%0 Journal Article
%T PV-¦È view of the zonal mean state of the atmosphere
%A Aarnout J. Van Delden
%A Yvonne B. L. Hinssen
%J Tellus A
%D 2012
%I Co-Action Publishing
%R 10.3402/tellusa.v64i0.18710
%X The relation between zonal mean potential vorticity (PV) in potential temperature (¦È) coordinates and the zonal mean zonal wind in January and in July is studied. PV-anomalies are defined with respect to a reference state that is at rest with respect to the rotating earth. Two important PV-anomalies are identified. One PV-anomaly, the ¡®Ex-UTLS PV-anomaly¡¯, coincides approximately with the extratropical tropopause (310¨C360 K). It is a permanent feature of the zonal mean state. The other PV-anomaly is located higher in the stratosphere. It exhibits a strong seasonal cycle, i.e. in winter, it is strongly positive, while in summer, it is weakly negative. In the Northern Hemisphere winter, the Ex-UTLS PV-anomaly and the stratospheric PV-anomaly are separated by a ¡®surf-zone¡¯, which is characterised by a negative PV-anomaly pole-wards of a positive PV-anomaly. Piecewise PV-inversion reveals that (1) the Ex-UTLS PV-anomaly induces the westerly winds in the troposphere and the lower stratosphere, including the subtropical jet, that (2) the positive stratospheric PV-anomaly induces the stratospheric polar night jet and that (3) the negative polar cap stratospheric PV-anomaly in summer reduces the westerly wind speeds in the troposphere and induces easterly winds in the stratosphere. The Ex-UTLS PV-anomaly is manifest mainly as an isentropic density- (or mass-) anomaly. Piecewise PV-inversion of these anomalies in isolation should account for this by an appropriate adjustment of the lower boundary condition.
%K general circulation
%K potential vorticity
%K polar vortex
%K subtropical jet
%K tropopause
%K annular mode
%U http://www.tellusa.net/index.php/tellusa/article/view/18710/pdf_1