Surface warming in the polar regions has important consequences for the stability of the lowest layers of the atmosphere and for atmospheric vertical movement. Here, using ERA5 reanalysis data and in situ measurements, we quantify the evolving static stability of the lowest 1 km of the Antarctic atmosphere and show that the Brunt–Väisälä frequency, a measure of atmospheric stability, has been steadily decreasing since the 1950s. Using satellite observations, reanalysis, and targeted climate simulations, we find that this reduced stability has prompted a shift in prevailing flow regimes over the Antarctic Peninsula by altering regional wind flow and enhancing the generation of orographic gravity waves. Increased gravity wave forcing from the Antarctic Peninsula can have important implications for global-scale circulation, polar vortex strength, ozone depletion, and midlatitude weather. We present consequences of Antarctic surface warming for the stability of the lower atmosphere since the 1950s. We show that the surface atmosphere over the Antarctic Peninsula has become less stable, and that this reduced stability favors the generation of atmospheric gravity waves from the Peninsula, one of the major sources of atmospheric waves on the planet. We provide a physically based explanation (i.e., a shift in flow regimes) for the increased gravity wave forcing that we find in an unprecedented set of reanalysis products, satellite observations, and model simulations, and that we present here for the first time. Gravity wave forcing changes can have profound ramifications for the global climate, from polar vortex strength to ozone depletion and midlatitude weather.

Atmospheric gravity waves (GWs) are a key driver of vertical energy and momentum transport in the atmosphere, with important implications for large-scale dynamics and chemistry. However, they remain difficult to predict in operational weather and climate models due to their small spatial scales relative to model resolution, and are typically not assimilated into numerical weather prediction (NWP) systems because of the large departures they introduce from model initial conditions.Here we use stratospheric temperature measurements from the Atmospheric Infrared Sounder (AIRS) and the Cross-track Infrared Sounder (CrIS) to evaluate how well archived operational analyses and forecasts from ECMWF’s Integrated Forecast System reproduce observed GW activity over Greenland, a major Northern Hemisphere source region for orographic GWs. The combined AIRS–CrIS sampling at high latitudes provides an unusually high measurement cadence, enabling assessment of forecast performance and time variability at relatively fine temporal resolution.Operational analyses and forecasts with lead times of up to 240 h are sampled at the AIRS and CrIS measurement footprints and regridded to a common resolution to allow consistent spectral analysis. A 2D+1 Stockwell Transform is applied to both synthetic and real observations to characterise GW amplitudes and spatial structure, producing directly comparable GW fields across forecast lead times.Using a Structure–Amplitude–Location (SAL) framework adapted from precipitation forecast verification, we quantify the evolution of GW forecast skill with lead time. We find that model performance exhibits only weak dependence on forecast range: across all lead times, the model systematically produces GWs with smaller horizontal scales and reduced amplitudes relative to observations, while errors in wave location increase only modestly with lead time. This behaviour is unexpected, as shorter lead times are associated with more accurate resolved winds, and would therefore be expected to yield more accurate GW generation. The results suggest that errors in simulated GW characteristics in operational forecasts are dominated by structural and representational limitations rather than by forecast wind errors alone.

Advances in computational power and model development have enabled the generation of global high-resolution models. These new models can resolve a large proportion of gravity waves (GWs) explicitly, reducing reliance on subgrid parametrizations. GWs are vital components of the middle and upper atmosphere, they transport energy and momentum both horizontally and vertically, driving the atmospheric circulation. Evaluating the realism of these resolved waves is a crucial step in advancing future model development.Here we provide the first global multi-model GW observational comparison that accounts for the observational filter. We assess the representation of stratospheric GWs in three high-resolution (3-5 km horizontal resolution) global free-running simulations (ICON, IFS and GEOS), for the period 20 January-29 February 2020, against AIRS satellite observations.Time-mean wave amplitudes are systematically lower in the models than observations, consistent with previous studies. GW occurrence rates are higher in all models than the observations, dominated by low amplitude waves in the models. During the first 10 d spatial patterns of GW occurrence rate, amplitudes and momentum flux agree across the models and observations but subsequently they diverge. Agreement is more consistent in the Northern Hemisphere (where orographic waves dominate) than in the Southern Hemisphere (where convective waves dominate).These results benchmark the current state of high-resolution modelling and demonstrate that whilst there are strengths in models' ability to capture the morphology of GWs (particularly orographically generated waves), there is room for improvement in modelling amplitudes, occurrence rates and zonal-mean flux magnitudes globally, with the largest discrepancies in the tropical convective regions.

