J. Perlwitz and N. Harnik, 2003: Observational Evidence of a Stratospheric
Influence on the Troposphere by Planetary Wave Reflection.
Submitted to J. Climate.


Recent studies have pointed out the impact of the stratosphere on the
troposphere by dynamic coupling. In the present paper, observational
evidence for an effect of downward planetary wave reflection in the
stratosphere on Northern Hemisphere tropospheric waves is given by
combining statistical and dynamical diagnostics.  A time-lagged
singular value decomposition analysis is applied to daily tropospheric
and stratospheric height fields recomposed for a single zonal wavenumber.
A wave geometry diagnostic for wave propagation characteristics which
separates the index of reflection into vertical and meridional components
is used to diagnose the occurrence of reflecting surfaces. For zonal
wavenumber 1, this study  suggests that there is one characteristic
configuration of the stratospheric jet which reflects waves back into
the troposphere - when the polar night jet peaks in the high latitude
mid-stratosphere.  This configuration is related to the formation of a
reflecting surface for vertical propagation at around 5\,hPa as a
result of the vertical curvature of the zonal mean wind and a clear
meridional waveguide in the lower to middle stratosphere, that
channels the reflected wave activity to the high latitude troposphere.