WRF-VIC: The Flux Coupling Approach

L. Ruby LeungPacific Northwest National Laboratory

BioEarth Project Kickoff Meeting

April 11-12, 2011

Pullman, WA

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What is WRFWRF is a “community model” that stands for Weather Research and Forecasting model – a free and shared resource with distributed development (NCAR, NOAA, AFWA, FAA, NRL, …) and centralized support (NCAR)

Since version 2.1 (2005), WRF has two dynamical cores: ARW and NMM – both non-hydrostatic, Eulerian mass, with terrain following vertical coordinates

Under the NCAR NRCM initiative (2003 – 2008), new features have been added to WRF for regional climate applications

WRF includes many options for physics parameterizations, including several land surface models

WRF-Chem includes ‘online’ chemistry to simulate trace gases and particulates simultaneously with the meteorological fields

PNNL scientists have been major contributors to WRF and WRF-Chem, including recent implementations of all CAM4 and CAM5 physics for consistency with CCSM

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What is VICVIC is a macroscale hydrologic model that includes features important for atmosphere-land-vegetation coupling

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Saturation excess runoff

Infiltration excess runoff

ARNO baseflow curve

Surface- and groundwater interactions

Parameterize subgrid variability of precipitation

Hydraulic redistributionInteractions of water

movement between the root system and soil porous

media

Coupling of VIC with Atmospheric Models

To enable VIC to be coupled to atmospheric models, VIC was modified from ‘time-before-space’ to ‘space-before-time’ coding structure (Liang et al. 2006)MM5 and VIC exchange fluxes through a subroutine call from MM5 (Fortran) to VIC (C)Map VIC land surface properties using those defined by the MM5 preprocessor for Noah LSMMM5-VIC surface properties and initialization follow the standard VIC procedures and applied to the North American monsoon region (Zhu et al. 2009)Added a groundwater parameterization (Liang et al. 2003) to simulate surface water – groundwater interactionsMM5-VIC applied to the U.S. at 60 km grid resolution for 1986 – 2002 (Leung et al. 2010)

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Terrestrial water storage anomaly

Leung et al. (2010)

The Flux Coupling ApproachRegional Arctic Coupled Model (RACM) and PNNL iRESM

WRF (v3.2) and VIC (v.4.0.4) have been added to the CESM repository and communicate with the flux coupler CPL7VIC surface and subsurface runoff parameterizations added to CLM4The flux coupling approach allows each model to be applied on its own grids and be maintained as separate models and utilized different CPUs

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Ocean (ROMS)RESM

Flux Coupler(CPL7)

Land/Veg/C/N(CLM/VIC)

Atmosphere(CAM)

Ocean (POP)

Sea Ice (CSIM)

CESM

Atmosphere(WRF/Chem)

GCM/Reanalysis

Running WRF-VIC

Configure WRF-VIC domain (only tested the same domain for WRF/VIC with no nesting) using WRF WPSGenerate a mapping file for mapping of fluxes between WRF and VIC using SCRIPCreate input data for WRF from global reanalysis or GCMs using WRF WPSCreate data for data ocean (if not coupled with an ocean model) based on SST from WPSCreate input data for VIC

Soil, vegetation, snowband parameter files based on global 0.05 degree dataRun offline VIC with atmospheric forcing interpolated from 1/8 degree data to generate initial conditions for VIC (e.g., 1-hour time step, energy mode)Create VIC initial conditions for WRF-VIC

Compile and run WRF-VIC in the CESM environment

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Testing of WRF-CLM/VIC

WRF-CLM has been tested using a global domain with CLM input data available from CCSMWRF-CLM has also been applied in a regional domain for western US at 12 km resolution using high resolution CLM data (0.05 degree) (2003/10 – 2004/9)WRF-VIC has been tested in a global domain and an Arctic domain (Chunmei Zhu, UW)PNNL will test WRF-VIC in a western US or PNW domain

Simulated rainfall from WRF-CLM on global domain Simulated skin temperature from WRF-CLM on

regional domain

Comparison of observed and WRF-CLM simulated fluxes

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Tonzi, CA

Green Ridge, OR

Discussion:Model domain

Nesting could be a big challengeRegion and resolutionComputational resources and wall clock time

WRF coupling with other componentsOnline/offline coupling with chemistry (WRF-CMAQ)?Offline coupling with emission (MEGAN)?Merging of codes that involve WRF coupled to other components

VIC coupling with other componentsOnline coupling with managed and unmanaged ecosystems and biogeochemistry models (CropSyst and RHESSys)Online coupling with river routing (RHESSys)?Offline coupling with water management and policy (ColSim)Merging of codes that involve VIC coupled to other components

Consistency across modelsHydrologic (VIC vs RHESSys) and biogeochemistry components

Code managementCommon code repositoryCentral input and output data archive

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