Katabatic Flow Research Articles

Investigating Stagnant Air Conditions in Almaty: A WRF Modeling Approach

This study investigates stagnant atmospheric conditions in Almaty, Kazakhstan, a city nestled within a complex terrain. These conditions, characterized by weak local winds and inversion layers, trap pollutants within the city, particularly during winter. The Weather Research & Forecasting (WRF) model was employed to simulate atmospheric conditions using Local Climate Zone data. Verification of the model’s accuracy was achieved through comparisons with data from weather stations and the Landsat-9 satellite. The model successfully reproduced the observed daily temperature variations and weak winds during the testing period (13–23 January 2023). Comparisons with radiosonde data revealed good agreement for morning temperature profiles, while underestimating the complexity of the evening atmospheric structure. The analysis focused on key air quality factors, revealing cyclical patterns of ground-level and elevated inversions linked to mountain-valley circulation. The model effectively captured anabatic and katabatic flows. The study further examined the urban heat island (UHI) using a virtual rural method. The UHI exhibited daily variations in size and temperature, with heat transported by prevailing winds and katabatic flows. Statistical analysis of temperature and wind patterns under unfavorable synoptic situations revealed poor ventilation in Almaty. Data from three Januaries (2022/2023/2024) were used to create maps showing average daytime and nighttime air temperatures, wind speed, and frequency of calm winds.

Eddy Scale-wise Topology Underlying Turbulence Anisotropy Illuminates the Dissimilar Transport of Momentum, Heat, and Moisture in a Stably Stratified Katabatic Flow

Eddy Scale-wise Topology Underlying Turbulence Anisotropy Illuminates the Dissimilar Transport of Momentum, Heat, and Moisture in a Stably Stratified Katabatic Flow

Downscaling air temperatures for high-resolution niche modeling in a valley of the Amazon lowland forests: A case study on the microclima R package.

The forests of the Amazon basin are threatened by climate and land use changes. Due to the transition towards a drier climate, moisture-dependent organisms such as canopy epiphytes are particularly affected. Even if the topography in the Amazon lowland is moderate, mesoscale nocturnal katabatic flows result from cold air production related to radiative cooling. From a certain level of mass the cold air starts to flow downslope towards the valley centers leading to temperature inversions. The resulting cooling in the valleys drives localized fog formation in the valleys at night. This correlates with high epiphyte abundance and diversity in the valleys, which is much less pronounced upslope. The underlying temperature dynamics are, however, not sufficiently included in coarse-resolution reanalysis models such as ERA5-Land. Since high resolution climate data are needed e.g. for proper niche modeling of locally distributed species such as canopy epiphytes, downscaling models such as microclima have been developed and include micro- and mesoscale effects. However, it is unclear how well the elevation-related diurnal course of air temperature can be simulated. Here, we test functions for downscaling coarse-resolution temperature data to high spatial resolution data implemented in the R-package microclima for the South American tropical lowland forests. To do so we compared microclima-downscaled ERA5-Land air temperature data with meteorological station data. We found that the microclima functions only properly detect 73 temperature inversions out of 412 nocturnal cold air drainage (CAD) events during the dry season study period and only 18 out of 400 during the wet season with default settings. By modifying default values such as the emissivity threshold and time frames of possible CAD condition detection, we found 345 of 412 CAD events during the dry season and 177 out of 400 during the wet season. Despite problems with the distinction between CAD and non-CAD events the microclima algorithms show difficulties in correctly modeling the diurnal course of the temperature data and the amplitudes of elevational temperature gradients. For future studies focusing on temperature downscaling approaches, the modules implemented in the microclima package have to be adjusted for their usage in tropical lowland forest studies and beyond.

Instabilities of rotating inclined buoyancy layers.

