Natalie Kaifler

Influences of source conditions on mountain wave penetration into the stratosphere and mesosphere

We present atmospheric gravity wave (GW) measurements obtained by a Rayleigh/Raman lidar at Lauder, New Zealand (45∘ S, 170∘ E) during and after the DEEPWAVE campaign. GW activity and characteristics are derived from 557 hours of high-resolution lidar data recorded between June and November 2014 in an altitude range between 28 and 76 km. In this period, strong GW activity occurred in sporadic intervals lasting a few days. Enhanced stratospheric GW potential energy density is detected during periods with high tropospheric wind speeds perpendicular to New Zealands Southern Alps. These enhancements are associated with the occurrence of quasi-stationary GW (mountain waves). Surprisingly, the largest response in the mesosphere is observed for conditions with low to moderate lower tropospheric wind speeds (2–12 m/s). On the other hand, large-amplitude mountain waves excited by strong tropospheric forcings often do not reach mesospheric altitudes, either due to wave breaking and dissipation in the stratosphere or refraction away from New Zealand.

Horizontal propagation of large‐amplitude mountain waves into the polar night jet

We analyze a large amplitude mountain wave event, which was observed by a ground-based lidar above New Zealand between 31 July and 1 August 2014. Besides the lidar observations, ECMWF data, satellite observations and raytracing simulations are utilized in this study. It is found that the propagation of mountain waves into the middle atmosphere is influenced by two different phenomena at different times during the event. At the beginning of the event, convective instabilities cause wave breaking in the lower stratosphere. During the course of the event the mountain waves propagate to higher altitudes and are refracted towards the polar night jet due to the strong meridional shear of the zonal wind. As the waves propagate out of the observational volume, the ground-based lidar observes no mountain waves in the mesosphere. However, raytracing simulations and satellite observations indicate that the waves reached mesospheric altitudes downstream of New Zealand. These results underline the importance of considering horizontal propagation of gravity waves when analyzing locally confined gravity wave observations.

High-Altitude (0-100 km) Global Atmospheric Reanalysis System: Description and Application to the 2014 Austral Winter of the Deep Propagating Gravity-Wave Experiment (DEEPWAVE)

AbstractA data assimilation system (DAS) is described for global atmospheric reanalysis from 0- to 100-km altitude. We apply it to the 2014 austral winter of the Deep Propagating Gravity Wave Exper...

Horizontal propagation of large amplitude mountain waves in the vicinity of the polar night jet

We analyze a large amplitude mountain wave event, which was observed by a ground-based lidar above New Zealand between 31 July and 1 August 2014. Besides the lidar observations, ECMWF data, satellite observations and raytracing simulations are utilized in this study. It is found that the propagation of mountain waves into the middle atmosphere is influenced by two different phenomena at different times during the event. At the beginning of the event, convective instabilities cause wave breaking in the lower stratosphere. During the course of the event the mountain waves propagate to higher altitudes and are refracted towards the polar night jet due to the strong meridional shear of the zonal wind. As the waves propagate out of the observational volume, the ground-based lidar observes no mountain waves in the mesosphere. However, raytracing simulations and satellite observations indicate that the waves reached mesospheric altitudes downstream of New Zealand. These results underline the importance of considering horizontal propagation of gravity waves when analyzing locally confined gravity wave observations.

Vertical propagation of large amplitude mountain waves in the vicinity of the polar night jet

We analyze a large amplitude mountain wave event, which was observed by a ground-based lidar above New Zealand between 31 July and 1 August 2014. Besides the lidar observations, ECMWF data, satellite observations and raytracing simulations are utilized in this study. It is found that the propagation of mountain waves into the middle atmosphere is influenced by two different phenomena at different times during the event. At the beginning of the event, convective instabilities cause wave breaking in the lower stratosphere. During the course of the event the mountain waves propagate to higher altitudes and are refracted towards the polar night jet due to the strong meridional shear of the zonal wind. As the waves propagate out of the observational volume, the ground-based lidar observes no mountain waves in the mesosphere. However, raytracing simulations and satellite observations indicate that the waves reached mesospheric altitudes downstream of New Zealand. These results underline the importance of considering horizontal propagation of gravity waves when analyzing locally confined gravity wave observations.