Abstract:
Stratospheric intrusions of high potential vorticity
(PV) air are well-known drivers of cyclonic development
throughout the troposphere. PV anomalies have been well
studied with respect to their effect on surface cyclogenesis.
A gap however exists in the scientific literature describing
the effect that stratospheric intrusion depth has on surface
cyclogenetic forcing. Numerical experiments using PV
inversion diagnostics reveal that stratospheric depth is crucial
in the intensity of cyclonic circulation induced at the
surface. In an idealized setting, shallow, high-PV intrusions
(above 300 hPa) resulted in a marginal effect on the surface,
whilst growing stratospheric depth resulted in enhanced surface
pressure anomalies and surface cyclonic circulation. It is
shown that the height above the surface that intrusions reach
is more critical than the vertical size of the intrusion when
inducing cyclonic flow at the surface. This factor is however
constrained by the height of the dynamical tropopause above
the surface. The width of the stratospheric intrusion is an additional
factor, with broader intrusions resulting in enhanced
surface cyclogenetic forcing.
