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What’s New in VIC 4.1.1

What’s New in VIC 4.1.1. Ted Bohn Hydro Seminar June 23, 2009. Outline. What is VIC 4.1.1, Anyway? Updates since 4.0.6 and 4.1.0 Features from 4.1.0 Features from 4.0.6 Completely New Backwards-compatibility New VIC Web Site VIC Needs Your Help! Testing VIC How To Get 4.1.1

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What’s New in VIC 4.1.1

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  1. What’s New in VIC 4.1.1 Ted Bohn Hydro Seminar June 23, 2009

  2. Outline • What is VIC 4.1.1, Anyway? • Updates since 4.0.6 and 4.1.0 • Features from 4.1.0 • Features from 4.0.6 • Completely New • Backwards-compatibility • New VIC Web Site • VIC Needs Your Help! • Testing VIC • How To Get 4.1.1 • Future Possibilities

  3. What is VIC 4.1.1, Anyway? • Successor to both 4.0.6 and 4.1.0 • 4.0.6 and 4.1.0 are not compatible • Some of 4.1.0’s new features broke some of the older features • 4.1.1 has “best” of both versions • 4.1.1 can (mostly) reproduce results of 4.0.6 and 4.1.0 • 4.1.1 has further improvements

  4. VIC Model Versions • 4.1.0_x Branch • Lake/wetland model • Blowing snow • Canopy energy balance • No treeline computation • 410-style aero_resist • Inconsistent aero_resist reporting • Grnd_flux correct • deltaH & fusion incorrect • 4.0.x Branch • No lake model • No blowing snow • No permafrost • No canopy energy balance • Treeline computation • 406-style aero_resist • Inconsistent aero_resist reporting • Grnd_flux & deltaH incorrect 4.0.3 • 4.1.0_r4 • Lakes v.1 • 24h water balance errors • Flexible output config • Output aggregation • 4.0.6 • Flexible output config • Output aggregation • 4.1.0_r5 • Lakes v.2 • Fixed 24h water balance • Permafrost Enhancements • 4.1.1 • Treeline computation • Lakes v.2 • Blowing snow • Canopy energy balance • Permafrost Enhancements • 406-style aero_resist • Consistent aero_resist reporting • Frozen soil bug fixes • Correct grnd_flux, deltaH, and fusion • Air pressure lapsing option • Snow pack improvements • 4.1.2 • Under development

  5. Updates Since 4.0.6 and 4.1.0:Features from 4.1.0 • Dynamic Lake/Wetland Model (Bowling, 2002, 2009) • Multi-layer lake model of Hostetler et al. 2000 • Energy-balance model • Mixing, radiation attenuation, variable ice cover • Dynamic lake area (taken from topography) allows seasonal inundation of adjacent wetlands • Currently not part of channel network Parameters • New wfrac parameter replaces max_depth, depth_frac and rate_frac – old parameter files won’t work • Set LAKES to lake parameter file name in global param file • Optionally specify lake basin shape in lake parameter file

  6. Linear Exponential Depth Updates Since 4.0.6 and 4.1.0:Features from 4.1.0 Permafrost Enhancements Global Param Options • IMPLICIT = implicit solver • EXP_TRANS = exponential node spacing User_def.h Options • EXCESS_ICE

  7. Excess Ground Ice and Subsidence Algorithm: • excess ice is the concentration of ice in excess of what the soil can hold were it unfrozen – we define it as n’-n, where n’ is the expanded soil porosity, and n is the unfrozen soil porosity • as excess ice in a soil layer melts (see example at left), the ground subsides • for the below runs, we utilize 8 soil layers, ranging in thickness from 0.1 to 0.6 m

  8. Updates Since 4.0.6 and 4.1.0:Features from 4.1.0 Soil T heterogeneity: “Spatial Frost” • Linear (uniform) distribution of soil T around mean • Allows some moisture movement in soil when avg T below freezing • Requires extra soil parameter: frost_slope • User_def.h (compile-time) option: • Set SPATIAL_FROST to TRUE • Set FROST_SUBAREAS (number of frost “bands”) Cherkauer et al. (2003)

