Changes In Wind Direction Research Articles

East Asian monsoon manipulates the richness and taxonomic composition of airborne bacteria over China coastal area

Airborne bacteria may have significant impacts on aerosol properties, public health and ecosystem depending on their taxonomic composition and transport. This study investigated the seasonal and spatial variations of bacterial composition and richness over the east coast of China and the roles of East Asian monsoon played through synchronous sampling and 16S rRNA sequencing analysis of airborne bacteria at Huaniao island of the East China Sea (ECS) and the urban and rural sites of Shanghai. Airborne bacteria showed higher richness over the land sites than Huaniao island with the highest values found in the urban and rural springs associated with the growing plants. For the island, the maximal richness occurred in winter as the result of prevailing terrestrial winds controlled by East Asian winter monsoon. Proteobacteria, Actinobacteria and Cyanobacteria were found to be top three phyla, together accounting for 75 % of total airborne bacteria. Radiation-resistant Deinococcus, Methylobacterium belonging to Rhizobiales (related to vegetation) and Mastigocladopsis_PCC_10914 originating from marine ecosystem were indicator genera for urban, rural and island sites, respectively. The Bray-Curits dissimilarity of taxonomic composition between the island and two land sites was the lowest in winter with the representative genera over island also typically from the soil. Our results reveal that seasonal change of monsoon wind directions evidently affects the richness and taxonomic composition of airborne bacteria in China coastal area. Particularly, prevailing terrestrial winds lead to the dominance of land-derived bacteria over the coastal ECS which may have a potential impact on marine ecosystem.

Estimating the Wind Dependency of Aerosol Optical Depth at Remote Oceanic Regions

In this article, the applicability of India’s indigenously developed scatterometer, Scatsat-1 for marine aerosol characterization and wind dependency of aerosol optical depth (AOD) was investigated using 3 years of satellite data. Wind data from Scatsat-1 and AOD with its size fraction from SNPP VIIRS from 2017 to 2019 were used for the investigation. A technique has been demonstrated for identifying remote oceanic regions with mostly marine aerosol using certain criteria like distance from land, higher fraction of coarse AOD, lower variation of AOD with wind direction, and so forth. Daily wind and AOD from 2017 to 2019 were used for studying the relationship between wind speed and AOD at remote oceanic locations away from terrestrial and anthropogenic influence. Five regions of interest (ROIs) of 5° by 5° were identified in different oceanic regions for carrying out the regression analysis. A linear increase of coarse mode AOD and total AOD with an increase in wind speed was observed for all five remote locations while fine mode AOD was unrelated. The slope of the linear relation agreed with Kiliyanpilakkil and Meskhidze (2011) for intermediate wind values. The remote regions also had a lower variation of AOD with change in wind direction implying less transport of aerosol from nearby landmasses.

Heavy snowfall event over the Swiss Alps: did wind shear impact secondary ice production?

Abstract. The change in wind direction and speed with height, referred to as vertical wind shear, causes enhanced turbulence in the atmosphere. As a result, there are enhanced interactions between ice particles that break up during collisions in clouds which could cause heavy snowfall. For example, intense dual-polarization Doppler signatures in conjunction with strong vertical wind shear were observed by an X-band weather radar during a wintertime high-intensity precipitation event over the Swiss Alps. An enhancement of differential phase shift (Kdp>1∘ km−1) around −15 ∘C suggested that a large population of oblate ice particles was present in the atmosphere. Here, we show that ice–graupel collisions are a likely origin of this population, probably enhanced by turbulence. We perform sensitivity simulations that include ice–graupel collisions of a cold frontal passage to investigate whether these simulations can capture the event better and whether the vertical wind shear had an impact on the secondary ice production (SIP) rate. The simulations are conducted with the Consortium for Small-scale Modeling (COSMO), at a 1 km horizontal grid spacing in the Davos region in Switzerland. The rime-splintering simulations could not reproduce the high ice crystal number concentrations, produced too large ice particles and therefore overestimated the radar reflectivity. The collisional-breakup simulations reproduced both the measured horizontal reflectivity and the ground-based observations of hydrometeor number concentration more accurately (∼20 L−1). During 14:30–15:45 UTC the vertical wind shear strengthened by 60 % within the region favorable for SIP. Calculation of the mutual information between the SIP rate and vertical wind shear and updraft velocity suggests that the SIP rate is best predicted by the vertical wind shear rather than the updraft velocity. The ice–graupel simulations were insensitive to the parameters in the model that control the size threshold for the conversion from ice to graupel and snow to graupel.

