WRF Version 4.3

The WRF Model has been updated to Version 4.3 on May 10, 2021.

Acknowledgements: We would like to thank Matthias Göbel (University of Innsbruck), Jaemo Yang and Yu Xie (NREL), Will Hatheway, Douglas Lowe (University of Manchester), Ted Mansell and Louis Wicker (NOAA/NSSL), Sam Elliott (TQI), Megan Bela and Stu McKeen (CU Boulder CIRES/NOAA CSL), Xinzhong Liang (University of Maryland), Tzu-Chin Tsai and Jen-Ping Chen (National Taiwan University), Robert Gilliam and Jonathan Pleim (US EPA), Alexander Ukhov (KAUST), Zhixiao Zhang (University of Utah), Adam Varble (PNNL and University of Utah), Katelyn Barber and Brian Gaudet (PNNL), Robert Arthur, Katie Lundquist, and Jeff Mirocha (LLNL), Sam Levis (SLevis Consulting), Andrea Zonato (University of Trento, Italy), Michael Toy (NOAA/GSL), Chunxi Zhang (NCEP) and Yuqing Wang (University of Hawaii), Eric A. Hendricks (NCAR/NSAP), James Ruppert (Penn State University), Isaac Rowe (University of Kentucky), Alex Montornès (University of Barcelona), Yunyao Li and Xin-Liang Zhong (University of Maryland), Jan Mandel (University of Colorado, Denver), Stacy Walters (formerly NCAR), Luke Conibear (University of Leeds), Sonia Lasher-Trapp (University of Illinois), T. Iguchi (NASA/Goddard), Wei Sun (Chinese Academy of Sciences), Greg Thompson (JCSDA), Prasanth Valayamkunnath, Pedro Jimenez, Jamie Bresch, Craig Schwartz, Jim Bresch, Cenlin He, Hugh Morrison, Masih Eghdami, Timothy W. Juliano, Negin Sobhani, Dave Lawrence, Bill Sacks, Jared Lee, Laura Fowler, and Mary Barth (NCAR)

Note: WRF v4.3 is the last release of the WRF model that will support the NMM dynamical core and HWRF capability. Beginning with WRF v4.3.1 and with all subsequent releases, the NMM and HWRF capabilities will incrementally be removed from the model source code.

New in Version 4.3

Physics

• A turbulence kinetic energy (TKE) and TKE dissipation rate (ε) based 1.5-order closure PBL parameterization (E–ε, EEPS) is added (Zhang et al. 2020, MWR). Works with surface layer options, 1, 91, and 5.

• An updated version of P3 now includes a one-ice category, 3-moment ice option. Milbrandt et al. (2021) [Milbrandt, J. A., H. Morrison, D. T. Dawson II, and M. Paukert, 2021: A triple-moment representation of ice in the Predicted Particle Properties (P3) microphysics scheme, J. Atmos. Sci., 78(2), 439-458, https://doi.org/10.1175/JAS-D-20-0084.1]

• The NTU (National Taiwan University) scheme (mp_physics = 56). It applies double moments for the liquid-phase and triple moments for the ice-phase hydrometeors together with the consideration for ice crystal shape and density variations. There are five major features to NTU scheme: condensation nuclei (CN) and ice nuclei (IN) are tracked separately for the processes of cloud/rain activation and ice deposition-nucleation using predicted supersaturation; applying the triple-moment (the zeroth, second, and third moments) closure method to describe the evolution of ice particle’s spectrum; solid-phase hydrometeors’ classification (pristine ice, snow aggregate, rimed ice, and hailstone) is redefined according to their key formation mechanisms; ice crystals’ shape and apparent density can evolve gradually according to the growth conditions; and fall speed of each moment for frozen particles depends on shape and density.

  For the detailed parameterizations in the NTU scheme, the liquid-based formulae of the bulk conversion rates are adopted from [1], and the technique for aerosol activation to rain/cloud is introduced in [2] and [3]. The triple-moment approach, representation of ice properties, mixed- and solid-based equation/kernels are illustrated in [4] and [5].

