1. Sensitivity to WRF microphysics/ Cu parametrisation
COPS 15th July:
Sensitivity to WRF microphysics/
Cu parametrisation
Ralph Burton, NCAS (Leeds)
Alan Gadian, NCAS (Leeds)
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2. 15th July: isolated deep convective cloud
Note the location and orientation (SW-NEish)
of the storm cloud

3. WRF: COPS domains
6.3 km resolution
2.1 km resolution

4. WRF: inner domain: 700m resolution

5.   Sensitivity Tests Run # Microphysics Cu Param. Vert. levels Cloud?1
Ferrier
Betts-Miller 81  2
Kain-Fritsch
121 3  4
Thompson 5 ??

6. WRF: sensitivity tests – CAPE and wind vectors: 15Z
Ferrier; Kain-Fritsch
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7. WRF: sensitivity tests – CAPE and wind vectors: 15Z
Thompson; Kain-Fritsch

8. WRF: sensitivity tests – CAPE and wind vectors: 15Z
Ferrier; Betts-Miller

9. WRF: skew-t and wind vectors: 15Z
Isosurface of
cloud water mixing ratio = 1E-4 kg/kg
Cloud is quite shallow

10. WRF: cloud evolution: Ferrier / Betts-Miller
12Z
13Z
14Z
15Z
16Z

11. Further work / comments
Vertical Resolution
Lean & Clark (2003) argued that 25m near surface,
50m through BL, 250m in troposphere is needed.
Change WRF vertical levels to suit this.
Horizontal Resolution
Petch (2006) argues you need 200/250m to capture the
growth from shallow to deep convection.
Change WRF grid resolution to suit this.

12. Conclusions The Ferrier / Betts-Miller appears to present the “best”
combination of microphysics and Cu parametrisation.
Cf. “An Experiment Using the High Resolution Eta and WRF
Models to Forecast Heavy Precipitation over India”, Pure & Applied
Geophysics, Rama Rao et al., Sept – same conclusion
Area of high(er) CAPE in the region of the cloud location.
Zone of convergence at the cloud location.
BUT
Even in the best case, the GFS surface analysis
appears to be too dry.
ECMWF analysis? Edit GFS analysis for surface moisture? …?