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Modelling of deep convective cloudsand orographic triggering of convectionduring the COPS experiment
Ralph Burton, NCAS (Leeds)Alan Gadian, NCAS (Leeds)Victoria Smith, ICAS, (Leeds)Stephen Mobbs, NCAS (Leeds)
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1. 15th July – deep convection.2. 12th August – outflows and convergence.3. Summary.
Outline of talk.
How well does WRF simulate these cases?
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Note the location and orientation (SW-NEish)of the storm cloud
15th July: isolated deep convective cloud
From the Science Directory (Evelyne Richard) Summary
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Observation of convective cloud, 15th July
15th July: isolated deep convective cloud
From the Science Directory (Evelyne Richard) Summary
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WRF convective cloud, 15th July
15th July: isolated deep convective cloud?
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WRF: inner domain: 700m resolution
Outer domain 6.3km
1st nest 2.1km
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Run # Microphysics Cu Param. Vert. levels Cloud?
1 Ferrier Betts-Miller 81 2 Ferrier Kain-Fritsch 121 3 Ferrier Betts-Miller 121 4 Thompson Kain-Fritsch 121
Sensitivity Tests
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Ferrier; Betts-Miller
WRF: sensitivity tests – CAPE and wind vectors: 15Z
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WRF: skew-t and wind vectors: 15Z
Cloud is quite shallowIsosurface of cloud water mixing ratio = 1E-4 kg/kg
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Comparison with observational data: AWS locations.
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Comparison with observational data: 2m temperatures.
Many thanks to Simon Hölzl and Alex Göhm
Black = obs.; red = WRF
tem
pera
ture
time of day
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1156m 1000m 669m
798m 842m 962m
507m 667m 928m
Many thanks to Simon Hölzl and Alex Göhm
Comparison with observational data: 2m temperatures.
Black = obs.; red = WRF
tem
pera
ture
time of day
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1156m 669m
Comparison with observational data: 2m RH.
Many thanks to Simon Hölzl and Alex Göhm
Black = obs.; red = WRF
rela
tive
hum
idity
time of day
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Comparison with observational data: vertical profiles.
OBS
WRF
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OBSGRID – Objective analysis.Boundary layer RH, outer domain. 06Z, 15th July
With thanks to Cindy Bruyere, NCAR
Achern andHornisgrinde Radiosonde data
Objective analysis: forcing the analysis with observations.
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Orographic triggering: 12th August Case.
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Rain water, 2m temps., wind vectors. 1145Z 12th August
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Cloud, 2m temps., wind vectors. 1145Z 12th August
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Rain water, wind vectors, orogrpahy. 1300Z 12th August.
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Relatively cool area
Note this cold area is over a roughly 2-D slope
2m temps., wind vectors, orogrpahy. 1300Z 12th August.
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Area of high(er) CAPE in the region of the “cloud” location.
Zone of convergence at the cloud location.
BUT
Sensitivity to model Cu and microphysics Other sensitivities… GFS analysis appears to be too dry. WRF does not seem to agree with obs. at higher elevations ( > ~ 850-900m) quite so well: under-predicts the 2m temp and over-predicts the RH: evaporative cooling?
• ECMWF T799 analysis – ready to try!• Objective analysis
Conclusions
15th July
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Outflow from clouds in model
Outflows appear to convergence, and cloud formed as a result
Good comparison with remote sensing data
Again, model agrees with obs. at lower elevations better than at higher elevations.
• Need higher temporal resolution runs (output every minute) to isolate the mechanisms of triggering.
12th August
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