9521383 Nielson-Gammon This award supports investigations of the dynamics of upper atmospheric troughs or short waves. These troughs trigger most extratropical cyclogenesis, but the source for these short waves is not well understood. The primary objectives are to determine the typical mechanism(s) of formation of upper-level mobile troughs, to understand the nature of the interaction between these troughs and high terrain, to explore the role of extratropical cyclones in creating a distribution of potential vorticity that is conducive to the growth and propagation of short-waves and the effect of such fields on the cyclone development. The principal investigator will employ a diagnostic technique known as piecewise potential vorticity inversion. Advances in the understanding of upper-level troughs and their role in extratropical cyclogenesis would be of considerable benefit to the improvement of weather forecasting and climate simulations. ***
