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FRAM Workshop

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... GEM Model ... The 2.5-km GEM configuration uses an explicit (grid-scale) ... microphysics scheme in the 2.5-km GEM model. Examples of fog simulations ... – PowerPoint PPT presentation

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Title: FRAM Workshop


1
Explicit Fog Forecasting with the High-Resolution
GEM Model
Jason Milbrandt Atmospheric Numerical
Prediction Research Section (RPN-A) Environment
Canada
FRAM Workshop 21 May 2008
2
BACKGROUND
  • The Canadian Meteorological Centre currently runs
    4 experimental high-resolution (?x 2.5 km) NWP
    grids using the limited-area version of the GEM
    model
  • The 2.5-km GEM configuration uses an explicit
    (grid-scale) condensation scheme to predict cloud
    fields and precipitation
  • In principle, the cloud water field can be used
    as a predictor for fog

3
OUTLINE
  • Overview of the cloud microphysics scheme in the
    2.5-km GEM model
  • Examples of fog simulations
  • Future developments

4
Background on Cloud Schemes
Current GEM-LAM-2.5 Grids
5
Background on Cloud Schemes
6
Background on Cloud Schemes
Hypothetical GEM-LAM-2.5 Grid
7
Background on Cloud Schemes
Single cloudy grid element
8
MICROPHYSICAL PROCESSES in a cloudy grid element
9
Background on Cloud Schemes
1 m3 (unit volume)
e.g. Cloud droplets (not to scale)
10
Background on Cloud Schemes
1 m3 (unit volume)
e.g. Cloud droplets (not to scale)
11
Background on Cloud Schemes
Example of Moments
pth moment
12
Background on Cloud Schemes
Example of Moments
Predict changes to specific moment(s) e.g.
qx
Implies changes to values of parameters
e.g. lx
pth moment
13
Background on Cloud Schemes
ICE CRYSTAL
? SNOW CRYSTAL / AGGREGATE
?
GRAUPEL
HAIL
LIQUID WATER
14
Background on Cloud Schemes
SNOW
LIQUID WATER
ICE
HAIL
GRAUPEL
15
Background on Cloud Schemes
SNOW
CLOUD
ICE
HAIL
GRAUPEL
RAIN
16
Background on Cloud Schemes
Milbrandt-Yau Bulk Microphysics Scheme
  • Six hydrometeor categories
  • 2 liquid cloud and rain
  • 4 frozen ice, snow, graupel and hail
  • 50 distinct microphysical processes

17
Background on Cloud Schemes SINGLE-MOMENT
Version
SNOW
CLOUD
ICE
HAIL
GRAUPEL
RAIN
18
Background on Cloud Schemes DOUBLE-MOMENT
Version
SNOW
CLOUD
ICE
QS
QC
QI
NS
NC
NI
HAIL
GRAUPEL
RAIN
QR
QH
QG
NH
NR
NG
19
Background on Cloud Schemes DOUBLE-MOMENT
Version
CLOUD
Explicit FOG
QC
NC
20
Background on Cloud Schemes Treatment of Nc
In DOUBLE-MOMENT scheme
In SINGLE-MOMENT scheme Nc is
fixed Maritime Nc 80 cm-3 Continental
Nc 200 cm-3
NC
QC
QC
CCN-dependent Nc nucleation
CLOUD
21
Background on Cloud Schemes Application to
Fog
Parameterization of VISIBILITY
VIS f ( ) i.e. VIS f (LWC,
Nd)
QC
NC
SOURCE Gultepe and Milbrandt (2007)
22
Example Case - 27 June 2006
Qc (Cloud Mixing Ratio)
g kg-3
23
Example Case - 27 June 2006
Nc (Cloud Number Concentration)
cm-3
24
Example Case - 27 June 2006
Dc (Cloud Mean-Mass Diameter)
?m
25
Example Case - 27 June 2006
QC g kg-1
LEVEL nk-3 (0.961) 340 m
VIS km
26
Example Case - 27 June 2006
QC g kg-1
LEVEL nk-2 (0.973) 230 m
VIS km
27
Example Case - 27 June 2006
QC g kg-1
LEVEL nk-1 (0.985) 130 m
VIS km
28
Example Case - 27 June 2006
QC g kg-1
LEVEL nk (0.995) 45 m
VIS km
29
Example Case - 27 June 2006
VIS km
p hPa
Level
30
Example FRAM L-2 Case, 18 June 2006
GOES fog product (green) 1132 UTC, 18 June 2006
GEM-Regional (15-km) CLOUD Field (2nd lowest
prognostic level, 130 m AGL)
31
Example FRAM L-2 Case, 18 June 2006
GEM-Regional (15 km)
GEM-LAM (2.5 km)
QC
32
Example FRAM L-2 Case, 18 June 2006
GEM-Regional (15 km)
QC g kg-1
RH
0.95
VIS km
33
Example FRAM L-2 Case, 18 June 2006
GEM-LAM (2.5 km)
QC
LEVEL nk-3 (0.961) 340 m
RH
LEVEL nk (0.995) 45 m
RH
34
Current Development CLOUD FRACTION Version
Lower Level
Upper Level
QC
RH
RHcrit 1.00 (no cloud-fraction)
35
Current Development CLOUD FRACTION Version
Lower Level
Upper Level
QC
RH
RHcrit 0.90 (cloud-fraction)
36
CONCLUSION
  • The Canadian Meteorological Centre currently runs
    4 high-resolution (?x 2.5 km) experimental NWP
    grids using a detailed single-moment bulk
    microphysics scheme
  • An optimized double-moment version of the
    microphysics scheme is planned to be implemented
    in 2009
  • Current developments include extending the scheme
    to allow for subgrid-scale condensation

37
THANK YOU jason.milbrandt_at_ec.gc.ca
38
Overview of New Scheme Features
New Precipitation Types from M-Y Scheme
RN1 Liquid Drizzle RN2 Liquid Rain FR1
Freezing Drizzle FR2 Freezing Rain SN1 Ice
Crystals SN2 Snow SN3 Graupel (snow
pellets) PE1 Ice Pellets (re-frozen rain) PE2
Hail (total) PE2L Large Hail
RN
FR
SN
PE
New output variables
Existing output variables now based on new
variables (for M-Y) e.g. SN SN1 SN2
SN3
39
Low-level QC
Cloud-Fraction, b
40
Example FRAM-C Case, 4 January 2006
VIS (Visibility km)
200 m
41
Example FRAM-C Case, 4 January 2006
Qc (LWC)
0.30 gm-3
42
Example FRAM-C Case, 4 January 2006
Nc (droplet number concentration)
130 cm-3
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