  References:
  [1] Chen, J.-P. and S.-T. Liu, 2004: Physically based two-moment bulkwater parameterization for warm-cloud microphysics. Quart. J. Roy. Meteor. Soc., 130, 51–78, doi:10.1256/qj.03.41.
  [2] Cheng, C.-T., W.-C. Wang, and J.-P. Chen, 2007: A modeling study of aerosol impacts on cloud microphysics and radiative properties. Quart. J. Roy. Meteor. Soc., 133, 283–297, doi:10.1002/qj.25.
  [3] Cheng, C.-T., W.-C. Wang, and J.-P. Chen, 2010: Simulation of the effects of increasing cloud condensation nuclei on mixed-phase clouds and precipitation of a front system. Atmos. Res., 96, 461–476, doi:10.1016/j.atmosres.2010.02.005.
  [4] Chen, J.-P. and T.-C. Tsai, 2016: Triple-moment modal parameterization for the adaptive growth habit of pristine ice crystals. J. Atmos. Sci., 73, 2105-2122, doi:10.1175/JAS-D-15-0220.1.
  [5] Tsai, T.-C. and J.-P. Chen, 2020: Multi-moment ice bulk microphysics scheme with consideration for particle shape and apparent density. Part I: Methodology and idealized simulation. J. Atmos. Sci., 77, 1821–1850, doi:10.1175/JAS-D-19-0125.1.

• Added a new option (ra_sw_eclipse) to model the effect of eclipses based on the Bessel's method in four radiation schemes: RRTMG, Dudhia, Goddard, and old Goddard. Additional output includes the location of the eclipse: ELAT_TRACK and ELON_TRACK. For reference, see this paper: Montornès, A., Codina, B., Zack, J. W., and Sola, Y.: Implementation of Bessel's method for solar eclipses prediction in the WRF-ARW model, Atmos. Chem. Phys., 16, 5949–5967, https://doi.org/10.5194/acp-16-5949-2016, 2016.

• A new orographic gravity wave drag option is added (gwd_opt = 3). The scheme includes large-scale orographic gravity wave drag in a similar way as in gwd_opt = 1. In addition, two subgrid-scale sources of orographic drag are added in this option. The additional schemes are applicable at coarse horizontal grid resolution (~100s km) down to fine resolutions on the order of 1km, and they account for small-scale ~1km topographic variations. Setting namelist option gwd_diags = 1 (default is "0") causes diagnostic data to be output to the wrfout_d0x files. The data include: 1) 2D vertically integrated momentum fluxes, i.e., surface stress, DUSFC_xx (x-direction) and DVSFC_xx (y-direction), where xx={LS,BL,SS,FD}, which are "large-scale", "blocking", "small-scale" and "form drag" contributions, respectively; and 2) 3D drag forces DTAUX3D_xx (x-direction) and DTAUY3D_xx (y-direction), where xx={LS,BL,SS,FD}. This scheme is contributed by NOAA/GSL.

• The multilayer BEP (Building Effects Parameterization) and BEP+BEM (BEP with the Building Energy Model) urban canopy models (UCMs) are added to the Yonsei University (YSU) planetary boundary layer parameterization. Reference: Hendricks, E. A., J. C. Knievel, and Y. Wang, 2020: Addition of multilayer urban canopy models to a nonlocal planetary boundary layer parameterization and evaluation using ideal and real cases, J. Appl. Met. Clim., 59, 1369-1392.

• Implementation of Local Climate Zone (LCZ using WUDAPT (31-41) landuse classes, along with standard urban classes (31-33). (Ref: Stewart, I.D. and Oke, T.R. (2012) Local Climate Zones for Urban Temperature Studies. Bulletin of the American Meteorological Society, 93, 1879-1900. http://dx.doi.org/10.1175/BAMS-D-11-00019.1). More information can be found at https://ral.ucar.edu/sites/default/files/public/product-tool/urban-canopy-model/WRF_urban_update_Readme_file_WRF4.3.pdf. Data from https://www.wudapt.org/ is required. Note that the parameters in the new urban table, URBPARM_LCZ.TBL, may vary greatly from city to city. The default values are probably not appropriate for any given city. Users should adapt these values based on the city they are working with.

