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Implementation of IPHOC in VVCM: Tests of GCSS Cases

This study presents the implementation and testing of IPHOC in VVCM, a prognostic closure model, for simulating various PBL clouds with variable large-scale and radiative forcings. The results show the capability of IPHOC to capture the cloud evolution and moments of vertical velocity. Further improvements are needed to capture the fine structure of cloud fields from benchmark LESs.

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Implementation of IPHOC in VVCM: Tests of GCSS Cases

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  1. Implementation of IPHOC in VVCM:Tests of GCSS Cases Anning Cheng1,2 and Kuan-Man Xu 2 AS&M, Inc. Science Directorate, NASA Langley Research Center

  2. Intermediately Prognostic Higher-Order Closure Model • Double-Gaussian distribution of liquid-water potential temperature, total water mixing ratio and vertical velocity • Skewnesses of these three third-order moments predicted • All first-, second-, third- and fourth-order moments, subgrid-scale condensation and buoyancy based on the same probability distribution function • A bulk microphysics scheme considering subgrid-scale variabilities has been developed and tested (Cheng and Xu 2008; in preparation)

  3. Experiment Design • Standard initial condition and forcing for GCSS ARM (continental shallow cumulus), BOMEX (shallow cumulus), ATEX (intermediate cloud regime) and ASTEX (stratocumulus) cases • 2-D Domain; 256 km in horizontal direction; 4.5 km for ARM; 3 km for ATEX and BOMEX, and 1.5 km for ASTEX in vertical direction • Resolution: 4 km in horizontal direction; 40 m for ARM, BOMEX and ATEX, and 25 m for ASTEX in vertical direction • Momentum fluxes from IPHOC are not used

  4. Cloud Evolution for BOMEX (%)

  5. Cloud Evolution for ARM (%)

  6. Mean Profile Averaged from 10h - 12h

  7. Fluxes Averaged from 10h - 12h

  8. Moments of w Averaged from 10h - 12h

  9. Cloud Evolution for ATEX (%)

  10. Mean Profile Averaged over Last Hour

  11. Fluxes Averaged Over Last Hour

  12. Moments of w Averaged Over Last Hour

  13. Cloud Evolution for ASTEX (%)

  14. Summary and Discussion • An IPHOC has been implemented in VVCM and tested with major GCSS cases • IPHOC is capable of simulating various PBL clouds with variable large-scale and radiative forcings using 4 km horizontal grid spacing • Further improvement of the IPHOC is needed to capture the fine structure of the cloud fields simulated from benchmark LESs • The LBA shallow-to-deep convective cloud transition case is under testing

  15. Thank You!

  16. Shallow Cumulus Clouds from the Focring of SP-CAM

  17. Mean Profile Averaged over Last 40 Hour

  18. Cloud Radiation Forcing

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