Prevailing Wind Speed Research Articles

Analysis of Surface Wind Speed at Minangkabau International Airport for the period 2011-2020 using the Windrose Method

Weather information is very much needed in flight operations because it is related to the smooth running of the aircraft from takeoff to landing. Weather information required by the runway surface wind data needs as important information in the landing process. Information on the surface wind components determines Minangkabau International Airport’s direction and average surface wind speed pattern. Analysis of changes in surface winds also determines the effect of wind on flight safety, especially in the process of taking off and landing aircraft. Wind direction and speed data obtained are from synoptic observations of the Minangkabau Meteorological Station for ten years (2011-2020). Surface wind data is processed using the windrose method with the WRPLOT (Wind Rose Plots for Meteorological Data) application which shows the direction and difference in wind speed and produces a wind pattern image in the form of a windrose diagram. The results of this study note that the dominant wind blows from the Southwest (203°-248°) with a percentage of 41.97%. The west direction (248°-293°) with a percentage of 27.93%. The south (158°-203°) with a percentage of 13.81%. The prevailing wind speed is 4.08 – 7 knots, with a percentage of 54.8%. The rate of 0.97 – 4.08 knots with a percentage of 38.1%, and the speed that occurs is 7-11.08 knots with a percentage of 6.1%. The condition of the overall average wind direction and speed that occurred from 2011-2022 at Minangkabau International Airport was still in the safe category for the takeoff and landing process.

Flexible torque control for wind turbines considering frequency response under wind speed crossing region

The operational range of a wind turbine is typically divided into two regions based on wind speed: below and above the rated wind speed. The turbine switches between these two regions depending on the prevailing wind speed; however, during the transition, the generator may undergo transient shocks in torque, which can negatively impact both the mechanical load of the turbine and the reliability of the power system. This article presents a flexible torque control method for wind turbines, specifically designed to handle the transition between wind speed regions when the turbine is participating in frequency regulation. First, the anomalies in generator torque caused by traditional torque control methods during frequency response scenarios are analyzed. Next, two methods—dynamic deloading and flexible torque control—are developed to address these issues. The developed methods set transition regions based on generator speed, which helps to reduce the impact of transient changes in generator torque. Importantly, the addition of transition regions does not require additional feedback, making the controller easy to implement. The response characteristics of the proposed methods are then analyzed under different deloading factors and wind speeds using model linearization. Simulation studies are presented to verify the effectiveness of the proposed methods. Overall, this study demonstrates the potential value of flexible torque control methods for wind turbines, which can help to mitigate the negative impact of torque shocks and improve the reliability and efficiency of wind power systems.

Iceland wind farm assessment case study and development: An empirical data from wind and wind turbine

This study aimed to apply empirical data to assess wind energy production at the Búrfell site in Iceland based on the E44 turbine model. The empirical data are 5 years of recordings at the site location by the Iceland Metrological office. The wind speed data are measured at a 10 m height from 2017 to 2021. There are two E44 wind turbines test installed on the site. In the previous studies, the wind farm capacity and Levelized cost of energy (LCOE) were reported without investigating the wake loss model and its impacts on LCOE and have an estimation applied. The previous research was based on the two installed wind turbines at the site, which are located in a straight line and perpendicular to the prevailing wind speed. This study applies the Jensen-Katic model to investigate wake loss. Downwind and crosswind ten-rotor diameters and five-rotor diameters are calculated respectively as the best options. Afterward, an appropriate number of wind turbines is suggested for 80MW production. In addition, this study's optimum capacity factor (CF) is 26.08%, which was reported at 37.9% - 38.38% before. On average, the turbines produce less than 30% of their rated power, which has been reported at 38.15% in prior studies. This study presents the LCOE as equal to 0.0659 USD/kWh, which is less than 0.0703 USD/kWh in the previous studies and the LCOE reported by the 2020 LCOE European report. The obtained LCOE in this study is based on the weighted average cost of capital in the energy project by Landsvirkjun, the national power company of Iceland. The obtained result from the model used, which matched the empirical measurements, displays Iceland's best rank for wind energy LCOE metric among European countries. The proposed method provides a vision to use the wake loss model output in deep learning training to predict power production, leading to a sustainable and reliable power grid.