The Low Frequency Array (LOFAR) is one of the most advanced radio telescopes in the world. When radio waves from a distant astronomical source traverse the ionosphere, structures in this plasma affect the signal. Results are presented from a statistical study using 2,810 hours of observations of Cassiopeia A from a LOFAR station located in the Netherlands (station CS032, located at 52.9o N; 6.9o E) between 28th June 2014 and 27th November 2016. Ionospheric structures were identified in 469 (~17 %) of these observations. A comparison with proxies for geomagnetic activity (the Kp index) and solar activity (the F10.7 cm solar radio flux) showed that geomagnetic or solar effects were not the primary driver of these ionospheric structures. Ionospheric structures were more common in summer and between ~21 LT – 02 LT. These patterns in season and local time showed similarities to the occurrence of lightning strikes. When ionospheric structures were present, the mean number of lightning strikes in a spatial region close to the LOFAR observations (51.9o – 56.5o N; 3.9o – 9.9o E) two hours prior to the LOFAR observations was (70 ± 25) per hour. This was substantially larger than the mean value of (19 ± 5) per hour when the ionospheric structures were absent. This suggests that quasi-upward propagating Atmospheric Gravity Waves (AGWs) launched by thunderstorm activity could be one of the sources of the ionospheric structures. Collectively, these observations show that LOFAR can be used to infer ionospheric signatures of vertical coupling processes in the mid-latitude atmosphere. Such observations have the potential to be used to develop or validate existing Global Circulation Models (GCMs) or new models of vertical coupling within the terrestrial atmosphere.

Modern numerical modelling simulations of the Earth's atmosphere have developed over the recent decades to ever finer spatial resolutions, allowing for a greater portion the atmospheric gravity wave (GW) spectrum to be resolved. Specialised global simulations with kilometre-scale resolutions have been performed offline that can resolve very large portions of the GW spectrum in the lower stratosphere and, as such, the balance between resolved and parameterised (unresolved) GW forcing in today's numerical simulations of the middle atmosphere is shifting. However, these kilometre-scale simulations are still too computationally costly to perform routinely and can quickly deviate from their initial conditions, which makes validating the resolved gravity waves in these simulations with satellite observations challenging. For this reason, a growing number of studies are using resolved GWs in lower-resolution stratospheric reanalyses as proxies for GWs in the real atmosphere, due to the apparent reliability, long timescale, global coverage and real-date data assimilation of these reanalysis products. However, these resolved GWs in reanalyses have not been widely tested or compared to satellite observations of GWs to assess their realism. One reason why such a comparison has been so challenging is due to the different ranges of GW wavelengths to which any given model or observational instrument is sensitive due to its grid spacing or sampling and resolution limits, an effect known as the observational filter. Therefore, any like-for-like assessment of resolved GWs in reanalysis using satellite observations must be able to sample the model using the exact sampling and resolution of the instrument. Here we use 3-D satellite observations from AIRS/Aqua to evaluate the realism of resolved stratospheric gravity waves in ERA5 reanalysis produced by the European Centre for Medium Range Weather Forecasts (ECMWF). We carefully apply the sampling and resolution limits of AIRS to the model using a full 3-D weighting function for each measurement footprint to create synthetic measurements of the ERA5 stratosphere as if were viewed by AIRS. We then follow identical processing steps to detrend, regrid and spectrally analyse both the real and synthetic measurements to recover localised GW amplitudes, wavelengths and directional momentum fluxes between 25 and 45 km altitude. We investigate the global momentum budget of GWs in reanalysis compared to observations and compare the seasonality and spectral properties of GWs over known stratospheric hot spots. Our preliminary results suggest that AIRS measurements exhibit more frequent large-amplitude wave events at larger horizontal wavelengths (greater than 150km) and larger net momentum fluxes overall than equivalent ERA5 measurements. Our satellite-sampling approach is applicable to any GW-resolving model, and sets out a potential roadmap towards more direct validation and comparison of resolved mesoscale dynamics in numerical models that could help to guide developments in the coming era of high-spatial resolution atmospheric modelling.