  9. Updates Since 4.0.6 and 4.1.0:Features from 4.1.0 Partial Snow Cover: “Spatial Snow” • If melting & avg SWE < depth_full_snow_cover, snow coverage is proportional to SWE • Requires extra soil parameter: depth_full_snow_cover • User_def.h (compile-time) option: • Set SPATIAL_SNOW to TRUE

  10. Updates Since 4.0.6 and 4.1.0:Features from 4.1.0 Canopy Energy Balance • Separate canopy temperature • Radiative fluxes between canopy and ground/snowpack surface • Can iterate between surface and canopy solutions for total balance: • Set CLOSE_ENERGY to TRUE in user_def.h (compile-time option) Blowing Snow • Blowing snow sublimation • Set BLOWING to TRUE in global param file

  11. Updates Since 4.0.6 and 4.1.0:Features from 4.0.6 24h water balance mode • Snow step was broken in 4.1.0 – now is fixed Treeline Computation • Use in conjunction with snow/elevation bands • Uses avg July T of forcings to determine which bands are above treeline • Above treeline, replaces any overstory veg tiles with non-overstory veg cover • Otherwise, runaway snowpack (“glaciers”) • Set COMPUTE_TREELINE to a veg class ID number in global param file (ID number of non-overstory class) • JulyAvgT can be supplied in soil file instead of computed from forcings: • Set JULY_TAVG_SUPPLIED to TRUE in global param file

  12. Updates Since 4.0.6 and 4.1.0:Completely New Potential ET • 6 Types of PET can now be output: OUT_PET_SATSOIL Saturated Soil OUT_PET_H2OSURF Water Surface (smooth/shallow) OUT_PET_SHORT Short Reference Crop OUT_PET_TALL Tall Reference Crop OUT_PET_NATVEG Natural Vegetation, no soil moisture limitation OUT_PET_VEGNOCR Natural Veg. with Rc = 0

  13. SatSoil > H2OSurf (rougher) VegNoCR is usually highest Trans is near NatVeg when soil is wet Trans declines as soil dries ECan + Trans > Most PETs

  14. Updates Since 4.0.6 and 4.1.0:Completely New T instability handling • In past, soil T solution often failed to converge in arctic climates • Jenny Adam’s permafrost enhancements solved most problems • Just in case, we now have better error handling: CONTINUEONERROR in global param file • FALSE: VIC exits completely when a grid cell encounters T failure • TRUE: VIC moves to next grid cell when T failure occurs • TFALLBACK: use previous timestep’s T value and continue with current grid cell • Applies to surface and canopy T solutions as well • NOTE: by the time the solution fails to converge, T values may have been unreasonable for days or weeks

  15. How effective is the TFALLBACK option? Arctic location, 15 Nodes, Linear distribution, Dp=4m, Constant Tb, explicit scheme Original TFALLBACK By the time convergence failure occurs, it’s too late

  16. Problem actually occurred much earlier – “cold nose” at 2nd deepest node Implicit scheme also fails…

  17. Other options… Deepening Dp to 20m fixes problem Node spacing appears to be an issue But constant Tb at 4m is unrealistic here

  18. Other options… Dp = 20m Exponential Node Distrib NOFLUX bottom boundary Explicit scheme Effect on surface T is small Effect at depth is large Implicit scheme may be more accurate/stable, but takes > 10 times longer! Note: node depths are different from linear case, except for T0 and T14

  19. Updates Since 4.0.6 and 4.1.0:Completely New Aerodynamic Resistance in Snow-filled Canopy • 4.0.6 and 4.1.0 handled differently; neither was correct • New global param option: AERO_RESIST_CANSNOW • AR_406: multiply Ra by 10 but only apply to latent heat • AR_406_LS: mult. by 10 and apply to both latent and sensible • AR_406_FULL: same as AR_406_LS but also use canopy Ra (no correction) when no snow • AR_410: apply stability correction to both L and S • AR_COMBO: apply stability correction and multiply by 10 • 410 accumulates more canopy snow than 406 due to higher Ra; 411 similar to 406 but lower sensible heat

