We present observations of winds in the mesosphere and lower thermosphere (MLT) from a recently installed meteor radar on the remote island of South Georgia (54° S, 36° W). We characterise mean winds, tides, planetary waves, and gravity waves in the MLT at this location and compare our measured winds with a leading climate model. We find that the observed wintertime winds are unexpectedly reversed from model predictions, probably because of missing impacts of secondary gravity waves in the model.

Small-scale turbulent structures are ubiquitous in the atmosphere, yet our understanding of their structure and dynamics is vastly incomplete. IDEAL aimed to improve our understanding of small-scale turbulent flow features in the lower atmosphere. A small, unmanned, fixed-wing aircraft was employed to make targeted observations of atmospheric columns. Measured data were used to guide atmospheric model simulations designed to describe the structure and dynamics of small-scale turbulence.

Little is known about the climate change of wind systems in the mesosphere and lower thermosphere at the edge of space at altitudes from 70–110 km. Meteor radars represent a well-accepted remote sensing technique to measure winds at these altitudes. Here we present a state-of-the-art climatological interhemispheric comparison using continuous and long-lasting observations from worldwide distributed meteor radars from the Arctic to the Antarctic and sophisticated general circulation models.

There is great scientific interest in extending atmospheric models upwards to include the upper atmosphere. The Met Office’s Unified Model has recently been successfully extended to include this region. Atmospheric tides are an important driver of atmospheric motion at these greater heights. This paper provides a first comparison of winds and tides produced by the new extended model with meteor radar observations, comparing key tidal properties and discussing their similarities and differences.

One limitation of numerical atmospheric models is spatial resolution. For atmospheric gravity waves (GWs) generated over small mountainous islands, the driving effect of these waves on atmospheric circulations can be underestimated. Here we use a specialised high-resolution model over South Georgia island to compare simulated stratospheric GWs to colocated 3-D satellite observations. We find reasonable model agreement with observations, with some GW amplitudes much larger than expected.

In this study, a 3–D Stockwell transform is applied to AIRS–Aqua satellite observations in the first extended 3–D study of stratospheric gravity waves over the Southern Ocean during winter. A dynamic environment is revealed that contains some of the most intense gravity wave sources on Earth. A particularly striking result is a large–scale meridional convergence of gravity wave momentum flux towards latitudes near 60 °S, something which is not normally considered in model parameterisations.

This work presents four events of mesosphere fronts observed on King George Island, Antarctic Peninsula, in the year 2011. The atmospheric background environment was analyzed to investigate the propagation conditions for all cases. To investigate the sources for such cases, satellite images were used. In two cases, we found that strong tropospheric instabilities were potential sources, and in the other two cases, it was not possible to associate them with tropospheric sources.

Recently, theoretical and laboratory studies have suggested an additional nighttime channel of transfer of vibrational energy of OH molecules to CO₂ in the mesosphere and lower thermosphere (MLT). We show that new mechanism brings modelled 4.3 μm emissions very close to the SABER/TIMED measurements. This renders new opportunities for the application of the CO₂ 4.3 μm observations in the study of the energetics and dynamics of the nighttime MLT.

We introduce a novel 3-D method of measuring atmospheric gravity waves, based around a 3-D Stockwell transform. Our method lets us measure new properties, including wave intrinsic frequencies and phase and group velocities. We apply it to data from the AIRS satellite instrument over the Southern Andes for two consecutive winters. Our results show clear evidence that the waves measured are primarily orographic in origin, and that their group velocity vectors are focused into the polar night jet.

Gravity waves are medium-sized momentum-carrying atmospheric waves that nearly all weather and climate models struggle to represent. Thus, the accurate global measurement of gravity-wave properties in the real atmosphere is of key importance. Here we use a new two-dimensional Stockwell transform (2-DST) method to measure key GW properties in 2-D satellite data. We show that our 2-DST approach greatly improves upon current methods, particularly if a new elliptical spectral window is used.

Seven gravity-wave-resolving instruments (satellites, radiosondes and a meteor radar) are used to compare gravity-wave energy and vertical wavelength over the Southern Andes hotspot. Several conclusions are drawn, including that limb sounders and the radar show strong positive correlations. Radiosondes and AIRS weakly anticorrelate with other instruments and we see strong correlations with local stratospheric winds. Short-timescale variability is larger than the seasonal cycle.

Gravity waves are fundamental to the dynamics of the mesosphere. In some years very strong winds are observed in the first phase of the MSAO. It has been proposed that this is due to filtering of ascending gravity waves. We report the first gravity-wave momentum flux observations from the Ascension Island (8° S, 14° W) meteor radar and show that anomalous fluxes were observed during one such event in 2002. Analysis of the underlying winds suggests the wave-filtering hypothesis is not valid.

In nearly all GCMs, unresolved gravity wave (GW) drag may cause the southern stratospheric winter polar vortex to break down too late. Here, we characterise GWs in this region of the atmosphere using GPS radio occultation. We find GWs may propagate into the region from other latitudes. We develop a new quantitative wave identification method to learn about regional wave populations. We also find intense GW momentum fluxes over the southern Andes and Antarctic Peninsula GW hot spot.

Global concentration fields of Mg and Mg+ in the Earth's upper mesosphere and lower thermosphere (70-150km) are presented. These are retrieved from SCIAMACHY/Envisat satellite grating spectrometer measurements in limb viewing geometry between 2008 and 2012. These were compared with WACCM-Mg model results and a large fraction of the available measurement results for these species, and an interpretation of the results is done. The variation of these species during NLC presence is discussed.