Experimental investigation of the tropospheric temperature gradient with Flightradar24

Sitting on the terrace on a warm summer evening and looking up at the sky, we often wonder where an airplane is going to fly. Based on the observed flight direction, we can make assumptions, but rarely check if they are really correct. The app Flightradar24 offers the possibility to confirm our assumptions. For this purpose, you just need to target the aircraft with your smartphone or tablet and then you will get augmented reality (AR) information for the flight displayed in the live image (Fig. 1): takeoff and destination, distance to the observer, airline, and type and photo of the aircraft. By tapping on the AR window, more detailed information on the flight times, the distance traveled, and the exact flight route is displayed on a map (Fig. 2). In this way, data of particular physical interest can also be retrieved, namely the aircraft’s current altitude, its speed, its position, the prevailing wind speed, and the outside temperature. This corresponds to a retrieval of measurement data, so that the app can also be used for physical quasi-experiments. At this point, the investigation of the temperature profile of the troposphere will be described. Many further quantitative analyses can be found in Ref. 2. This approach to modeling also provides an example of handling real data in the sense of data literacy.

The effect of wind and plume height reconstruction methods on the accuracy of simple plume models — a second look at the 2010 Eyjafjallajökull eruption

Real-time monitoring of volcanic ash plumes with the aim to estimate the mass eruption rate is crucial for predicting atmospheric ash concentration. Mass eruption rates are usually assessed by 0D and 1D plume models, which are fast and require only a few observational input parameters, often only the plume height. A model’s output, however, depends also on the plume height data handling strategy (sampling rate, gap reconstruction methods and statistical treatment), especially in long-term eruptions with incomplete plume height records. To represent such an eruption, we used Eyjafjallajökull 2010 to test the sensitivity of six simple and two explicitly wind-affected plume models against 22 data handling strategies. Based on photogrammetric measurements, the wind deflection of the plume was determined and used to recalibrate radar-derived height data. The resulting data was then subjected to different data handling strategies, before being used as input for the plume models. The model results were compared to the erupted mass measured on the ground, allowing us to assess the prediction accuracy of each combination of data handling strategy and model. Combinations that provide highest prediction accuracies vary, depending on data coverage, eruption intensity and fragmentation mechanism. However, for this type of moderate-to-weak eruption (VEI 3 in terms of maximum intensity), the most important factor was found to be the prevailing wind speed. When wind speeds exceed 20 m/s, most combinations of strategies and models provide predictions that underestimate the erupted mass by more than 40%. Under such conditions, the optimal choice of data handling strategy and plume model is of particular importance.

Full Operational Envelope Control of a Wind Turbine Using Model Predictive Control

This study presents a full operational envelope controller for a full nonlinear 5 MW Supergen exemplar wind turbine based on multivariable model predictive control (MPC). Below the rated wind speed, the primary objective of the controller is to maximize the energy capture. Above the rated wind speed, the controller maintains the rated power. The controller switches between control modes according to the prevailing wind speed to maintain control over the full envelope of operating regions. A linearized model is derived from a model of an exemplar 5 MW Supergen wind turbine in state-space form. The linearized model is then used to realize a feedback MPC (FB-MPC) and feedforward MPC (FF-MPC) to consider the lack and incorporation, respectively, of wind speed information. The switching strategy is tracked on the torque–speed plane. Simulations are performed at multiple wind speeds to evaluate the robustness and switching performances of the designed controllers by applying them to a full nonlinear 5 MW Matlab/SIMULINK model of the same exemplar Supergen wind turbine. Improved tracking is achieved over the full envelope with FF-MPC rather than FB-MPC. Simulation results are presented in the time and frequency domain in addition to the torque–speed plane demonstrating that the control performance is improved without an increase in the control activity (i.e., pitch action) of the turbine; that is, the controller’s gain crossover frequency remains within the acceptable range, around 1 rad/s. Note that most work presented in the literature focus on specific wind speeds only; that is, either only below rated wind speed or above rated wind speed. In contrast, the controllers reported here cover the full envelope of operation regions, making this work more practical and novel.

Ambient crosswind effect on the first integrated pilot of a floating solar chimney power plant: experimental and numerical approach

Floating Solar Chimney Power Plant (FSC) proposed by Papageorgiou is regarded as a novel type of Solar Aero-Electric Power Plants with fundamental characteristics of low cost and unaffected seismic chimney. The main disadvantage of the proposed system is the tilting of the floating chimney in windy conditions compared with a conventional reinforced concrete one. In the present research, the ambient crosswind (ACW) effect is studied on an FSC with experimental and numerical approaches. An experimental floating chimney integrated with an appropriate solar collector was designed, built, and tested under real-world conditions, and the experimental results were used for validations of the numerical analysis. Three-dimensional numerical analysis was performed to study the performance of the tilted floating solar chimney exposed to the ACW and then compared with a conventional type. Numerical results show that a tilting FSC with lower apparent height can operate more efficiently than a vertical concrete chimney in windy conditions due to eliminating adverse effects of tip vortices on updraft flow in the system. The results also show that an optimum tilting angle (OTA) exists for the specified plant and critical or prevailing wind speed, making ACW adverse effects minimum. Floating solar chimney design can be enhanced significantly based on achieving optimum tilting angle in windy conditions.

