011: task 5 “Revision of snow analysis and snow model” Inna Rozinkina, Inna.Rozinkina@mail.ru, Ekaterina Kazakova, Catherine.Kazakova@mail.ru,

2. Why Roshydromet? Near 95% of territory of Russia (incl 85 % of modeling domain of COSMO-RU07 and 100% of COSMO-RU02c) is covered by snow during winter period The data of hydrological monitoring (from Roshydrometnetwork) permits to realize the verification of snow modeling results (from polar to subtropical zones) During 3-5 cold months the quality of COSMO-Ru weather forecasts depends on success of snow-cover parameterization

3. Review of results 2008-2009: The new multi-layer snow parameterization scheme was developed (Lykosov, Machulkaya)with description of metamorphism and snow compression, cooling/melting of snow layers, penetration of solar radiation, water dynamic with phase perturbation (melting & freezing) and heat release. Ekaterina Machulskaya (Roshydromet) realized this scheme, made the validation (based on the data of Valday observatory, 1-d stand-alone experiments), adapted the codes of new multi-layer snow scheme to TERRA soft. In development of this activities the new multi-layer scheme was included into MeteoSwiss forecast system (data assimilation system) and also into operational COSMO versions since 4.11 . Tests for some points in Swiss mountains were carried out.

4. General Meeting 2011, COLOBOC Workshop Review of results 2009-2010: Analysis of effects of new multi-layer snow parameterization scheme coupled to TERRA into COSMO-model is made for European part of Russia: The measurements more than 30 hydrological stations with special snow measurements in northern, central, south parts of European Russia were used during 2-6 months The different criteria of scores were analyzed. North Centre South

5. Snow layer appeared warmer Freezing after melting General Meeting 2011, COLOBOC Workshop Review or results 2009-2010 • It was established: • TERRA with multi-layer snowscheme simulates more accurately the process of snow melting; • TERRA with multi-layer now schemeproduces more accurately T2m for the night – timeduring the period of snow melting; • There is some underestimation of fresh snow density (immediately after snow-fall events) by multi-layer snow scheme

6. General Meeting 2011, COLOBOC Workshop Review or results 2009-2010 • It was established, that in independemce of use snow parameterisation: • There arelarge errors (150-300%)of COSMO-model simulations of snow water equivalent (SWE). They are due to large errors in the prescribed SWE as initial data. On the other hand, the initial data of values of snow height (SH) are convenient. Also SH is well simulated by the COSMO-model • There arelarge errors (2-15°C) of COSMO-model simulations of T2m during the melting period. They are originated from the fact that TS within the cell, covered by snow, can not be more thanmelting-point

7. General Meeting 2011, COLOBOC Workshop Review or results 2009-2010 Next recommendations were obtained: • - To refresh TERRA code usingSH instead of SWE; • - To change the algorithms of TERRA to improve the calculationsof Ts and TGof fractional snow covered cells with possible valuesabove the melting point; • - To propose and to validate the new algorithms for determinationthe initial values of snow density(to include into codes preparation of the start information); • - Toinclude the multi-layer snow scheme into operational codes of COSMO-Model. The more important effects should appear in systems of long-term integrations (f.ex, DAS, CLM)

8. General Meeting 2011, COLOBOC Workshop Review of results 2010-2011: 1. T2m forecasting: Some changes in TERRA were made to improve T2m forecasts during snow-melt period. T2m forecast errors were significantly reduced for test forecasts for winters of 2009-2010 and 2010-1011 in COSMO-Ru07 and COSMO-Ru14 Since 4th Apr 2011 the modifications were included in operational codesfor COSMO-Ru07 and COSMO-RUSib. The results of mechanisms of such changes were analyzed. Date of changing operational codes COSMO-RU

9. General Meeting 2011, COLOBOC Workshop T2m(experiment)-T2m(ctrl) Review or results 2010-2011 36h forecast 48h forecast T2m temperature raised up to 10ºC on the territory where according to model data snow cover was below 40 cm

10. General Meeting 2011, COLOBOC Workshop Review or results 2010-2011 • Snow-density • Some parameterizations for the start values of snow-density are proposed and tested. The more realistic variant was selected. The data of the tests for 33 stations in different climatic zones were used. • motivation: large errors in initial SWE. No regular observation data Example of start field of snow density in COSMO- model. 25 March 2010

