New Developments for LM-Z

H. W. Bitzer (AWGeophys)

and J. Steppeler (DWD)

State of project

•Version 1.4 tested on a large set of cases: Overachievement of project plan• Strong increase of forecast quality for 1.4 •Several error corrections and important further developments have been done: Overachievement of project plan•Operational efficiency has bee acheved

•New versions and further developments are not sufficiently and separately tested•No common library to combine the further developments

On the positive side:

On the downside:

Version LM_Z 1.4•Tested on a large set of cases • Strong increase of forecast quality•dt=.25 dt operational >> 4 times operational run time >> not operationally feasible •Some error corrections in Version LM_Z 1.5 (not sufficiently tested)•Further error corrections•Version 1.5 offers also the possibility to avoid the splitting error. This option is untested.

New Developments•Improved horizontal diffusion near mountains• Possibility of increased timestep (>> about operational efficiency) using the thin wall approximation•new advection •Better implementation of free slip boundary at mountains•Avoiding instability of divergence damping in lowest layer (this is also present in LM_tf)

Improved horizontal diffusion near mountains

•A 2nd order polynomial is fitted to the points in the atmosphere

•The target point is replaced by the interpolated value.

•Theoretical evaluation of the scheme has not yet been done.

LM_Z version 3.6 w-velocityshallow mountain dx=2

km,dt=10sec

LM_Z version 3.6 u-velocityhigh mountain: 2300 m dx=2

km,dt=10sec

LM_Z version 3.6 w-velocityhigh mountain: 2300 m dx=2

km,dt=10sec

LM_Z version 3.6 v-velocityhigh mountain dx=2 km,dt=10sec

LM_Z version 3.6 v-velocitySKANIA Case Total precip, 12 hr forecast dx=7

km, dt=30sec

LM_Z version 3.6 v-velocitySKANIA Case Cloud water in lowest 250 m

12 hr forecast dx=7 km, dt=30sec

LM_Z version 3.6 v-velocitySKANIA Case,12 hr forecast dx=7 km, dt=30sec

Conclusions•The new version of LM_Z offers the possibility of operational application, subject to testing• The cost of the revised scheme depends on the percentage of the operational time step to be used (Subject to testing): 100%: no cost; 75%: cost = 25% of fast wave

scheme >> Projected cost for newest cycle = 3% of total run time•Creation of a library with all improvements and correction outstanding•Suggested further work: Testing and preparation for operational use