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REGIONAL SEA ICE FORECASTING
The Finnish Meteorological Institute (FMI) provides forecasts of ice motion, concentration, thickness, ridges and deformations for the Baltic Sea. The operational model is a multi-category sea ice model developed originally for climate research. The model physics and numerics are the same in both operational and climate simulations, with the only differences being the horizontal resolution and atmospheric forcing. The model resolves ice thickness distribution, i.e., ice concentrations of variable thickness categories, redistribution of ice categories due to deformations, thermodynamics of sea ice, horizontal components of ice velocity and internal stress of the ice pack. Presently, no assimilation is used for the model predictions. Horizontal resolution of the model is 1 nm. The model produces forecasts of the following variables:
Swedish Meteorological and Hydrological Institute (SMHI) provides operational ice forecasts based on HIROMB (High-Resolution Operational Model for the Baltic). This is a three-dimensional, fully baroclinic circulation model for the ocean. In three nested grids it currently covers the North Sea (12 nm resolution), the Skagerrak (3 nm resolution), the Kattegat, and the Baltic Sea (1 nm resolution). The model includes a fully thermodynamic coupling with the atmosphere and a sea ice module. The latter contains prognostic variables for ice concentration, level ice thickness, total ice thickness, ice ridge density, and ice ridge height. HIROMB is forced by the atmospheric model HIRLAM 22 km (11 km in the near future) and a larger-scale storm-surge model provides HIROMB with boundary conditions of sea. Daily river runoff data are obtained from a hydrologic model. The model makes 48-hour forecasts twice a day, at 00 UTC and 12 UTC. A test version of HIROMB is currently running with assimilation of nearreal- time data from ice charts provided by the Swedish Ice Service as well as profiles of salinity and temperature. The following variables are forecasted:
The service is provided through two service chains implemented at FMI and SHMI, respectively. In the case of FMI, initial conditions for sea ice thickness, concentration and sea surface temperature are obtained from the digitized ice charts. The ice charts include all available EO data (RADARSAT, ASAR) and in-situ observations. The sea ice model is forced by the HIRLAM atmospheric forecast and sea ice forecast is made once a day with prediction period of 54 hours.
In the case of SMHI, the following service chain is used during the Baltic ice season (normally beginning in mid-November, ending in late May/early June): 1. Existing sea ice is monitored and mapped by use of satellite information from SAR (ENVISAT and RADARSAT), NOAA AVHRR and (in the future) METOP in combination with in-situ reports from ice breakers, merchant vessels and shorebased reporting stations such as pilots and harbour captains, ship brokers etc. 2. The ice conditions (ice edge, concentration, thickness as well as areas of ridged ice) + the current SST-values are fed into HIROMB, resulting in:
The feedback to the '10-day ice formation problem' are closely evaluated by the ice meteorologists. Comments to, and probabilities for, the different scenarios are produced. Finally, resulting ice forecasts and relevant comments are made available to the users via SMHI web-site (or distributed via ftp or e-mail). FMI Ice Forecast (January 25, 2006)
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