d. Open access institutional repositoriesThe AMS understands there is increasing demand for institutions to provide open access to the published research being produced by employees, such as faculty, of that institution. In recognition of this, the AMS grants permission to each of its authors to deposit the definitive version of that author's published AMS journal article in the repository of the author's institution provided all of the following conditions are met: The article lists the institution hosting the repository as the author's affiliation.  The copy provided to the repository is the final published PDF of the article (not the EOR version made available by AMS prior to formal publication; see section 6).  The repository does not provide access to the article until six months after the date of publication of the definitive version by the AMS.  The repository copy includes the AMS copyright notice. T he Deep Propagating Gravity Wave Experiment (DEEPWAVE) was the first comprehensive measurement program devoted to quantifying the evolution of gravity waves (GWs) arising from sources at lower altitudes as they propagate, interact with mean and other wave motions, and ultimately dissipate from Earth's surface into the mesosphere and lower thermosphere (MLT). Research goals motivating the DEEPWAVE measurement program are summarized in Table 1. To achieve our research goals, DEEPWAVE needed to sample regions having large horizontal extents because of large horizontal GW propagation distances for some GW sources. DEEPWAVE accomplished this goal through airborne and ground-based (GB) measurements that together provided sensitivity to multiple GW sources and their propagation to, and effects at, higher altitudes. DEEPWAVE was performed over and around the GW "hotspot" region of New Zealand (Fig.1, top) during austral winter, when strong vortex edge westerlies provide a stable environment for deep GW propagation into the MLT.DEEPWAVE airborne measurements employed two research aircraft during a core 6-week airborne field program based at Christchurch, New Zealand, from 6 June to 21 July 2014. The National Science 425MARCH 2016 AMERICAN METEOROLOGICAL SOCIETY | Foundation (NSF)/National Center for Atmospheric Research (NCAR) Gulfstream V (GV) provided in situ, dropsonde, and microwave temperature profiler (MTP) measurements extending from Earth's surface to ~20 km throughout the core field program (see Table 2). The GV also carried three new instruments designed specifically to address DEEPWAVE science goals: 1) a Rayleigh lidar measuring densities and temperatures from ~20 to 60 km, 2) a sodium resonance lidar measuring sodium densities and temperatures from ~75 to 100 km, and 3) an advanced mesosphere temperature mapper (AMTM) measuring temperatures in a horizontal plane at ~87 km with a field of view (FOV) of ~120 km along track and 80 km cross track. AMTM measurements were augmented by two side-viewing infrared (IR) airglow "wing" cameras also viewing an ~87-km altitude that extended the cross-track FOV to ...

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, European Centre for Medium‐Range Weather Forecasts (ECMWF) data, satellite observations, and ray tracing simulations are utilized in this study. It is found that the propagation of mountain waves into the middle atmosphere is influenced by two different processes at different stages of the event. At the beginning of the event, instabilities in a weak wind layer cause wave breaking in the lower stratosphere. During the course of the event the mountain waves propagate to higher altitudes and are refracted southward toward 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. Ray tracing simulations indicate that the mountain waves propagated to mesospheric altitudes south of New Zealand where the polar night jet advected the waves eastward. These results underline the importance of considering horizontal propagation of gravity waves, e.g., when analyzing locally confined observations of gravity waves.

Capsule summaryThe SOUTHTRAC-GW airborne mission explored the dynamics of gravity waves in the region of the Southern Andes and Antarctic Peninsula during the extraordinary southern hemisphere SSW of September 2019.

This paper describes the results of a comprehensive analysis of the atmospheric conditions during the Deep Propagating Gravity Wave Experiment (DEEPWAVE) campaign in austral winter 2014. Different datasets and diagnostics are combined to characterize the background atmosphere from the troposphere to the upper mesosphere. How weather regimes and the atmospheric state compare to climatological conditions is reported upon and how they relate to the airborne and ground-based gravity wave observations is also explored. Key results of this study are the dominance of tropospheric blocking situations and low-level southwesterly flows over New Zealand during June–August 2014. A varying tropopause inversion layer was found to be connected to varying vertical energy fluxes and is, therefore, an important feature with respect to wave reflection. The subtropical jet was frequently diverted south from its climatological position at 30°S and was most often involved in strong forcing events of mountain waves at the Southern Alps. The polar front jet was typically responsible for moderate and weak tropospheric forcing of mountain waves. The stratospheric planetary wave activity amplified in July leading to a displacement of the Antarctic polar vortex. This reduced the stratospheric wind minimum by about 10 m s−1 above New Zealand making breaking of large-amplitude gravity waves more likely. Satellite observations in the upper stratosphere revealed that orographic gravity wave variances for 2014 were largest in May–July (i.e., the period of the DEEPWAVE field phase).

The Polar Mesospheric Cloud Turbulence (PMC Turbo) experiment was designed to observe and quantify the dynamics of small‐scale gravity waves (GWs) and instabilities leading to turbulence in the upper mesosphere during polar summer using instruments aboard a stratospheric balloon. The PMC Turbo scientific payload comprised seven high‐resolution cameras and a Rayleigh lidar. Overlapping wide and narrow camera field of views from the balloon altitude of ~38 km enabled resolution of features extending from ~20 m to ~100 km at the PMC layer altitude of ~82 km. The Rayleigh lidar provided profiles of temperature below the PMC altitudes and of the PMCs throughout the flight. PMCs were imaged during an ~5.9‐day flight from Esrange, Sweden, to Northern Canada in July 2018. These data reveal sensitivity of the PMCs and the dynamics driving their structure and variability to tropospheric weather and larger‐scale GWs and tides at the PMC altitudes. Initial results reveal strong modulation of PMC presence and brightness by larger‐scale waves, significant variability in the occurrence of GWs and instability dynamics on time scales of hours, and a diversity of small‐scale dynamics leading to instabilities and turbulence at smaller scales. At multiple times, the overall field of view was dominated by extensive and nearly continuous GWs and instabilities at horizontal scales from ~2 to 100 km, suggesting sustained turbulence generation and persistence. At other times, GWs were less pronounced and instabilities were localized and/or weaker, but not absent. An overview of the PMC Turbo experiment motivations, scientific goals, and initial results is presented here.