A preferred scale for landscape forced mesoscale circulations?

The Regional Atmospheric Modeling System was used in two previous studies to simulate mesoscale circulations forced by surface heterogeneity in the Central U. S. and Amazonia. In this work, spectral analysis is used to compare the horizontal length scales of these simulated circulations with the scale of the surface heterogeneity. For both cases, the organized mesoscale circulations are confined within a preferred length scale range (10-20 km) that is significantly different from the dominant length scale of the surface heterogeneity. Multiscale landscape patchiness in these two regions tend to produce eddies at a wide range of scales, but the land-atmosphere interaction processes act as a medium-pass filter to select intermediate-scale circulations. This scale of response remains relatively unchanged despite significant day-to-day variations in the synoptic situation and the mean surface heat flux.