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WRF-VIC: The Flux Coupling Approach

WRF-VIC: The Flux Coupling Approach. L. Ruby Leung Pacific Northwest National Laboratory BioEarth Project Kickoff Meeting April 11-12, 2011 Pullman, WA. What is WRF.

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WRF-VIC: The Flux Coupling Approach

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  1. WRF-VIC: The Flux Coupling Approach L. Ruby Leung Pacific Northwest National Laboratory BioEarth Project Kickoff Meeting April 11-12, 2011 Pullman, WA 1

  2. What is WRF • WRF 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 2

  3. What is VIC • VIC is a macroscale hydrologic model that includes features important for atmosphere-land-vegetation coupling Parameterize subgrid variability of precipitation Infiltration excess runoff Surface- and groundwater interactions Saturation excess runoff ARNO baseflow curve Hydraulic redistribution Interactions of water movement between the root system and soil porous media 3

  4. 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 LSM • MM5-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 interactions • MM5-VIC applied to the U.S. at 60 km grid resolution for 1986 – 2002 (Leung et al. 2010) 4

  5. Terrestrial water storage anomaly Leung et al. (2010) 5

  6. The Flux Coupling Approach • Regional 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 CPL7 • VIC surface and subsurface runoff parameterizations added to CLM4 • The flux coupling approach allows each model to be applied on its own grids and be maintained as separate models and utilized different CPUs GCM/Reanalysis Flux Coupler (CPL7) Atmosphere (WRF/Chem) Ocean (ROMS) RESM Land/Veg/C/N (CLM/VIC) Ocean (POP) Sea Ice (CSIM) Atmosphere (CAM) CESM 6

  7. Running WRF-VIC • Configure WRF-VIC domain (only tested the same domain for WRF/VIC with no nesting) using WRF WPS • Generate a mapping file for mapping of fluxes between WRF and VIC using SCRIP • Create input data for WRF from global reanalysis or GCMs using WRF WPS • Create data for data ocean (if not coupled with an ocean model) based on SST from WPS • Create input data for VIC • Soil, vegetation, snowband parameter files based on global 0.05 degree data • Run 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 7

  8. Testing of WRF-CLM/VIC • WRF-CLM has been tested using a global domain with CLM input data available from CCSM • WRF-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 8

  9. Comparison of observed and WRF-CLM simulated fluxes Green Ridge, OR Tonzi, CA 9

  10. Discussion: • Model domain • Nesting could be a big challenge • Region and resolution • Computational resources and wall clock time • WRF coupling with other components • Online/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 components • Online 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 models • Hydrologic (VIC vs RHESSys) and biogeochemistry components • Code management • Common code repository • Central input and output data archive 10

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