  20. Updates Since 4.0.6 and 4.1.0:Completely New Ground Flux • 4.0.6 and 4.1.0 handled differently; 4.1.0 more correct but not perfect • New global param option: GRND_FLUX_TYPE • GF_406: use (flawed) formulas for grnd_flux, deltaH, and fusion • GF_410: use correct formula for grnd_flux (Liang et al 1999) but deltaH and fusion don’t take surf_atten into account • GF_FULL: use correct formula for grnd_flux and take surf_atten into account in deltaH and fusion • 410 and 411 have larger grnd_flux than 406

  21. Updates Since 4.0.6 and 4.1.0:Completely New Snow Albedo • New global param file option: SNOW_ALBEDO • USACE (default): previous algorithm, from US Army Corps; prescribed date of beginning of melt season (optimized for US) • SUN1999: melt condition = function of cold content only (applicable globally) Snow Density • New global param file option: SNOW_DENSITY • DENS_BRAS (default): previous algorithm, taken from Bras (1992) • DENS_SNTHRM: algorithm taken from SNTHRM model • No computations depend on snow density, but good for validation of model results against observations

  22. Updates Since 4.0.6 and 4.1.0:Completely New Pressure Lapsing • Previously, when P and density computed during forcing disaggregation, set to constant 400m-elevation values • P and density were lapsed to cell or band elevation for canopy evap & transpiration calculations • But sensible heat used un-lapsed values • Cold bias at high elevations, warm bias at low elevations • Magnitude of effect unknown • New global param option: PLAPSE • FALSE: previous behavior • TRUE (default): lapse pressure to grid cell average elevation

  23. Updates Since 4.0.6 and 4.1.0:Backwards Compatibility Compatibility with 4.1.0 • Global Param Options (run-time) AERO_RESIST_CANSNOW AR_410 GRND_FLUX_TYPE GF_410 COMPUTE_TREELINE FALSE (or omit) JULY_TAVG_SUPPLIED FALSE (or omit) MIN_LIQ FALSE (or omit) PLAPSE FALSE

  24. Updates Since 4.0.6 and 4.1.0:Backwards Compatibility Compatibility with 4.0.6 • Global Param Options (run-time) AERO_RESIST_CANSNOW AR_406 GRND_FLUX_TYPE GF_406 IMPLICIT FALSE (or omit) EXP_TRANS FALSE (or omit) EQUAL_AREA FALSE (or omit) LAKES FALSE (or omit) LAKE_PROFILE FALSE (or omit) BLOWING FALSE (or omit) MIN_LIQ FALSE (or omit) PLAPSE FALSE SNOW_ALBEDO USACE (or omit) SNOW_DENSITY DENS_BRAS (or omit) • User_def.h Options (compile-time) CLOSE_ENERGY FALSE SPATIAL_FROST FALSE SPATIAL_SNOW FALSE EXCESS_ICE FALSE

  25. New Web Site www.hydro.washington.edu/Lettenmaier/Models/VIC/new/ • Under Construction • Up-to-date Documentation • Consolidation / Reorganization • Easier Navigation • Suggestions?

  26. VIC Needs Your Help! “Beta” testing • Two questions: • Can 4.1.1 reproduce older results with appropriate settings? • How much different is 4.1.1 with default settings? • Use your current VIC setup: • Run current VIC • Run VIC 4.1.1 with backwards-compatibility settings • Run VIC 4.1.1 with defaults • Compare these at a single grid cell • R script • Compare hydrographs if appropriate • How to get VIC 4.1.1 & R scripts ftp.hydro.washington.edu/pub/tbohn/vic_code/

  27. Future Possibilities Model Physics • Wind profile • VPD biases • Enthalpy formulation • Distributed Water Table • Carbon • Lakes with channel inflows • “Image” mode

  28. Future Possibilities Model Organization • Fewer options • How many of the current options are really used? • Some new options are intended to be temporary • Simpler code (data structure overhaul) • Related to options • Separate initial conditions from parameters • Graphical Interface?

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