jason milbrandt recherche en pr é vision num é rique [rpn]
DESCRIPTION
A New Multi-Moment Cloud Microphysics Package for the GEM-LAM. Jason Milbrandt Recherche en Pr é vision Num é rique [RPN] Meteorological Research Division, Environment Canada GEM Workshop, June 12, 2007. Why develop a new cloud scheme for GEM? Computer resources increasing - PowerPoint PPT PresentationTRANSCRIPT
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Jason Milbrandt
Recherche en Prévision Numérique [RPN]Meteorological Research Division, Environment Canada
GEM Workshop, June 12, 2007
A New
Multi-Moment Cloud Multi-Moment Cloud
Microphysics PackageMicrophysics Package
for the GEM-LAM
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Why develop a new cloud scheme for GEM?
• Computer resources increasing
• High-resolution NWP grids are becoming mainstream
• Important to predict cloud processes as well as possible
• GEM-LAM-2.5 has systematic problems with the precipitation forecasts
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1. Background on bulk schemes
2. Description of the new microphysics package
3. Some advantages of the multi-moment approach
OUTLINE
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One of the goals of NWP model:
Predict the effects of the clouds
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MODEL GRID:(hypothetical NWP model)
PARTLYCLOUDY(RH < 100%)
CLOUDY(RH = 100%)
CLOUD-FREE
CPS
EXPLICITSCHEME
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Single cloudy grid element:
CLOUDY(RH = 100%)
EXPLICITSCHEME
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INPUT:w, T, p, qv
Single cloudy grid element – interaction with NWP model:
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MICROPHYSICAL PROCESSES in the cloudy grid element
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Single cloudy grid element – interaction with NWP model:
Changes to
w, T, p, qv
and
qc, qr, qi, ...
Advectionand
Turbulent Mixing
MICROPHYSICALPROCESSES
OUTPUT:• Latent heating• Hydrometeors (cloud, rain, ice,…) qc, qr, qi, ...
INPUT:w, T, p, qv
qc, qr, qi, ...
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Single cloudy grid element: Slight magnification
= cloudy (saturated) air
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Single cloudy grid element: Extreme magnification
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Single cloudy grid element: Extreme magnification
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1 m3
(unit volume)
[e.g. Cloud droplets]
(not to scale)
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N (D)
D [ m]
100
[m-3 m-1]
20 40 60 800
101
100
10-1
10-2
1 m3
(unit volume)
[e.g. Cloud droplets]
(not to scale)
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(Example of observed
cloud droplet spectrum)
N (D)
D [ m]
100
[m-3 m-1]
20 40 60 800
101
100
10-1
10-2
1 m3
(unit volume)
[e.g. Cloud droplets]
(not to scale)
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DISCRETE SIZE BINS
SPECTRAL METHOD
Representing the size spectrum
N (D)
D [ m]
100
[m-3 m-1]
20 40 60 800
101
100
10-1
10-2
1 m3
(unit volume)
[e.g. Cloud droplets]
(not to scale)
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1 m3
(unit volume)
BULK METHOD
N (D)
D [ m]
100
[m-3 m-1]
20 40 60 800
101
100
10-1
10-2
ANAYLTICAL FUNCTION
[e.g. Cloud droplets]
(not to scale)
Representing the size spectrum
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Gamma Distribution Function:
DeDNDN 0)(
* Q = q (mass content)
INCREASINGVALUES(of , N0 and )
log N(D) log N(D) log N(D)
D [mm] D [mm]D [mm]
Varying :(N0 and constant)
Varying :(Q* and N0 constant)
Varying N0:( and constant)
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BULK METHOD
Size Distribution Function:
Dxx
xxeDNDN 0)(
pth moment:
xpx
xxx
px
pNdDDNDpM
100
1)()(
N (D)
D10020 40 60 800
101
100
10-1
10-2
HydrometeorCategory x
Total number concentration, NTx
)0()(0
xxTx MdDDNN
Radar reflectivity factor, Zx
)6()(0
6xxx MdDDNDZ
Mass mixing ratio, qx
)3(6
)(6 0
3x
xx
xx MdDDNDq
Example of Moments:
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BULK METHOD
Size Distribution Function:
Dxx
xxeDNDN 0)(
pth moment:
xpx
xxx
px
pNdDDNDpM
100
1)()(
Total number concentration, NTx
)0()(0
xxTx MdDDNN
Radar reflectivity factor, Zx
)6()(0
6xxx MdDDNDZ
Mass mixing ratio, qx
)3(6
)(6 0
3x
xx
xx MdDDNDq
Example of Moments:Predict changes to specific moment(s) e.g. qx, NTx, ...
