Idealized wintertime cloud simulations as performed

by Meso-NH

J.-P. Chaboureau and J.-P. PintyLaboratoire d’Aérologie, Toulouse

1. IMPROVE orographic precipitation (CASE3)

2. Cold air outbreak over the Japan Sea (CASE4)

2 bulk microphysical schemes

5 species: cloud, rain, ice, snow, graupel• 1-moment (Pinty and Jabouille 1998)

– Prognostic {rc} + {rr} + {ri} + {rs} + {rg}

– Diagnostic {Nc} + {Nr} + {Ni} + {Ns} + {Ng}

• 2-moment (Pinty 2002)

– Prognostic {rc, Nc} + {rr, Nr} + CCNact (Cohard and Pinty 2000)

{ri, Ni} + {rs} + {rg} + INnuc

– Diagnostic {Ns} + {Ng} with Ns/g=Cxas deduced from Field (1999) and

others

IMPROVE set-up• 2D domain

– 1-km mesh with 360 points (instead of 344)– 50 levels from 20 m (bottom) to 750 m (9-16 km)

• Open boundaries/6-h run• Initialization with RS (ice/snow set to 0)

Rela

tive

Hu

mid

ity

00

10 10 kmkm

Vertical X-sections after 4-h runMNH 1-m

clou

d

MNH 2-m

w +

tem

p

MM5

00

10 10 kmkm

Accumulated Precipitation

Domain-maximum mixing ratio time series

MM5 MNH 1-m MNH 2-m

00 6 h6 h 6 h6 h6 h6 h00 00cloud ice

cloud water

snowrairai

nn graupel

11

00

3030

344 km344 km 344 km344 km 344 km344 km

Japan Sea cloud set-up• 2D domain

– 2-km mesh with 512 points– 50 levels from 50 m (bottom) to 500 m (top)

• 24-h run / SST forcing• Initialization with Japan Sea sounding

(00 UTC 29 Jan 1993)

SST273 K

283 K

268 K

0 m

600 m

Vertical X-sections after 24-h runRel Hum %ice

MN

H 2

-mM

NH

1-m

Surface flux (H, LE) w and

0 km0 km-60 W/m2

4 km4 km240 W/m2

2 km2 km

200200 00

Vertical X-sections after 24-h runGraupel

MN

H 2

-mM

NH

1-m

Cloud water/ice Snow

Cloud top varying from 1.8 km to 2.5 km (close to the coast)

4 km4 km

2 km2 km

0 km0 km

Ice conc/mix ratio

Domain-maximum mixing ratio time series

MNH 1-m MNH 2-m

0024 h24 h 24 h24 h

1 g/kg1 g/kg

2-moment scheme: less cloud water and ice more snow

00

Conclusion

• 1-moment cloud scheme– Standard results

• 2-moment cloud scheme– More degree of freedom– Need further tests