Determining the cascade of
passive scalar variance in the lower stratosphere
In previous studies the mesoscale (10-500 km) spectra of temperature,
ozone, and other passive tracers, in the upper troposphere and the
lower stratosphere, have been found to depend on wavenumber
approximately as k-5/3. It is a reasonable conjecture that
the underlying physical mechanism behind these spectra is a cascade in
which large structures are broken down to small structures. In this
letter we give observational evidence that there is, indeed, such a
cascade, and we also determine its strength. Using aircraft data from
7630 commercial flights, we determine the flux of temperature and
ozone variance from large to small scales in the lower stratosphere.
The relation that we use for this purpose is a form of the classical
Yaglom relation for the third-order scalar-velocity structure
function. We find that this function is negative and that it depends
linearly on separation distance in the mesoscale range for temperature
as well as ozone.
Send e-mail to erikl@mech.kth.se for
a copy of the complete article. Return to publications list.