Observations and Modelling of Fronts and Frontogenesis

temperature variations, but again presumably mostly on scales
larger than 10 km.
Over 900-km space and two-week time scales and despite
variable atmospheric conditions, the spectral shapes were
roughly constant. This suggests that processes that
contribute substantially to the variance must be
statistically homogeneous over these scales. Near-inertial
currents, which respond strongly to storms, would appear not
to meet this criterion.
Finally, we note that the -3 power law temperature
spectrum differs from that predicted for a passively advected
scalar in a turbulent flow. In that case the scalar
spectrum, not the gradient spectrum, is inversely
proportional to wavenumber (atchelor, 1959).
11.6 Summary
The thermistor tows yield a detailed two-dimensional
description of surface layer temperature along 1400 km of tow
tracks in the Eastern North Pacific Subtropical Frontal Zone
during January 1980. In brief, we find:
(1) The dominant features have wavelengths of 10-100 km,
amplitudes of 0.2 to 1.0 °C, and no preferred orientation
with respect to the mean meridional gradient (Figure 11.4).
These features, which could be created from the
climatological mean sea surface temperature field by
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