Proceedings - C-SRNWP Project

In parallel, a direct radar observation operator has been developed and is used in case studies
for reflectivity monitoring and model-to-reflectivity applications. The radar observation
operator also allows to study and improve carefully the quality control checks to be operated
later on in a routine operational manner. So far, conclusions are the following:
►1D retrieval seems able to correct for humidity,
►Quality control of data and observation operator evaluation (M. Jurašek, LACE)
►Implementation in Arome is well advanced
Future work:
►More 1D + 3D-VAR high resolution cases
►Perform cycled assimilation experiments,
Collaborations:
►Introduce beam blockage in observation operator (G. Haase, Hirlam)
4. The Arome assimilation prototype: a R.U.C.
Decision has been taken to start the preparation and the early evaluation of an Arome model
based assimilation system in the context of a Rapid Update Cycle. The RUC typically is
started 12 or 24 hours before the target initial time of interest, allowing thus for 5 to 9 3D-
VAR data analyses in a 3-hourly frequency (13 to 25 in a 1-hourly mode). While we still wish
to carefully evaluate the spin-up properties (especially in the 1 hour cycle), work also needs to
be performed in order to tune the system with respect to data density. Also, in 2007, further
case studies are planned, still focussing on severe cases of heavy precipitating events. Figure
7 shows one such case, a typical strong event triggered by the advection of moist, warm air
from the Mediterranean Sea over South-East of France. This air is orographically forced over
the Cévennes mountain ridge, with some additional forcing from a synoptic upper-air trough.
The result is a heavy convective mesoscale system, usually fairly stationary for several hours,
which represents a major threat to the surrounding areas. Some critical aspects for a good
forecast here are a good initial state for humidity, low level winds and the position and
orientation of the upper air trough.
199