1. Bucharest 2006 J. Steppeler (DWD)
LM_Z Project
Bucharest 2006
J. Steppeler (DWD)

2. LM_Z
Coordinates cut into mountains
The finite volume cut cell is used for discretisation / unstructured grid
Boundary structures are kept over mountains
The violation of an approximation error is avoided

3. Formal state of project
All PDE delivered except task 7 by Meteo Swiss (.1 PDE)
Some over-achievements, some useful work, but not exactly to plan
Main original first milestone to show usefulness of the principle of Z-discretisation was achieved.
Main project aims achieved, but not all (Improvement shown for resolutions 7 km and 14 km only)
Strong increase of forecast quality for version 1.4 (the big number of cases is an overachievement over the plan)
An optimistic revision of plan by evaluation committee achieved only by 80%
Some further developments towards operational use (Version x1.7, Overachievement) and new error corrections (Version x1.6)
The new versions x1.6 and x1.7 are insufficiently tested
Version x1.7 offers the use of large time-steps and thereby operational efficiency
LM_Z report in print in MWR

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

5. Frequ. Bias and threat score
LM_Z:
RMS of Winds and temp. against radiosondes

6. Precipitation

7. New Developments (Version x1.7, Bitzer)
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)
Operational efficiency and full unstructured gridding for boundary layer achieved
Testing of these features is yet very preliminary

8. New Developments (Cesari)
New version exists
Intgrated within the common LM_Z library
Physics interface needs some work
not yet realistically tested (next year)

9. 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.

10. LM_Z version 3.6 w-velocity shallow mountain dx=2 km,dt=10sec

11. LM_Z version 3.6 w-velocity high mountain: 2300 m dx=2 km,dt=10sec

12. LM_Z version 3.6 v-velocity SKANIA Case Cloud water in lowest 250 m 12 hr forecast dx=7 km, dt=30sec

13. LM_Z version 3.6 v-velocity SKANIA Case,12 hr forecast dx=7 km, dt=30sec

14. Conclusions LM_Z To be done next term:
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
To be done next term:
Combining and of different error corrections and developments
Thorough testing of different error corrections and developments
preparation for operational use and minor development for Euler version
SL_Version

15. Supporting developments:
DFG “Einzelantrag” (LM_Z)
VHREM LM_Z (Long term research)