Tropical cyclone wind hazard assessment for Donghaitang wind farm (Zhejiang Province, China): Case study

Currently, offshore and coastal wind power resources are growing rapidly around the world, especially in China. However, systematic research on the hazard assessment of wind farms under tropical cyclone conditions remains lacking. This study simulated the wind field of tropical cyclones based on a parameterized tropical cyclone wind field model, and analyzed the characteristics of historical tropical cyclones in Donghaitang wind farm (Zhejiang, China). Four extreme tropical cyclone hazard factors including the maximum wind speed (Vmax), maximum duration of wind direction change (Tmax), maximum cumulative wind direction change (Δθmax) and maximum rate of change in wind direction (ΔDmax) were proposed and examined. Then a comprehensive hazard assessment model for wind farms based on the analytic hierarchy process was established, and the risk to the Donghaitang wind farm represented by tropical cyclones during 1949–2021 was evaluated. Results showed that the number and intensity of tropical cyclones made landfall near the coast of Donghaitang wind farm gradually increased with time, which results in a gradual increase in the composite tropical cyclone risk level of the Donghaitang wind farm with time. The numbers and risk levels of tropical cyclones traveling northwestward were much larger than those traveling northward or northeastward. Moreover, the average composite risk index for tropical cyclones passing to the left of the wind farm was 14.3% higher than that for tropical cyclones passing to the right. The large values of Vmax and ΔDmax are main reasons for the high risk of the wind farm, while the other two hazard factors (Tmax, Δθmax) proposed to account for the wind turbine backup power are also of great importance in the design, selection and operation stages of offshore wind turbines. The findings of this study could provide support for hazard assessment of offshore and coastal wind farms exposed to tropical cyclones, including macro site selection of wind farms and type selection of wind turbines.

A Novel Wavelet Packet Transform-Fuzzy Pattern Recognition-Based Method for Leakage Fault Diagnosis of Sail Slewing Hydraulic System

When the wind direction changes, rotating the sail to keep it at the optimal angle of attack can effectively utilize offshore wind resources to improve the ship’s energy efficiency. The hydraulic system usually drives the slewing of the sail onboard. The functioning, as well as the safety of hydraulic system will be directly affected in case of leakage failure occurs. Therefore, the leakage fault diagnosis is essential to improve the sail-assisted effect as well as the reliability of the sail slewing system. In this paper, a novel wavelet packet transform (WPT)–fuzzy pattern recognition (FPR) based leakage fault diagnosis method is proposed. In order to analyze the different leakage fault features of the hydraulic system, a simulation model is established, and its effectiveness is verified by the hydraulic testbed. Then, the sensitive feature of flow and pressure signal for different leakage faults is extracted by a WPT-based method. On this basis, an FPR-based leakage fault diagnosis method is proposed. The diagnosis results show that the proposed method has an accuracy of 94% for nine leakage fault modes. This work contributes to realizing the greenization of the shipping industry by improving the utilization rate of offshore wind resources.

Analysis of the Effect of Fiber Orientation on Mechanical and Elastic Characteristics at Axial Stresses of GFRP Used in Wind Turbine Blades.

