INVESTIGADORES
DE LA TORRE Alejandro
artículos
Título:
Interpretation of gravity wave signatures in GPS radio occultations
Autor/es:
ALEXANDER P., A. DE LA TORRE Y P. LLAMEDO
Revista:
JOURNAL OF GEOPHYSICAL RESEARCH
Editorial:
AGU
Referencias:
Lugar: Washington; Año: 2008 vol. 113 p. 1 - 12
ISSN:
0148-0227
Resumen:
The horizontal averaging of global positioning system radio occultation retrievals
produces an amplitude attenuation and phase shift in any plane gravity wave, which may
lead to significant discrepancies with respect to the original values. In addition,
wavelengths cannot be straightforwardly inferred due to the observational characteristics.
If the waves produce small departures from spherical symmetry in the background
atmosphere and under the assumption that the refractivity kernel may be represented
by a delta function, an analytical expression may be derived in order to find how the
retrieved amplitudes become weakened (against the original ones). In particular, we
study the range of waves that may be detected and the consequent reduction in
variance calculation, which is found to be around 19%. A larger discrepancy was
obtained when comparing an occultation variance with the one computed from a numerical
simulation of that case. Wave amplitudes can be better resolved when the fronts are nearly
horizontal or when the angle between the occultation line of sight and the horizontal
component of the wave vector approaches p/2. Short horizontal scale waves have a high
probability of becoming attenuated or of not being detected at all.We then find geometrical
relations in terms of the relative orientation between waves and sounding, so as to
appropriately interpret wavelengths extracted from the acquired data. Only inertio-gravity
waves, which exhibit nearly horizontal fronts, will show small differences between
detected and original vertical wavelengths. Last, we analyze the retrieval effect on wave
phase and find a shift between original and detected wave that generally is nonzero and
approaches p/4 for the largest horizontal wavelengths.
probability of becoming attenuated or of not being detected at all.We then find geometrical
relations in terms of the relative orientation between waves and sounding, so as to
appropriately interpret wavelengths extracted from the acquired data. Only inertio-gravity
waves, which exhibit nearly horizontal fronts, will show small differences between
detected and original vertical wavelengths. Last, we analyze the retrieval effect on wave
phase and find a shift between original and detected wave that generally is nonzero and
approaches p/4 for the largest horizontal wavelengths.
p/2. Short horizontal scale waves have a high
probability of becoming attenuated or of not being detected at all.We then find geometrical
relations in terms of the relative orientation between waves and sounding, so as to
appropriately interpret wavelengths extracted from the acquired data. Only inertio-gravity
waves, which exhibit nearly horizontal fronts, will show small differences between
detected and original vertical wavelengths. Last, we analyze the retrieval effect on wave
phase and find a shift between original and detected wave that generally is nonzero and
approaches p/4 for the largest horizontal wavelengths.p/4 for the largest horizontal wavelengths.
vol 113, D16117, doi:10.1029/2007JD009390