The boundary layer near a cooled inclined plate, which is immersed in a stably stratified fluid rotating about an axis parallel to the direction of gravity, is a model for katabatic flows at high latitudes. In this paper the base flow of such an inclined buoyancy layer is solved analytically for arbitrary Prandtl numbers. By applying linear stability analyses, five unstable modes are identified for both the fixed temperature and the isoflux boundary conditions, i.e., the stationary longitudinal roll (LR) mode, the oblique roll with low streamwise wave-number (OR-1) and high streamwise wave-number (OR-2) modes, and the Tolmien-Schlichting (TS) wave with low streamwise wave-number (TS-1) and high streamwise wave-number (TS-2) modes. It is indicated that the Coriolis effect induced by the rotation leads the critical modes to be three dimensional, and a larger tilt angle of the plate and stronger Coriolis effect cause both TS wave modes to be more unstable for both thermal boundary conditions. When the Coriolis effect is considered, the OR-1 and OR-2 modes are the most unstable mode at low and high tilt angles, respectively, but the TS-1 wave mode may be the most unstable one when the plate is nearly vertical. In addition, the spanwise phase velocities of the TS wave modes change directions as the tilt angle passes some threshold values for both thermal boundary conditions except for the TS-1 wave mode with a fixed temperature boundary condition, which propagates in the same spanwise direction for all explored tilt angles.

Combining Weather Station Data and Short-Term LiDAR Deployment to Estimate Wind Energy Potential with Machine Learning: A Case Study from the Swiss Alps

Wind energy potential in complex terrain is still poorly understood and difficult to quantify. With Switzerland’s current efforts to shift to renewable energy resources, it is now becoming even more crucial to investigate the hidden potential of wind energy. However, the country’s topography makes the assessment very challenging. We present two measurement campaigns at Lukmanier and Les Diablerets, as representative areas of the complex terrain of the Swiss Alps. A general understanding of local wind flow characteristics is achieved by comparing wind speed measurements from a near-surface ultra-sonic anemometer and from light detection and ranging (LiDAR) measurements further aloft. The measurements show how the terrain modifies synoptic wind for example through katabatic flows and effects of local topography. We use an artificial neural network (ANN) to combine the data from the measurement campaign with wind speed measured by weather stations in the surrounding area of the study sites. The ANN approach is validated against a set of LiDAR measurements which were not used for model calibration and also against wind speed measurements from a 25-meter mast, previously installed at Lukmanier. The statistics of the ANN output obtained from multi-year time series of nearby weather stations match accurately the ones of the mast data. However, for the rather short validation periods from the LiDAR, the ANN has difficulties in predicting lowest wind speeds at both sites, and highest wind speeds at Les Diablerets.

Shallow Katabatic Flow in a Complex Valley: An Observational Case Study Leveraging Uncrewed Aircraft Systems

Shallow Katabatic Flow in a Complex Valley: An Observational Case Study Leveraging Uncrewed Aircraft Systems

Turbulence characteristics and mixing properties of gravity currents over complex topography

Understanding gravity currents developing on complex topography, which involve turbulence and mixing processes on a wide range of spatial and temporal scales, is of importance for estimating near ground fluxes in oceanic and atmospheric circulation. We present experimental results, based on high resolution velocity and density measurements, of constant upstream buoyancy supply gravity currents flowing from a horizontal boundary onto a tangent hyperbolic shaped slope. The mean flow, turbulence characteristics, and mixing properties, the latter expressed in terms of mixing lengths and eddy coefficients, are determined, highlighting their dependency on topography. These mean flow and mixing characteristics are compared with the field measurements in katabatic winds by Charrondière et al. [“Mean flow structure of katabatic winds and turbulent mixing properties,” J. Fluid Mech. 941, A11 (2022)], which are gravity flows that develop over sloping terrain due to radiative cooling at the surface. The results obtained show that the mean katabatic flow structure is substantially different from that of the upstream buoyancy supply gravity current. However interestingly, dimensionless mixing lengths and eddy coefficients compare well despite the difference in the mean flow structure and a two order of magnitude difference in the Reynolds number.

Shallow katabatic flow on a non-uniformly cooled slope

We examine katabatic flow driven by a non-uniformly cooled slope surface but unaffected by Coriolis acceleration. A general formulation is given, valid for non-uniform surface buoyancy distributions over a down-slope length scale Lgg delta _0, where delta _0=nu /(Nsin alpha )^{1/2} is the slope-normal Prandtl depth, for a kinematic viscosity nu, buoyancy frequency N and slope angle alpha. We demonstrate that the similarity solution of Shapiro and Fedorovich (J Fluid Mech 571:149–175, 2007) can remain quantitatively relevant local to the end of a non-uniformly cooled region. The usefulness of the steady similarity solution is determined by a spatial eigenvalue problem on the L length scale. Broadly speaking, there are also two modes of temporal instability; stationary down-slope aligned vortices and down-slope propagating waves. By considering the limiting inviscid stability problem, we show that the origin of the vortex mode is spatial oscillation of the buoyancy profile normal to the slope. This leads to vortex growth in a region displaced from the slope surface, at a point of buoyancy inflection, just as the propagating modes owe their existence to an inflectional velocity. Non-uniform katabatic flows that detrain fluid to the ambient are shown to further destabilise the vortex mode whereas entraining flows lead to weaker vortex growth rates. Rayleigh waves dominate in general, but the vortex modes become more significant at small slope angles and we quantify their relative growth rates.

