Joint Centre for Mesoscale Meteorology (JCMM)
JCMM Internal Report No.73
Attribution and its application to mesoscale structure associated with tropopause folds
by Alan J Thorpe
It is important in meteorology to be able to establish a link between various features. This link in its strongest form would be referred to as "cause and effect" but this is extremely difficult to establish for atmospheric flows. A weaker, but nonetheless powerful, link is "attribution" which attempts to provide a way to associate various fundamental features such as potential vorticity anomalies to weather events involving regions of ascent. Attribution is not new and it is implicit in the way that atmospheric evolution is usually described. In this paper an attempt is made to define more precisely what are the steps and assumptions being made in such a method. These ideas become more concrete by applying them to a simple model of a two-dimensional front at which there is a tropopause fold. The aim is to find the vertical motion attributable to the descended tropopause fold in an extra-tropical cyclone. This is the first step in a longer programme of research designed to provide a test of the hypothesis that such a descended tropopause can trigger mesoscale phenomena such as convection and cyclones.