Abstract
Abstract. The significant distortions introduced in the measured atmospheric gravity wavelengths by soundings other than those in vertical and horizontal directions, are discussed as a function of the elevation angle of the sounding path and the gravity wave aspect ratio. Under- or overestimation of real vertical wavelengths during the measurement process depends on the value of these two parameters. The consequences of these distortions on the calculation of the energy and the vertical flux of horizontal momentum are analyzed and discussed in the context of two experimental limb satellite setups: GPS-LEO radio occultations and TIMED/SABER ((Atmosphere using Broadband Emission Radiometry/Thermosphere–Ionosphere–Mesosphere–Energetics and Dynamics)) measurements. Possible discrepancies previously found between the momentum flux calculated from satellite temperature profiles, on site and from model simulations, may to a certain degree be attributed to these distortions. A recalculation of previous momentum flux climatologies based on these considerations seems to be a difficult goal.
Highlights
In the last few years, we have observed the ongoing development of several techniques to sound the lower, middle and upper atmosphere (e.g. Wu and Waters, 1996; Tsuda et al, 2000; Preusse et al, 2002; Alexander et al, 2011; Hertzog et al, 2012; John and Kumar, 2013; Lieberman et al., 2013; Oliver et al, 2013; Alexander, 2015; de Wit et al, 2017)
Regarding the retrieval of information on atmospheric dynamics from satellite measurements, we know that both satellite limb and nadir observing techniques are needed to resolve different parts of the gravity wave (GW) spectrum (Wu et al, 2006) and that a better understanding of GW complexities requires joint analyses of these data and high-resolution model simulations
From TA95 and A08, it is clear that when an on-site or remote sensing instrument sounds the atmosphere along a given direction, which is different from the vertical or the horizontal plane, the measured vertical and horizontal wavelengths are expected to considerably differ from “real” values
Summary
In the last few years, we have observed the ongoing development of several techniques to sound the lower, middle and upper atmosphere (e.g. Wu and Waters, 1996; Tsuda et al, 2000; Preusse et al, 2002; Alexander et al, 2011; Hertzog et al, 2012; John and Kumar, 2013; Lieberman et al., 2013; Oliver et al, 2013; Alexander, 2015; de Wit et al, 2017). Some years before A08, de la Torre and Alexander (1995) (TA95) already observed and established analytically the discrepancies to be expected between measured and real horizontal and vertical wavelengths during balloon soundings, taking into account the motion of the gondola with respect to the constant GW phase surfaces. This analysis was performed both from the intrinsic and the ground frame of reference.
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