Centre for Atmospheric Science
Department of Applied Mathematics and Theoretical Physics
Department of Chemistry
University of Cambridge, UK
E.F.Shuckburgh@amtp.cam.ac.uk

My PhD thesis, Transport and Mixing in Atmospheric Flows investigated the use of "effective diffusivity" and "equivalent length" as diagnsotics of transport and mixing.

I have used effective diffusivity to quantify isentropic mixing in the upper troposphere and lower stratosphere, and to characterise the seasonal evolution of the barriers to isentropic transport at the tropopause and at the stratospheric polar vortex edge, as well as the stratospheric "tropical reservoir" region of weak mixing. See Haynes and Shuckburgh 2000a,b.

I have investigated the modulation by the quasi-biennial oscillation of the tropical winds of the isentropic mixing in the tropics and subtropics. See Shuckburgh et al. 2000.

I am currently trying to understand decadal and longer timescale variations in the strength of the Arctic polar vortex.

I am also investigating mixing and transport in chaotic advection flows.

A brief introduction to the diagnostics, together with the results of some calculations, can be obtained here.

The equivalent length can be calculated, as a function of "equivalent latitude" from any tracer that is monotonic in latitude. In the atmosphere, all long-lived tracers have either a maximum or a minimum at the equator. To calculate equivalent length from such tracers, the calculation must be performed separately on each latitude band within which the tracer is monotonic.

A fortran-90 program for calculating the equivalent length from any tracer is avaliable. Any queries about this program should be addressed to E.F.Shuckburgh@amtp.cam.ac.uk. Details of the calculation can be found in Shuckburgh et al 2000.