Transatlantic aviation is a major industry and even small flight time changes have major economic and environmental implications. While our ability to optimise these flights for background wind variations at day-to-day scales is excellent, at the longer timescales needed for sustainability planning and fuel cost hedging these capabilities are more limited. Here, we quantify the association between four climate indices (the El Ni & ntilde;o-Southern Oscillation, the North Atlantic Oscillation, the Quasi-Biennial Oscillation and solar irradiance) and transatlantic flight times using thirty years of commercial flight data. This allows us to identify whether these indices can be used to identify systematic flight time shifts. We find that ENSO and the NAO are associated with statistically-significant changes in one-way flight times of up to 82.2 +/- 3.5 min, and changes in round-trip times of 4.8 +/- 0.5 and 4.0 +/- 0.8 min respectively, while the QBO and TSI have weaker but significant effects. Together, these indices plus a linear trend explain up to 27 % of variation depending on season and direction, and are associated with month-to-month fuel cost & CO2 emission variations of up to 27MUSD & 120 kT for one-way trips and USD 5 million & 23 kT for round trips. We also show that westward, round-trip and non-winter-eastward flight times have increased by several minutes per decade since the 1990s. Our results provide the first observational quantitative basis for aviation fuel and carbon cost management at monthly and longer timescales.

Gravity wave sources such as convection are known to have a diurnal cycle, so it is expected that gravity waves should also follow a diurnal cycle. However, although this cycle can be simulated in models and observed in ground based data at fixed locations, it is difficult to observe in global satellite observations, due to their low time resolution, particularly since most gravity wave resolving instruments have sun-synchronous orbits and therefore always observe the same local solar time. In this study, GNSS radio occultation (GNSS-RO) data are used to investigate whether a diurnal cycle in gravity wave amplitudes can be seen in the stratosphere using these observations. Radio occultation uses GNSS signals received by a satellite that measures the bending angles and phase delay, due to these signals passing through the atmosphere. These measurements are randomly distributed in local solar time and have the high vertical resolution required to accurately resolve gravity waves. Specifically, in this work, GNSS-RO dry temperature data are used from multiple satellite missions, including COSMIC 1 and 2, Metop-A, -B and -C, and CHAMP. Wave amplitudes are found using the 1D S-Transform and the amplitudes are then binned in local solar time and averaged for each month, using all available data from the years 2001-2023. Consistent with theoretical observations, a diurnal cycle in gravity wave activity can be seen in the results and comparisons to convection data sets suggest this is strongly linked to convection. These results are also compared to wind data, which will affect the generation and filtering of the waves.