Case studies of the wind field around Ny-Ålesund, Svalbard, using unmanned aircraft

The wind field in Arctic fjords is strongly influenced by glaciers, local orography and the interaction between sea and land. Ny-Ålesund, an important location for atmospheric research in the Arctic, is located in Kongsfjorden, a fjord with a complex local wind field that influences measurements in Ny-Ålesund. Using wind measurements from UAS (unmanned aircraft systems), ground measurements, radiosonde and reanalysis data, characteristic processes that determine the wind field around Ny-Ålesund are identified and analysed. UAS measurements and ground measurements show, as did previous studies, a south-east flow along Kongsfjorden, dominating the wind conditions in Ny-Ålesund. The wind measured by the UAS in a valley 1 km west of Ny-Ålesund differs from the wind measured at the ground in Ny-Ålesund. In this valley, we identify a small-scale catabatic flow from the south to south-west as the cause for this difference. Case studies show a backing (counterclockwise rotation with increasing altitude) of the wind direction close to the ground. A katabatic flow is measured near the ground, with a horizontal wind speed up to 5 m s-1. Both the larger-scale south-east flow along the fjord and the local katabatic flows lead to a highly variable wind field, so ground measurements and weather models alone give an incomplete picture. The comparison of UAS measurements, ground measurements and weather conditions analysis using a synoptic model is used to show that the effects measured in the case studies play a role in the Ny-Ålesund wind field in spring.

Distinguishing Time Scales of Katabatic Flow in Complex Terrain

To examine spatial and temporal scales of katabatic flow, a distributed temperature sensing (DTS) optical fiber was deployed 2 km down a mild slope irregularly interrupted by small-scale drainage features as part of the Mountain Terrain Atmospheric Modeling and Observation (MATERHORN) experiment conducted at the U.S. Army Dugway Proving Ground, Utah. The fiber was suspended at two heights near the surface, enabling measurement of variations in lapse rate near the surface at meter-scale spatial resolution with 1-min temporal resolution. Experimental results derived from the DTS and tower-mounted instrumentation indicate that airflow through small-scale drainage features regulated the local cooling rate whereas topographic slope and distance along the drainage strongly influenced the larger-scale cooling rate. Empirical results indicate that local cooling rate decays exponentially after local sunset and basin-wide cooling rate decreases linearly with time. The difference in the functional form for cooling rate between local and basin-wide scales suggests that small-scale features have faster timescales that manifests most strongly shortly after local sunset. More generally, partitioning drainage flow by scale provides insight and a methodology for improved understanding of drainage flow in complex terrain.

A Local Similarity Function for Katabatic Flows Derived From Field Observations Over Steep‐ and Shallow‐Angled Slopes

AbstractKatabatic flows are notoriously difficult to model for a variety of reasons. Notably, the assumptions underpinning Monin‐Obukhov similarity theory (MOST) are inherently violated by the sloping terrain, causing the traditional flux‐gradient relations used in numerical weather prediction models to break down. Focusing on turbulent momentum transport, we show significant flux divergence, further violating MOST assumptions, and that the traditional parameterizations fail even with local scaling for katabatic flow. In response, we propose a modified local‐MOST stability‐correction function, informed by near‐surface turbulence observations collected over two mountainous slopes with inclination angles () of and . The proposed relation includes directly, making data from both slopes collapse with unprecedented agreement. RMSE between measured fluxes and estimates from the proposed and Businger et al. (1971, https://doi.org/10.1175/1520-0469(1971)028<0181:FPRITA>2.0.CO;2) relations show significant improvement. Results can be used to inform future development of wall‐model and turbulence closures in the katabatic flow layer.

