The current standard version of the Whole Atmosphere Community Climate Model (WACCM) simulates Southern Hemisphere winter and spring temperatures that are too cold compared with observations. This “cold-pole bias” leads to unrealistically low ozone column amounts in Antarctic spring. Here, the cold-pole problem is addressed by introducing additional mechanical forcing of the circulation via parameterized gravity waves. Insofar as observational guidance is ambiguous regarding the gravity waves that might be important in the Southern Hemisphere stratosphere, the impact of increasing the forcing by orographic gravity waves was investigated. This reduces the strength of the Antarctic polar vortex in WACCM, bringing it into closer agreement with observations, and accelerates the Brewer–Dobson circulation in the polar stratosphere, which warms the polar cap and improves substantially the simulation of Antarctic temperature. These improvements are achieved without degrading the performance of the model in the Northern Hemisphere stratosphere or in the mesosphere and lower thermosphere of either hemisphere. It is shown, finally, that other approaches that enhance gravity wave forcing can also reduce the cold-pole bias such that careful examination of observational evidence and model performance will be required to establish which gravity wave sources are dominant in the real atmosphere. This is especially important because a “downward control” analysis of these results suggests that the improvement of the cold-pole bias itself is not very sensitive to the details of how gravity wave drag is altered.

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 ...

[1] A function that approximates atmospheric tidal behavior in the polar regions is described. This function is fitted to multistation radar measurements of wind in the mesosphere and lower thermosphere with the aim of obtaining a latitude-longitude-height description of the variation of tides over the whole Antarctic continent. Archival wind data sets are combined with present-day ones to fill the spatial distribution of the observations and to reduce the potential effects of spatial aliasing. Multiple years are combined through the compilation of monthly station composite days, yielding results for each month of the year. Despite potential problems associated with year-to-year variations in the tidal phase, a useful climatology of Antarctic zonal and meridional tidal wind components is compiled. The results of the fits reproduce the major features of the high-latitude tidal wind field: the dominance of the semidiurnal migrating mode in the winter months and the presence of a semidiurnal zonal wave number one component in the summer months. It is also found that the summer semidiurnal tide contains a zonal wave number zero component.

An unprecedented major stratospheric warming occurred in the Antarctic winter of 2002. We present measurements of winds in the mesosphere‐lower thermosphere (MLT) made with MF radars located at Davis (69°S, 78°E), Syowa (69°S, 40°E) and Rothera (68°S, 68°W). The mesospheric wind field in 2002 was found to be considerably different to other years due to increased planetary wave activity throughout the winter. Zonal winds were weaker than usual during the 2002 winter and also during the transition to the summer circulation. The MLT zonal winds showed a reversal about one week earlier than the stratospheric reversal associated with the warming. Meridional winds showed oscillations consistent with the presence of traveling wave‐1 planetary waves with periods ∼14 days. The results are compared with similar mesospheric observations made during northern hemisphere stratospheric warmings. Some similarities between hemispheres were found, notably that the reversal in the mesospheric winds precedes the warming events.