Innovative virtual computational domain based on wind rose diagrams for micrositing small wind turbines

The use of computational fluid dynamics (CFD) as design tool is widespread in engineering applications, including wind engineering. The objective of this research was to implement a new scheme for wind energy evaluation by integrating CFD studies for the optimal placement of small wind turbines in an urban environment. This approach is a cost-effective method, as compared to conventional methods, to develop feasibility studies for the implementation of wind projects. Traditional CFD wind studies are performed using the prevailing wind speed, i.e., unidirectional flows. As an innovation, in this work, CFD simulations of multidirectional flows, such as those depicted by the wind roses, are proposed. This approach makes it possible to characterize the wind resource as triacontakaihexagonal prism, named the virtual computational domain (VCD). The VCD implementation enables simulations with greater representation of and fidelity to the behavior of wind in the environment, thereby making it possible to locate wind emplacements optimally. In addition, factors such as turbulence, roughness, wind speed, and direction are considered. The VCD is found to be accurate, with balance between the efficiency of computational speeds and memory requirements. The results show that VCD improved the micrositing of wind turbines, as compared with conventional CFD studies.

МОДЕЛИРОВАНИЕ ЗАКОНОВ РАСПРЕДЕЛЕНИЙ МОЩНОСТИ ВЕТРОЭНЕРГЕТИЧЕСКИХ И СОЛНЕЧНЫХ СТАНЦИЙ

Актуальность. Мощность, выдаваемая генерирующими станциями на возобнов­ляемых источниках энергии, ветроэнергетическими и солнечными, зависит от состояния природной среды в конкретной географической точке, доминирующих скоростей ветра и уровня солнечной инсоляции. Закономерности, характеризующие скорости ветра и солнечную инсоляцию, зависят от местности, времени года и носят вероятностный характер. Это значит, что вероятностный характер имеет и мощность, выдаваемая генерирующими станциями на возобнов­ляемых источниках энергии. Риски, связанные с неточным знанием вероятностных закономерностей, описывающих эти источники, а также непредсказуемость (неопределённость) природной среды являются причинами, из-за которых системные операторы не учитывают такие станции в расчетах баланса мощности. Это, в свою очередь, не позволяет рассматривать генерирующие станции на возобновляемой энергии как полноценных участников рынка, прикрывая поток инвестиций в подобные проекты. Уточнение законов распределения вероятностей скорости ветра и солнечной инсоляции на основании статистического анализа соответствующих рядов измерений, а также уточнение на их основе законов распределения вероятностей для мощности соответствующих электростанций может оказать существенную помощь системному оператору при прогнозировании мощности, генерируемой станциями на «зеленой» энергии. Цель: построение моделей законов распределения, наилучшим образом описывающих результаты наблюдений скорости ветра и солнечной инсоляции, а также моделей законов распределения для вырабатываемой мощности ветроэнергетической и солнечной станций. Методы: методы оценки параметров законов распределения, методы проверки статистических гипотез. Результаты. Показано, что в отличие от наиболее часто используемого в этих целях закона Вейбулла, наилучшими моделями законов распределения вероятностей для рядов измерения скорости ветра и солнечной инсоляции на рассматриваемой территории являются законы семейства бета-распределений 3-го рода, а также смеси этих законов. То же самое касается описания распределения вероятностей мощности ветроэнергетической и солнечной станций. Построены модели законов распределения (по месяцам) для скорости ветра, солнечной инсоляции и мощности соответствующих станций. Показано, что на основании закона распределения скорости ветра и математических соотношений, связывающих мощность со скоростью ветра, можно строить хорошие модели для распределений вероятностей мощности ветроэнергетических станций. Построенные модели могут использоваться в качестве вспомогательного инструмента для системных операторов энергосистем для прогнозирования выдаваемой мощности.

