ALADIN developments in Prague during the second quarter of 2000

1. Data assimilation related developments.

a. Tuning of spectral blending.

The tuning of the spectral part of the blending technique continued for the parameters of external DFI. The retouch of the DFI parameters used in the normal forecast runs was settled: we can use a little bit weaker filter thanks to better intrinsic balance of the fields after blending compared to the fields after our standard full-pos interpolation to the finer grid. There are still validation works at place, till now giving quite satisfactory results. After the remaining checks being successfully completed, blending should enter the operational suite. It should also be mentioned that blending technique may be quite helpful in designing the data assimilation strategy for a limited area model having relatively small domain.

b. ALADIN/LACE background error statistics to be used in Jb term of penalty function.

A comprehensive report on the recent background error statistics research was written by Maria Siroka and it will be available soon in a post-script format. Further research using new Jb statistics was done in Toulouse with ALADIN/FRANCE domain, please, refer to the reports of Waafa Sadiki and Adam Dziedzic.

c. Diag.pack

There was no special development on diag.pack regarding the part of CANARI in the second quarter, but there were developments of various diagnostics, which will be common with other configurations, reported in the section on the physics.

2. Developments in the physics.

2.1) CYCORA II

In June the tests to prepare the package CYCORA II were pursued. It concerned the study of convective entrainment and to further detail the evidence brought by the sensitivity tests made on Christmas storm.

2.2) Diagnostics of CAPE, PBL height and wind guests

In April, the strategy to compute several new fields for practical diagnostics was defined; it concerned CAPE, moisture convergence (MOCON), height of PBL and wind gusts. More details could be find in a report of Ryad el Khatib. Within LACE, the development of CAPE, PBL and wind guests diagnostics was taken. The necessary code was written and partly validated.

2.3) Horizontal diffusion of humidity

This subject is somewhere in between physics and dynamics and it has been initiated due to a known weakness of precipitation patterns: there is too much precipitation on the upward slope of the mountains and almost none on the lee side while in reality it rains everywhere.

3. Developments in the dynamics.

3.1) Quasi-Academic Test SCANIA

A 3D quasi-academic test on stationary orographic forcing was proposed to be tested in ALADIN by Mike Cullen (ECMWF) and Piotr Smolarkiewicz (NCAR/ECMWF). Work took place from March to May, using the hydrostatic (operational) version of ALADIN. The test consists in studying an idealized equivalent barotropic flow past complex terrain, concretely Scandinavian peninsula orography (where from the name SCANIA). It revealed several interesting conclusions on the time-stepping, orographic resonance treatment, tuning of horizontal diffusion, usage of the linear grid. For both ARPEGE and ALADIN the tests using linear grid together with filtered orography (the same like in case of quadratic grid) have already started (in ALADIN/LACE it is the test "aba"). SCANIA results were presented essentially at the ECMWF workshop on high resolution global modelling (5-7 June 2000, Reading), at CNRM Seminar and also like an extra lecture at ALATNET training school in Radostovice (15-26 May 2000). An extended abstract will be published in ECMWF Workshop Proceedings and it is also available in post-script format.

3.2) Non-hydrostatic dynamics

The SCANIA test also became a subject of study with the non-hydrostatic dynamical kernel, especially regarding the discretization of the top boundary condition. The study shall continue in July and results will be reported in the next Newsletter.

4. Developments in the diagnostics.

c.f. efforts on CAPE, PBL and wind guests.

5. Developments in the verification.

There was no development of the verification tools in the second quarter of 2000.

6. Technical developments.

Beside the continuation of SMS preparation, a port of the configuration e923 to sx4 has started, however not yet fully completed.

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