Concave Terrain Research Articles

Research on the response of different flight modes under concave and convex terrain by Semi-Airborne Transient Electromagnetic Method (SATEM)

With the development and utilization of various mineral resources in horizontal terrain areas gradually becoming saturated, the study of transient electromagnetic method has gradually shifted from flat terrain areas to complex fluctuating and high altitude areas. Due to the characteristics of transmitting source on the ground and receiving point in the air, the Semi-Airborne transient electromagnetic method (SATEM) has advantages such as superior working efficiency, large exploration depth and higher signal-to-noise ratio of collected signals. At present, there are few researches on the influence of the flight mode of the UAV on the collected data. In this paper, the concave terrain and convex terrain are described by using unstructured tetrahedral mesh, and the response of terrain model is calculated. Then the terrain response under different flight modes has been researched and analyzed systematically. The corresponding relative error graph is obtained and compared to summarize the law. Through simulation with different influence parameters, it is found that when the flight mode of the UAV is the same altitude, the SATEM response is less affected by the fluctuating terrain, and when the flight mode of the UAV is along the terrain, the SATEM response is more affected by the fluctuating terrain. The study of the response of UAV to the undulating terrain under different flight modes can provide a reference for the processing and interpretation of SATEM data in the undulating terrain region.

LES application to wind pressure prediction for tall building on complex terrain

This study conducted numerical simulations based on the large eddy simulation (LES) model, which employs an unstructured grid system and exhibits high performance in parallel computing, to investigate the effects of a circumferential environment, such as real terrain and surrounding buildings, on the unsteady pressure fields acting on a tall building with a rectangular section. There are three numerical examples using an irregularly shaped high-rise building (aspect ratios: height/length = 7/4 and length/width = 24/11), the same building on a complex terrain, and the same building with surrounding buildings on a complex terrain. To elucidate the statistical pressure characteristics, we focused on the mean, fluctuating, and peak values on the surfaces of the target building. The pressures for the present models were validated through a comparison with experimental data obtained under the same conditions. Subsequently, the velocity and pressure fields directly influenced by the complex local terrain and surrounding buildings were studied. A concave terrain located on the leeward side of the target building could cause a large negative pressure on the side surfaces as a result of access to the deformed separating flow. In addition, the surrounding buildings led to the movement of the stagnation point to a higher location on the windward surface and intensification of the conical vortex attached to the side surface.

Assessing the Heterogeneity and Conservation Status of the Natura 2000 Priority Forest Habitat Type Tilio–Acerion (9180*) Based on Field Mapping

Priority habitat types (HTs) within the Natura 2000 network are of the highest importance for conservation in Europe. However, they often occur in smaller areas and their conservation status is not well understood. One such HT is that of the Tilio–Acerion forests of slopes, screes and ravines (9180*). The Natura 2000 study site, Boč–Haloze–Donačka gora, in the Sub-Pannonian region of eastern Slovenia is characterized by a matrix of European beech forests and includes rather small, fragmented areas covered by Tilio–Acerion forests. The goal of this research was to examine the heterogeneity and conservation status of the selected HT through field mapping, which was performed in the summer of 2020. As the conservation of HT calls for a more detailed approach, we distinguished between the following four pre-defined habitat subtypes: (i) Acer pseudoplatanus-Ulmus glabra stands growing mostly in concave terrain, (ii) Fraxinus excelsior stands growing on slopes, (iii) Tilia sp. stands with thermophilous broadleaves occurring on ridges and slopes, (iv) Acer pseudoplatanus stands occurring on more acidic soils with an admixture of Castanea sativa. Field mapping information was complemented with the assessment of habitat subtype characteristics using remote sensing data. The results showed that habitat subtypes differed significantly in terms of area, tree species composition, forest stand characteristics, relief features and the various threats they experienced (e.g., fragmentation, tree mortality, ungulate browsing pressure). The differences between subtypes were also evident for LiDAR-derived environmental factors related to topography (i.e., terrain steepness and Topographic Position Index). This study provides a baseline for setting more realistic objectives for the conservation management of priority forest HTs. Due to the specificities of each individual habitat subtype, conservation activities should be targeted to the Natura 2000 habitat subtype level.