11. General Meeting 2011, COLOBOC Workshop Review or results 2010-2011 It was etablished: • The values ofsnow density are in dependenceof weather during the full winterperiod, using of constant values of snow density led to large errors in most part of snow-covered regions • Connection between typical (climatic) snow density values andtypes of vegetation cover may be showed • - The algorithm of calculations of snow density as function of sum of positives values of T2m duringfull snow period andclimatic values of snow density (Vg, LAI and Zo) was proposed and tested for stations in different zones. The algorithm can be recommended to be included into COSMO- forecasting technologies

12. General Meeting 2011, COLOBOC Workshop The distribution snow density before melting like the allocation of plants cover Average snow density (g/cm3) at maximum ten-day snow height Types of vegetation 0,28-0,30 tundra, forest-tundra; south - steppe 0,20-0,22 swamp vegetation, taiga (spruce); west - broadleaf forests (with predominance of oak and hornbeam) 0,26-0,28 north - forest-tundra;steppe and broadleaf forests (with predominance of birch) <0.20 taiga (with predominance of larch) 0,22-0,26 taiga (spruce; spruce with a touch of oak); south - steppe

13. General Meeting 2011, COLOBOC Workshop Review or results 2010-2011 Taiga (spruce predominance): - Sum of positive average daily temperatures Broad-leaved forest (oak predominance): With spruce/pine With birch The errors of initial values of SWE were decreased from 200-300% to 25-50% on the must part of stations Steppe Forest-steppe

14. General Meeting 2011, COLOBOC Workshop Review or results 2010-2011 The errors of initial values of WE were decreased from 200-300% to 25-50% on the must part of stations

15. General Meeting 2011, COLOBOC Workshop Review or results 2010-2011 Summary for 2010-2011 • It is not enough to change the fractional snow cover parameter in TERRA to take into account the thermal effects of thawed patches. (It is needed to made the changes into codes of calculations of T of soil layers, radiation fluxes, effective TG) • The success for T2m prediction can be achieved with the introduction in scheme  of artificial heating surface ( looks like the effects of routes, buildings, tree branches without snow) or with modeling of more rapid melting of snow. As alternative, the mosaic approach can be developed, with mosaic calculations for some soil layers • The values of snow density are in dependence of weather during the full winter period, the using of constants led to large errors • It is existed the connection between typical (climatic) snow density values and types of vegetation.

16. General Meeting 2011, COLOBOC Workshop 2011 – start of participation of Roshydromet in the SRNWP  Data Exchange Programme EUMETNET.The necessary preliminary jobs for organization of activities on Valday observatory were carried out Review or results 2010-2011

17. General Meeting 2011, COLOBOC Workshop Observatory Valday Valdaywater-balanceresearchstationinRussia (57º58'N, 33º 14'E)locatedinaborealforestarea. - Seasonalvariationswithanannualtemperature: rangeof 35ºC - Annualaverageprecipitationof 730 mm(themaximuminthesummerand autumn). - Persistentsnowcover period: fromNovemberuntilApril. Smirnova T.Parameterization of cold-season processes in the MAPS land-surface scheme // Journalof Geophysical Research, Vol. 105, NO. D3, 2000.

18. General Meeting 2011, COLOBOC Workshop Valday principal observations: Precipitation polygon: Valday observations Measured parameters: precipitation, precipitation intensity, evaporation, wind Gagingstation: Measured parameters: daily runoff on 9 stations of river Polomet’ and its tributaries, maximal snow survey

19. General Meeting 2011, COLOBOC Workshop Meteorological station Valday observations Measured parameters: solarradiometry, standart meteorological measurements, frostpenetration Weir Measured parameters: runoff, frostpenetration, precipitation, snowreserves, evaporation from soil

20. General Meeting 2011, COLOBOC Workshop Gradientmeasurements Valday observations Measurements: Turbulent fluxes Meteorological radar

21. General Meeting 2011, COLOBOC Workshop Plans Plans for 2011-2012:  1. A new parameterization of the snow pack density should be tested  and adapted to operational snow analysis step 2. The geographical maps of values of climatic density will be prepared (or algorithms for its calculating as function of vegetation parameters) 3. Proposals for modification of TERRA codes for fractional covering (heating effects of near- surface air) should be formalized

22. General Meeting 2011, COLOBOC Workshop THANK YOU!