| The presence of sea ice on the ocean's surface has a significant impact on the
air-sea interactions. Compared to an open water surface the sea ice completely
changes the surface characteristics in terms of albedo and roughness, and
therefore substantially changes the surface radiative balance and the turbulent
exchange of momentum, heat and moisture between air and sea. In order to deal
with these processes the operational global model GME at the German Weather
Service (DWD) includes a sea ice scheme. This scheme was now also implemented
in DWD's limited area model COSMO-EU, covering almost all Europe using a mesh
size of 7 km. The sea ice scheme accounts for thermodynamic processes, while no
ice rheology is considered. It basically computes the energy balance at the
ice's surface, using one layer of sea ice. From this the evolution of the ice
surface temperature and the ice thickness are deduced. This allows for a
better thermodynamically coupled treatment of sea ice in the COSMO model as
lower boundary condition for the atmosphere. This means, the scheme allows for
a diurnal cycle of sea ice surface temperature which was not present in the
COSMO model before. As input the scheme needs the sea ice distribution which
is provided by the operational analysis of sea surface temperature (SST).
Results of a continuous numerical experiment during the sea ice season in the
Baltic Sea in early 2010 are presented. Improvements are found in particular in
the 2-m temperature and the humidity. |