RUCLSM

The RUC LSM repository, that includes implementations in CCPP (UFS), MPAS and WRF.

Author: Smirnova Tanya

12 June 2025

This land surface model (LSM) was originally developed as part of the NOAA Rapid Update Cycle (RUC) model development effort; with ongoing modifications, it is now used as an option for the WRF, UFS (ccpp) and MPAS community models. The RUC weather model, its WRF-based NOAA successor, the Rapid Refresh (RAP) and High-Resolution Rapid Refresh (HRRR), and the UFS-vased RRFSv1 are hourly updated systems that have an emphasis on short-range, near-surface forecasts including aviation-impact variables and pre-convective environment. Coupling to this LSM (hereafter the RUC LSM) has proven to be critical to provide accurate lower boundary conditions into the atmospheric boundary layer of these models.

The RUC LSM became operational at the NOAA/National Centers for Environmental Prediction (NCEP) first, as part of the RUC from 1998–2012, and then as part of the RAP from 2012 through the present and as part of HRRR from 2014 through the present. The UFS-based RRFSv1 is going into the operations in 2025. The simple treatments of basic land surface processes in the RUC LSM (Smirnova et al. 1997, 2000, 2016, 2025) have proven to be physically robust and capable of realistically representing the evolution of soil moisture, soil temperature, and snow in cycled models. Extension of the RAP domain to encompass all of North America and adjacent high-latitude ocean areas necessitated further development of the RUC LSM for application in the tundra permafrost regions and over Arctic sea ice (Smirnova et al. 2000). Other modifications include refinements in the snow model and a more accurate specification of albedo, roughness length, and other surface properties. These recent modifications in the RUC LSM are described and evaluated in Smirnova et al. 2016, 2025.

International projects for intercomparison of land surface and snow parameterization schemes were essential in providing the testing environment and afforded an excellent opportunity to evaluate the RUC LSM with different land use and soil types and within a variety of climates. The RUC LSM was included in phase 2(d) of the Project for the Intercomparison of Land Surface Prediction Schemes [PILPS-2(d)], in which tested models performed 18-yr simulations of the land surface state for the Valdai site in Russia (Schlosser et al. 1997; Slater et al. 2001; Luo et al. 2003). The RUC LSM was also tested during the Snow Models Intercomparison Project (SnowMIP, SnowMIP2, ESM-SnowMIP), with emphasis on snow parameterizations for both grassland and forest locations in different parts of the world (Etchevers et al. 2002, 2004; Essery et al. 2009; Rutter et al. 2009, Krinner et al. 2018). The analysis of RUC LSM performance over 10 reference sites in ESM-SnowMIP rated it on the 5th place among the 26 participating models.

Major characteristics of RUC LSM model include:

1. Implicit solution of energy and moisture budgets in the layer spanning the ground surface
2. 9 soil levels with high vertical resolution near surface RUC LSM has more levels in oil than GFS Noah Land Surface Model model with higher resolution near the interface with the atmosphere
3. Prognostic soil moisture variable ( θ−θr) The prognostic variables for soil moisture is volumetric soil moisture content minus residual value of soil moisture which is tied to soil particles and does not participate in moisture transport.
4. Frozen soil physics algorithm RUC LSM has a different approach to take into account freezing and thawing processes in soil.
5. Treatment of mixed phase precipitation It accounts for mixed phase precipitation provided by Thompson Aerosol-Aware Microphysics Scheme used in RAP and HRRR.
6. Simple treatment of sea ice which solves heat diffusion in sea ice and allows evolving snow cover on top of sea ice
7. Sub-grid-scale heterogeneity of surface parameters in RUC LSM.
8. Simle irrigation scheme for cropkand areas
9. Water/snow interception bu canopy as function of vegetation fraction and leaf area index (LAI)
10. 2-layer snow model: when SWE < 1.6 cm - snow layer is combined with top soil layer
11. Fractional snow cover (SWE < 3 cm): weighted average of snow-covered and snow-free areas to compute snow paramters (roughness, albedo)
12. "mosaic" approach for patchy snow