Stability analysis for direct‐drive permanent magnet synchronous generator based wind farm integration system considering wind speed

The interaction between wind farm and power grid may cause the stability issue in the wind farm integration system. Practically, the integration system contains many collector feeders, and one feeder connects a large number of wind turbine generators. Moreover, frequency coupling effect is introduced in all parts of the wind farm system due to the asymmetrical controller of the wind turbine converter. So, it is complicated to analyse the stability of the whole integration system. This study proposes the modular admittance model for wind farm, which is easy to expand for modelling and analysis of the whole integration system. In addition, the operation condition of wind turbine generators in wind farm varies with the prevailing wind speed. The system stability may alter constantly according to the wind speed. How to effectively evaluate the system stability in the entire wind speed operation space is also a challenge. Thus, for wind farm system, this study develops an approach with two-variable admittance model and criterion based on magnitude and phase contours plot to overcome this problem. The proposed admittance model and stability analysis approach are verified by simulation.

Impact of Roughness Length on WRF Simulated Land‐Atmosphere Interactions Over a Hyper‐Arid Region

AbstractThe aerodynamic roughness length is a crucial parameter that controls surface variables including the horizontal wind, surface temperature, and heat fluxes. Despite its importance, in the Weather Research and Forecasting (WRF) model, this parameter is typically assigned a predefined value, mostly based on the dominant land‐use type. In this work, the roughness length is first estimated from eddy‐covariance measurements at Al Ain in the United Arab Emirates (UAE), a hyper‐arid region, and then ingested into WRF. The estimated roughness length is in the range 1.3–2.2 mm, one order smaller than the default value used in WRF. In line with previous studies, and from WRF model simulations during the warm and cold seasons, it is concluded that, when the roughness length is decreased by an order of magnitude, the horizontal wind speed increases by up to 1 m s−1, the surface temperature rises by up to 2.5°C, and the sensible heat flux decreases by as much as 10 W m−2. In comparison with in situ station and eddy covariance data, and when forced with the updated roughness length, WRF gives more accurate 2‐m air temperature and sensible heat flux predictions. For prevailing wind speeds >6 m s−1, the model underestimates the strength of the near‐surface wind, a tendency that can be partially corrected, typically by 1–3 m s−1, when the updated roughness length is considered. For low wind speeds (<4 m s−1), however, WRF generally overestimates the strength of the wind.

Monitoring and Modeling Roof-Level Wind Speed in a Changing City

Results of an observational campaign and model study are presented demonstrating how the wind field at roof-level in the urban area of Vienna changed due to the construction of a new building nearby. The investigation was designed with a focus on the wind energy yield of a roof-mounted small wind turbine but the findings are also relevant for air dispersion applications. Wind speed profiles above roof top are simulated with the complex fluid dynamics (CFD) model MISKAM (Mikroskaliges Klima- und Ausbreitungsmodell, microscale climate and dispersion model). The comparison to mast measurements reveals that the model underestimates the wind speeds within the first few meters above the roof, but successfully reproduces wind conditions at 10 m above the roof top (corresponding to about 0.5 times the building height). Scenario simulations with different building configurations at the adjacent property result in an increase or decrease of wind speed above roof top depending on the flow direction at the upper boundary of the urban canopy layer (UCL). The maximum increase or decrease in wind speed caused by the alternations in building structure nearby is found to be in the order of 10%. For the energy yield of a roof-mounted small wind turbine at this site, wind speed changes of this magnitude are negligible due to the generally low prevailing wind speeds of about 3.5 m s−1. Nevertheless, wind speed changes of this order could be significant for wind energy yield in urban areas with higher mean wind speeds. This effect in any case needs to be considered in siting and conducting an urban meteorological monitoring network in order to ensure the homogeneity of observed time-series and may alter the emission and dispersion of pollutants or odor at roof level.

Investigation of use small wind turbines under local wind conditions in Rabka-Zdrój

The paper presents an analysis of wind conditions for the health resort of Rabka-Zdrój. Rabka-Zdrój is a town located in southern Poland in the Rabczańska Valley surrounded by numerous hills. Archival meteorological data were obtained from the Institute of Meteorology and Water Management – National Research Institute, which until 2012 had a retention station in Rabka-Zdrój. A detailed analysis of the basic wind parameters has shown that prevailing wind speeds are in the range of 0.6-1.8 m/s. In addition, the dominant wind direction is west and southwest. For these directions, the average wind speeds in the analysed period are the highest, with the maximum recorded speed of 2.8 m/s for the south-west direction. What is more, in the health resort area, one can observe the frequent occurrence of atmospheric silence, from 16% to 45% in the analysed years. The total energy that can be obtained using a small wind turbine is low, therefore the possibility of using hybrid renewable energy sources should be considered.

