Recent COSYNA Product Developments
Sebastian Grayek, Emil V. Stanev
Two-Way Coupler for the NEMO
Framework
Domain nests are connected via a temporal/spatial adaptive nudging
approach. The minimum forecast period is one day. The exchanged
between nested models data is linearly interpolated onto individual
model grids and time.
In Fig. 1 and Fig. 2 an example application is given. The coupled
system includes three models covering the North Sea, the Baltic Sea
and the high resolution Danish Strait domain. Ist performance is
compared against a coarse-resolution setup for the whole area called
reference run. The latter includes both basins and uses a 2 nm
resolution. The horizontal resolution for the North Sea and the Baltic
Sea in the nested setup is as coarse as in the reference model. The
nested model in the Danish Strait area has a horizontal resolutionof
0.5 nm. Velocities, temperature and salinity are exchanged between the
three models. The timestepping of coarse resolution models is
segmented in a one day hindcast and a one day forecast phase. During
the hindcast phase the coarse resolution models receive the enhanced
fine resolution information via a nudging approach. During the forecast
phase of the coarse resolution model no nudging is applied and the
models run in a free prognostic mode. In the next cycle of coupling
procedure the fine resolution model is rerun for the whole hindcastforecast period of the coarse resolution models using interpolated
coarse resolution output as boundary condition.
Daily Enhanced Forecast and Model Error
Prediction for the German Bight's Noon
Temperature and Salinity
Background statistics are estimated from the GETM pre-operational
simulation. The assimilation tool combines both the OSTIA SST
comprehensive analysis and the sparse Lev.2P AVHRR data. The
correlation lengths used for the localization, as well as the influence of
SST on the shape of temperature profiles are optimally determined
from the current observing systems’ configuration. The data
assimilation improves the forecast for salinity and residual currents.
Planed online products for users are: Daily noon temperature 24h
Forecast for the next day (~1km); Daily noon temperature model
forecast error (~1km).
Figure 3: OSTIA (~5 km) analysis from GHRSST
Figure 4: Merged Lev.2P AVHRR data products (1-
for 08/03/2011
5 km) from PODAC for 08/03/2011
Figure 5: GETM noon SST 24h forecasting error for
Figure 6: Annual depth integrated salinity RMSE
08/03/2011.
between simulations with and without AVHRR data
assimilation.
Figure 1: Bathymetries of model domains in
meters; Coarse resolution North Sea nest (2nm,
top), coarse resolution Baltic Sea nest (2nm,
right-hand side) and fine resoluiton Danish Strait
nest (0,5, top right-hand side). The coarse
resolution reference model, which is used for
comparisions, consists of the North Sea and
Baltic Sea model domains.
Figure 2: Snapshot of surface salinity from the low resolution reference simulation (left-hand side) and
the nested high resolution Danish Strait model domain (right-hand side) for 08/03/2010.
OSE / OSSE Tool Box
The OSE/OSSE tool box developed
and currently used in the KSD will be
made available to interested users.
The tool box is written in Fortran 90
code and its functions are easy to
access via NetCDF inputs.
The covariance information and
representation errors are autonomously calculated by the tool box
from given proxy data. The proxy
data can either be a period of model
output or eigenvectors of an
empirical orthogonal function (EOF)
analysis. Results of the OSE/OSSE
are provided via NetCDF output.
Observations
Positioning
Proxy Data
Representation
Error
Estimates
Instrument
Errors
Observation
Error
Estimates
Reconstruction
Matrix
Covariance
Information
NetCDF Input
NetCDF
Output
Reconstruction
Error
Estimates
Figure 7: Data flow, input (green boxes) and
output (blue boxes) in the OSE/OSSE tool box.
Figure 8: Example of two OSEs for the MARNET observation network forecasting the mean salinity
(MDS) of the German Bight. For one station (left-hand side) and the whole network (rigth-hand side).
Position of the MARNET Stations are marked by numbers in the figures: Nordseeboje II (1);
Nordseeboje III (2); Deutsche Bucht (3); Ems (4); Fino 1 (5).
Helmholtz-Zentrum Geesthacht • Max-Planck-Straße 1 • 21502 Geesthacht / Germany • Phone +49 (0)4152 87-0 • Fax +49 (0)4152 87-1403 • contact@hzg.de • www.hzg.de
Contact: Dr. Sebastian Grayek • Phone +49 (0)4152 87-1504 • Fax +49 (0)4152 87-2020 • sebastian.grayek@hzg.de