• Seperate treatment of energy and moisture budgets for snow-covered and snow-free portions of the grid cell
• Aggregate solutions at the end of time step
• Reduced cold bias for areas with thin snow

13. Iterative snow melting algorithm
14. Density of snow on the ground - a function of compaction parameter and snow depth and temperature
15. Snow albedo - a function of temperature and snow fraction
16. Snow interception by canopy - a function of vegetation fraction and LAI
17. Density of falling snow/graupel/ice precipitation

• empirical temperature-dependent equations;
• averaged density of frozen precipitation is defined from weighted contribution of each hydrometeor species

18. The depth of new snow is defined from its liquid equivalent and density of frozen precipitation

With the certain level of confidence in the skill of the model, the next requirement is to provide land static fields and surface parameters with the best possible accuracy. RAP and HRRR use the same datasets as GFS Noah Land Surface Model. But instead of specifying surface parameters for the dominant soil and land-use category in the grid box, RUC LSM takes into account the sub-grid scale heterogeneity in the computation of such parameters as roughness length, emissivity, soil porosity, soil heat capacity and others. The difference in roughness between the mosaic and dominant category presented on figure 2 is positive from contribution of the forests, which helped to reduce high biases of surface wind speeds in these regions. Roughness lenghth has also seasonal variability in the cropland regions, which again helped to improve the wind forecasts during the warm season.

RUC LSM has a land and a sea ice components.

Main module in WRF and CCPP:

• module module_sf_ruclsm

  This module contains both land and ice components of the RUC LSM model, which is a soil/veg/snowpack and ice/snowpack land-surface model to update soil moisture, soil/ice temperature, skin temperature, snowpack water content, snowdepth, and all terms of the surface energy balance and surface water balance.

Main modules in MPAS

MPAS has separate modules for RUC land and ice components called out of lsm_driver and seaice_driver:

• module module_ruc_land
• module module_ruc_ice

Subroutines include:

• sfctmp - top subroutine to compute evergy and moisture budgets.

• soil - this subroutine calculates energy and moisture budget for vegetated surfaces without snow, and heat diffusion and Richards eqns in soil.

  • it calls soiltemp subroutine to update soil temerature and skin temprature.
  • it calls soilmoist subroutine to compute soil moisture and surface runoff.

• snowsoil - this subroutine is called for snow covered areas of land. It solves energy and moisture budgets on the surface of snow, and on the interface of snow and soil.

  • it calls snowtemp subroutine to computes skin temperature, snow temperature, soil tmperature and moisture, surface runoff, snow depth and snow melt.
  • it calls soilmoist subroutine to compute soil moisture and surface runoff

• soilprop - computes thermal diffusivity and diffusional and hydraulic conductivities.

• tranf - compoutes transpiration function.

• vilka - this subroutine finds the solution of energy budget at the surface from the pre-computed table of saturated water vapor mixing ratio and estimated surface temperature.

  • 'AVOST IN VILKA' means that the energy budget cannot be resolved, the most likely reason is that the input to RUC LSM is inconsistent or wrong.
  • The computations will stop in WRF and MPAS, although they will continue in the UFS, but the points with AVOST will have bad values of skin temperature and water vapor mixing ratio.

• soilvegin - this subroutine computes effective land and soil parameters in the grid cell from the weighted contribution of soil and land categories represented in the grid cell.

• sice - this subroutine is called for sea ice without accumulated snow on its surface.

  • it solves heat diffusion inside ice and energy budget at the surface of ice, computes skin temperature and temerature inside sea ice.

• snowseaice - this subroutine is called for sea ice with accumulated snow on its surface.

  • It solves energy budget on the snow interface with atmosphere and snow interface with ice, calculates skin temperature, snow and ice temperatures, snow depth and snow melt.