• WRF-urban updates for green roof, solar panel, and new building drag coefficient for BEP+BEM. The paper describing the green roof update is under development. The new building drag coefficient is based on Santiago and Martilli (2010) and Gutierrez et al. (2015).
  [1] Santiago, J. L. and Martilli, A. (2010). A Dynamic Urban Canopy Parameterization for Mesoscale Models Based on Computational Fluid Dynamics Reynolds-Averaged Navier-Stokes Microscale Simulations. Boundary-Layer Meteorology, 137(3):417-439.
  [2] Gutí errez. E., Martilli, A., Santiago, J. L., and González, J. E. (2015). A Mechanical Drag Coefficient Formulation and Urban Canopy Parameter Assimilation Technique for Complex Urban Environments. Boundary-Layer Meteorology, 157(2):333-341.
  [3] A. Zonato, A. Martilli, E. Gutierrez, F. Chen, C. He, M. Barlage, D. Zardi, and L. Giovannini (2021): Exploring the effects of rooftop mitigation strategies on urban temperatures and energy consumption, Atmospheric Chemistry and Physics (under review).

• A new dynamic irrigation scheme is implemented in NoahMP to estimate irrigation water requirements and apply water in the irrigated croplands. This new scheme irrigates the croplands based on sprinkler, micro, or surface flooding methods. The various options are selected from the namelist, and are described in the run/README.namelist file.

• The capability to couple Community Terrestrial Systems Model (CTSM) with WRF via LIghtweight Land Atmosphere Coupler (LILAC) is added and activated by setting namelist option sf_surface_physics to 6. This is the initial beta release of WRF-CTSM coupling capability. For instructions on how to run WRF with CTSM please check instructions on using CTSM with WRF. See the WRF-CTSM User’s Guide (https://escomp.github.io/ctsm-docs/versions/master/html/lilac/specific-atm-models/wrf.html). Questions regarding this capability can be addressed to the CTSM Forum (https://bb.cgd.ucar.edu/cesm/forums/ctsm-clm-mosart-rtm.134/).

Other New Options

• The Implicit-Explicit Vertical Advection (IEVA) scheme has been implemented that permits a larger time step by partitioning the vertical transport into an explicit piece, which uses the normal vertical schemes present in WRF, and an implicit piece which uses implicit transport (which is unconditionally stable). The combined scheme permits a larger time step than has previously been used, and reduces w-filtering. The scheme will be useful for CONUS-scale CAM (convection allowing model) simulations (dx ~ 2-3 km) when the number of vertical levels > 50. In these cases, time steps can increase to as large as 25 s, depending on the problem. Overall integration efficiency increases ~ 15%, and the IEVA solutions are closer to a benchmark run using a smaller time step. The option is activated by setting zadvect_implicit = 1 in &dynamics.
  Note: Must set reasonable_time_step_ratio to enable the use of larger time steps. ( Wicker, L. J., and W. C. Skamarock, 2020: An Implicit–Explicit Vertical Transport Scheme for Convection-Allowing Models. Mon. Wea. Rev., 148, 3893–3910)

• A new namelist, w_crit_cfl, is added in &dynamics. This is the threshold CFL when W damping starts if w_damping option is on. When IEVA is activated, w_crit_cfl may be set to 2.0.

• MAD-WRF: A solar irradiance nowcasting system that combines the benefits of data assimilation and the philosophy of advecting cloud properties of MADCast, and the cloud physics of WRF-Solar (https://ral.ucar.edu/projects/mad-wrf)

• A new README file (README.physics_files) is now available in the run directory (and is linked to the test/em_real directory during the compile). This file lists all physics options that require additional files for running, and the files necessary for each scheme. These additional files are already in the run/ directory and are linked automatically to the test/em_real directory during compile.

• In combination with updates to the cloud fraction scheme (icloud=3), a new feature permits the usage of the cloud fraction scheme as part of real.exe, specifically designed to use with "cold start" simulations to reduce the spin-up problem of clouds and associated radiation.

• The git commit information is now part of the WRF modeling system standard output, one of the strings within the executables, and also in the output of the ./compile command.

