Quantification of stratospheric mixing from turbulence microstructure measurements

In the stratosphere, turbulence is confined within shallow, localised patches. The resulting vertical mixing of tracers is highly intermittent and difficult to quantify. Here a new technique is employed to estimate from high‐resolution, lower stratospheric mid‐latitude balloon data a well‐defined vertical diffusivity associated with this mixing. The technique, which is based on a stochastic model of the distribution of turbulent patches, emphasises the dependence of the diffusivity on the typical patch lifetime. Assuming a lifetime of a few hours, the diffusivity is found to be in the range 0.01–0.02m²s−1. This value is an order of magnitude smaller than those previously derived from radar measurements. The potential of the technique for the analysis of ocean microstructure measurements is noted.