The quasi-biennial oscillation (QBO) is a slowly repeating cycle of winds which dominates tropical lower-stratospheric dynamics and has been described as the “heartbeat of the stratosphere”. However, it is challenging to represent in weather and climate models because its periodicity and magnitude are controlled by small-scale gravity waves (GWs) that cannot be resolved on model grids. To quantify this GW driving we require high-resolution measurements, ideally from satellites to ensure full spatial coverage. Since 2002, the SABER instrument on the TIMED satellite has provided such data, facilitating long-term studies of QBO GW driving. However, SABER is expected to be decommissioned later this year, and no replacement is planned. Here, we assess the possibility of using GNSS-RO data to extend the 23-year SABER record. GNSS-RO cannot be used as a simple replacement for long-term studies because data volumes are too low before 2006 and for most of the late 2010s, and thus, we ideally wish to supplement rather than replace the SABER record. However, while the two datasets have broadly similar lower stratospheric resolutions when compared to the full Earth observation constellation, GNSS-RO measurements are higher resolution in all three dimensions than SABER and are oriented differently in 3D space. As a result of this, GNSS-RO GW measurements exhibit much larger GW potential energies (GWPE) and shorter vertical wavelengths than those from SABER. To understand these differences, we use a high-resolution run of the GEOS model to produce synthetic GW measurements, then systematically vary the measurement characteristics between those of the two real instruments. This allows us to identify the key drivers of the different GW properties they measure. We demonstrate that the differences between QBO-driving GW properties measured by the two instruments are primarily due to vertical resolution, with horizontal resolution (either along or across line of sight) and orientation angle playing a negligible role. We further demonstrate that, with a simple vertical smoothing of the GNSS-RO data in the vertical before analysis for GWs, the measured GW properties become near-identical, allowing us to use SABER and GNSS-RO data near-equivalently for this use case. Since GNSS-RO data are now a crucial component of the global numerical weather prediction constellation and are hence highly likely to be available in the long term, this allows us to produce a consistent long-term record of QBO GW forcing from 2002 onwards without key gaps which would be otherwise present in the early 2000s and late 2010s.

In this study, we have investigated short-period (1 hr) atmospheric gravity waves (AGWs) in the Arctic mesosphere-lower thermosphere (MLT) region during January of 2014, 2015, and 2016. We used OH (3,1) band emission data from the Advanced Mesospheric Temperature Mapper (AMTM) at the Arctic Lidar Observatory for Middle Atmosphere Research (ALOMAR), Norway. By applying a three-dimensional spectral analysis technique (Matsuda-transform), we derived phase velocity spectra of AGWs and characterized both intraday and day-to-day variability by examining wave power across multiple directional bins and phase speed ranges. Our results reveal significant year-to-year differences in AGW activity with markedly reduced spectral power and shifted propagation directions in January 2015 compared to 2014 and 2016. We compared these wave characteristics with the directional distribution of critical-level filtering between 0 and 50 km, utilizing ERA5 reanalysis winds and with the Arctic Oscillation (AO) index. We found that dominant wave propagation directions closely aligned with critical-level filtering below 50 km and that the reduced AGW activity in January 2015 was associated with stronger polar vortex conditions (higher AO values). In contrast, weaker polar vortex conditions (lower AO values) in 2014 and 2016 allowed more diverse AGW spectra to reach mesospheric altitudes. These findings highlight the crucial role of stratospheric wind structures in driving AGW variability in the Arctic MLT region during winter.

Convective gravity waves are important for the forcing of the quasi biennial oscillation (QBO). There is a wave component that is stationary with respect to the convective cells that is triggered by convection acting like a barrier to the background flow (moving mountain mechanism). Waves from this mechanism have only been observed in a few case studies and are not parameterized in climate models. However, the representation of the whole spectrum of gravity waves is crucial for the simulation of the QBO, especially in the lowermost stratosphere (below 50 hPa) where the QBO amplitudes are under‐estimated in current global circulation models. In this study, we present analysis of convective gravity wave observations from superpressure balloons in boreal winter 2019 and 2021, retrieving phase speeds, momentum fluxes, and drag. We also identify waves generated by the moving mountain mechanism using the theory of the Beres scheme as a basis. These waves do not have a specific period, but are of smaller horizontal scale, on average around 300 km, which is similar to the scale of convective systems. Our results show that gravity waves contribute up to 2/3 to the QBO forcing below 50 hPa and waves from the moving mountain mechanism are responsible for up to 10% of this forcing.