RUC LSM use in MPAS:

• namelist_init_atmosphere
  • config_nsoillevels = 9
• namelist_atmosphere
  • config_lsm_scheme = 'sf_ruc'
  • num_soil_layers = 9

RUC LSM use in CCPP:

• input.nml
  • lsm = 3
  • lsoil_lsm = 9

RUC LSM use in WRF (HRRR)

• wrf.nl
  • sf_surface_physics = 3
  • num_soil_layers = 9

CCPP argument list:

Local_name........standard_name............long_name........................................................units.......type.....dimensions...kind...intent...optional

• iter..........ccpp_loop_counter.....loop counter for subcycling loops in CCPP.............index.......integer......()............in...................False
• me.............mpi_rank.............current MPI-rank......................................index.......integer......()............in...................False
• master.........mpi_root.............master MPI-rank....index.....integer.....().....in.....False
• kdt............index_of_time_step...current number of time steps.....index.....integer.....().....in.....False
• im.............horizontal_loop_extent....horizontal loop extent count.....integer.....().....in.....False
• nlev...........vertical_dimension........number of vertical levels count.....integer.....().....in.....False
• lsoil_ruc......soil_vertical_dimension_for_land_surface_model.......number of soil layers internal to land surface model.....count.....integer.....().....in.....False
• lsoil..........soil_vertical_dimension..............................soil vertical layer dimension............................count.....integer.....().....in.....False
• zs.............depth_of_soil_levels_for_land_surface_model..........depth of soil levels for land surface model m real (soil_vertical_dimension_for_land_surface_model).....kind_phys.....inout.....False
• t1.............air_temperature_at_lowest_model_layer................mean temperature at lowest model layer............K.....real.....(horizontal_dimension).....kind_phys....in.....False
• q1.............water_vapor_specific_humidity_at_lowest_model_layer....water vapor specific humidity at lowest model layer.....kg kg-1.....real.....(horizontal_dimension).....kind_phys.....in.....False
• qc.............cloud_condensed_water_mixing_ratio_at_lowest_model_layer.....moist (dry+vapor, no condensates) mixing ratio of cloud water at lowest model layer.....kg kg-1.....real.....(horizontal_dimension).....kind_phys.....in.....False
• soiltyp........soil_type_classification.............................soil type at each grid cell...........index.....integer.....(horizontal_dimension).....inout....False
• vegtype........vegetation_type_classification..............vegetation type at each grid cell.....index.....integer.....(horizontal_dimension).....inout....False
• sigmaf.........vegetation_area_fraction.......areal fractional cover of green vegetation.....frac.....real.....(horizontal_dimension).....kind_phys.....in.....False
• laixy..........leaf_area_index................leaf area index..........none.......real.......(horizontal_dimension)......kind_phys.....in.....False
• sfcemis........surface_longwave_emissivity_over_land_interstitial....surface lw emissivity in fraction over land (temporary use as interstitial).....frac.....real....horizontal_dimension) .....kind_phys.....inout......False
• dlwflx.........surface_downwelling_longwave_flux.......surface downwelling longwave flux at current time.....W m-2.....real.....(horizontal_dimension).....kind_phys.....in......False
• dswsfc.........surface_downwelling_shortwave_flux......surface downwelling shortwave flux at current time.....W m-2.....real.....(horizontal_dimension).....kind_phys.....in.....False
• snet...........surface_net_downwelling_shortwave_flux.....surface net downwelling shortwave flux at current time.....W m-2.....real.....(horizontal_dimension).....kind_phys.....in.....False
