FRAM Workshop

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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
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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

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OUTLINE

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

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Background on Cloud Schemes
Current GEM-LAM-2.5 Grids
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Background on Cloud Schemes
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Background on Cloud Schemes
Hypothetical GEM-LAM-2.5 Grid
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Background on Cloud Schemes
Single cloudy grid element
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MICROPHYSICAL PROCESSES in a cloudy grid element
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Background on Cloud Schemes
1 m3 (unit volume)
e.g. Cloud droplets (not to scale)
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Background on Cloud Schemes
1 m3 (unit volume)
e.g. Cloud droplets (not to scale)
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Background on Cloud Schemes
Example of Moments
pth moment
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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
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Background on Cloud Schemes
ICE CRYSTAL
? SNOW CRYSTAL / AGGREGATE
?
GRAUPEL
HAIL
LIQUID WATER
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Background on Cloud Schemes
SNOW
LIQUID WATER
ICE
HAIL
GRAUPEL
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Background on Cloud Schemes
SNOW
CLOUD
ICE
HAIL
GRAUPEL
RAIN
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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

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Background on Cloud Schemes SINGLE-MOMENT
Version
SNOW
CLOUD
ICE
HAIL
GRAUPEL
RAIN
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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
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Background on Cloud Schemes DOUBLE-MOMENT
Version
CLOUD
Explicit FOG
QC
NC
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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
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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)
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Example Case - 27 June 2006
Qc (Cloud Mixing Ratio)
g kg-3
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Example Case - 27 June 2006
Nc (Cloud Number Concentration)
cm-3
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Example Case - 27 June 2006
Dc (Cloud Mean-Mass Diameter)
?m
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Example Case - 27 June 2006
QC g kg-1
LEVEL nk-3 (0.961) 340 m
VIS km
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Example Case - 27 June 2006
QC g kg-1
LEVEL nk-2 (0.973) 230 m
VIS km
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Example Case - 27 June 2006
QC g kg-1
LEVEL nk-1 (0.985) 130 m
VIS km
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Example Case - 27 June 2006
QC g kg-1
LEVEL nk (0.995) 45 m
VIS km
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Example Case - 27 June 2006
VIS km
p hPa
Level
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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)
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Example FRAM L-2 Case, 18 June 2006
GEM-Regional (15 km)
GEM-LAM (2.5 km)
QC
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Example FRAM L-2 Case, 18 June 2006
GEM-Regional (15 km)
QC g kg-1
RH
0.95
VIS km
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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
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Current Development CLOUD FRACTION Version
Lower Level
Upper Level
QC
RH
RHcrit 1.00 (no cloud-fraction)
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Current Development CLOUD FRACTION Version
Lower Level
Upper Level
QC
RH
RHcrit 0.90 (cloud-fraction)
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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

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THANK YOU jason.milbrandt_at_ec.gc.ca
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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
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Low-level QC
Cloud-Fraction, b
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Example FRAM-C Case, 4 January 2006
VIS (Visibility km)
200 m
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Example FRAM-C Case, 4 January 2006
Qc (LWC)
0.30 gm-3
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Example FRAM-C Case, 4 January 2006
Nc (droplet number concentration)
130 cm-3