Due to its physical and mechanical properties, glass-fiber-reinforced polymer (GFRP) is utilized in wind turbine blades. The loads given to the blades of wind turbines, particularly those operating offshore, are relatively significant. In addition to the typical static stresses, there are also large dynamic stresses, which are mostly induced by wind-direction changes. When the maximum stresses resulting from fatigue loading change direction, the reinforcing directions of the material used to manufacture the wind turbine blades must also be considered. In this study, sandwich-reinforced GFRP materials were subjected to tensile testing in three directions. The parameters of the stress-strain curve were identified and identified based on the three orientations in which samples were cut from the original plate. Strain gauge sensors were utilized to establish the three-dimensional elasticity of a material. After a fracture was created by tensile stress, SEM images were taken to highlight the fracture's characteristics. Using finite element analyses, the stress-strain directions were determined. In accordance to the three orientations and the various reinforcements used, it was established that the wind turbine blades are operational.

Experimental and numerical evaluation of a novel dual-channel windcatcher with a rotary scoop for energy-saving technology integration

With the increasing requirements for fresh air supply in buildings after the COVID-19 pandemic and the rising energy demand from buildings, there has been an increased emphasis on passive cooling techniques such as natural ventilation. While natural ventilation devices such as windcatchers can be a sustainable and low-cost solution to remove indoor pollutants and improve indoor air quality, it is not as reliable as mechanical systems. Integration with low-energy cooling, heating or heat recovery technologies is necessary for operation in unfavourable outdoor conditions. In this research, a novel dual-channel windcatcher design consisting of a rotary wind scoop and a chimney was proposed to provide a fresh air supply irrespective of the wind direction. The dual-channel design allows for passive cooling, dehumidification and heat recovery technology integration to enhance its thermal performance. In this design, the positions of the supply and return duct are “fixed” or would not change under changing wind directions. An open wind tunnel and test room were employed to experimentally evaluate the ventilation performance of the proposed windcatcher prototype. A Computational Fluid Dynamic (CFD) model was developed and validated to further evaluate the system's ventilation performance. The results confirmed that the system could supply sufficient fresh air and exhaust stale air under changing wind directions. The ventilation rate of the rotary scoop windcatcher was higher than that of a conventional 8-sided multidirectional windcatcher of the same size.

Multi-objective optimization for simultaneously designing active control of tower vibrations and power control in wind turbines

For wind turbines operating in the full load region, stabilizing the generated power at its nominal value is a key objective. Furthermore, the control of tower vibrations is a major constraint in wind turbine structures because diverse loading sources can induce fatigue damage. These goals are often conflicting, and a trade-off solution must be found. To reduce tower vibrations, an additional damping method can be implemented by ensuring coordination between the pitch and torque control scheme. This study proposes a control scheme that balances these two objectives: power generation and tower vibration reduction. The control design is based on a collective pitch combined with two active tower damping controls: one for frontal oscillations to the wind, which generates an extra pitch component, and another for lateral displacements, which produces an additional component of the generator torque. The control parameters are tuned through multi-objective optimization and multi-criteria decision methods with FAST software along with MATLAB/Simulink. The proposed control scheme was simulated according to the extreme wind direction change in the IEC 61400–1 standard. The results show that the proposed procedure achieves a notable reduction in tower vibrations, whereas the generated power is almost unaffected. To support this conclusion, a set of performance indices and the time and frequency responses are analyzed from the simulations Comparisons with other control schemes illustrate the superior performance of the proposed methodology.

Identification of wake vortices using a simplified automobile model under parallel running and crosswind conditions

Previous studies have revealed that the change in aerodynamic drag on a test automobile under a parallel running condition is mainly because of the pressure effect, which is caused by the pressure field of the parallel running vehicle, and the effect of the change in wind direction caused by the parallel running vehicle. Apart from the drag change, which can be estimated by assuming a uniform crosswind, the change in wind direction has other effects. In this study, to clarify the other effects, the differences in the wake vortices associated with the change in drag between parallel running and uniform crosswind conditions were identified from the numerical simulation results. The surface pressure on the back excluding the pressure effect under the parallel running condition was lower on the opening side than that under the uniform crosswind condition. In addition, the wake vortices near the region of low surface pressure and their related vortices were focused. Visualizing the flows related to these vortices indicates that the non-uniformity of the flow along the upstream side and the strengthening of the entrainment at the rear end owing to the interference affect the change in the drag in the parallel running condition compared with the uniform crosswind condition. These results are useful for developing control methods to suppress the increase in drag in the parallel running condition.

