NAMKF and MesoNAM

[Andrew Revering]

Does anyone know if this...
http://www.nssl.noaa.gov/etakf/

is using Kain-Fritsch or is it with convective parameterization turned off? I believe at this URL it used to be a KF flavor, but is now with it turned off, but the URL makes me wonder. I should also note that the same directory can be pulled from http://www.nssl.noaa.gov/wrf/ so that doesnt necessarily mean the etakf directory means anything.

 

[Jeff Duda]

The lower the resolution, the better the model can 'naturally' handle convection, so you can actually 'turn off' convective parameterization. If the model is down under 10km (some would argue much less than that), your model will handle thunderstorms better without convective parameterization because CP is essentially stunting the growth of convection and sizing it to fit within the large grid spacing of say a 30km model for example. A storm is not that large, so you need to try to mathematically grow the storm on a more natural scale. If your grid spacing is closer to that of a real storm (say 2-5km) the storm will grow naturally within the grid spacing so you can shut off CP. With that said, if you have to use CP; Kain Fritsch I believe is pretty well accepted as one of the best to use.

Like Brian 2001...that article said domain spacing of O(100m) would be necessary to explicitly model convection.

 

[Andrew Revering]

well its recommended to shut it off under 10km in the WRF software itself.

NSSL runs a 4km with no CP I believe.

 

[Geoff Manikin]

That was a special run that NSSL used to make of
the Eta with the K-F.

I've actually solved the mystery here with the help of
the SPC science and operations officer. One of the possibilties I threw out there in a previous message actually stuck to the wall. The NAM-KF is the control Eta member of the SREF (short-range ensemble forecasting system) with the K-F scheme. The displays SPC uses to look at this forecast incorrectly identify it as NAM-KF; I think that when the operational Eta became the NAM, they changed *all* Eta references to NAM, but this one should have been left alone.

This run is at 32 km, and SPC likes to look at it in cases in which capping issues relative to convective initiation are in play. The BMJ scheme is famous for erroneously eliminating strong caps and initiating deep convection in otherwise hostile environments, and the K-F which is better at maintaining inversions offers an alternate solution. The fact that it's at lower resolution and uses a different initial condition than the operational NAM (they're offset by 3 hours), though, adds limitations to a true comparison.

Does anyone know if this...
http://www.nssl.noaa.gov/etakf/

is using Kain-Fritsch or is it with convective parameterization turned off? I believe at this URL it used to be a KF flavor, but is now with it turned off, but the URL makes me wonder. I should also note that the same directory can be pulled from http://www.nssl.noaa.gov/wrf/ so that doesnt necessarily mean the etakf directory means anything.

 

[Geoff Manikin]

NCEP runs its 4 km WRF with no convective parameterization too:
http://www.emc.ncep.noaa.gov/mmb/mpyle/cent4km/conus/12/

The rainfall totals in this 4 km NMM run are out of whack (although that's being worked on), and the solutions are sometimes WAY off, but it does often show some remarkable skill in terms of initiation and mode.

The forecast soundings, though, are not very good. It turns out that while it looks like turning off deep (precipitating) convection works reasonably well, we may need to have shallow convection back in the picture to help with the evolution of boundary layer structure.

well its recommended to shut it off under 10km in the WRF software itself.

NSSL runs a 4km with no CP I believe.