A cold-air cyclogenesis study using a potential vorticity inversion method

Abstract

A cold-air cyclogenesis is studied using a potential vorticity (PV) inversion method. In this study, the method is coupled with the French spectral operational model ARPEGE which is initialized by four-dimensional variational reanalyses. Sensitivity studies are performed for Intensive Observation Period 18 (IOP18) (low 44, 19-24 February 1997) of the Fronts and Atlantic Storm-Track EXperiment (FASTEX). This event is one of the Type C cyclogeneses recently identified in the FASTEX dataset. The triggering role of a coherent tropopause disturbance on the cyclogenesis is discussed by comparing a reference forecast and a simulation in which the tropopause coherent structure is removed. Interactions between the atmospheric upper level and the cyclogenesis are found significant. A second important factor is the influence of the surface temperature. Evaluations of vertical motions for different surface temperature distributions show that the warmer the sea surface, the deeper the low. The location of the low with respect to the ice-shelf limit is also an important factor. © Royal Meteorological Society, 2004.