Investigating the mechanisms driving the seasonal variations in surface PM<sub>2.5</sub> concentrations over East Africa with the WRF-Chem model

Most previous studies on surface PM<sub>2.5</sub> concentrations over East Africa focused on short-term in situ observations. In this study, the WRF-Chem model combined with in situ observations is used to investigate the seasonal variation in surface PM<sub>2.5</sub> concentrations over East Africa. WRF-Chem simulations are conducted from April to September 2017. Generally, the simulated AOD is consistent with satellite retrieval throughout the period, and the simulations depicted the seasonal variation in PM<sub>2.5</sub> concentrations from April to September but underestimated the concentrations throughout the period due to the uncertainties in local and regional emissions over the region. The composition analysis of surface PM<sub>2.5</sub> concentrations revealed that the dominant components were OIN and OC, accounting for 80% and 15% of the total concentrations, respectively, and drove the seasonal variation. The analysis of contributions from multiple physical and chemical processes indicated that the seasonal variation in surface PM<sub>2.5</sub> concentrations was controlled by the variation in transport processes, PBL mixing, and dry and wet deposition. The variation in PM<sub>2.5</sub> concentrations from May to July is due to wind direction changes that control the transported biomass burning aerosols from southern Africa, enhanced turbulent mixing of transported aerosols at the upper level to the surface and decreased wet deposition from decreased rainfall from May to July.

Emergent behaviour and neural dynamics in artificial agents tracking odour plumes

Tracking an odour plume to locate its source under variable wind and plume statistics is a complex task. Flying insects routinely accomplish such tracking, often over long distances, in pursuit of food or mates. Several aspects of this remarkable behaviour and its underlying neural circuitry have been studied experimentally. Here we take a complementary in silico approach to develop an integrated understanding of their behaviour and neural computations. Specifically, we train artificial recurrent neural network agents using deep reinforcement learning to locate the source of simulated odour plumes that mimic features of plumes in a turbulent flow. Interestingly, the agents’ emergent behaviours resemble those of flying insects, and the recurrent neural networks learn to compute task-relevant variables with distinct dynamic structures in population activity. Our analyses put forward a testable behavioural hypothesis for tracking plumes in changing wind direction, and we provide key intuitions for memory requirements and neural dynamics in odour plume tracking.

Examining the influence of mid-tropospheric conditions and surface wind changes on extremely large fires and fire growth days

Background Previous work by the author and others has examined weather associated with growth of exceptionally large fires (‘Fires of Unusual Size’, or FOUS), looking at three of four factors associated with critical fire weather patterns: antecedent drying, high wind and low humidity. However, the authors did not examine atmospheric stability, the fourth factor. Aims This study examined the relationships of mid-tropospheric stability and dryness used in the Haines Index, and changes in surface wind speed or direction, to growth of FOUS. Methods Weather measures were paired with daily growth measures for FOUS, and for merely ‘large’ fires paired with each FOUS. Distributions of weather and growth were compared between the two fire sets graphically and statistically to determine which, if any, weather properties correspond to greater growth on FOUS than on large fires. Key results None of the factors showed a robust difference in fire growth response between FOUS and large fires. Conclusions The examined measures, chosen for their anecdotal or assumed association with increased fire growth, showed no indication of that association. Implications Focus on wind changes and mid-tropospheric properties may be counterproductive or distracting when one is concerned about major growth events on very large fires.

