Workshop: Aspects of regional modelling – at GKSS Contributions by Hans von Storch, Frauke Feser,...
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Transcript of Workshop: Aspects of regional modelling – at GKSS Contributions by Hans von Storch, Frauke Feser,...
Workshop: Aspects of regional modelling – at GKSS
Contributions by Hans von Storch, Frauke Feser, Insa Meinke and
Burkhardt Rockel
Ouranos, Montreal 7.9.2004
Issues
• Generation of gravity waves
• Experiments with digital filtering and pre-filtering by subtraction of 2d polynomials
• An example of divergence in terms of cloudiness
• Castro’s hypothesis – in large area simulations, lateral control is insufficient to maintain large scale states.
Generation of gravity waves?
v
uSLP
Intensity of temporal variance on time scales between 2 and 6 hours
No SN = no spectral nudging SN = with spectral nudging
No SN No SNSN SN
Experiments with digital filtering and pre-filtering by
subtraction of 2d polynomials
),( yxPkf
),(),,(),,( yxFyxFyxF sf
mf
lf
),(),(),(),(),( yxFyxFyxFyxPyxf sf
mf
lf
kf
With representing a fitted polynomial of order k,
and filtered components representing large, medium and small spatial scales:
Digital filters
The filters are almost isotropic digital filters, obtained by solving an optimization problem
10m wind speed fields (m/s) for the storm ’Anatol’ on December 3rd, 1999, 6 p.m., of a LAM simulation: (a) Unfiltered, (b) low-pass filtered, (c) bandpass filtered, and (d) high-pass filtered data.
After subtraction of fitted polynomial of 2nd order.
Precipitation fields (mm) for the storm ’Anatol’ accumulated for December3rd, 1999, of a LAM simulation: (a) Unfiltered, (b) low-pass filtered, (c)band-pass filtered, and (d) high-pass filtered data.
Mean sea level pressure (hPa) for the storm ’Anatol’ for December 3rd, 1999, 6 p.m. of a LAM simulation: (a) Unfiltered, (b) low-pass filtered,(c) band-pass filtered, and (d) high-pass filtered data.
Castro’s hypothesis – in large area simulations, lateral control is insufficient to maintain large scale states.
Castro, C.L., and R.A. Pielke, Sr., 2004: Dynamical Downscaling: Assessment of value restored
and added using the Regional Atmospheric Modelling
System. submitted
NCEP
small 50 km
500 hPa height, 0000 UTC, 12 May 1993
Lateral constraint too weak to maintain large-scale in the interior if flushing time too long (Example: May 1993; strongly non-zonal flow) - Castro and Pielke, 2004.
small-- large integration area
The finding of Castro & Peilke is not specific to RAMS – but emerges also in CLM (Rockel, pers. comm)
CLM
NCEP
13. May 1993, 00 UTC
The Rinke & Dethloff study on regional modelling of the Arctic atmosphere
Rinke, A., and K. Dethloff, 2000: On the sensitivity of a regional Arctic climate model to initial and boundary conditions. Clim. Res. 14, 101-113.
Ensemble standard deviation 500 hPa height [m²/s²]
Inst
itu
t fü
r K
üst
enfo
rsch
un
g
I f K
The problem of regional noise