• Air pressure was added as a new height-level diagnostic, which is useful for a model validation against barometers mounted above ground (e.g., on a wind turbine nacelle). Also, the vertical interpolation of pressure to height surfaces was switched to linear in ln(p). The resultant pressure and relative humidity changes are negligible in the lowest 1 km AGL.

• A new namelist option is included that allows a user to avoid double stagger averaging of omega (coordinate velocity) in the vertical advection of geopotential. The new namelist option phi_adv_z allows switching between the two formulations: phi_adv_z = 1 (the old formulation, which remains the default), and phi_adv_z = 2 (the new formulation).

Improvements and Bug Fixes

Physics

Microphysics

• NSSL microphysics updates:

  • Enabled regeneration of CCN by droplet evaporation and by nudged restore in cloud-free air (mp_physics=18; default 1-hr time constant for nudging)
  • Enabled radar reflectivity from cloud ice
  • Added internal option for ice crystal nucleation by DeMott et al. (2010, PNAS)
  • Allow greater fraction of hail to melt in one time step
  • Reduced minimum number concentration (based on CAPS input)
  • Increased resolution of lookup table for incomplete gamma functions
  • Bug fix to limit fall speed air density factor for high model lids
  • Fixed issue of spurious creation of large concentrations of very small droplets and transient large condensation
  • Fixed issue of negligible "seed" values of graupel
  • Fixed effective radius calculation of snow

• Thompson MP scheme: Fixed a problem with a single constant that caused approximately 4x too much fake surface aerosol emissions. Relatively small tunings for one-moment graupel Y-intercept parameter diagnosis, creating a better fit to Paul Field et al (2019) analysis of T-28 aircraft hail data.

Cumulus

• Deng shallow cumulus scheme: Check is added for water vapor mixing ratio (Qv), if negative, setting it to a small positive number. Previously, the scheme died when taking the log of negative Qv.

• Deng shallow cumulus scheme: When the updraft top reached the domain top, the model would crash due to accessing out of bounds memory. The modification is to limit the vertical index of the updraft top.

• Fixed staggering of shallow cumulus tendencies of u and v at periodic boundaries with a PERIOD communication.

Radiation

• A fix is introduced to the RRTMG SW parameterization. When the model top is relatively low, and the threshold for tropopause pressure is not reached, laytrop = nlayers. In this case, some indices in sfluxzen can be filled with junk, ultimately leading to NaN values for SWDOWN and failure in the radiation driver. The modification is to initialize sfluxzen to zero before being filled.

• Three-dimensional clear sky radiative heat tendencies are now available as output variables when using the following radiation schemes: RRTM longwave (ra_lw_phys=1), CAM shortwave and longwave (ra_sw_phys, ra_lw_phys=3), RRTMG shortwave and longwave (ra_sw_phys, ra_lw_phys=4), RRTMG-fast version shortwave and longwave (ra_sw_phys, ra_lw_phys=24), and RRTMG-K shortwave and longwave (ra_sw_phys, ra_lw_phys=14). Similar to the all-sky longwave and shortwave radiative heat tendencies (RTHRATLW and RTHRATSW), the clear-sky tendencies are not included in the default history output stream, but can now be added to it. They can be found in Registry.EM_COMMON as RTHRATLWC for longwave clear-sky heating rate and RTHRATSWC for shortwave clear-sky heating rate.

• Fixed a bug in surface downward diagnostic output of long- and short-wave fluxes and two other bugs involving wrong numerical values used in the RRTMG-K code.

PBL

• UW PBL: input radiative tendency corrected to be T tendency instead of theta (small effect of temperature vs theta, up through the top of the PBL).

• The namelist option ysu_topdown_pblmix for the YSU PBL scheme has been turned on by default in the Registry files. To turn it off, set ysu_topdown_pblmix=0 in the &physics namelist record (single entry).

• A minor fix to BouLac PBL tendency cleans up the assignment, no longer assuming that the tendency is cumulative (no effect on model results).

• Modifications to the ACM2 PBL scheme for rare crashes. The overall effects of these changes are generally small although the indexing fix will prevent model crashes in extreme terrain (e.g. Tibet).

• Fixed a few bugs for the 3DTKE scheme: 1) Fixed a bug when converting surface heat flux from dry to moist theta when use_theta_m is enabled, which is the default; 2) Fixed divide by zero; 3) Fixed computed vertical index that is out of range.

