1. New Directions for WRF Land Surface Modeling 1 Polar WRF Workshop – 3 November 2011 Michael Barlage Research Applications Laboratory (RAL) National Center for Atmospheric Research

2. 2 Noah LSM in NCEP Eta, MM5 and WRF Models (Pan and Mahrt 1987, Chen et al. 1996, Chen and Dudhia 2001, Ek et al., 2003) Gravitational Flow Internal Soil Moisture Flux Internal Soil Heat Flux Soil Heat Flux Precipitation Condensation on bare soil on vegetation Soil Moisture Flux Runoff Transpiration Interflow Canopy Water Evaporation Direct Soil Evaporation Turbulent Heat Flux to/from Snowpack/Soil/Plant Canopy Evaporation from Open Water Deposition/ Sublimation to/from snowpack  = 10 cm  = 30 cm  = 60 cm  = 100 cm Snowmelt

3. 3 Noah LSM in NCEP Eta, MM5 and WRF Models (Pan and Mahrt 1987, Chen et al. 1996, Chen and Dudhia 2001, Ek et al., 2003) Gravitational Flow Internal Soil Moisture Flux Internal Soil Heat Flux Soil Heat Flux Precipitation Condensation on bare soil on vegetation Soil Moisture Flux Runoff Transpiration Interflow Canopy Water Evaporation Direct Soil Evaporation Turbulent Heat Flux to/from Snowpack/Soil/Plant Canopy Evaporation from Open Water Deposition/ Sublimation to/from snowpack Snowmelt  = 10 cm  = 30 cm  = 60 cm  = 100 cm

4. 4 Noah LSM Performance 4 Noah does some things well –Surface fluxes without snow present –Summertime simulation in general –Noah is relatively simple, less parameters Noah structure good for satellite-derived surface properties –Albedo, observed from satellite, is a bulk property (vegetation, snow, soil) –Vegetation properties like green vegetation fraction are easily used as prescribed vegetation condition

5. 5 Noah LSM Deficiencies Related to Snow Physics –Combined snow/vegetation/soil layer –No explicit canopy or liquid water retention –Currently one-layer snow Results in: –Under-prediction of snow throughout season –Snow melts too early in spring –Surface skin temperature is limited to (near) freezing with snow on ground (cannot produce a “warm” canopy) –Limits 2m temperature in cases of warm air advection and when significant energy absorbed by canopy

6. 6 Noah LSM Deficiencies Flagstaff WRF T 2m simulation compared to METAR observations February Courtesy Mike Leuthold, U. Arizona

7. 7 Noah LSM Deficiencies Flagstaff WRF T 2m simulation compared to METAR observations Cold bias during the day results from capped surface temperature at freezing Bias recovers during the night When snow is gone, bias is low February

8. 8 Noah LSM Deficiencies Flagstaff WRF T 2m simulation compared to METAR observations Cold bias during the day results from capped surface temperature at freezing Bias recovers during the night When snow is gone, bias is low February

9. 9 Noah LSM Deficiencies Flagstaff WRF v3.2 T 2m simulation compared to METAR observations Cold bias during the day results from capped surface temperature at freezing Bias recovers during the night When snow is gone, bias is low February

10. 10 Simulations compared to SNOTEL observations Legend legend GS: GOES SW forcing ML: model level forcing LV: Livneh albedo TA: terrain adjustment CH: WRF MYJ stability 85: Max albedo = 0.85 ZE: Zo = f(exposed veg) SWE, snow melt and sublimation between the control simulation and simulation with all changes Sublimation reduced consistently throughout simulation Resulting pack increase melts in spring Noah v3.0 Modified Noah

11. 11 Simulations compared to Niwot Ridge observations Diurnal average sensible heat flux for January 2007 Both Noah-MP and Noah-UA do better with fluxes at night Noah-MP does very well with daytime flux Noah-UA improves greatly upon both version of current Noah 11 Keep snow at the expense of energy