• delt...........time_step_for_dynamics..........physics time step.....s......real.....().....kind_phys.....in.....False
• tg3 deep_soil_temperature deep soil temperature K real (horizontal_dimension) kind_phys in False
• cm surface_drag_coefficient_for_momentum_in_air_over_land surface exchange coeff for momentum over land none real (horizontal_dimension) kind_phys in False
• ch surface_drag_coefficient_for_heat_and_moisture_in_air_over_land surface exchange coeff heat & moisture over land none real (horizontal_dimension) kind_phys in False
• prsl1 air_pressure_at_lowest_model_layer mean pressure at lowest model layer Pa real (horizontal_dimension) kind_phys in False
• zf height_above_ground_at_lowest_model_layer layer 1 height above ground (not MSL) m real (horizontal_dimension) kind_phys in False
• wind wind_speed_at_lowest_model_layer wind speed at lowest model level m s-1 real (horizontal_dimension) kind_phys in False
• shdmin minimum_vegetation_area_fraction min fractional coverage of green vegetation frac real (horizontal_dimension) kind_phys in False
• shdmax maximum_vegetation_area_fraction max fractional coverage of green vegetation frac real (horizontal_dimension) kind_phys in False
• alvwf mean_vis_albedo_with_weak_cosz_dependency mean vis albedo with weak cosz dependency frac real (horizontal_dimension) kind_phys in False
• alnwf mean_nir_albedo_with_weak_cosz_dependency mean nir albedo with weak cosz dependency frac real (horizontal_dimension) kind_phys in False
• snoalb upper_bound_on_max_albedo_over_deep_snow maximum snow albedo frac real (horizontal_dimension) kind_phys in False
• sfalb surface_diffused_shortwave_albedo mean surface diffused sw albedo frac real (horizontal_dimension) kind_phys inout False
• flag_iter flag_for_iteration flag for iteration flag logical (horizontal_dimension) in False
• flag_guess flag_for_guess_run flag for guess run flag logical (horizontal_dimension) in False
• isot soil_type_dataset_choice soil type dataset choice index integer () in False
• ivegsrc vegetation_type_dataset_choice land use dataset choice index integer () in False
• fice sea_ice_concentration ice fraction over open water frac real (horizontal_dimension) kind_phys inout False
• smc volume_fraction_of_soil_moisture total soil moisture frac real (horizontal_dimension, soil_vertical_dimension) kind_phys inout False
• stc soil_temperature soil temperature K real (horizontal_dimension, soil_vertical_dimension) kind_phys inout False
• slc volume_fraction_of_unfrozen_soil_moisture liquid soil moisture frac real (horizontal_dimension, soil_vertical_dimension) kind_phys inout False
• lsm_ruc flag_for_ruc_land_surface_scheme flag for RUC land surface model flag integer () in False
• lsm flag_for_land_surface_scheme flag for land surface model flag integer () in False
• land flag_nonzero_land_surface_fraction flag indicating presence of some land surface area fraction flag logical (horizontal_dimension) in False
• islimsk sea_land_ice_mask sea/land/ice mask (=0/1/2) flag integer (horizontal_dimension) in False
• rdlai flag_for_reading_leaf_area_index_from_input flag for reading leaf area index from initial conditions for RUC LSM flag logical () in False -imp_physics flag_for_microphysics_scheme choice of microphysics scheme flag integer () in False
• imp_physics_gfdl flag_for_gfdl_microphysics_scheme choice of GFDL microphysics scheme flag integer () in False
• imp_physics_thompson flag_for_thompson_microphysics_scheme choice of Thompson microphysics scheme flag integer () in False
• smcwlt2 volume_fraction_of_condensed_water_in_soil_at_wilting_point soil water fraction at wilting point frac real (horizontal_dimension) kind_phys inout False
• smcref2 threshold_volume_fraction_of_condensed_water_in_soil soil moisture threshold frac real (horizontal_dimension) kind_phys inout False
• do_mynnsfclay do_mynnsfclay flag to activate MYNN surface layer flag logical () in False
