P Vectors as a Diagnostic Tool for Synoptic-Scale Circulations
Nuss, Wendell A.
MetadataShow full item record
The quasigeostrophic geopotential tendency equation is derived using P vectors in both pressure and entropy coordinates. This vector form of the geostrophic forcing in the geopotential tendency equation is similar to the Q-vector form of thew equation. It is shown that the horizontal components of Pare the advection of geostrophic momentum, and the vertical component of P is the horizontal temperature advection. The P vectors are shown to be related to Q and C vectors, as well as the ageostrophic circulation. The three-dimensional pseudocurl of the P vector gives the C vector that equals the ageostrophic pseudovorticity in the quasigeostrophic model. The horizontal components of the pseudocurl of P are perpendicular and proportional to the Q. The horizontal divergence of the P vector is the geostrophic absolute vorticity advection while the three-dimensional divergence of the P vector is the geostrophic quasigeostrophic potential vorticity advection. The ageostrophic wind can be partitioned into the P vector (geostrophic advective) and isallobaric wind contributions. A numerical simulation of an idealized cyclone is used to characterize the distribution of the P vectors and P-vector diagnostics in order to demonstrate their potential application to the diagnosis of synoptic-scale circulations. The distribution of the P vectors clearly indicates the advections of geostrophic momentum and temperature that characterize cyclogenesis. An examination of the P vectors and the isallobaric wind demonstrates that the P vectors provide insight into the ageostrophic circulation of the cyclone. Diagnoses of the three-dimensional P-vector divergence and curl are shown to produce useful depictions of cyclonic vortex spinup and the propagation of both the large- and smaller-scale features of the system. These diagnostics can be interpreted from a variety of perspectives, including the height tendency and the advection of quasigeostrophic potential vorticity .. The use of P vectors to diagnose synoptic-scale circulations appears to provide potentially useful insights into the dynamics of synoptic-scale disturbances not readily obtained from other diagnoses.
RightsThis publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.
Showing items related by title, author, creator and subject.
Circulation in the Alboran Sea as Determined by Quasi-Synoptic Hydrographic Observations. Part I: Three-Dimensional Structure of the Two Anticyclonic Gyres Viúdez, Álvaro; Tintoré, Joaquín; Haney, Robert L. (American Meteorological Society, 1996);The circulation and dynamics of the Modified Atlantic Water have been studied using data from an intensive field experiment carried out between 22 September and 7 October 1992. Data included 134 CTD casts, ADCP, and satellite ...
Titley, David W. (Monterey, California. Naval Postgraduate School, 1991-06);Accurate short term (0-6 h) forecasts of rapid cyclogenesis are important to both civilian and military maritime interests. Because upper-air observations over the ocean are sparse, the relatively plentiful surface synoptic ...
Montenegro, Gonzalo (Monterey, California. Naval Postgraduate School, 1993-03);Hydrographic data has traditionally been used only to determine dynamical features, specifically dynamic topography and geostrophic currents relative to an assumed level of no motion. However, the assumption of geostrophic ...