12. 12 Addressing with Two Approaches Noah-UA Wang et al. 2010 –Canopy shading effect –Reduce exchange coefficient under canopy –Adjust roughness length for snow and vegetation fraction –Additional snow cover fractions Advantages –Easy to implement –Maintains Noah structure (added as namelist option) Disadvantages –Skin temperature still limited Noah-MP Liang/Niu et al. 2011 –Explicit canopy –Multiple snow layers –Snow liquid water retention –Two-stream canopy radiation –Multiple temperatures Advantages –More physical surface representation –Surface exchange consistent with LSM Disadvantages –Complexity/cost –More parameters

13. 13 Noah-UA: Canopy Shading SW dn SHSW dn SH + Δ can (1-α)  SW dn (1-α)  SW dn - Δ can Δ can Noah Noah-UA Δ can = solar radiation intercepted by canopy = f(LAI, canopy reflectance, snow albedo)

14. 14 Noah-MP: Canopy Fluxes Separate exchange coefficients –Bare ground to atmosphere –Under-canopy ground to canopy –Canopy to atmosphere –Leaf to canopy Flux balance –Iterate leaf and canopy temperatures so that heat flux to atmosphere is balanced with flux from canopy to leaf and canopy to ground Canopy FractionBare Fraction

15. 15 Simulations compared to SNOTEL observations Noah-MP improves both peak SWE simulation and spring melt timing Noah Modified Noah Noah v3.1 Noah v3.1+ Noah-MP

16. 16 Simulations compared to Niwot Ridge observations Diurnal average sensible heat flux for January 2007 Both Noah-MP and Noah-UA do better with fluxes at night Noah-MP does very well with daytime flux Noah-UA improves greatly upon both version of current Noah 16

17. 17 Simulations compared to Niwot Ridge observations Diurnal average sensible heat flux for January 2007 Both Noah-MP and Noah-UA do better with fluxes at night Noah-MP does very well with daytime flux Noah-UA improves greatly upon both version of current Noah 17

18. Coupling Noah-MP to WRF Noah-MP is coupled to WRF and currently going through testing 12 Km horizontal resolution with NARR data is used as initial condition WRF Runs starts 1 March 2008, 12Z –Using WRFV3.3/Noah –Using WRFV3.3/Noah-MP Models are integrated for 15 days. Results are compared –Noah vs Noah-MP

19. Sensible Heat Flux at Niwot Ridge, CO Noah-MP Noah Obs

20. Coordinated effort by NCAR to compare surface processes within snow components of land models Volunteer participation by several universities Phase-1a: Control experiment at SNOTEL sites. All forcing comes from WRF simulation except GOES observed solar radiation Phase-1b: Same as Phase-1a except daily precipitation from SNOTEL observations Phase-1c: Same as Phase-1b except diurnal hourly precipitation distribution is based on WRF monthly-averaged diurnal distribution Phase-1d: Same as Phase-1a except that SWE is reset to SNOTEL observed SWE on the date of maximum Phase-2a: 2004-2008 simulations for AmeriFlux sites (Niwot Ridge and GLEES). Forcing comes from NARR except precipitation(NLDAS) and solar radiation – Phase-2a1: Replacing the 2m Temperature forcing data with the 21m forcing. – Phase-2a2: Ameriflux SW/LW replacing GOES/NARR SW/LW (no obs 2004-2005) – Phase-2a3: 2a1+2a2 – Sensitivity with forcing height (ZLVL) 20 Snow Model Intercomparison

21. LEAF VIC SAST CLM Noah NoahMP

22. Snow Model Intercomparison LEAF VIC SAST CLM Noah NoahMP

23. 23 Summary Other Noah-MP features –Dynamic vegetation –Groundwater treatment –Photosynthesis-based canopy resistance A new model (Noah-MP) and new processes within the existing Noah (Noah-UA) are planned to be released in the next WRF release –Both models attempt to address Noah deficiencies in snow treatment –Noah-MP contains several options for physical parameterizations within the LSM