Comparisons between observed and model‐resolved gravity waves (GWs) are crucial for evaluating general circulation model (GCM) simulation accuracy and understanding wave characteristics. However, observational noise often obscures waves, complicating such comparisons. To address this, we have developed a GW detection method using a convolutional neural network (CNN). The CNN is trained on Atmospheric Infrared Sounder (AIRS) temperatures with labels indicating wave presence based on Berthelemy et al. (2025, https://doi.org/10.5194/egusphere‐2025‐455 ). Their method detects noise‐induced pixel‐to‐pixel variations in horizontal wavelengths; in contrast, the CNN robustly identify waves even when applied to smoothly varying model data. Using this method, we compare stratospheric GWs in boreal winters between AIRS observations and a high‐top GW‐permitting GCM, Japanese Atmospheric GCM for Upper Atmosphere Research (JAGUAR). The results agree well and exhibit similar interannual variability, with discrepancies also identified, including a more zonally elongated distribution of tropical GWs in JAGUAR. This method is broadly applicable to the future use of satellites for guiding wave‐resolving atmospheric model development.

Abstract. The quasi-biennial oscillation (QBO) is the most important phenomenon in the tropical stratosphere. It is mainly driven by small-scale gravity waves. Still, the representation of QBO in models is challenging because small-scale gravity waves are not well resolved in the models and the majority of the parametrization schemes are limited to vertical propagation only of gravity waves. One solution to this is to use high-resolution satellite observations to understand the gravity wave (GW) forcing on the QBO. However, the results can vary from one observation to another due to the unique observational filter of each instrument. Here we investigate how these differences in the observational filters between SABER and GNSS-RO satellite measurements affect our ability to capture the interactions between GWs and the QBO. To test this, we sample temperatures from the high-resolution GEOS model as if they were observed by SABER and GNSS-RO and estimate synthetic GW potential energy (Ep) observations. We then systematically vary the viewing angle and the vertical and horizontal resolutions of the instruments to determine which aspects have the most significant effect on the observed GW Ep. This allows us to understand how the observational filter of each instrument influences the observation of GW-QBO interaction and if we can bring the two observations close enough to get nearly the same results. Our results reveal that vertical resolution is the most significant factor deriving the differences between the results of both instruments. By adjusting the vertical resolution of GNSS-RO temperatures to match that of SABER, we found that the GW Ep and vertical wavelength measurements from both instruments could be brought into very close agreement. This study not only focuses on the importance of selecting appropriate observational methods for gravity wave research but also highlights the potential of GNSS-RO to extend the long-term studies of GW interaction with the QBO that has been carried out by SABER for more than 23 years, especially as SABER approaches the end of its operational lifespan. Our findings contribute to a more comprehensive understanding of GW observations in the tropics and provide a foundation for future applications using merged GNSS-RO observations.

Atmospheric gravity waves (GWs) are an important mechanism for vertical transport of energy and momentum through the atmosphere. Their impacts are apparent at all scales, including aviation, weather, and climate. Identifying stratospheric GWs from satellite observations is challenging due to instrument noise and effects of weather processes, but they can be observed from nadir sounders such as the AIRS instrument onboard Aqua. Here, a new method (hereafter “neighbourhood method”) to detect GW information is presented and applied to AIRS data. This uses a variant of the 3D S-transform to calculate the horizontal wavenumbers of temperature perturbations, then find areas of spatially constant horizontal wavenumbers (assumed to be GWs), which allow for creating a binary wave-presence mask. We describe the concept of the neighbourhood method and use it to investigate GW amplitudes, zonal pseudomomentum fluxes, and vertical wavelengths over 5 years of AIRS data. We compare these results to those calculated from GWs detected using another widely used method based on an amplitude cutoff. 35 % of regions of wave activity detected using the neighbourhood method have amplitudes lower than is visible using the amplitude cutoff method. Three regions are studied in greater depth: the Rocky Mountains, North Africa, and New Zealand/Tasmania. GWs detected using the neighbourhood method have wave phase propagation angles consistent with linear theory. Using the neighbourhood method produces new statistics for regional and global GW studies, which compare favourably to the amplitude cutoff GW detection method.

