Dr Emily Shuckburgh

Research interests

Effective diffusivity

My research is focused towards a greater understanding of the processes acting to transport chemical species to different parts of the atmosphere.

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. 2001.

I have also investigated mixing and transport in chaotic advection flows, see Shuckburgh and Haynes 2002..

I am currently applying the effective diffusivity technique to the Antarctic circumpolar current in the Southern Ocean in a collaborative project with John Marshall and his group at MIT. See this website for more details.

The effective diffusivity and equivalent length diagnostics quantify the geometric complexity of a tracer. In a region of strong mixing a tracer will develop a complex geometric structure, whereas in a region is weak mixing it will retain a simple geometric structure.

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@damtp.cam.ac.uk. Details of the calculation can be found in Shuckburgh et al 2001.