Proceedings - C-SRNWP Project

addition, research on the construction of transparent lateral boundary conditions will be
continued.
Surface modelling and data assimilation both are believed to become of increasing
importance at higher resolutions. Mesoscale surface developments will be based on the
externalized SURFEX scheme. For the time being, new developments in both the surface
modelling and data assimilation will first take place and be evaluated on synoptic scales, and
then ported to SURFEX. Areas in which HIRLAM is likely to contribute to the mesoscale
surface assimilation and modelling system, are: the improved snow and forest descriptions by
Stefan Gollvik, the assimilation of OSI-SAF sea surface temperature and sea ice, and the
introduction of a lake model component, the development of which has recently started in
close cooperation with RSHU.
For mesoscale data assimilation, 2006 has been a year of learning and preparation.
HIRLAM researchers have received training in the use of the ALADIN 3D-VAR and ODB
systems; they have begun implementing the ALADIN 3D-VAR system locally for further
study of the relevant differences between the ALADIN and HIRLAM 3D-VAR. It is intended
to begin developing a joint 3D-VAR system within the IFS framework in 2007.
Joint research with Météo-France on the assimilation of radar reflectivities has
started. For other relevant types of observation, such as satellite radiances and profiles, in-situ
screen level observations, GPS and radar winds, the impact of assimilation will first be tested
on synoptic scales, and after that on mesoscales. A plan has been proposed to achieve
convergence between the ALADIN and HIRLAM formulation of observation operators; both
sides are preparing a description of the treatment of observation operators in their own
systems, after which a common formulation will be chosen. A planning meeting to determine
the strategy on how to develop a mesoscale data assimilation capability during the coming
years, will be held in October.
A mesoscale verification working group has been set up as an outcome of the Oslo
workshop (December 2005). This group has selected a set of relevant cases of typical
mesoscale weather situations of importance, which is to be used to validate the performance
of (new versions of) the mesoscale models against. Extended case studies are expected to
begin in early 2007.
Synoptic scale developments:
For the synoptic model, the testing and preparation for the introduction of 4D-VAR has been
a major area of attention in 2006. A breakthrough has been achieved with the introduction of a
statistical balance formulation and the detection of a nasty bug; 4D-VAR now is performing
consistently and significantly better than 3D-VAR. Extensive testing and tuning of the 4D-
VAR system has been carried out through the summer, in preparation of its implementation in
the HIRLAM Reference System. After that, the impact of using more sophisticated (moist)
physics in the TL/AD model will be investigated.
The number of remote sensing data to be assimilated in the model will increase
significantly this year. The assimilation of AMSU-A over sea has been introduced in
Reference version 7.0. This will be followed by the inclusion of AMV and MODIS winds,
screen level parameters, OSI SAF sea ice and SST, and scatterometer data in early 2007.
Research on the assimilation of AMSU-B, AMSU-A over land, (slant) GPS, and radar winds
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