[1] This study examines various climatological features related to multiple tropopause events (MT events). The analysis is based on the lapse rate definition of the tropopause and is performed on a radiosonde data subset taken from the Integrated Global Radiosonde Archive database. The global statistics of MT events are analyzed, taking into consideration both their seasonal and geographical variations. Our results are in moderate qualitative agreement with those of earlier studies. They reinforce the analytical findings of other researchers, but at the same time highlight important differences in both the number and position of the maximum occurrence of MT events. We found a latitudinal band of multiple tropopause occurrence in the Northern Hemisphere and three centers in the Southern Hemisphere, which coincided with identified zones of maximum cyclogenesis. The climatological features of pressure, temperature, and vertical separation of MT events revealed the complexity of these phenomena, which behave very differently according to latitude and season.

Based on a linear regression/correlation analysis of monthly mean atmospheric sea level pressure (SLP) data from the National Centers for Environmental Prediction (NCEP) reanalysis (1948–2000), we find a significant anticorrelation between pressure in the northern North Atlantic and North Pacific only if the stratospheric circulation is in the “strong polar vortex” regime but not when the vortex is weak. Since some general circulation models (GCMs) (e.g., European Center/Hamburg (ECHAM4)) are biased toward the strong vortex regime (SVR), they tend to reproduce this anticorrelation already in the mean. The pattern of the “Arctic Oscillation” (AO) is shown to be consistent with the mean surface pressure differences between the two stratospheric regimes. The typical SW‐NE tilt of the node line of the North Atlantic Oscillation (NAO) found with linear analyses (i.e., with such that do not take the regime character of the stratospheric circulation into account) in Northern Hemisphere winter is due to a superposition of correlation patterns based on physical processes working in the troposphere (a strictly meridional dipole and the pattern resulting from planetary wave refraction in the strong vortex regime) and those produced by the rapid transition from one stratospheric regime to the other with subsequent downward propagation of the signal. This result underlines the necessity of the application of nonlinear statistics or the restriction of linear statistics to variations in the stable (quasi‐linear) environment of natural regimes.

[1] The dynamical connection between Northern Hemisphere blocking events and the variability of the stratospheric polar vortex strength is studied. The analysis is based on the composite time evolution of the energy of baroclinic planetary waves during regional blocking occurrence. During Euro-Atlantic blocking events, an in phase forcing of stationary zonal wavenumber 1 occurs. The enhanced wave amplitude is associated with a stratospheric polar vortex deceleration, which may result, at times, in Sudden Stratospheric Warming (SSW) events of displacement type. Pacific blocking composites reveal an in phase forcing of stationary zonal wavenumber 2. In most cases, the amplification of the wavenumber 2 does not reduce the vortex strength, being even accompanied by a mean vortex acceleration. However, if the amplification of wavenumber 2 is preceded by an amplification of wavenumber 1, the initial vortex deceleration forced by wavenumber 1 may be continued by wavenumber 2, and a SSW event of splitting type may occur. Citation: Castanheira, J. M., and D. Barriopedro (2010), Dynamical connection between tropospheric blockings and stratospheric polar vortex, Geophys.

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[1] We herein propose a method for identifying breaks in the subtropical tropopause as found in the ERA Interim reanalysis data. The method uses the identification of double tropopauses and allows the quantification of the extension of the overlap between the tropical and extratropical tropopauses. The correlations between the meridional extension of the superposition of tropopauses and the fields of geopotential, potential vorticity, or potential temperature, reveal baroclinic wave patterns. Similar wave patterns were also identified in the potential temperature fields derived from GPS radio occultation COSMIC data. The zonal propagation velocity of the anomalies in the meridional extension of the overlap was estimated using Hovmöller diagrams. The estimated zonal velocities suggest that the variability in the superposition of the tropopauses is associated with baroclinic Rossby wave patterns in the subtropical upper troposphere and lower stratosphere.Citation: Castanheira, J. M., and L. Gimeno (2011), Association of double tropopause events with baroclinic waves,