Calculations of horizontal exchange coefficients using Eulerian time series current meter data from the Baltic Sea.

Type: Report
Series: RO 1
Author: Lars Gidhagen, Lennart Funkquist and Ray Murthy


A method is described which relates observed eularian current fluctuations to horizontal exchange coefficients. The method is applied to current meter time series from the southern and the central parts of the Baltic Proper and from the Bothnian Sea.

Energy spectras suggest that current fluctuations with a time scale shorter than 24 hours can be considered as turbulence in large scale circulation models and parameterized by an exchange coefficient.

The horizontal exchange is found to be horizontally uniform. The calculated exchange coefficients have a vertical variation ranging from 10-50 m s in the surface layer to 1-3 m s below 70 metres . Inertial or near-inertial oscillations are the most important physical processes that produce horizontal exchange.