Observation of abnormal coastal cold-water outbreak in the Taiwan Strait and the cold event at Penghu waters in the beginning of 2008

Abstract The Penghu archipelago locates near the Tropic of Cancer, guarding the southern entrance of the Taiwan Strait (TWS). Since the archipelago is usually surrounded by warm waters from the Kuroshio branch and the South China Sea, the marine ecosystem in the waters surrounding the archipelago is mainly tropical. However, this area may be invaded by cold water, which can cause serious ecological disasters. Among the few rare events ever documented, the cold event in early 2008 represented a typical case in this regard. In this paper, we investigated this event using in situ measurements and remote sensing data. Our analyses show that during the destructive snow and ice storm of early 2008, strong cold winds persisted for ~40 days over the TWS area, with a mean prevailing wind speed of about 15 m/s, and the water temperature in the strait dropped sharply, especially along the mainland coast. On the other side of the strait, the Penghu area experienced extremely low temperatures, leading to a cold event. Note that the time of temperature reduction in Penghu was earlier than the time of temperature reduction in the area farther north along the coast of Taiwan. This indicates that a cross-strait outbreak of the mainland coastal cold-water (MCCW) caused the cold event, and thus triggered the cold disaster. The outbreak resulted from the combined effect of favorable background hydrographic conditions, persistent strong northeasterly, strong mainland coastal current (MCC), and the interaction of current and waves with the bottom topography of the Taiwan Bank (TWB). Remotely generated coastal trapped waves (CTWs) may also play a role.

Observation-based estimates of land availability for wind power: a case study for Czechia

BackgroundThe availability of land for the installation of wind power turbines is restricted by numerous factors. Besides climatic conditions, the deployment of wind energy is limited by technical, social, economic, and environmental factors. Typically, assessments of land availability for wind power use legal and technical criteria to estimate the potential for wind power expansion. In contrast, we use observed characteristics of wind power generation sites existing in Austria and Denmark to estimate its potential expansion in Czechia. We combined data on wind turbine locations with data on land use, wind speeds, human impact on land, and nature conservation areas.ResultsOur analysis shows that the density of wind power in Austria is variable, but higher on average (4.79 MW km−2) than in Denmark (1.76 MW km−2). Austrian wind turbines have been installed in areas where the human impact on land is mostly higher than the Austrian average, while in Denmark, no difference is observed. Regarding the land use composite, the share of agricultural land on sites with wind turbines is on average much higher (86%), while the share of forest is much lower (7%) in both countries. We identified a maximum potential area in Czechia of 543 km2 with Austrian and 421 km2 with Danish characteristics. When conservatively assuming observed historical power densities, this area translates to 2295 MW and 741 MW of installed wind power capacity, respectively. These results are a magnitude of order lower than the potentials found in existing studies. In a sensitivity analysis, we have examined that the availability of potential sites depends mainly on the population density, the human impact on land, prevailing wind speeds, and the height above sea level.ConclusionsWe estimated available land area for potential wind turbine installations in Czechia using our newly developed methodology based on observed site characteristics of today’s wind power infrastructure in Austria and Denmark. Available land area indicated possible overestimation of wind power capacities proposed in the recent studies on the renewable energy transition. Hence, more rigorous consideration of land availability is required for assessments of potential wind power expansion.

An empirical test of the impact of drying events and physical disturbance on wind erosion of zooplankton egg banks in temporary ponds

Most temporary pond zooplankton species produce drought-resistant eggs that accumulate in the sediment and form an egg bank. When a pond dries and the egg bank is exposed, wind erodes eggs and wind action has been suggested as an important determinant of population demographics. While field observations suggest that egg bank erosion may be highest shortly after pond drying and physical disturbance of the sediment crust, this remains to be tested empirically. We performed a laboratory wind tunnel experiment to assess the effects of wind speed and sediment characteristics on egg pickup rates over time in a controlled environment. We used sediment samples in which an egg bank of the fairy shrimp Branchipodopsis wolfi was embedded and compared the number of eggs that blew away from dry, drying and disturbed egg banks as a function of time. Few eggs were picked up when the egg bank was dry prior to exposure, even at winds of 70 km h−1. Most eggs were eroded when the egg bank was exposed to wind before it dried out, after the last water evaporated. Likewise, physical disturbance resulted in strong erosion fluxes. Overall, our results suggest that the state of the egg bank may be more important for egg bank erosion rates than the prevailing wind speed or the wind exposure time. Also, our findings are worrying in the context of climate change since they imply that predicted increases in drying events and reduced inundation lengths may compromise egg bank persistence in temporary ponds.