Effects of the atmospheric forcing resolution on simulated sea ice and polynyas off Adélie Land, East Antarctica

Coastal polynyas of the Southern Ocean play a central role in the ventilation of the deep ocean and affect the stability of ice shelves. It appears crucial to incorporate them into climate models, but it is unclear how to adequately simulate them. In particular, there is no consensus on the atmospheric forcing resolution needed to appropriately model the sea ice in coastal Antarctica. A high resolution might be required to represent the local winds such as katabatic winds which are key drivers of coastal polynyas. To fill in this gap, we have tested the sensitivity of sea ice and air-sea-ice interactions to the resolution of the atmospheric forcing in a high-resolution ocean–sea ice model. A set of regional atmospheric simulations at horizontal resolutions of 20, 10, and 5 km are performed with an atmospheric regional model and used to force three ocean–sea ice simulations in the Adélie Land sector, East Antarctica. Due to the better representation of topography with a refined grid, the offshore component of coastal winds becomes stronger at increased resolution. The wind intensification is particularly strong down valleys channelizing the katabatic flow, with increase in wind speed ranging between 1 and 3 m/s. Under a higher resolution forcing, polynyas open more frequently and are wider. This fosters the growth rate of sea ice in polynyas, while landfast ice and pack ice are weakly affected. In polynyas, the production of sea ice is increased by up to 30% at 5 km resolution compared to 20 km resolution. Polynyas downstream of the katabatic wind pathway are more affected than the ones driven by easterly winds, highlighting the importance of the local wind conditions. Brine rejection associated with these higher sea ice production rates affects the salinity budget of the ocean and enhances both the volume and density of the dense Shelf Water produced off Adélie Land. These results underpin the need to better account for local coastal winds and polynyas in ocean and climate models.

Characteristics of the summer 3‐D katabatic flow in a semi‐arid zone—The case of the Dead Sea

AbstractThe katabatic winds have been studied over the slopes surrounding the Dead Sea (DS, in brevity), located at altitude of 433 m below sea level focusing on the summer season when the katabatic winds are most frequent, persistent and pronounced due to the summer stable weather conditions. The study observes the katabatic wind pulses, which are intermittent, via 3‐D innovative measurement tools with high time and space resolution employing Energy Balance Stations, Radiosondes and Lidars. The nocturnal katabatic pulses were investigated employing vertical depth, wind direction/intensity, duration, number of pulses and the time intervals separating them, as well as the begin and termination times during August 2014. The average direction of the pulses depends on the nearby slopes orientations while the intensity depends on the station's elevation and its location relative to the slope. The average katabatic number of pulses, duration, time intervals and their beginning and terminating times were found to strongly depend on the other local flows. The average vertical depth of the katabatic layer from both sides of the DS, in Israel and Jordan, was found to be at 450–950 m above ground level, depending on the measurement time period as well as the tools' sensitivities employing the “KIT cube system”—an advanced integrated atmospheric observation system, which allows 3‐D accurate analysis of the detailed katabatic wind pulses over the DS. The average number of the katabatic pulses was found to be ~2.9–3.5 pulses·night−1. The average duration of each pulse was ~69–94 min and the time interval separating them ~32–44 min depending on the flows which interrupt the pulses. The starting time of first katabatic pulse in local time was 0113 LST (±0119). These findings are of great relevance for the DS evaporation as well as bio‐meteorological and pollution aspects.

Neyo: A katabatic dry wind

The objective of this study is to explain how the Neyo wind stream develops and how it can damage crops and endanger people’s lives in the Darfur Region of Sudan. Due to lack of official meteorological observations, the data was retrieved from NOAA Air Resources Laboratory (ARL) used by the Hybrid Single Particle Lagrangian Integrated Trajectory Model (HYSPLIT). Three scenarios for katabatic flow were formulated. Forces acting on air parcels were calculated for different slope angles. HYSPLIT vertical soundings revealed a reservoir of dry air over the area. Air parcels moving down slope allow dry air to flow across the thermal inversion layer. Due to the moisture deficit between the down flowing air and the humid grass surface, the leaves get dehydrated.