Implies changes to values of
parameters
i.e. N0x, x, ...
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* (May contain traces of supercooled water)
T < 0C *
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T < 0C
= ICE CRYSTAL
(May contain traces of supercooled water)
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T < 0C
= ICE CRYSTAL
= SNOW CRYSTAL / AGGRETATE
(May contain traces of supercooled water)
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T < 0C
= ICE CRYSTAL
= SNOW CRYSTAL / AGGREGATE
= GRAUPEL
(May contain traces of supercooled water)
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T < 0C
= ICE CRYSTAL
= SNOW CRYSTAL / AGGREGATE
= GRAUPEL
= HAIL
(May contain traces of supercooled water)
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= ICE CRYSTAL
= SNOW CRYSTAL / AGGREGATE
= GRAUPEL
= HAIL
= LIQUID WATER
T < 0C
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ICE SNOW
GRAUPEL HAIL
LIQUID WATER
PARTITIONING THE HYDROMETEOR SPECTRUM
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ICE SNOWCLOUD
GRAUPEL HAILRAIN
PARTITIONING THE HYDROMETEOR SPECTRUM
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ICE SNOWCLOUD
GRAUPEL HAILRAIN
BULK METHOD
Drr
rr eDNDN 0)(
Dii
iieDNDN 0)( Dss
sseDNDN 0)(
Dgg
gg eDNDN 0)(D
hhhheDNDN 0)(
ccc DDNDN ccc exp)( 1)1(
0
PARTITIONING THE HYDROMETEOR SPECTRUM
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Full TRIPLE-MOMENT Version:
• Six hydrometeor categories:– 2 liquid: cloud and rain– 4 frozen: ice, snow, graupel and hail
• ~50 distinct microphysical processes
• Warm-rain scheme based on Cohard and Pinty (2000a)
• Ice-phase based on Murakami (1990), Ferrier (1994), Meyers et al. (1997), Reisner et al. (1998), etc.
• Predictive equations for Zx added for triple-moment*
*Milbrandt and Yau (2005a,b) [J. Atmos. Sci.]
Milbrandt-Yau Cloud Scheme *
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Diagnostic-Dispersion DOUBLE-MOMENT Version:
Identical to full version except:
• Diagnostic-x relations added for double-moment*
Milbrandt-Yau Cloud Scheme *
Recall:Size Distribution Function:
Dxx
xxeDNDN 0)(
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CURRENT VERSIONS AVAILABLE FOR GEM:
GEM_v3.2.2 / PHY_4.4 available upon request**
GEM_v3.3.0 / PHY_4.5 part of official RPN/CMC library
Single-moment version– Six hydrometeor categories
– Single-moment (Qx) for each
Double-moment version– Six hydrometeor categories– double-moment (Qx,, Nx) for each
– fixed-x
Milbrandt-Yau Cloud Scheme
**(also available for MC2_v4.9.8)
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UPCOMING VERSION AVAILABLE FOR GEM:
Prototype cloud scheme for the 2010 Winter Olympics
“Olympic” version *CLOUD double-moment (Qc, Nc)
RAIN double-moment (Qr, Nr) [diagnostic-r ]
ICE/SNOW double-moment (Qi, Ni) [hybrid category]
GRAUPEL single-moment (Qg)
HAIL double-moment (Qh, Nh) [diagnostic-h ]
Milbrandt-Yau Cloud Scheme
* To be implemented in GEM-LAM 2.5 km AUTUMN 2007
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Prognostic Nc
Double-Moment “CLOUD” Category:
• Condensation rate based on saturation adjustment
• Nc initialization is air-mass (CCN) dependent
Advantages of multi-moment approach:
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CCN-dependent Nc nucleation:
MARITIME
CONTINENTAL
103
100
10-1
0.01 0.1 1.00 10.0
SUPERSATURATION (%)
101
NCCN