Atmospheric gravity waves (GWs) are one of the most important drivers of the circulation of the middle and upper atmosphere. Usually generated in the lower atmosphere and propagating upwards through the atmospheric layers, the aggregated forcing of these waves drives circulations in the middle atmosphere that are far from that expected under radiative equilibrium. Circulations in the mesosphere and lower thermosphere (MLT) and above, especially in polar regions, have shown extreme sensitivity to GW parameterisations in recent high-top modelling simulations and can exhibit significant and limiting biases compared to observations. This uncertainty in the role of GW dynamics between models has made predictions of how these high-altitude circulations are expected to respond to a changing climate very challenging. This is confounded by a relative scarcity of global observations of GW activity in the middle and upper atmosphere with which to understand these connections over climate timescales. Since the early 2000s, satellite and ground-based instrumentation has provided an unprecedented observational view of middle atmospheric dynamics and composition, especially for the study of GWs. However, due to different instrument capabilities and limited hardware lifetimes, examining long term trends of GW properties observationally has been challenging due to the need to re-establish baselines. Here we examine results from some of the longest known single-instrument records of GW activity in the middle and upper atmosphere spanning more than two decades. We explore changes in GW amplitudes, wavelengths and directional momentum flux in the stratosphere from a 22-year climatology derived from global 3-D satellite observations from the AIRS/Aqua, the longest single-instrument climatology of this type. We also explore changes in wind, temperature and large-scale GW activity in the polar MLT from nearly 20 years of single-station meteor wind radar observations in the Arctic and Antarctic. We compare these trends to equivalent analysis of other long-term satellite GW datasets and resolved GW activity in ERA5 stratospheric reanalysis. Finally, we discuss limitations and best practise for considering observed trends in GW observations, such as how changes in circulation can affect GW propagation and their apparent sensitivity to satellite remote sensing techniques.

Two-way coupling between the stratosphere and troposphere is recognized as an important source of subseasonal-to-seasonal (S2S) predictability and can open windows of opportunity for improved forecasts. Model biases can, however, lead to a poor representation of such coupling processes; drifts in a model's circulation related to model biases, resolution, and parameterizations have the potential to feed back on the circulation and affect stratosphere–troposphere coupling. We introduce a set of diagnostics using readily available data that can be used to reveal these biases and then apply these diagnostics to 22 S2S forecast systems. In the Northern Hemisphere, nearly all S2S forecast systems underestimate the strength of the observed upward coupling from the troposphere to the stratosphere, downward coupling within the stratosphere, and the persistence of lower-stratospheric temperature anomalies. While downward coupling from the lower stratosphere to the near surface is well represented in the multi-model ensemble mean, there is substantial intermodel spread likely related to how well each model represents tropospheric stationary waves. In the Southern Hemisphere, the stratospheric vortex is oversensitive to upward-propagating wave flux in the forecast systems. Forecast systems generally overestimate the strength of downward coupling from the lower stratosphere to the troposphere, even as most underestimate the radiative persistence in the lower stratosphere. In both hemispheres, models with higher lids and a better representation of tropospheric quasi-stationary waves generally perform better at simulating these coupling processes.

The quasi-biennial oscillation (QBO) was unexpectedly disrupted for only the second time in the historical record during the 2019/2020 boreal winter. As the dominant mode of atmospheric variability in the tropical stratosphere and a significant source of seasonal predictability globally, understanding the drivers behind this unusual behaviour is very important. Here, novel data from Aeolus, the first Doppler wind lidar (DWL) in space, are used to observe the 2019/2020 QBO disruption. Aeolus is the first satellite able to observe winds at high resolution on a global scale, and it is therefore a uniquely capable platform for studying the evolution of the disruption and the broader circulation changes triggered by it. This study therefore contains the first direct wind observations of the QBO from space, and it exploits measurements from a special Aeolus scanning mode, implemented to observe this disruption as it happened. Aeolus observes easterly winds of up to 20 m s−1 in the core of the disruption jet during July 2020. By co-locating with radiosonde measurements from Singapore and the ERA5 reanalysis, comparisons of the observed wind structures in the tropical stratosphere are produced, showing differences in equatorial wave activity during the disruption period. Local zonal wind biases are found in both Aeolus and ERA5 around the tropopause, and the average Aeolus-ERA5 Rayleigh horizontal line-of-sight random error is found to be 7.58 m s−1. The onset of the QBO disruption easterly jet occurs 5 d earlier in Aeolus observations compared with the reanalysis. This discrepancy is linked to Kelvin wave variances that are 3 to 6 m2 s−2 higher in Aeolus compared with ERA5, centred on regions of maximum vertical wind shear in the tropical tropopause layer that are up to twice as sharp. The enhanced lower-stratospheric westerly winds which are known to help disrupt the QBO, perhaps with increasing frequency as the climate changes, are also stronger in Aeolus observations, with important implications for the future predictability of such disruptions. An investigation into differences in the equivalent depth of the most dominant Kelvin waves suggests that slower, shorter-vertical-wavelength waves break more readily in Aeolus observations compared with the reanalysis. This analysis therefore highlights how Aeolus and future DWL satellites can deepen our understanding of the QBO, its disruptions and the tropical upper-troposphere lower-stratosphere region more generally.