Обучение биатлонистов различной спортивной квалификации знаниям правил стрельбы и умениям их применять: мнение экспертов

Knowledge of the rules of shooting and the ability to apply them allow biathletes to perform well in sports competitions. Biathlon competitions are often held under conditions of changing wind forces and direction. The wind displaces the bullet relative to the center of the target, which results in an inaccurate shot. Therefore, in order to ensure accurate shooting in wind conditions, biathletes should know and be able to apply such rules of shooting as making adjustments to the sights and aim-off shooting. The aim of this study is to determine at what point in the long-term biathlon training athletes should know and be able to apply certain shooting rules. The study examines shooting rules - shot mark; determination of the mean point of impact; amendments to the sight; aim-off shooting in wind conditions - that biathletes should learn at various stages of athletic training. The results of the research can be used in the development of biathlon sports training programmes, namely, normative and methodological parts, credit requirements for general and special shooting training. Expert interviews were used as the research method. The experts were distinguished coaches of Russia, coaches of the highest qualification in biathlon who work with athletes of national teams of the Russian Federation, with athletes of sports training centers and schools of the Olympic reserve of the constituent entities of the Russian Federation. The experts' opinions were checked for consistency by calculating the concordance coefficient and assessing the statistical reliability of the estimates. The consensus opinion of the experts on the methodology of training biathletes in shooting rules and in the application of these rules is that training should be carried out in a cumulative manner, taking into account the athletes' qualifications, and in the following sequence: biathletes should be trained shot mark starting from the youth category, determination of the mean point of impact starting from the sports category, amendments to the sight starting from the sports category; aim-off shooting starting with the “candidate in the master of sports” qualification.

Penggerombolan Desa di Jawa Barat Berdasarkan Daerah Rawan Bencana

Indonesia is one of the countries that has a large potential for natural disasters. Indonesia's position at the confluence of 4 continental plates makes the potential for earthquakes even greater. The tropical climate with 2 seasons makes changes in weather, temperature and wind direction quite extreme. These climatic conditions combined with the relatively diverse surface and rock topography conditions, these conditions can cause several bad consequences for the community such as hydrometeorological disasters such as floods, landslides, forest fires, and droughts. Particularly in West Java province, natural disasters that have occurred include: landslides, droughts, cyclones/typhoons, tidal waves, fires, volcanic eruptions, tsunamis, and other disasters. The purpose of this study was to cluster villages in the West Java region based on the level of disaster-prone in 2018. The research was carried out using K-Prototypes clustering and testing evaluation using the silhouette coefficient. The results showed that the optimal number of clusters in this study was nine clusters. These clusters can be distinguished based on the disaster category and the characteristics of the area.

FVM-RANS Modeling of Air Pollutants Dispersion and Traffic Emission in Dhaka City on a Suburb Scale

The present study aims to investigate the impact of air pollutants dispersion from traffic emission under the influence of wind velocity and direction considering the seasonal cycle in two major areas of Dhaka city: namely, Tejgaon and Gazipur. Carbon monoxide (CO) mass fraction has been considered as a representative element of traffic-exhausted pollutants, and the distribution of pollutants has been investigated in five different street geometries: namely, single regular and irregular, double regular and irregular, and finally, multiple irregular streets. After the grid independence test confirmation as well as numerical validation, a series of case studies has been presented to analyze the air pollutants dispersion, which mostly exists due to the traffic emission. The popular Reynolds-averaged Navier–Stokes (RANS) approach has been considered, and the finite volume method (FVM) has been applied by ANSYS FluentTM. The k−ϵ turbulence model has been integrated from the RANS approach. It was found that the wind velocity as well as wind direction and the fluid flow fields can play a potential role on pollution dispersion in the Dhaka city street canyons and suburbs. Inhabitants residing near the single regular streets are exposed to more traffic emission than those of single irregular streets due to fewer obstacles being created by the buildings. Double regular streets have been found to be a better solution to disperse pollutants, but city dwellers in the east region of double irregular streets are exposed to a greater concentration of pollutants due to the change of wind directions and seasonal cycles. Multiple irregular streets limit the mobility of the pollutants due to the increased number of buildings, yet the inhabitants near the multi-irregular streets are likely to experience approximately 11.25% more pollutants than other dwellers living far from the main street. The key findings of this study will provide insights on improving the urbanization plan where different geometries of streets are present and city dwellers could have less exposure to traffic-exhausted pollutants. The case studies will also provide a template layout to map pollutant exposure to identify the alarming zone and stop incessant building construction within those regions by creating real-time air quality monitoring to safeguard public safety.