LSM

• NoahMP:

  • Corrected code that forced users to turn on the crop scheme when using the irrigation scheme (iopt_irr=2). Now the irrigation scheme can be used without turning on the crop scheme.
  • Change local variable QRAINXY (rain rate on the ground after canopy interception) to output variable.
  • Several snow-relevant enhancements and new features to improve snow simulations based on NCAR Noah-MP LSM team tests. These are: (1) new snow retention process improves streamflow modeling (tested with Noah-MP in National Water Model); (2) optimized parameter values for snow cover parameters (SCFFAC & MFSNO) improve snow water equivalent (SWE), snow depth, and surface albedo simulation; (3) new snow emissivity value improves WRF surface temperature simulation; (4) new wet-bulb temperature snow-rain partitioning scheme (opt_snf=5) improves SWE simulation see Wang et al. 2019 GRL; (5) enhanced flexibility of tuning model parameters by bringing the above-mentioned parameters from hard-coded values to MPTABLE; (6) Fix the incorrect values for wind-canopy absorption coefficient (CWPVT) parameter and the unrealistic value range of bulk leaf boundary layer resistance (RB). (He et al., 2021, in preparation)

• Modifications to the Pleim-Xiu LSM. The overall effects of these changes are generally small, where the biggest effects on surface statistics was the added evaporation from the ground in vegetative fraction of the grid cell. This, by nature, increases near surface water vapor mixing ratio. In some of our tests this increased the bias in some areas.

Surface Layer

• Several surface layer schemes are made thread-safe if the fractional seaice option is used. These are revised MM5, original MM5, MYJ, QNSE and PX surface layer scheme (sf_sfclay_physics = 1, 91, 2, 4, and 7).

• Fixed a problem that caused the input field “wspd” to not be defined when the combination of MYJ surface layer, MYNN PBL, and the fractional seaice option are used.

Dynamics

• Corrected the tke seed value for km_opt 2 and 5 to be non-zero if and only if the surface heat and momentum fluxes are zero depending on isfflx, diff_opt, and bl_pbl_physics.

• Fixed a bug in hybrid vertical coordinate option 3. Those using the default with the hybrid option activated (hyb_opt=2), or those reverting back to a terrain following coordinate (hyb_opt=0) are not impacted.

• Vertical nesting now works with the hybrid vertical coordinate.

• Vertical nesting now works with the moist theta option use_theta_m=1. The redundant "rebalance" option 2 was removed. The rebalance option must now be set to 1 when vertical refinement is turned on.

• Bug fix to use correct rho value in cal_titau subroutines. In the cal_titau subroutines in module_diffusion_em, rho was not always interpolated to the correct location on the staggered grid. This issue affected the subgrid stress terms when sfs_opt .gt. 1. Additionally, when sfs_opt .eq. 0 and m_opt .eq. 1, the actual subgrid stresses applied in the code were correct, but the output was wrong. A rhoavg variable was added to cal_titau_12_21, cal_titau_13_31, and cal_titau_23_32 and used instead of the cell-centered rho variable.

• Missing corner points are set when setting boundary conditions of 3D variables and all staggered variables are treated equally in symmetric BC. Thereby the periodic BC becomes cleaner and more consistent with set_physical_bc2d and the symmetric BC are fixed as horizontal deformation is treated now as a staggered variable which leads to correct BC for SGS momentum fluxes at the northern boundaries.

Others

• Corrected the incorrect treatment of cloud transmittances of diffuse radiation by clouds in the FARMS system. The impact of these modifications is small.

• A fix is introduced to the FARMS parameterization. When the cosine of solar zenith angle is small, the ice cloud optical thickness can be negative, and the model can crash due to log10 of a negative number. The modification is to limit the value of cloud optical thickness.

• Check is put in to avoid using Deng shallow convection scheme with icloud_bl (MYNN PBL).

• Fixed a restart problem when using 3 or more total domains with feedback turned on, and using RRTMG with o3input=2 (default). Restart now works at all times.

• Fixed a restart problem for nested runs when feedback and smooth_option are both on.

