QPFDS
A climatology-based QPF downscaling smartInit
The QPFHelper tools create a “downscaled” QPF field, by calculating the percentage of the monthly
QPF climatology at specified points – then doing an objective analysis on those percentages to get a
percentage grid – then multiplying that percentage grid by the monthly climatology grid to get a final
QPF grid that has the spatial “character” of the underlying monthly climo QPF grid. This method is
essentially replicated here in smartInits for the ECMWF, GFS40, SREF, DGEX, and NAM12 models.
However, rather than having it depend on the location of specific points, we instead compare the
model forecast QPF to the MODEL’s monthly climatological QPF.
Since the model is at a much lower resolution than the final GFE grids, the MODEL’s monthly
climatological QPF should also be at that lower resolution. Since the model’s true climatology is not
available to us, we estimate it by smoothing the PRISM climatology to a resolution that should be
consistent with the resolution of the model data that we receive. The QPF created by this different
downscaling procedure is stored in each model as the parm name: QPFDS. In addition, the raw,
unadjusted QPF from the model is stored in the GFE databases as QPFRaw. Furthermore, the
percentage of the model monthly climo is also stored in the GFE databases as QPFPct.
Most smartInits calculate the PoP based on the QPF. Since these smartInit adjustments make a new
field called QPFDS, and leave the current QPF smartInit alone, the PoP will still be based on the old
QPF smartInit code. Similarly any smartInit’s for snowAmt, etc. will all still use the old QPF value. In
the future, we may want to switch these smartInits to also use the QPF output from this new
downscaling procedure.
AWIPS Model Resolution
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