Performance of the VIC land surface model in coupled simulations Development of a Regional Arctic Climate System Model (RACM) --- Performance of the VIC land surface model in coupled simulations Chunmei Zhu1, Dennis Lettenmaier1, Juanxiong He2, Tony Craig3, Wieslaw Maslowski4 1Department of Civil and Environmental Engineering, Box 352700, University of Washington, Seattle, WA 98195 2International Arctic Research Center, Fairbanks, AK; 3National Center for Atmospheric Research; 4Naval Postgraduate School 3 9 6 Surface and soil Temperature (Jan . 2003) Surface Runoff Field (Jan 2003) Coupling Guideline WRF/VIC WRF Surface First Layer 1 Introduction In CCSM4, the communication process is separated from the component integration process. All communication processes are performed by Cpl7 and the components run by themselves. Our coding work therefore is mainly focused on replacing CLM with VIC. Most of the coding doesn’t involve Cpl7 directly. Key aspects of the work include: ● Extract VIC as it runs in an existing MM5-VIC coupling system for interaction with the flux coupler (because VIC in MM5 is in image mode, i.e., runs at all space for a given time step, as contrasted with point mode, which runs all time steps at a given grid node before proceeding to the next grid node). ● Current versions of VIC don’t have the capacity for parallel operation. ● VIC and the flux coupler exchange fields hourly (the time step at which VIC runs). This allows WRF and VIC to run at different time steps. Intensified warming of the Arctic region is expected to affect not only global climate but also change the climate and hydrology of the constituent land areas. Hence, understanding the functioning of the Arctic climate system is important both for its contribution to, and response from global change. To address these issues, a state-of-the-art Regional Arctic Climate system Model (RACM) is being constructed which includes high-resolution atmosphere, ocean, sea ice, and land hydrology components. As part of the RACM development, we have successfully coupled the macroscale Variable Infiltration Capacity (VIC) hydrology model with the Weather Research and Forecasting (WRF) regional climate model through the new Community Climate System Model (CCSM) flux coupling architecture CPL7. At present, the WRF/VIC coupled system has been run over the Arctic region in the wr50a grid for more than 3 months with ocean and sea ice conditions prescribed (“data model”) and is ready for long-time simulation. The ability of the WRF/VIC in RACM to reproduce hydrological processes will be preliminarily evaluated by comparing model simulations with precipitation and temperature observations. To preliminarily evaluate the model performance, we also compared the surface runoff, snow water equivalent, latent heat, surface temperature and first layer soil temperature from WRF/VIC, WRF (noah) and NCEP/NCAR reanalysis 2 data for Jan 2003. These efforts will later be part of the foundation to explore the complex interactions and feedbacks among the components of the Arctic climate system that contribute to observed and predicted changes in Arctic climate. WRF/VIC NCEP-2 WRF WRF produced higher surface runoff than WRF-VIC and NCEP-2, which is consistent with precipitation pattern. NCEP-2 4 Precipitation ( JFM 2003) NCEP-2 7 Snow Water Equivalent Field (Jan 2003) WRF WRF/VIC Observation WRF/VIC NCEP 2 Jan. 1-15 2 Model Description WRF/VIC produces warmer surface and soil than WRF (noah) over most Arctic area, which is related to the surface thermal scheme. WRF/VIC and NCEP-2 exhibits similar spatial pattern than WRF (noah). 10 Future Work Generally, WRF/VIC exhibits much drier climate than observation. But the deviation of WRF-VIC seems less than WRF(NOAH). WRF/VIC produces much higher snow depth than WRF- noah and NCEP-2 reannalysis. Parrellizing VIC land model in CCSM to improve computing performance. WRF JFM Implement VIC routing model into RACM Performing multi-year simulation to evaluate the model performance 5 Surface Air Temperature Summary Latent Heat (Jan 2003) 8 The macroscale hydrology model VIC has been successfully coupled with WRF through CCSM4 flux coupler CPL7. WRF/VIC successfully runs more than 3 months over Arctic in wr50a grid with ocean and sea ice as a data model. Currently WRF/VIC is basically ready for long-time (multi-year) simulation since VIC has restart function and also is able to produce its own output. Currently WRF/VIC produces drier climate especially over Russia, Finland, Sweden and Norway, and basically captures temperature pattern but has significantly cold bias over Russia. Observation WRF WRF/VIC NCEP-2 Model features: multiple vegetation classes in each cell energy and water budget closure at each time step subgrid infiltration and runoff variability non-linear baseflow generation critical elements relevant to high latitude implementations: a snow model, a frozen soil algorithm, a lake/wetland model, and a blowing snow model. WRF/VIC Jan. 1-15 Generally, WRF/VIC still captures the spatial temperature pattern, but exhibits much colder climate than observation especially over Russia. WRF-VIC and WRF-noah produce comparable magnitude of latent heat, but are much less than NCEP-2. WRF JFM