• con_cp specific_heat_of_dry_air_at_constant_pressure specific heat !of dry air at constant pressure J kg-1 K-1 real () kind_phys in False
• con_rv gas_constant_water_vapor ideal gas constant for water vapor J kg-1 K-1 real () kind_phys in False
• con_rd gas_constant_dry_air ideal gas constant for dry air J kg-1 K-1 real () kind_phys in False
• con_g gravitational_acceleration gravitational acceleration m s-2 real () kind_phys in False
• con_pi pi ratio of a circle's circumference to its diameter none real () kind_phys in False
• con_hvap latent_heat_of_vaporization_of_water_at_0C latent heat of vaporization/sublimation (hvap) J kg-1 real () kind_phys in False
• con_fvirt ratio_of_vapor_to_dry_air_gas_constants_minus_one rv/rd - 1 (rv = ideal gas constant for water vapor) none real () kind_phys in False
• weasd water_equivalent_accumulated_snow_depth_over_land water equiv of acc snow depth over land mm real (horizontal_dimension) kind_phys inout False
• snwdph surface_snow_thickness_water_equivalent_over_land water equivalent snow depth over land mm real (horizontal_dimension) kind_phys inout False
• tskin surface_skin_temperature_over_land_interstitial surface skin temperature over land use as interstitial K real (horizontal_dimension) kind_phys inout False
• tskin_wat surface_skin_temperature_over_ocean_interstitial surface skin temperature over ocean (temporary use as interstitial) K real (horizontal_dimension) kind_phys inout False
• rainnc lwe_thickness_of_explicit_rainfall_amount_from_previous_timestep explicit rainfall from previous timestep m real (horizontal_dimension) kind_phys in False
• rainc lwe_thickness_of_convective_precipitation_amount_from_previous_timestep convective_precipitation_amount from previous timestep m real (horizontal_dimension) kind_phys in False
• fice lwe_thickness_of_ice_amount_from_previous_timestep ice amount from previous timestep m real (horizontal_dimension) kind_phys in False
• snow lwe_thickness_of_snow_amount_from_previous_timestep snow amount from previous timestep m real (horizontal_dimension) kind_phys in False
• graupel lwe_thickness_of_graupel_amount_from_previous_timestep graupel amount from previous timestep m real (horizontal_dimension) kind_phys in False
• srflag flag_for_precipitation_type snow/rain flag for precipitation flag real (horizontal_dimension) kind_phys inout False
• smois volume_fraction_of_soil_moisture_for_land_surface_model volumetric fraction of soil moisture for lsm frac real (horizontal_dimension, soil_vertical_dimension_for_land_surface_model) kind_phys inout False
• tslb soil_temperature_for_land_surface_model soil temperature for land surface model K real (horizontal_dimension, soil_vertical_dimension_for_land_surface_model) kind_phys inout False
• sh2o volume_fraction_of_unfrozen_soil_moisture_for_land_surface_model volume fraction of unfrozen soil moisture for lsm frac real (horizontal_dimension, soil_vertical_dimension_for_land_surface_model) kind_phys inout False
• keepfr flag_for_frozen_soil_physics flag for frozen soil physics (RUC) flag real (horizontal_dimension, soil_vertical_dimension_for_land_surface_model) kind_phys inout False
• smfrkeep volume_fraction_of_frozen_soil_moisture_for_land_surface_model volume fraction of frozen soil moisture for lsm frac real (horizontal_dimension, soil_vertical_dimension_for_land_surface_model) kind_phys inout False
• canopy canopy_water_amount canopy water amount kg m-2 real (horizontal_dimension) kind_phys inout False
• trans transpiration_flux total plant transpiration rate W m-2 real (horizontal_dimension) kind_phys out False
• tsurf surface_skin_temperature_after_iteration_over_land surface skin temperature after iteration over land K real (horizontal_dimension) kind_phys inout False
