Abstract: In this paper a simple 2D linear quasigeostrophic model is used to investigate how the development of local confined cyclonic perturbations is dependent on the perturbation scale, location, and tilt in Eady-type basic ...

Abstract: Through analysis of the spectra of a Dirac delta function the notion of believable and unbelievable scales in a spectral transform model is quantified. The smallest resolved local features are shown to have an average ...

Abstract: A comprehensive climatology of Northern Hemisphere blocking is described based on a PV?? wave-breaking index at the latitude of the climatological storm track and using the 40-yr ECMWF Re-Analysis (ERA-40) dataset. The ...

Abstract: The morphology of regional blocking in the Northern Hemisphere is discussed using the 40-yr ECMWF Re-Analysis (ERA-40) dataset and a measure of blocking based on the reversal at storm-track latitudes of meridional ? contrasts ...

Abstract: A dry baroclinic spectral model is used to study the initation of frontal cyclones in a baroclinic life cycle. The mature cyclone exhibits a frontal cyclone development associated with a finite amplitude interaction between ...

Abstract: The existence of boundary baroclinic instability (as exemplified by the Eady or Charney problems) and internal baroclinic instability, which requires the potential vorticity gradient to take both signs in the fluid interior, ...

Abstract: Rossby wave breaking on the dynamical tropopause in the Southern Hemisphere (the ?2-PVU surface) is investigated using the ERA-40 dataset. The indication of wave breaking is based on reversal in the meridional gradient of ...

Abstract: A three-dimensional semi-geostrophic model is used to study the nonlinear development of baroclinic waves on a zonal jet in a model atmosphere with a large change in potential vorticity in the region of the tropopause. The ...

Abstract: The summer subtropical circulation in the lower troposphere is characterized by continental monsoon rains and anticyclones over the oceans. In winter, the subtropical circulation is more strongly dominated by the zonally ...

Abstract: A detailed view of Southern Hemisphere storm tracks is obtained based on the application of filtered variance and modern feature-tracking techniques to a wide range of 45-yr European Centre for Medium-Range Weather Forecasts ...