The mesosphere and lower thermosphere (MLT) plays a critical role in linking the middle and upper atmosphere. However, many General Circulation Models do not model the MLT and those that do remain poorly constrained. We use long-term meteor radar observations (2005-2021) from Rothera (67 degrees S, 68 degrees W) on the Antarctic Peninsula to evaluate the Whole Atmosphere Community Climate Model with thermosphere-ionosphere eXtension (WACCM-X) and investigate interannual variability. We find some significant differences between WACCM-X and observations. In particular, at upper heights, observations reveal eastwards wintertime (April-September) winds, whereas the model predicts westwards winds. In summer (October-March), the observed winds are northwards but predictions are southwards. Both the model and observations reveal significant interannual variability. We characterize the trend and the correlation between the winds and key phenomena: (a) the 11-year solar cycle, (b) El Nino Southern Oscillation, (c) Quasi-Biennial Oscillation and (d) Southern Annular Mode using a linear regression method. Observations of the zonal wind show significant changes with time. The summertime westwards wind near 80 km is weakening by up to 4-5 ms-1 per decade, whilst the eastward wintertime winds around 85-95 km are strengthening at by around 7 ms-1 per decade. We find that at some times of year there are significant correlations between the phenomena and the observed/modeled winds. The significance of this work lies in quantifying the biases in a leading General Circulation Model and demonstrating notable interannual variability in both modeled and observed winds. The mesosphere and lower thermosphere (MLT), at heights of 80-100 km is an important region for the coupling of the middle and upper atmosphere. We carry out a study of the winds above Rothera (Antarctic Peninsula) for the years 2005-2021. We use observations from a meteor radar which measures winds at heights of 80-100 km and compare with the eXtended version of the Whole Atmosphere Community Climate Model (WACCM-X), a leading general circulation model. We find that although most of the seasonal cycle in the winds is captured well, WACCM-X exhibits biases in the winds at upper heights. In wintertime, the zonal winds are westwards whereas in observations they are eastward. In summertime WACCM-X model meridional winds at 90-100 km are southwards but observations northwards. The observed and modeled winds also display significant interannual variability. We characterize the trends of the winds and the correlation with various drivers (the 11-year solar cycle, El Nino Southern Oscillation, the Quasi-Biennial Oscillation and the Southern Annular Mode), using a multi-linear regression method. The study uses a uniquely long data set of Antarctic MLT winds to test and further develop general circulation models and quantifies the relationship between these winds and drivers such as the solar cycle. We characterize the variability of monthly mean winds in the mesosphere and lower thermosphere (MLT) over 17 years at Rothera using meteor radar observations and the eXtended version of the Whole Atmosphere Community Climate Model (WACCM-X) WACCM-X displays biases in the wintertime winds in the upper MLT. Observed winds are eastwards whilst WACCM-X winds are westwards Significant variability, trends and intermittent correlations with the solar cycle, Quasi-Biennial Oscillation and Southern Annular Mode are found in the observed and modeled winds