• tsnow snow_temperature_bottom_first_layer snow temperature at the bottom of first snow layer K real (horizontal_dimension) kind_phys inout False
• zorl surface_roughness_length_over_land_interstitial surface roughness length over land (temporary use as interstitial) cm real (horizontal_dimension) kind_phys inout False
• sfcqc cloud_condensed_water_mixing_ratio_at_surface moist cloud water mixing ratio at surface kg kg-1 real (horizontal_dimension) kind_phys inout False
• sfcdew surface_condensation_mass surface condensation mass kg m-2 real (horizontal_dimension) kind_phys inout False
• tice sea_ice_temperature_interstitial sea ice surface skin temperature use as interstitial K real (horizontal_dimension) kind_phys inout False
• sfcqv water_vapor_mixing_ratio_at_surface water vapor mixing ratio at surface kg kg-1 real (horizontal_dimension) kind_phys inout False
• sncovr1 surface_snow_area_fraction_over_land surface snow area fraction frac real (horizontal_dimension) kind_phys inout False
• qsurf surface_specific_humidity_over_land surface air saturation specific humidity over land kg kg-1 real (horizontal_dimension) kind_phys inout False
• gflux upward_heat_flux_in_soil_over_land soil heat flux over land W m-2 real (horizontal_dimension) kind_phys out False
• drain subsurface_runoff_flux subsurface runoff flux kg m-2 s-1 real (horizontal_dimension) kind_phys out False
• evap kinematic_surface_upward_latent_heat_flux_over_land kinematic surface upward evaporation flux over land kg kg-1 m s-1 real (horizontal_dimension) kind_phys out False
• hflx kinematic_surface_upward_sensible_heat_flux_over_land kinematic surface upward sensible heat flux over land K m s-1 real (horizontal_dimension) kind_phys out False
• rhosnf density_of_frozen_precipitation density of frozen precipitation kg m-3 real (horizontal_dimension) kind_phys out False
• runof surface_runoff_flux surface runoff flux kg m-2 s-1 real (horizontal_dimension) kind_phys out False
• runoff total_runoff total water runoff kg m-2 real (horizontal_dimension) kind_phys inout False
• srunoff surface_runoff surface water runoff (from lsm) kg m-2 real (horizontal_dimension) kind_phys inout False
• chh surface_drag_mass_flux_for_heat_and_moisture_in_air_over_land thermal exchange coefficient over land kg m-2 s-1 real (horizontal_dimension) kind_phys inout False
• cmm surface_drag_wind_speed_for_momentum_in_air_over_land momentum exchange coefficient over land m s-1 real (horizontal_dimension) kind_phys inout False
• evbs soil_upward_latent_heat_flux soil upward latent heat flux W m-2 real (horizontal_dimension) kind_phys out False
• evcw canopy_upward_latent_heat_flux canopy upward latent heat flux W m-2 real (horizontal_dimension) kind_phys out False
• sbsno snow_deposition_sublimation_upward_latent_heat_flux latent heat flux from snow depo/subl W m-2 real (horizontal_dimension) kind_phys out False
• stm soil_moisture_content soil moisture content kg m-2 real (horizontal_dimension) kind_phys inout False
• wetness normalized_soil_wetness_for_land_surface_model normalized soil wetness frac real (horizontal_dimension) kind_phys inout False
• acsnow accumulated_water_equivalent_of_frozen_precip snow water equivalent of run-total frozen precip kg m-2 real (horizontal_dimension) kind_phys inout False
• snowfallac total_accumulated_snowfall run-total snow accumulation on the ground kg m-2 real (horizontal_dimension) kind_phys inout False
• flag_init flag_for_first_time_step flag signaling first time step for time integration loop flag logical () in False
• flag_restart flag_for_restart flag for restart (warmstart) or coldstart flag logical () in False
• errmsg ccpp_error_message error message for error handling in CCPP none character () len=* out False
• errflg ccpp_error_flag error flag for error handling in CCPP flag integer ()

MPAS log:

2 June 2025 a5f54275a - dded option to not initialize RUC LSM state variables for restart or cycling.