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Development and evaluation of a mosaic/tiling approach in the WRF-Noah framework

The 14th Annual WRF Users' Workshop. Development and evaluation of a mosaic/tiling approach in the WRF-Noah framework. Dan Li 1 Elie Bou-Zeid 1 , Michael Barlage 2 , Fei Chen 2 , James A. Smith 1 1: Department of Civil and Environmental Engineering, Princeton University

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Development and evaluation of a mosaic/tiling approach in the WRF-Noah framework

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  1. The 14th Annual WRF Users' Workshop Development and evaluation of a mosaic/tiling approach in the WRF-Noah framework Dan Li1 Elie Bou-Zeid1, Michael Barlage2, Fei Chen2, James A. Smith1 1: Department of Civil and Environmental Engineering, Princeton University 2: Research Applications Laboratory (RAL), National Center for Atmospheric Research

  2. Outline • Introduction to the mosaic/tiling approach • Evaluation against observations • Case 1: a clear day, 2009-07-14 • Case 2: a rainfall period, 2008-07-21 to 2008-07-27 • Conclusions

  3. Forest 9% Real World: multiple “tiles” within a “grid cell” Urban 27% Grassland 54% Water 6% Wetland 4% dx dy

  4. Modelling World: dominant vs mosaic WRF-Noah WRF-Noah-mosaic (N=3) Forest 10% Urban 30% Grassland 100% Grassland 60%

  5. Hypothesis • Urban environments provide a good test bed for this mosaic/tiling approach due to the considerable surface heterogeneities and the substantial differences between different surface types (e.g., impervious surface and vegetated surface). • Despite that high-resolution (~1–3 km) numerical simulations are usually conducted in urban environments, the sub-grid scale variability of land surface characteristics remains important.

  6. Domain configuration • NLCD2006: 30 m resolution, 3 urban categories

  7. WRF other physics and forcing • the Rapid Radiative Transfer Model (RRTM) scheme for longwave radiation • the Dudhia scheme for shortwave radiation • the 2D Smagorinsky scheme for horizontal diffusion • the Mellor-Yamada-Janjic planetary boundary layer scheme • the WSM-6 scheme for microphysics • the Single-layer Urban Canopy Model for urban physics • North America Regional Reanalysis (NARR)

  8. Outline • Introduction to the mosaic/tiling approach • Evaluation against observations • Case 1: a clear day, 2009-07-14 • Case 2: a rainfall period, 2008-07-21 to 2008-07-27 • Conclusions

  9. A clear-day case: fluxes at Cub hill Deciduous broadleaf forest 22% Dryland cropland 25% Others 13% Low density urban 40% dy= 1km dx= 1km

  10. A clear-day case: fluxes at Cub hill Rn G

  11. A clear-day case: fluxes at Cub hill LE H

  12. A clear-day case: MODIS over d03 • MODIS-observed land surface temperature pattern over d03 at about 12:30 PM.

  13. A rainfall period: Boundary layer profiles

  14. A rainfall period: Boundary layer profiles

  15. A rainfall period: rainfall distribution

  16. The impact of N

  17. Conclusions • A mosaic/tiling approach is developed and tested within the WRF-Noah framework. • It generally shows better performance over the dominant approach in the domain that we examined here, especially under clear-sky conditions. • Simulated results are sensitive to the number of tiles.

  18. Acknowledgements: This work is supported by NSF under grant CBET-1058027 and by the Mid-Infrared Technology for Health and the Environment (MIRTHE) NSF center at Princeton University (Grant EEC-0540832). The simulations were performed on the supercomputing clusters of the National Center for Atmospheric Research and of Princeton University. The authors also thank Mary Lynn at Princeton University for helping us process some of the experimental data sets. Thank you !

  19. A few assumptions • The atmospheric properties are uniform across the grid. • The land-atmosphere coupling is uniform across the grid. • Each land-cover tile has a soil tile associated with it, but the soil properties are uniform across the grid. • For grid cells that are dominated by water/sea-ice, the mosaic approach is not used. For grid cells that are not dominated by water/sea-ice, water/sea-ice tiles are not considered.

  20. A clear-day case SWin LWin

  21. The thermal roughness (zot) parameterization • Previous studies have shown that the thermal roughness parameterization has an importance impact on the simulated land surface temperature1,2. • Zilitinkevich vs CZ093 1, Li and Bou-Zeid (2013) Synergistic Interactions between Urban Heat Islands and Heat Waves: the Impact in Cities is Larger than the Sum of its Parts. J Appl Meteorol Clim. (in press). 2, Li and Bou-Zeid (2013) Quality and Sensitivity of High-Resolution Numerical Simulation of Urban Heat Islands. Environmental Research Letters. (in review). 3, Chen and Zhang (2009) On the coupling strength between the land surface and the atmosphere: From viewpoint of surface exchange coefficients Geophys. Res. Lett.36 L10404

  22. 1, Li and Bou-Zeid (2013) Synergistic Interactions between Urban Heat Islands and Heat Waves: the Impact in Cities is Larger than the Sum of its Parts. J Appl Meteorol Clim. (in press). 2, Li and Bou-Zeid (2013) Quality and Sensitivity of High-Resolution Numerical Simulation of Urban Heat Islands. Environmental Research Letters. (in review). 3, Chen and Zhang (2009) On the coupling strength between the land surface and the atmosphere: From viewpoint of surface exchange coefficients Geophys. Res. Lett.36 L10404

  23. The UCM temperature

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