Yanjun Jiao and Colin Jones

University of Quebec at Montreal

September 20, 2006

The Performance of the Canadian Regional Climate Model in the Pacific Ocean

OUTLINE:

1. Experiment configurations

2. Results from original CRCM (precipitation, cloud and relative humidity)

3. Modification to the CRCM model physics

4. Results of CRCMM

5. Summary

CRCM4 domain in cylindrical projection

CRCM4 domain in PS projection

180km (60ºN) resolution

11575 grid points

29 Gal-Chen levels

15-min time step

Output every 3hrs

1. Experiment configurations

Sponge zone (9 grid points)

GPCI 2D domain (5ºS-45ºN,160ºE-120ºW)

GPCI cross-section (13 points)

ISCCP cloud cover (JJA 1998)

CRCM4

0.25º TRMMStratiform precipitation

Convective precipitation

Total precipitation

ISCCP

CRCM4Total cloud

Siebesma et al. (2004)

1) The eddy diffusivities calculation of the ECMWF.

2) A switch to turn off the shallow convection.

3) The trigger function of shallow convection (DTRH).

4) The cloud base mass flux closure=f (w*).

5) Variable cloud radius of the deep convection=f(wLCL).

6) Variable minimum cloud-depth=f(TLCL).

7) A dilute updraft ascent.

8) Xu-Randall cloud scheme.

9) Evaporation of falling large scale precipitation.

3. Modification to the model physics of CRCM4

zpbl

0.1zpbl

buofxs < 0 buofxs > 0

3.1 Modification to vertical diffusion

(ECMWF documentation CY28r1)

Revised Louis scheme

KM lM2 U

zfM (Ri)

K H lH2 U

zf H (Ri)

fM (Ri) 1

110Ri(1 Ri) 1 2

f H (Ri) 1

110Ri(1 Ri)1 2

M ( ) (1 16 ) 1 4

H ( ) (1 16 ) 1 2

KM lM

2

M2

U

z

K H lM2

MH

U

z

KM kzwturb (1z

zi

)2

K H kzwturb (1 z

zi

)2 M

H

wturb (u*3 0.6w*

3)1

3

K H CentrQov

z

v

(v )k1 2 1

Cpd

(sk sk1 0.5( )(qk qk1)(sk sk1)

KM kzu(1z

zi

)2 1

M

K H kzu(1 zzi

)2 1H

Troen and Mahrt (1986)

• Non-local diffusion when eddies have a similar size as the PBL

• Explicit entrainment parameterization in the PBL top

(vmix v

env )Tv

Tv

RH

0 Tv

0.2 (P

P0

)Rd

C pd

2) The trigger function of shallow convection

1) A switch to turn off the shallow convection once deep convection has been detected on the same grid point

3.2 Modification to shallow convection (BKF)

TvRH

0.20(RHLCL 0.70)q mix /qs

t0.70 RHLCL 0.90

(1.0 /RHLCL 1.0)q mix /qs

tRHLCL 0.90

Mb 0.03w

w*gzb

v

(w''v )s

13

3) The closure of cloud base mass flux (Grant 2001 and Neggers et al. 2004)

free convective vertical velocity scale

-0.01

0

0.01

0.02

0.03

0.04

0.05

0.06

0.5 0.6 0.7 0.8 0.9 1 1.1

Relative Humidity

DTR

H

CAPE adjustment closure: mass flux at cloud base is totally controlled by the conditions in the cloud layer

Mb f (CAPE)

Subcloud convective velocity scaling closure: links the mass flux at cloud base to the TKE in subcloud layer.

Based on the observation that shallow cumulus clouds (visible part because of condensation) often root deeply into the subcloud mixed layer (invisible dry thermal)

CTL

LCL

wDeep convection is driven by latent heat release in the convective cloud

Cdepth 3500

Cdepth 2000 TLCL 0C

2000100TLCL 0 TLCL 20C

4000 TLCL 20C

Rmin 1500

Rmin 1000 WLCL 0

1000(1 0.1WLCL ) 0 WLCL 1.0

2000 WLCL 1.0

2) The minimum cloud-depth threshold has been parameterized according to the cloud-base temperature rather than remaining constant.

1) Cloud radius of the deep convection vary with the vertical velocity at lifting condensation level (LCL)

3.3 Modification to deep convection

Kain (2004)

3) A dilute updraft ascent has been used to calculate CAPE, which provides a more accurate calculation in convection rainfall and mass flux

3.3 Modification to deep convection

(e )lup

(e )l1env

(e )l1up

pumf l1

puerl1

pudrl1

pumf l

(e )lenv

l 1

l

(e )l1up (e )l

up (e )LCLup

(e )l1up (e )l1

env (1 )(e )lup

puerl1 (pumf l pudrl1 puerl1)

Equivalent potential temperature in undilute updraft (produces a significant larger CAPE than actual one)

Equivalent potential temperature in dilute updraft

• Reduces the CAPE value in highly unstable regimes (especially for dry condition)

• Reduces the precipitation and the degree of stabilization

CAPE g eup

eenv 1

LCL

ETL dz

CLS RH p 1 exp( q l

[(1 RH)qsat ] )

, if RH 1

1.0, if RH 1

3.4 Modification to cloud scheme

Xu and Randall (1996)

where p 0.25 100. 0.49

q l is cloud liquid water

3.5 Modification to large scale precipitation

(evaporation of falling precipitation from ECMWF)

E prec 5.44 10 4 (1. cld)(1. RH)qsat (p

ps

)1 2 Pl1

5.910 3

0.577

Kessler (1969)

CRCM4

CRCMM

0.25º TRMM

JJA 1998 precipitation over GPCI 2D domain

CRCM4

CRCMM

ISCCP

CRCMM

CRCM4

JJA 1998 total cloud over GPCI 2D domain

CRCMM

CRCM4

Vertical profile of the relative humidity

Siebesma et al. (2004)

Vertical profile of the cloud cover

Vertical profile of vertical velocity (Pa/s)

Thanks to the GPCI, some deficiencies in the CRCM4 have been found.

The CRCMM is better than CRCM4 in the field of:

1) Precipitation

2) Total cloud cover (shallow cumulus region).

3) Vertical profiles of relative humidity, cloud and vertical velocity.

4) Still have some space to improve in convective precipitation (too strong), PBL (too moist and sharp), and LWP (too low in stratocumulus region) ……

•Testing the sensitivities to horizontal and vertical resolutions

(180km ~ 90km ~ 45km and L29 ~ L47)

• Testing over the North America (AMNO domain)

(CLASS, winter and summer)

5. Summary