Mean winds and momentum fluxes over Jicamarca, Peru, during june and august 1987
Abstract
Data 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.
Description
Date
1992-02-20
Keywords
Mesosphere , Momentum flux , Quasi- biennial oscillation , Stratosphere , Tropics , Wind
Citation
Hitchman, 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;2
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Publisher
American Meteorological Society