234 Lennart Funkquist and Rans Dahlin
networks is partly changing the aim of the monitoring from the descriptive role to
the role of supporting and validating ocean forecasting. An increased exchange of
real time data between the Baltic countries and the installation of online automatic
fixed stations or moored buoys is planned and will definitely increase the support
of ocean forecasting.
12.4Sea ice
To continue shipping and to keep the harbours open also during severe winters,
sea ice forecasting is a task of great economic importance for the countries around
the Baltic Sea. Since 1971, Finland and Sweden have, due to strong icebreakers
and good ice surveillance, been able to keep the traffic going in spite of some very
severe winters. To increase the efficiency and keep the costs down, the ice-breaking services rely upon the national ice information services, which produce diagnostic ice-maps and forecasts. The ice-breaking services are continuously
requesting more and better support for their decisions and the responsible agencies
in Finland and Sweden have funded a Winter Navigation Research Board, which
oversees the development of surveillance methods and forecast models by funding
relevant research.
The thickness of ice and its horizontal distribution together with sea surf ace temperature are routinely analysed every third day in a uniquely designed system
(ICEMAP) with the help of in situ measurements and satellite data. However, as
the data coverage is stiH too coarse to automatically create gridded data, a manual
subjective analysis is needed for the final product.
Sea ice is modelled by the BOBA model, which covers the Baltic Sea by a 10
nautical miles grid and is composed of three different sub-models, a shallow water
model for the interface stress between the ice and water, a one-dimensional model
for the vertical salinity and temperature profile applied to 31 quasi-homogeneous
regions and a Hibler-type (Hibler, 1979) ice model for the ice dynamics. The sea
surface temperature in the model is updated regulady by a simplified nudging procedure and the model is also coupled to the atmospheric model by introducing the
latest ice forecast into the HIRLAM assimilation procedure (Gustafsson et al.,
1997). Fig. 12.2 shows an overview of the coupling between the active modules.
The PROBE model is the one-dimensional part of BOBA and divides the Baltic
Sea and the Kattegat into 13 sub-basins, which are coupled through horizontal
flows. The model runs for the whole year and supplies the BOBA model with initial vertical stratification when the ice-season starts. However, when forced by climatology, it is also a valuable tool for long-term forecast of the risk for ice
formation. This is an important application for an efficient use of the ice-breaking
service, because the later the ice-breakers have to be manned and put into operation, the less is their stand-by cost.
networks is partly changing the aim of the monitoring from the descriptive role to
the role of supporting and validating ocean forecasting. An increased exchange of
real time data between the Baltic countries and the installation of online automatic
fixed stations or moored buoys is planned and will definitely increase the support
of ocean forecasting.
12.4Sea ice
To continue shipping and to keep the harbours open also during severe winters,
sea ice forecasting is a task of great economic importance for the countries around
the Baltic Sea. Since 1971, Finland and Sweden have, due to strong icebreakers
and good ice surveillance, been able to keep the traffic going in spite of some very
severe winters. To increase the efficiency and keep the costs down, the ice-breaking services rely upon the national ice information services, which produce diagnostic ice-maps and forecasts. The ice-breaking services are continuously
requesting more and better support for their decisions and the responsible agencies
in Finland and Sweden have funded a Winter Navigation Research Board, which
oversees the development of surveillance methods and forecast models by funding
relevant research.
The thickness of ice and its horizontal distribution together with sea surf ace temperature are routinely analysed every third day in a uniquely designed system
(ICEMAP) with the help of in situ measurements and satellite data. However, as
the data coverage is stiH too coarse to automatically create gridded data, a manual
subjective analysis is needed for the final product.
Sea ice is modelled by the BOBA model, which covers the Baltic Sea by a 10
nautical miles grid and is composed of three different sub-models, a shallow water
model for the interface stress between the ice and water, a one-dimensional model
for the vertical salinity and temperature profile applied to 31 quasi-homogeneous
regions and a Hibler-type (Hibler, 1979) ice model for the ice dynamics. The sea
surface temperature in the model is updated regulady by a simplified nudging procedure and the model is also coupled to the atmospheric model by introducing the
latest ice forecast into the HIRLAM assimilation procedure (Gustafsson et al.,
1997). Fig. 12.2 shows an overview of the coupling between the active modules.
The PROBE model is the one-dimensional part of BOBA and divides the Baltic
Sea and the Kattegat into 13 sub-basins, which are coupled through horizontal
flows. The model runs for the whole year and supplies the BOBA model with initial vertical stratification when the ice-season starts. However, when forced by climatology, it is also a valuable tool for long-term forecast of the risk for ice
formation. This is an important application for an efficient use of the ice-breaking
service, because the later the ice-breakers have to be manned and put into operation, the less is their stand-by cost.