Estimation of length scales from mesoscale networks

This paper reports on the spatial scales of meandering motions using recent data from three mesoscale networks. Although the mesoscale motions extend over a wide range of scales, and time series do not reveal a spectral peak, the examination of the spatial coherence does identify a preferred spatial scale. Several independent methods reveal the same preferred spatial scale for horizontal coherence for a given network. However, the spatial scale differs by a factor of two between the different networks examined here, presumably due to the different topography and surface conditions.

The preferred spatial scale increases roughly linearly with range of time scales included in the evaluation. However, the details of this increase do not seem to be predictable, again partly due to site-specific conditions. The preferred spatial scales are of the order of a few kilometres for time scales less than an hour, but may reach tens of kilometres for time scales of several hours.

The preferred horizontal length scale determines the area over which the flow features are statistically coherent. Measurements at a single location can be considered as representative for an area comparable to or smaller than the preferred scale.