Lake stability and anoxia dynamics revealed from high frequency vertical profiling in a eutrophic polymictic reservoir

ABSTRACT High-frequency water quality monitoring is rapidly growing in freshwater research and management. Sensor deployments at fixed depths in naturally formed lakes dominate the current understanding of ecosystem dynamics, with comparatively few studies focusing on reservoirs. Here we examined how environmental parameters affect the water column stability and dissolved oxygen (DO) dynamics in a North Texas eutrophic reservoir. We used an autonomous water quality monitoring profiler that recorded temperature, DO, and pH as well as wind speed, wind direction, and air temperature from an on-platform mounted weather station. Data were collected every 2 h from 25 April to 29 October 2019, with each profile spanning from the surface to 10 m depth at 0.5 m steps. Throughout most of the sampling period, the lake had no distinct thermocline, but we observed an oxycline throughout most of the monitoring period, with multiple mixing events. Near the sediments, periods of anoxia lasting hours to days were first observed in May, and July through September were chronically anoxic. In August and September, DO was frequently <2.0 mg L−1 throughout the entire water column, with 2 periods of total water column anoxia. Surface DO measurements for each 2 h interval were highly synchronous with Schmidt stability. During decreasing and low Schmidt stability or Lake Number, the oxycline destabilized in association with changes in wind direction and speed. Our results indicate that DO can be highly dynamic in polymictic reservoirs, with strong implications for carbon and nitrogen biogeochemical cycles.

A fast-response, wind angle-sensitive model for predicting mean winds in row-organized canopies

Parallel arrays of long, porous, fence-like objects (row-organized canopies) are common in agricultural and rural settings. Examples include trellised canopies like vineyards, series of windbreaks, snow fences, and some orchards. A computationally efficient model of the mean flow in such arrays has been developed and deployed in a GPU-accelerated, fast-response, mass-consistent diagnostic wind solver called Quick Environmental Simulation-Winds (QES-Winds). QES-Winds reduces computational cost by conserving mass only. The effects of forces and momentum conservation, such as drag, wakes, recirculation, and buoyancy, are added to the mean velocity field around objects and terrain using low-order models. The row-organized canopy (ROC) model imposes a wake and upwind pressure zone around each row and models the roughness adjustment near the canopy’s leading edge. Rather than solving equations of motion, the model accomplishes this using algebraic expressions, some of which are derived from scale analysis. The model output is compared and some parameters tuned to particle image velocimetry (PIV) data from a wind-tunnel experiment. Sonic anemometer data from a field experiment in a vineyard was used for validation. The model responded appropriately to changes in incident wind direction and captured transport-critical features of the mean wind with similar accuracy as other models implemented in QES. The model offers significant improvements over existing computationally inexpensive models of canopy flow that ignore the highly ordered structure of the array elements; in the field data validation, mean relative error in wind speeds was reduced by 42% and mean absolute error in wind direction in the canopy was reduced by 45% compared with a homogeneous canopy model. These results highlight the importance of resolving spatial heterogeneity in this class of canopies.

The Control of the Desert Locusts (Schistocerca Gregaria) in Somalia During the Upsurge Between 2019 and 2021

The desert "empty quarter" area of Saudi Arabia, together with Oman and, Yemen, was hit by a cyclone in May 2018, that resulted in vegetation flourishing and enabled the locust population present to increase 400-fold over the following six months. Following a second cyclone in October 2018, the population continued to increase an estimated 8000-fold. Swarms of these locusts in March 2019 flew east into southern Iran and thence to India and Pakistan. A change in wind direction enabled others to fly south into Yemen, where a civil war hindered any control operations. From Yemen, swarms moved to Ethiopia and Somalia in October 2019 and later into Kenya. In contrast to most countries, nomadic pastoralists in Somalia are nearly two-thirds of the population and occupy about two-thirds of the country. The ecology of nomadic pastoralism is an adaptation to an environment in which the availability of water and grass are critical factors. The life of pastoralists differs significantly from sedentary agriculturalists and is based on natural resource management that respects the limitations imposed on their environment, the necessity for mobility. The programme confirmed the importance of using the biopesticide to protect the environment from the use of potentially hazardous chemical insecticides and the use of the less hazardous IGR pesticide as a barrier treatment on large areas of hopper bands to reduce the number and size of swarms enabling easier targeting with the biopesticide. It also indicated that there were a number of Key challenges that had to be faced, namely: Difficulty in carrying out field evaluations during intensive control operations. Remoteness of control areas where caged experiments could not be conducted. Limited number of government officers capable of carrying out field/laboratory assessments. Lack of suitable laboratory facilities to carry out subsequent observations on field collected samples. Narrow daily window for control operations with Metarhizium acridum operations are required as the air temperature quickly rises beyond 30° C as early as 11.00 am. Sparse vegetation cover in semiarid areas affecting barrier treatment approach using aircraft

