Distortions in calculated gravity wave parameters during slanted atmospheric soundings and future possibilities from collocated profiles

DE LA TORRE, A.; ALEXANDER, P.; SCHMIDT, T.; LLAMEDO, P.; HIERRO, R.

Potsdam

Workshop; 7th IAGA/ICMA/SCOSTEP Workshop on Vertical Coupling in the Atmosphere-Ionosphere System; 2018

Gravity waves (GW) are anessential feature in the transport of energy and momentum flux(MF) from the low to the upper atmosphere. The significant distortions introduced in the measured atmosphericgravity wavelengths by soundings other than in vertical and horizontaldirections, are discussed as a function of elevation angle of the sounding pathand the GW aspect ratio. Under- or overestimation of real vertical andhorizontal wavelengths during the measurement process depends basically on thevalue of these two parameters. The consequences of these distortions on the calculationof the energy and MF are analyzed and discussed in the context of twoexperimental limb satellite setups: GPS-LEO radio occultations (RO) andTIMED/SABER measurements. Possible discrepancies previously found between theMF calculated from satellite temperature profiles, on site and from modelsimulations, may, to a certain degree, be attributed to these distortions. Arecalculation of previous MF climatologies based on these considerations seemsto be a difficult goal. Present procedures often provide GW absolute MF,ambiguous 3D propagation direction and apparent vertical wavelengths. Weintroduce a method with close GPS RO quartets which allows the calculation forGW of the net MF, the definite propagation direction and "real"wavelengths. Our procedure is illustrated by an example under requirements thattend to ensure that the 4 GPS RO soundings are observing the same GW. Thefuture increase of satellite measuring devices due to new missions (includingGPS RO) will lead to a higher spatial and temporal density of profiles. Thismay eventually allow the attainment of GW climatologies of net MF, propagationdirection and "real" vertical wavelengths. At present, a practicalapplication of the method is proposed to be applied at the southern tip of theAndes mountains. Making use of the simultaneous vertical T profiles retrievedby two operational Rayleigh lidars at this region, two from the four requiredprofiles involved in each sounding quartet may be guaranteed. This should allowthe measurement of GW parameters for different aspect ratio regimes