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Song-You Hong (Yonsei Univ) Jimy Dudhia (NCAR) Shu-Hua Chen (U.C. Davis)

A new ice microphysical processes for a commonly used bulk parameterization of cloud and precipitation. Song-You Hong (Yonsei Univ) Jimy Dudhia (NCAR) Shu-Hua Chen (U.C. Davis). Background A revised cloud scheme Idealized case experiment Heavy rainfall case experiment

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Song-You Hong (Yonsei Univ) Jimy Dudhia (NCAR) Shu-Hua Chen (U.C. Davis)

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  1. A new ice microphysical processes for a commonly used bulk parameterization of cloud and precipitation Song-You Hong (Yonsei Univ) Jimy Dudhia (NCAR) Shu-Hua Chen (U.C. Davis)

  2. Background A revised cloud scheme Idealized case experiment Heavy rainfall case experiment Ice cloud – radiation interaction Conclusion List of presentation A tip for the MRFPBL

  3. The highest level for the PBL is the half of the total number of vertical layers KLPBL = KL/2 (currently in WRF & MM5)  The PBL mixing is ill-posed with many layers near the surface as done for the air pollution application Correction : In the “mrfpbl.F”, change KLPBL = 1 (modified one)

  4. Community model: NCAR, NCEP, FSL, AFWA, NSSL, and University communities Real time fcsts : NCAR (22km, 10km), NSSL(34km), AWFA(45km), Italy (20km) MRF PBL, Kain-Fritsch cumulus RRTM, Dudhia Radiation Lin or NCEP simple ice microphysics WRF (Weather and Research Forecasting Model) http://wrf-model.org

  5. - Hong et al. (1998), NCEP RSM cloud physics - NCEP cloud microphysics v1.0 (Hong et al. 1998, with some modifications) - NCEP cloud microphysics v1.1 (Jimy’s bug fix in computing Vr, Vs) - > solves the too much precip. - NCEP cloud microphysics v1.2 (Hong et al. 2002, the new scheme) NCEP Cloud Microphysics

  6. NCEP (Hong) Cloud schemes NCEP CLOUD 3 (simple ice) and CLOUD 5 (mixed phase) qv (qci,qrs) (qc,qi,qr,qs) Modifications after Dudhia (1989) and Rutledge and Hobbs (1983)

  7. Lin et al. (1983) and Rutledge and Hobbs (1983) -> core part of microphyscs A typical problem -> too much cirrusdue to Ni from Fletcher Different assumptions in microphysics ( Meyers et al. 1992, Kruger et al. 1995, Reisner et al. 1998, Rotstayn et al. 2000, Ryan 2001 ) Sedimentation of ice crystals (Manning and Davis, 1997, Wang 2001) Background

  8. Ice crystal property (Mass, Diameter, Mixing ratio, Ice number)

  9. Rotstayn 2000 Ryan 1996 Ryan 2000 Observed and formulated Ni

  10. Fletcher : D89, RH83 - qicrit has small range of T : 0.1 and 1 gkg-1 for –27 and –32C This study - qicrit=0.18gkg-1, at T=-40C, P=300 mb

  11. RH83,D89 This study Comparison of deposition rate of water vapor onto ice as a function of cloud temperature, with the assumption that cloud ice mixing ratio is 0.1 gkg-1 and the air is supersaturated with respect to ice by 10 %.

  12. LW radiation : RRTM SW radiation : Dudhia Vertical diffusion : MRF Cumulus scheme : Kain-Fritsch Microphysics : NCEP (HONG) simple ice Grid size : 45 km, 15 km Time step : 120 s, 60 s Initial time : 1200 UTC 23 June 1997 Integration : 48 hrs Initial and BDY : NCEP GDAS WRF version 1.1-beta

  13. Exp1 : Dudhia microphysics (OLD) Exp2 : Dudhia + sedimentation of qi Exp3 : New microphysics Exp4 : New + sedimentation of qi (NEW) Sensitivity Experiments

  14. Cloud and Precipitation after 30 min. qci Lin HDC3 qrs

  15. Exp1 Exp4 Exp3 Exp2 Exp3,4 Exp1, 2 qci qrs Fig. 3. Profiles of domain-averaged (a) cloud/ice water and (b) snow/rain water mixing ratio (gkg-1) for the Exp1 (thin solid line), Exp2 (dotted line), Exp3 (dashed line), and Exp4 (thick solid line) experiments.

  16. (a) (b) A A heavy rainfall case : 1997.6.25

  17. OBS EXP1 EXP2 EXP3 EXP4 45-km experiment : 24-hr precipitation (mm) > 90 mm

  18. Cloudiness at 36-h fcst (0000UTC 25 June) Exp1 Exp4

  19. Volume-averaged qci Domain averaged 300 hPa T Exp1 Exp1 Exp2 Exp3 Exp2 Exp4 Exp3 ANAL Exp4

  20. Exp1 : Dudhia microphysics (too much cloud ice -> warm bias) NORA : Exp1 but without radiation feedback due to ice cloud) NOLW : Exp1 but without LW radiation feedback due to ice cloud) NOSW : Exp1 but without SW radiation feedback due to ice cloud) Ice cloud - radiation feedback

  21. Volume-averaged qci Domain averaged 300 hPa T NOSW EXP1 EXP1 NOSW ANAL NOLW NORA NORA NOLW

  22. Ice cloud - radiation feedback More cloud ice Less SW heating More LW heating Tropospheric cooling Upper level heating Less SFC buoyancy Less cloud ice Less explicit rain Less implicit rain Less Precipitation, Warmer Troposphere

  23. New scheme produces better cloudiness (remove high cloud bias) New scheme alleviates the discontinuity problem of small and large ice particles Reduction of ice clouds induces more surface precipitation Combined effects of improved microphysics and the inclusion of sedimentation of ice crystals are attributed to the improvement of precipitation, cloudiness, and large-scale features Sedimentation of HD1990 dominates the effects of detailed ice-microphysical processes Concluding Remarks

  24. Thank you Regional climate Seasonal prediction Climate mechanism Severe weather NWP

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