Articles | Volume 17, issue 24
Research article
18 Dec 2017
Research article |  | 18 Dec 2017

Quasi 18 h wave activity in ground-based observed mesospheric H2O over Bern, Switzerland

Martin Lainer, Klemens Hocke, Rolf Rüfenacht, and Niklaus Kämpfer

Abstract. Observations of oscillations in the abundance of middle-atmospheric trace gases can provide insight into the dynamics of the middle atmosphere. Long-term, high-temporal-resolution and continuous measurements of dynamical tracers within the strato- and mesosphere are rare but would facilitate better understanding of the impact of atmospheric waves on the middle atmosphere. Here we report on water vapor measurements from the ground-based microwave radiometer MIAWARA (MIddle Atmospheric WAter vapor RAdiometer) located close to Bern during two winter periods of 6 months from October to March. Oscillations with periods between 6 and 30 h are analyzed in the pressure range 0.02–2 hPa. Seven out of 12 months have the highest wave amplitudes between 15 and 21 h periods in the mesosphere above 0.1 hPa. The quasi 18 h wave signature in the water vapor tracer is studied in more detail by analyzing its temporal evolution in the mesosphere up to an altitude of 75 km. Eighteen-hour oscillations in midlatitude zonal wind observations from the microwave Doppler wind radiometer WIRA (WInd RAdiometer) could be identified within the pressure range 0.1–1 hPa during an ARISE (Atmospheric dynamics Research InfraStructure in Europe)-affiliated measurement campaign at the Observatoire de Haute-Provence (355 km from Bern) in France in 2013. The origin of the observed upper-mesospheric quasi 18 h oscillations is uncertain and could not be determined with our available data sets. Possible drivers could be low-frequency inertia-gravity waves or a nonlinear wave–wave interaction between the quasi 2-day wave and the diurnal tide.

Short summary
We report on middle-atmospheric water vapor measurements above Bern from the ground-based microwave radiometer MIAWARA (NDACC affiliated) during two winter periods of 6 months. Quasi 18 h oscillations of mesospheric water vapor above 0.1 hPa are observed. Further, the 18 h wave is seen in a zonal wind data set from the Doppler wind radiometer WIRA. Inertia-gravity-wave-induced fluctuations or a nonlinear coupling between tides and quasi 2-day waves are considered as possible drivers.
Final-revised paper