modelling of deep convective clouds and orographic triggering of convection

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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