Dissipation rates of turbulence kinetic energy in the free atmosphere: MST radar and radiosondes

摘要

Our knowledge of the spatio-temporal variability of the dissipation rates of turbulence kinetic energy (TKE) in the free atmosphere is severely limited because of the difficulty and expense of making these measurements globally. A few MST/ST radar facilities that are still in operation around the globe have provided us with valuable data on temporal variability of the dissipation rate in the atmospheric column above the radars but the data covers an extremely tiny fraction of the global free atmosphere. Moreover, there are limitations to these data also, since restrictive hypotheses are necessary for making these measurements. It appears that simple radiosondes launched from the existing global sonde network might be able to provide a much wider coverage, provided the technique for deducing the dissipation rates from overturns detected by the sondes can be calibrated and validated against existing techniques. An intensive field campaign conducted over the Harrow ST radar site located in western Ontario, Canada, during the summer of 2007 provided precisely such an opportunity. In this paper, we report on the comparison of the TKE dissipation rates derived from the PTU measurements made by ozonesondes launched during the campaign with those obtained from direct ST radar measurements. We find encouraging agreement between the two, which suggests that routine measurements of TKE dissipation rates by radiosondes in the global free atmosphere might indeed be feasible.