INVESTIGADORES
ALEXANDER Pedro Manfredo
congresos y reuniones científicas
Título:
Recent results on GW activity and propagation in Southern Andes and Antarctic Peninsula UTLS with GPS radio occultations
Autor/es:
DE LA TORRE, A.; ALEXANDER, P.; LLAMEDO, P.; HIERRO, R.; A. ROLLA; SCHMIDT, T.; WICKERT, J.
Reunión:
Congreso; AGU Meeting of the Americas; 2010
Resumen:
The global distribution, generation and variability
of horizontal and vertical gravity waves (GWs) propagation, their energy
content and the vertical flux of horizontal momentum are basic ingredients in
the understanding of the lower and middle atmosphere dynamics. The Global
Positioning System (GPS) Radio Occultation (RO) technique has global coverage
and is capable of generating high vertical resolution temperature (T) profiles
of the troposphere and stratosphere with sub-Kelvin accuracy and long-term
stability, regardless of weather conditions. The UTLS region above the southern
Andes Range, Drake Passage and Antarctic Peninsula constitute a natural laboratory where the
effect of orographic and non-orographic GW sources compete between them in the
total balance of wave energy. In this
talk, we discuss recent results focused to this region. We first describe a
long-term seasonal and geographical GW amplitudes, vertical wavelengths and activity
from the CHAllenging Minisatellite Payload (CHAMP) GPS RO T data. The observed
features complement observations in the same zone by other satellite passive
remote sensing instruments, which are able to detect different height regions
and other spectral intervals of the wave spectrum. A significant seasonal
variation of wave activity is observed. Topography is an important source and some
strong wave activity is also found over open ocean. Critical level filtering is
shown to have an attenuation effect, implying that a large fraction of the observed
activity can be considered to be an outcome of mountain waves. The wave fronts,
nearly aligned with the North-South direction, are easily detected by the
nearly meridional line of sight characterizing most of the GPS RO observations.
Then we adapt a previous method for the determination of horizontal propagation
of large amplitude GWs by Ern et al (2004), intending to optimize the available
information from the highly inhomogeneous geographic distribution of GPS RO soundings.
To remove the remaining p-phase uncertainty in the horizontal wave propagation
vectors we apply physical arguments. The geographic distribution of estimated
uncertainties in the determination of mean specific potential energy is
discussed. Finally, taking advantage of the anomalously high density of occultation
events during the initial mission months of COSMIC (Constellation Observing
System for Meteorology, Ionosphere and Climate) we choose two pairs of GPS RO,
both containing occultations that occurred close in time and space. One pair
shows a significant difference between both T profiles. Numerical simulations with
a mesoscale model were performed in order to understand this discrepancy, which
may be attributed to the presence of a non-isotropic structure.