• The feedback and smoothing are removed for all GWD input fields.

• Fix for instances of dt = 0 when using adaptive time stepping together and when step_to_output_time is set to true.

• A few updates to the diagnostic schemes were added. The most unstable (MU) layer and precipitable water (PWAT) were inconsistent with the conventional definitions used by the meteorological communities. LFC, CAPE and CIN calculations previously did not work well while dealing with multiple inversion layers.

• It is no longer necessary to execute a 'run_me_first.csh' script for any of the idealized cases. All necessary physics input files and look-up tables are linked to the corresponding directory during the compilation step

• A bug fix was added to handle the incorrect handling file I/O by the ARW real program when both the following are activated: all_ic_times and multi_bdy_files. The real program effectively skipped outputting some of the processed metgrid time periods by putting the data into an incorrect time. If a user has not seen this failure mode, then this PR does not impact them.

• Added missing OMP directives in ARW solve for the option do_avgflx_em=1. Many OpenMP implementations assume the "END PARALLEL DO", but it is more conventional within WRF to have it.

• Bug fix for idealized fire case that caused a fatal error when simulations were run with a nested domain.

• The netcdf diffwrf program no longer by-passes integer data, but considers these types of gridded fields as eligible for comparison.

• The files HLC.TBL, and wind-turbine-1.tbl are now removed from the test/ directories when doing 'clean -a'.

• Namelist variable spec_bdy_final_mu is removed. It is no longer used.

• The namelist.input file in test/em_real directory has been modified to update several variables to bring case location/date/time to a more recent event (2019 Hurricane Dorian), to include settings for current recommendations, and to be consistent with the updated namelist.wps file.

WRFDA

• Added new capability for assimilating surface pm2.5, pm10, O3, CO, NO2, SO2 using 3DVar. (Sun, W., Liu, Z., Chen, D., Zhao, P., and Chen, M., 2020: Development and application of the WRFDA-Chem three-dimensional variational (3DVAR) system: aiming to improve air quality forecasting and diagnose model deficiencies, Atmos. Chem. Phys., 20, 9311-9329.)

• Added new capability for Multi-Resolution Incremental 4DVar (MRI-4DVar).
  (Liu, Z., J. Ban, J.-S, Hong, and Y.-H. Kuo, 2020: Multi-resolution incremental 4D-Var for WRF: Implementation and application at convective scale, Q. J. R. Meteorol. Soc., 146, 3661-3674.)

• WRFDA gen_be_v3 is updated for cv_options=5 and ensemble applications. Please see var/gen_be_v3/README.gen_be_v3.

WRF-Chem

• KPP is now compiled unoptimized. This will help with compiling WRF-Chem on ubuntu (and other smaller memory) systems. Timing tests indicate that this does not cause a significant timing impact on the WRF build time (less than 5%).

• A fix to ensure NH3, CH4, CO2 fire emissions are correctly read-in to WRF-Chem when using RACM chemical mechanisms. Prior to this fix, values for those parameters were low. Users should now expect significantly higher values when using RACM chemical mechanisms.

• The CLM surface scheme and associated subroutines in the physics and chemistry packages have been modified to be made consistent with the MEGANv2.1 biogenic emission model, as opposed to earlier code, which used MEGANv2.0. This upgrade to WRF-CLM parallels the use of MEGANv2.1 in CLM4.0, as described in Guenther et al. (2012, GMD). Within module_sf_clm.F, the emissions for 150 species are computed, and then mapped to the chemistry packages (e.g., SARPC99) in WRF-Chem. Emissions are a function of plant functional type (PFT) and emission factors that depend on temperature, light, and LAI.

• Improvements related to convective transport of trace gases. Addition of the trace gases and aerosol subgrid-scale convective transport (Grell and Freitas, 2014; Li et al., 2018), subgrid-scale wet scavenging (including the improvement of ice retention factors and the conversion ratio of cloud water to rainwater, Li et al., 2019), and aqueous chemistry to the GF cumulus parameterization.

• pH diagnostics added for mozart_mosaic_4bin_aq chemistry.

WRF-Hydro

• WRF-Hydro has been updated to version v5.2.0.