Diagnosis of the origin and dynamical influence of upper-tropospheric negative PV anomalies

In the limit of balanced flow it can be shown that regions of localized low PV values (<<1 pvu) in the extratropics connote major flow and thermal signatures. There is also growing evidence that at tropospheric levels such anomalies contribute significantly to the strength of the extratropical jet stream, the development of positive PV filaments and the evolution of large-scale flow patterns.

Here diagnostic studies are undertaken using the ECMWF re-analysis (ERA) data set to examine the origin, extent, evolution and dynamics of such anomalies in the extratropics. On the basis of extensive computations of Lagrangian trajectories and statistical-dynamical analyses estimates are derived for the ratio of their tropical versus diabatic sources, their preferred geographical/dynamical location, the dynamical history and the link to the formation of coherent structures.