Eddy dissipation rates derived from observations of propagating diurnal tides

The vertical structure of nonmigrating diurnal tides observed in High Resolution Doppler Imager horizontal winds and temperatures are used to infer thermal dissipation rates. The calculated thermal dissipation coefficients show a scale dependence between the modes that is in agreement with theory. An equivalent gravity wave model that incorporates linear dissipation and mean zonal winds is used to derive Prandtl numbers from the thermal dissipation and the observed complex vertical wavenumbers. These calculated Prandtl numbers are of order one. Mechanical dissipation is then computed from the Prandtl number and thermal dissipation. The derived dissipation coefficients are roughly two to three times larger than those of more constrained previous studies.