Generalized moist potential vorticity and its application in the analysis of atmospheric flows

Potential vorticity (PV) serves as an important dynamic tracer for large-scale motions in the atmosphere and oceans. Significant progress has been made on the understanding and application of PV since the work of Hoskins et al., who introduced an “IPV thinking” of a dynamical system in a purely dry atmosphere. In particular, there has been a substantial amount of work done on the PV in a general moist atmosphere. In this paper, the generalized moist potential vorticity (GMPV) and its application in the mesoscale meteorological fields are reviewed. The GMPV is derived for a real atmosphere (neither completely dry nor saturated) by introducing a generalized potential temperature instead of the potential temperature or equivalent potential temperature. Such a generalization can depict the moist effect on PV anomaly in the non-uniformly saturated atmosphere. The effect of mass forcing induced by rainfall on the anomaly of GMPV is also reviewed and a new dynamic variable, the convective vorticity vector (CVV), is introduced in connection with GMPV.