(cm-3)
102
Advantages of multi-moment approach:
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Qc (Cloud Mixing Ratio)
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Nc (Cloud Number Concentration)
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Dc (Cloud Mean-Mass Diameter)
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The warm-rain coalescence process
Radius [cm]
Bin-resolving coalescence modelSOURCE: Berry and Reinhardt (1974)
RAINCLOUD
DRIZZLE
Mas
s D
ensi
ty [
g m
-3 (
lnr)
-1]
Tim
e [m
in]
Advantages of multi-moment approach:
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0.1–1 mm
RAIN
DRIZZLE
STRATIFORM RAIN
Qr
Mass Content[g m-3]
Dr
Mean Diameter[mm]
Advantages of multi-moment approach: DRIZZLE vs. RAIN
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z[km]
Q [g m-3] Dm [mm]NT [m-3] Ze [dBZ]
Contours every 5 min
MassContent
Total NumberConcentration
EquivalentReflectivity
Mean-MassDiameter
5 min
10 min
15 min
20 min
INITIAL
Analytic bin model calculation: (1D column)
Advantages of multi-moment approach: SEDIMENTATION
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z
Vq
t
q xqx
SEDI
x
xqV = mass-weighted fall velocity
SM
z
VN
t
N xNx
SEDI
x
xNV = number-weighted fall velocity
DM
z
VZ
t
Z xZx
SEDI
x
xZV = reflectivity-weighted fall velocity
TM
SEDIMENTATION: Bulk scheme
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SINGLE-moment scheme (SM):
ANALYTIC BIN model (ANA):
z[km]
Q [g m-3] Dm [mm]NT [m-3] Ze [dBZ]
z[km]
Q [g m-3] Dm [mm]NT [m-3] Ze [dBZ]
5 min
10 min
15 min
20 min
INITIAL
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DOUBLE-moment scheme, FIXED DISPERSION ( = 0):
ANALYTIC BIN model (ANA):
z[km]
Q [g m-3] Dm [mm]NT [m-3] Ze [dBZ]
z[km]
Q [g m-3] Dm [mm]NT [m-3] Ze [dBZ]
5 min
10 min
15 min
20 min
INITIAL
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ANALYTIC BIN model (ANA):
DOUBLE-moment scheme, DIAGNOSTIC DISPERSION, = f (Dm):
z[km]
Q [g m-3] Dm [mm]NT [m-3] Ze [dBZ]
z[km]
Q [g m-3] Dm [mm]NT [m-3] Ze [dBZ]
5 min
10 min
15 min
20 min
INITIAL
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TRIPLE-moment scheme:
ANALYTIC BIN model (ANA):
z[km]
Q [g m-3] Dm [mm]NT [m-3] Ze [dBZ]
z[km]
Q [g m-3] Dm [mm]NT [m-3] Ze [dBZ]
5 min
10 min
15 min
20 min
INITIAL
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MassContent
Bulk schemes:
Analytic model:z
[km]
Q [g m-3]
5 min
10 min
15 min
20 min
INITIAL
Q [g m-3] Q [g m-3] Q [g m-3]
z[km]
DOUBLE-MOMENT
Fixed SINGLE-MOMENT
DOUBLE-MOMENT
Diagnosed
Q [g m-3]
TRIPLE-MOMENT
Prognosed
Advantages of multi-moment approach: SEDIMENTATION
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0.1 - 4 mm
SNOW (large crystals / aggregates)
Qs
Mass Content[g m-3]
Ds
Mean Diameter[mm]
(equivalent sphere)
Advantages of multi-moment approach: MASS ≠ SIZE
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SUMMARY
• Efficient single-moment and double-moment versions of the Milbrandt-Yau scheme are available for GEM-LAM
• Single-moment version will be proposed as the operational scheme for GEM-LAM_2.5 by fall 2007
• New version (“semi-double-moment”) will be developed and tested for implementation by spring 2007
• Large-scale version (diagostic cloud-fraction; fewer prognostic variables) to be developed soon
• For code, support, bug reports, or question:
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MERCIMERCI