Operational forecasts of algae blooms in the Baltic Sea

Abstract

During the fall of 2007 a project was initiated with the main aim to set up a test system for algae forecasts. Secondly the project was to, within its scope, perform a crude validation of the results. The final task for the project, which lasted until the end of December, was to present the results on the internal web. The system was based on the coupling between the ocean model HIROMB and the biogeochemical model SCOBI. The operational three-dimensional baroclinic ocean model HIROMB (High Resolution Operational Model for the Baltic Sea) covers the whole North Sea/Baltic Sea area and is run operationally in the resolutions 1, 3 and 12 nautical mile (nmi). In the test system the 3 nmi resolution was coupled, through turbulence and advection, to the one-dimensional biogeochemical model SCOBI (Swedish Coastal and Ocean BIogeochemical model) to form a forecast system for algae blooms in Skagerrak, Kattegat and the Baltic Sea. The SCOBI model includes the following variables: NO3, NH4, PO4, O2, H2S, detritus, diatoms, flagellates, cyanobacteria, zooplankton, bottom nitrogen and bottom phosphorus, of which only algae concentration was presented in this first stage. The forcing of the system was based upon HIRLAM C22 (high resolution limited area model, resolution 22 km) for the atmospheric parameters (wind and cloudiness) and HBV-Baltic (parted into 43 different sub-basins representing runoff areas) for fresh-water runoff and nutrients (phosphate, nitrate). For water level, including tides at the open sea border towards the NE Atlantic, the storm surge model NOAMOD was used and salinity and temperature at the open boundaries were based on monthly mean values. The set-up of the system was successfully performed and a crude validation for a nine-year hindcast period implied reasonable results. The project will during 2008 continue with the set-up of operational daily runs which will be presented together with satellite images on the internal Web (accessible also by an external reference panel) and with further validation of the forecasts. This will hopefully result in a system producing high quality daily algae forecasts which can be used in environmental surveillance and monitoring purposes.