A novel analytical approach for advection diffusion equation for radionuclide release from an area source

Abstract The method of the Laplace transform has been used to obtain an analytical solution of the three-dimensional steady state advection diffusion equation for the airborne radionuclide release from any nuclear installation such as the power reactor in an area source. The present treatment takes into account the removal of the pollutants through the nuclear reaction. We assume that the pollutants are emitted as a constant rate from the area source. This physical consideration is achieved by assuming that the vertical eddy diffusivity coefficient should be a constant. The prevailing wind speed is a constant in x − direction and a linear function of the vertical height z. The present model calculations are compared with the other models and the available data of the atmospheric dispersion experiments that were carried out in the nuclear power plant of Angra dos Reis (Brazil). The results show that the present treatment performs well as the analytical dispersion model and there is a good agreement between the values computed by our model and the observed data.

The Evaluation of Khorasan Razavi Range for the construction of wind power plants through multi-criteria decision making in GIS environment

The purpose of this research was to determine the suitable location of wind power plants in Khorasan Razavi province according to the climate criteria and conditions (wind speed, prevailing wind speed, pressure and temperature), geography (elevation, slope), socioeconomic factors (distance, distance from the cities and distance from the villages), environmental factors (distance from protected areas, land use and distance from the river) and geology (distance from faults). The process has been carried out in the geographical information system environment using the analytical hierarchical process. Based on the role and effect of these factors, a map of the Effective Factors was prepared in ArcGIS10.6 environments. The weight of the criteria was determined by the Analytical Hierarchy Process Analysis (AHP) method in the EC2000 software environment. The ArcGIS10.6 software was used for spatial modelling, analysis and overlaying the different layers. The final map of suitable wind power plants was carried out in four different classes (very suitable, suitable, somewhat suitable and unsuitable). The results showed that 10.37% (1239871 ha) of the area was identified as very suitable for construction, including areas in the northwest of the province (around Sabzevar) and relatively slightly in the southeast (around Taibad) and eastern area (around Sarakhs). The results also showed that the GIS, as a decision support system in building a power plant, can be used to prepare data and prioritize experts’ models and opinions regarding various factors in choosing the appropriate location for an effective wind power plant.

Influence of Synoptic Pattern and Low‐Level Wind Speed on Intensity and Diurnal Variations of Orographic Convection in Summer Over Pearl River Delta, South China

AbstractBased on 5 years of operational Doppler radar data, the influences of atmospheric synoptic patterns and low‐level prevailing wind speed on the intensity and diurnal variations of summer orographic convection occurrence frequencies over Pearl River Delta, South China, have been investigated. Results show that the inland orographic convection and rainfall generally occurs under synoptic pattern characterized with the prevailing southwesterly wind within the lower troposphere. The summer orographic convection over the mountains in northeastern Pearl River Delta is not only controlled by the orographic thermal conditions but also the dynamic forcing with the increase of wind speed. Owing to the strong windward mechanical lifting and moisture transport associated with the strong ambient onshore winds, the number of convection occurrences characterized by a dominant diurnal afternoon peak occurs much more frequently in the high‐wind speed days. While due to the weak orographic mechanical lifting and moisture supply in the low‐wind speed days, the number of convection occurrences in the afternoon decreases considerably and two comparable peaks occur in the afternoon and early morning. The nighttime peak in the low‐wind speed days is mainly attributed to the nocturnal acceleration of the low‐level southwesterly wind associated with the inertial oscillation and the corresponded enhanced windward lifting effects.

Longitudinal MLT wind structure at higher mid-latitudes as seen by meteor radars at central and Eastern Europe (13°E/49°E)

The mid-latitude mesosphere and lower thermosphere (MLT) wind speeds measured by two SKiYMET meteor radars (MRs) at Collm (51°N, 13°E) and Kazan (56°N, 49°E) during 2016–2017 were analyzed to study longitudinal wind structures. The differences between monthly mean prevailing wind speeds and tidal amplitudes were compared with the corresponding differences obtained from TIMED/TIDI satellite winds and gradient wind speeds from the AURA/MLS instrument. It is shown that the MR wind difference between the two sites is statistically significant. The difference of the horizontal prevailing winds can be explained by a superposition of the background zonal flow, which is different at the two latitudes, with stationary planetary waves of different origin. Non-migrating tides contribute significantly to the difference of the semidiurnal tidal winds between the two sites.