Quasigeostrophic Dynamics of the Tropopause

Abstract

Abstract The dynamical properties of potential temperature anomalies on the tropopause are analyzed for quasigeo-strophic flow on an f plane. The potential vorticity is taken to he piecewise constant, with a single discontinuity at the tropopause. The tropopause potential temperature, on scales too small to feel the lower boundary, is found to be proportional to the tropopause geopotential height. The constant of proportionality is the geometric mean of the stratospheric and tropospheric lapse rates. Results from a general circulation model are found to be in agreement with this prediction. The streamfunction associated with a combination of anomalies on the lower boundary and tropopause is also derived. The solution, determined completely by the potential temperature distributions, in general has a nonzero velocity at the lower boundary. Applying the theory to the time-mean zonal-mean jets, which must have a near-zero velocity at the ground, imposes a constraint on parameters defining the jet. The dynami...