Katabatic Winds over Steep Slopes: Overview of a Field Experiment Designed to Investigate Slope-Normal Velocity and Near-Surface Turbulence

We describe a new field campaign over a steep, snowy \(30^{\circ }\) alpine slope, designed to investigate three recurrent issues in experimental studies of steep-slope katabatic winds. (1) Entrainment is known to be present in katabatic jets and has been estimated at the interface between the jet and the boundary layer above it. However, to our knowledge, the slope-normal velocity component has never been measured in the katabatic jet. (2) It is hard to accurately measure turbulence in the first tens of centimetres above the surface using standard sonic anemometry due to the filtering effect of the long instrument path. The present field experiment used a three-dimensional multi-hole pitot-type probe with a high sampling frequency (1250 Hz) that was positioned as close to the surface as 3 cm. It provides three-dimensional mean velocity and Reynolds stress tensor from which dissipation can be estimated, as well as spectra for the turbulent quantities. Energy spectra reveal a well-developed inertial range and capture the inertial scales and some of the dissipative scales. (3) Measuring turbulence on a mast usually provides information about mean and turbulent quantities at certain discrete heights because the sensors are sparsely located inside the jet. We present the first measurements of well-developed katabatic flows where the full wind-speed and temperature profiles acquired, from tethered balloon are available at the location of the measurement mast, which comprises three-dimensional anemometry and thermometry.

Spatio-temporal flow variations driving heat exchange processes at a mountain glacier

Abstract. Multi-scale interactions between the glacier surface, the overlying atmosphere, and the surrounding alpine terrain are highly complex and force temporally and spatially variable local glacier energy fluxes and melt rates. A comprehensive measurement campaign (Hintereisferner Experiment, HEFEX) was conducted during August 2018 with the aim to investigate spatial and temporal dynamics of the near-surface boundary layer and associated heat exchange processes close to the glacier surface during the melting season. The experimental set-up of five meteorological stations was designed to capture the spatial and temporal characteristics of the local wind system on the glacier and to quantify the contribution of horizontal heat advection from surrounding ice-free areas to the local energy flux variability at the glacier. Turbulence data suggest that temporal changes in the local wind system strongly affect the micrometeorology at the glacier surface. Persistent low-level katabatic flows during both night and daytime cause consistently low near-surface air temperatures with only small spatial variability. However, strong changes in the local thermodynamic characteristics occur when westerly flows disturbed this prevailing katabatic flow, forming across-glacier flows and facilitating warm-air advection from the surrounding ice-free areas. Such heat advection significantly increased near-surface air temperatures at the glacier, resulting in strong horizontal temperature gradients from the peripheral zones towards the centre line of the glacier. Despite generally lower near-surface wind speeds during across-glacier flow, peak horizontal heat advection from the peripheral zones towards the centre line and strong transport of turbulence from higher atmospheric layers downward resulted in enhanced turbulent heat exchange towards the glacier surface at the glacier centre line. Thus, at the centre line of the glacier, exposure to strong larger-scale westerly winds promoted heat exchange processes, potentially contributing to ice melt, while at the peripheral zones of the glacier, stronger sheltering from larger-scale flows allowed the preservation of a katabatic jet, which suppressed the efficiency of the across-glacier flow to drive heat exchange towards the glacier surface by decoupling low-level atmospheric layers from the flow aloft. A fuller explanation of the origin and structure of the across-glacier flow would require large-eddy simulations.

A comparative study of mesoscale flow-field modelling in an Eastern Alpine region using WRF and GRAMM-SCI

Recently, the mesoscale model GRAMM-SCI has been further developed to make use of the freely available global ERA5 reanalysis dataset issued by the ECMWF. In this study, first results are discussed for the federal state of Styria, which is situated in the eastern Alps of Austria. Additional simulations were made with the mesoscale model WRF, which serve as a benchmark in this work. The model runs covered one week in summer and another one in winter dominated by fair weather conditions. These were characterized by the development of complex mountain wind systems in the Alps, which play an important role for the dispersion of pollutants. Regarding the bias and the root mean square error both models perform very well in comparison with existing studies for Alpine areas and are able to capture the main features of observed surface flows such as valley-wind systems or katabatic flows at slopes. In addition, observed calm wind conditions at many stations during the winter period were reproduced by the models. However, the correct simulation of wind directions in these conditions was found to be extremely challenging. Existing model quality criteria for wind direction seem to be too strict for low-wind-speed conditions. Therefore, based on theoretical and empirical considerations, a new model evaluation benchmark for wind direction is proposed, which takes into account the random nature of horizontally meandering flows in stagnant weather situations.

