Development of a Regional Arctic Climate System Model (RACM) ---

1. 4 3 12 Surface Runoff Field (JFM 2003) Surface and soil Temperature (JFM. 2003) 7 Simulations Coupling Guideline 1 Introduction Intensified warming of the Arctic region is expected to affect not only global climate but also 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-POP-CICE fully coupled system has been run over the Arctic region in the wr50a grid for more than 6 months and is ready for long-time simulation. The ability of RACM to reproduce hydrological processes will be evaluated primarily by comparing model simulations with precipitation and temperature observations. For preliminary model performance evaluation, we also compared the surface runoff, snow water equivalent, latent heat, surface temperature and first layer soil temperature from WRF-VIC-POP-CICE with VIC/obs (VIC offline simulation driven by observation meteorological forcing ). These efforts will later be part of a 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. Snow Water Equivalent Field (JFM 2003) 8 9 13 5 Future Work Precipitation ( JFM 2003) 2 Model Description Summary Latent Heat (JFM 2003) Ground Heat Flux (JFM 2003) Sensible Heat (JFM 2003) 11 10 6 Surface Air Temperature 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 RACM VIC/Obs NCEP 2 Surface First Layer 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. RACM RACM produces higher surface runoff than VIC/Obs over North America which is consistent with its precipitation patterns. RACM VIC/Obs NCEP 2 VIC/Obs RACM: WRF-VIC-POP-CICE fully coupled simulation over the Arctic region in the wr50a_a9v4 grid (Jan. – Jun. 2003) with real sea ice condition. NCEP 2 RACM produces greater snow depths than VIC/Obs over western Europe and Canada. VIC/Obs: VIC Offline Simulations of the Arctic domain (1995-2004) at wr50a resolution driven by meteorological observation (provided by Princeton University). RACM VIC/Obs NCEP 2 RACM produces colder surface than VIC/Obs over most Arctic area. RACM and NCEP-2 exhibits similar spatial pattern. RACM Observations RACM is much wetter than observations over northern North America. It matches observations more closely over Siberia. Parrellizing VIC land model in CCSM to improve computing performance. The magnitude and spatial pattern of latent heat of RACM matches VIC/Obs quite well Implement VIC routing model into RACM Performing multi-year simulation to evaluate the model performance VIC/Obs NCEP 2 RACM • The macroscale hydrology model VIC has been successfully coupled with WRF through CCSM4 flux coupler CPL7. • WRF-VIC-POP-CICE successfully runs more than 6 months over Arctic in wr50a grid. • Currently RACM is basically ready for long-time (multi-year) simulation since VIC has restart function and also is able to produce its own output. • Currently RACM produces wetter climate especially over Canada and northern part America, and basically captures temperature pattern but has significantly warm bias over northeast Siberia. RACM – Obs. 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. RACM Generally, RACM and VIC/Obs produce comparable sensible heat. RACM VIC/Obs Generally, RACM produces less ground heat flux than VIC/Obs by about 5 W/m2. Generally, RACM captures the spatial patterns of temperature, but is much warmer than observations, especially over northeastern Siberia. Observation