Morphology and distribution of Martian wedge dunes and their terrestrial analogs

Wedge dunes are widespread on Mars and contain important information about Mars surface processes and environmental characteristics. These dunes are wedge-shaped in plan-view, similar in scale to a barchan dune, with two slip faces intersecting at an obtuse angle and extending outward toward the main ridge downwind. And, the length of its main ridge does not exceed its width. At present, our understanding of wedge dunes and their development in nature is limited. The type, morphology, distribution and spatial composition of wedge dunes on Mars and Earth were investigated using high-resolution satellite image data. The results reveal that wedge dunes are simple in type and similar in size to barchan dunes. Martian wedge dunes are similar in shape to terrestrial wedge dunes but larger in size. The average angles between the sub-ridges of Martian and terrestrial wedge dunes are similar, at about 116°. Martian wedge dunes are mainly located in Abalos Undae, Siton Undae, and Aspledon Undae in the North Polar region, accounting for about 5% of the total area covered by dune fields. Wedge dunes are rare on Earth and can only be found on the edge of a few contiguous dune fields. These dunes indicate acute bimodal or obtuse bimodal wind regimes. Wedge dunes have distinct transitional characteristics and may be the initial stage of the development of various dune patterns. The implications of these findings are discussed, in particular the periodic changes in the regional wind direction reflected by the wedge dunes, as well as the significance of the distinctive transitional features of the wedge dunes for improving our understanding of the genesis of complex dune patterns.

The dynamic, thermal and material structures of sea-land breeze circulation at the coastal of Ningbo, East China Sea

The high-resolution dynamic, thermal and material structures of sea-land breeze circulation (SLB) were observed at the coastal of Ningbo, East China Sea from November 2019 to May 2020, with wind profile lidar, microwave radiometer and particulate matter lidar. The results show that SLB occurs more frequently in spring (22 days) than in winter (18 days). The horizontal wind speed is generally less than 8 m·s−1, and the vertical wind speed is less than 0.17 m·s−1. The maximum U wind component is 3.2 m·s−1 and 2.4 m·s−1 in spring and winter, respectively. The U wind component and its gradient show that the circulation heights of sea breeze in winter and spring are 1.3 km and 1.8 km, respectively. The heights of land breeze (LB) in winter and spring are 0.65 km and 1.1 km, respectively. The horizontal wind speed shows that the prevailing heights of sea breeze (SB) in winter and spring are 0.9 km and 1.3 km, respectively. The prevailing heights of LB in winter and spring are 0.4 km and 0.7 km, respectively. The boundary layer height during SB is about 1.1 km, and the residual layer height during LB is about 0.6 km at night. The development of SLB in winter is obviously different from that in spring, the transition process is about 2 h shorter than that in spring. With the rapid change of wind speed and direction, the turbulent kinetic energy reaches 3.5m2·s−2 on about 1.0–1.2 km in the circulation. The maximum of TKE in spring is higher than that in winter. The changes of temperature and absolute humidity are similar in winter and spring. Particulate matter was confined within the boundary layer of SLB, much lower than the circulation height. When the SB speed increases, the PM10 concentration decreases. PM10 has a zonal distribution at 400 m in spring.