Buoyancy Effects in the Turbulence Kinetic Energy Budget and Reynolds Stress Budget for a Katabatic Jet over a Steep Alpine Slope

Katabatic winds are very frequent but poorly understood or simulated over steep slopes. This study focuses on a katabatic jet above a steep alpine slope. We assess the buoyancy terms in both the turbulence kinetic energy (TKE) and the Reynolds shear-stress budget equations. We specifically focus on the contribution of the slope-normal and along-slope turbulent sensible heat fluxes to these terms. Four levels of measurements below and above the maximum wind-speed height enable analysis of the buoyancy effect along the vertical profile as follow: (i) buoyancy tends to destroy TKE, as expected in stable conditions, and the turbulent momentum flux in the inner-layer region of the jet below the maximum wind-speed height $$z_j$$ ; (ii) results also suggest buoyancy contributes to the production of TKE in the outer-layer shear region of the jet (well above $$z_j$$ ) while consumption of the turbulent momentum flux is observed in the same region; (iii) In the region around the maximum wind speed where mechanical shear production is marginal, buoyancy tends to destroy TKE and our results suggest it tends to increase the momentum flux. The present study also provides an analytical condition for the limit between production and consumption of the turbulent momentum flux due to buoyancy as a function of the slope angle, similar to the condition already proposed for TKE. We reintroduce the stress Richardson number, which is the equivalent of the flux Richardson number for the Reynolds shear-stress budget. We point out that the flux Richardson number and the stress Richardson number are complementary stability parameters for characterizing the katabatic flow apart from the region around the maximum wind-speed height.

The Orinoco Low‐Level Jet: An Investigation of Its Mechanisms of Formation Using the WRF Model

AbstractThe Orinoco low‐level jet (OLLJ) is characterized using finer horizontal, vertical, and temporal resolution than possible in previous studies via dynamical downscaling. The investigation relies on a 5‐month‐long simulation (November 2013 to March 2014) performed with the Weather Research and Forecasting (WRF) model, with initial and boundary conditions provided by the Global Forecast System (GFS) analysis. Dynamical downscaling is demonstrated to be an effective method not only to better resolve the horizontal and vertical characteristics of the OLLJ but also to determine the mechanisms leading to its formation. The OLLJ is a single stream tube over Colombia and Venezuela with wind speeds greater than 8 m s−1 and four distinctive cores of higher wind speeds varying in height under the influence of sloping terrain. It is an austral summer phenomenon that exhibits its seasonal maximum wind speed and largest spatial extent (2,100 km × 450 km) in January. The maximum diurnal mean wind speeds (13–17 m s−1) at each core location occur at different times during the night and early morning (2300–0900 LST). The momentum balance analysis in a natural coordinate system reveals that the OLLJ results from four phenomena acting together to accelerate the wind: a sea breeze penetration, katabatic flow, three expansion fans, and diurnal variation of turbulent diffusivity. The latter, in contrast to the heavily studied nocturnal low‐level jet in the U.S. Great Plains region, plays a secondary role in OLLJ acceleration. These results imply that LLJs near the equator may originate from processes other than the inertial oscillation and topographic thermal forcing.

Gravity Wave Excitation during the Coastal Transition of an Extreme Katabatic Flow in Antarctica

Abstract The offshore extent of Antarctic katabatic winds exerts a strong control on the production of sea ice and the formation of polynyas. In this study, we make use of a combination of ground-based remotely sensed and meteorological measurements at Dumont d’Urville (DDU) station, satellite images, and simulations with the Weather Research and Forecasting Model to analyze a major katabatic wind event in Adélie Land. Once well developed over the slope of the ice sheet, the katabatic flow experiences an abrupt transition near the coastal edge consisting of a sharp increase in the boundary layer depth, a sudden decrease in wind speed, and a decrease in Froude number from 3.5 to 0.3. This so-called katabatic jump manifests as a turbulent “wall” of blowing snow in which updrafts exceed 5 m s−1. The wall reaches heights of 1000 m and its horizontal extent along the coast is more than 400 km. By destabilizing the boundary layer downstream, the jump favors the trapping of a gravity wave train—with a horizontal wavelength of 10.5 km—that develops in a few hours. The trapped gravity waves exert a drag that considerably slows down the low-level outflow. Moreover, atmospheric rotors form below the first wave crests. The wind speed record measured at DDU in 2017 (58.5 m s−1) is due to the vertical advection of momentum by a rotor. A statistical analysis of observations at DDU reveals that katabatic jumps and low-level trapped gravity waves occur frequently over coastal Adélie Land. It emphasizes the important role of such phenomena in the coastal Antarctic dynamics.