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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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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)


List of presentation

Background parameterization of cloud and precipitation

A revised cloud scheme

Idealized case experiment

Heavy rainfall case experiment

Ice cloud – radiation interaction

Conclusion

List of presentation

A tip for the MRFPBL


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)


Wrf weather and research forecasting model http wrf model org

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


Ncep cloud microphysics

- Hong et al. (1998), NCEP RSM cloud physics communities

- 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


NCEP (Hong) Cloud schemes communities

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)


Background

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


Ice crystal property of microphyscs

(Mass, Diameter, Mixing ratio, Ice number)


Rotstayn 2000 of microphyscs

Ryan 1996

Ryan 2000

Observed and formulated Ni


Fletcher : D89, RH83 of microphyscs

- 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


RH83,D89 of microphyscs

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 %.


LW radiation : RRTM of microphyscs

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


Sensitivity experiments

Exp1 : Dudhia microphysics ( of microphyscsOLD)

Exp2 : Dudhia + sedimentation of qi

Exp3 : New microphysics

Exp4 : New + sedimentation of qi (NEW)

Sensitivity Experiments


Cloud and Precipitation after 30 min. of microphyscs

qci

Lin

HDC3

qrs


Exp1 of microphyscs

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.


A heavy rainfall case 1997 6 25

(a) of microphyscs

(b)

A

A heavy rainfall case : 1997.6.25


OBS of microphyscs

EXP1

EXP2

EXP3

EXP4

45-km experiment : 24-hr precipitation (mm)

> 90 mm



Volume-averaged qci of microphyscs

Domain averaged 300 hPa T

Exp1

Exp1

Exp2

Exp3

Exp2

Exp4

Exp3

ANAL

Exp4


Exp1 of microphyscs : 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


Volume-averaged qci of microphyscs

Domain averaged 300 hPa T

NOSW

EXP1

EXP1

NOSW

ANAL

NOLW

NORA

NORA

NOLW


Ice cloud - radiation feedback of microphyscs

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


Concluding remarks

New scheme produces of microphyscsbetter 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


Thank you of microphyscs

Regional climate

Seasonal prediction

Climate mechanism

Severe weather

NWP


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