Hitchman, M.Fritts, D.Coy, L.Kudeki, E.Bywaters, K.Sudan, R.2019-02-112019-02-111992-02-20Hitchman, M., Bywaters, K., Fritts, D., Coy, L., Kudeki, E., & Surucu, F. (1992). Mean winds and momentum fluxes over Jicamarca, Peru, during june and august 1987.==$Journal of the Atmospheric Sciences, 49$==(24), 2372-2383. https://doi.org/10.1175/1520-0469(1992)049<2372:MWAMFO>2.0.CO;2http://hdl.handle.net/20.500.12816/4070Data from the mesosphere-stratosphere-troposphere (MST) radar at Jicamarca, Peru, together with other available data, are used to diagnose the mean structure of winds and gravity-wave momentum fluxes from the surface to 90 km during two ten-day campaigns in June and August of 1987. In the stratosphere a layer of maximum eastward flow associated with the quasi-biennial oscillation (QBO) was seen to strengthen and descend rapidly from June to August, overlying persistent westward flow. A layer of enhanced signal return, suggestive of a turbulent layer, was observed just above the descending QBO eastward maximum. Notable zonal asymmetries were present during this transition and the local meridional circulation departed from zonal-mean QBO theory. A substantial northeastward momentum flux was found below 25 km, which may be related to topographic gravity waves excited by southeastward flow across the Andes. In the lower mesosphere a relatively weak “second” mesopause semiannual oscillation is confirmed. Gravity-wave zonal and meridional momentum fluxes usually opposed the flow, yielding body forces of 10–100 m s−1 day−1. In both the lower stratosphere and mesosphere, body forces were comparable in magnitude to inferred Coriolis torques.application/pdfenginfo:eu-repo/semantics/restrictedAccessMesosphereMomentum fluxQuasi- biennial oscillationStratosphereTropicsWindinfo:eu-repo/semantics/articlehttp://purl.org/pe-repo/ocde/ford#1.05.01Journal of the Atmospheric Scienceshttps://doi.org/10.1175/1520-0469(1992)049<2372:MWAMFO>2.0.CO;2