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Yuqing Wang and Chunxi Zhang International Pacific Research Center

On Improved Representation of MBL Clouds in ARW–WRF with a Modified Tiedtke Cumulus Parameterization Scheme. Yuqing Wang and Chunxi Zhang International Pacific Research Center University of Hawaii at Manoa , Honolulu, Hawaii. PreVOCA regional simulations using WRF.

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Yuqing Wang and Chunxi Zhang International Pacific Research Center

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  1. On Improved Representation of MBL Clouds in ARW–WRF with a Modified Tiedtke Cumulus Parameterization Scheme Yuqing Wang and Chunxi Zhang International Pacific Research Center University of Hawaii at Manoa, Honolulu, Hawaii

  2. PreVOCA regional simulations using WRF • UCLAand UCHILE both used ARW–WRF as the regional climate model. Their mean geographic distributions of cloud fraction and boundary layer depth are biased compared to the observations. • iRAM (IPRC Regional Atmospheric Model) has shown its skill in simulating marine low-clouds over the eastern Pacific. • Can improved WRF simulation of low-clouds be achieved using iRAM’s modified TiedtkeCu parameterization?

  3. 4. Implementation of a modified Tiedtke scheme into ARW– WRF • Tiedtke (1989), moisture convergence closure • Nordeng (1995), CAPE closure • Roeckner et al. (1996), ECHAM4, cloud-top detrained hydrometeor partitioned into liquid and ice phases • Wang et al. (2003), convective trigger •  Wang et al. (2004, 2007), adjusted entrainment rates for shallow/deep convection based on LES results.

  4. 5. Model Configuration and Experimental design ARW– WRF version 3.2.1 October 2006 27 km horizontal resolution and 31 full σ-levels in the vertical (14 levels below 700hPa and model top at 50hPa) 320*300 horizontal grid points 9 grid points in the buffer zone on each side Physics Schemes Cloud microphysics: WSM6 Land Surface Model: Noah Short and long wave radiation: CAM Daily SST update, Diurnal cycle in SST Gravity wave drag

  5. Cloud fraction below 3km height Cu param affects SE Pac cloud frac Tiedtke scheme also reduces E Pac circulation biases MODIS cloud fraction

  6. 5 days mean (Oct 16 - 20) Cu param strongly affects 20S vertical structure

  7. Cloud fraction below 3km height PBL scheme has less impact on SE Pac cldfrac, LWP MODIS cloud fraction

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