Observations of heavy short-term rainfall hotspots associated with warm-sector episodes over coastal South China

Coastal South China is frequently exposed to substantial rainfall within fronts-free environments during the presummer rainy season, which recurrently leads to severe disasters due particularly to the heavy short-term rainfall (HSR). The present study is motivated to identify the HSR hotspots over coastal South China through 10 notorious episodes of warm-sector heavy rainfall, with emphasis on the mesoscale features linking with the HSR hotspots. These episodes suggest complex rainfall features in the occurrence frequency and intensity. HSR mainly occurs rather over the coastal areas than the windward piedmont farther inland, and contributes over 80% to the rainfall accumulation in the regions of Yangjiang and Shanwei. Mesoscale topographies in both regions play an important role in the presence of HSR hotspots, but in different ways. Convergence perturbation line related to the inland mountains migrates southward, and enhances the preexisting convection along the coast resulted from the differential surface friction between land and ocean as well as small hills, which is the primary cause for the high frequency of HSR in coastal Yangjiang. While concave terrain drives cyclone-like perturbation, modulating the convection activity prior to the presence of HSR over Shanwei region. A cold dome induced by the previous convection dominates the mesovalley, furthering the subsequently convective enhancement at coastal zone. Collectively, both inland mountains and ocean-to-land friction regulate the mesoscale surface processes by governing the convergent wind perturbations and upscale convective growth, responsible for the HSR hotspots over the low-altitude coastal areas.

Effect of concave terrain on explosion-induced ground motion

During blasting application, ground motions are inevitably induced and have an adverse impact on the safety of surrounding structures. An artificial or natural concave terrain may cause the amplification or reduction of ground motion due to the complex interactions between the explosion-induced seismic waves and the concave terrain. It is essential to analyze the complex interactions, and to estimate the effectiveness of the ground motion amplification or reduction by the concave terrain. Field tests were firstly conducted to acquire the ground particle velocities . It is primarily found from the monitored data that the ground motions before the concave terrain are amplified, while those on the bottom and behind the concave terrain are reduced. In order to explore the mechanism, the boundary integral equation method was then adopted to obtain the motions of the whole field. By comparisons with the results from the finite element method (FEM) and the field tests, the present method was proved to be effective. The complex interactions were described in detail between those explosion-induced seismic waves and a rectangular concave terrain. The wave reflection, as well as the mode conversions among compressional, shear and Rayleigh waves , causes the amplification or reduction of ground motion. The depth of concave terrain has a negligible effect on the ground motion amplification before the concave terrain. On the contrary, ground motion intensity becomes lower on the bottom and behind deeper concave terrain.

Dynamics and emplacement mechanisms of the successive Baige landslides on the Upper Reaches of the Jinsha River, China

Two successive Baige landslides are presented in this study to investigate the dynamics and emplacement mechanisms. Field survey shows that the deposit characteristics of the first landslide are affected by the extremely fractured rock masses and the complex spatial distribution of lithologies in the source area. This deposit consists of abundant angular megablocks on the surface supported by clasts, with a relatively abundant content of rubble ranging from micrometre to decimetre sizes, and rarely well-preserved original stratigraphic sequence, diapiric structure, and convoluted structure. These sedimentological characteristics imply that a simple differential shear process, induced by compression, is distributed through the entire avalanche masses with low internal disturbance during the emplacement of the first landslide. The three-dimensional discrete element simulations show that: (i) the first landslide reaches its maximum average velocity of 41 m/s in ~28 s and eventually is bulldozed to a halt in the river within ~80 s. (ii) The second landslide is controlled by entrainment, which impedes the avalanche from further accelerating, and simultaneously imparts kinematic energy to the substrate, eventually becoming entirely mobilized and reaching a maximum average velocity of 35 m/s in ~36 s. In the dynamic process of the second landslide, the significant entrainment-induced enlarged volume (its entrainment ratio reaches 3.3) is associated with the steep concave terrain, water-bearing substrate and lower-roughness substrate basal boundary, and overloading-impact-induced erosion is proposed to be the most significant contribution to this entrainment.

Convection Initiation and Growth at the Coast of South China. Part II: Effects of the Terrain, Coastline, and Cold Pools

AbstractThrough conducting dynamic and thermodynamic diagnoses as well as a series of numerical sensitivity simulations, we investigated the effects of the terrain, coastline, and cold pools on convection initiation (CI) and its subsequent upscale convective growth (UCG) during a case of heavy rainfall along the coast of South China. CI occurred at the vertex of the coastal concave mountain geometry as a combined result of coastal convergence, orographic lifting, and mesoscale ascent driven by the terminus of a marine boundary layer jet (MBLJ). In numerical simulations with the coastline or terrain of South China removed, the coastal CI does not occur or becomes weaker as the MBLJ extends farther north, suggesting that the coastline and terrain play a role in CI. In addition, local small-scale terrain can modulate the detailed location and timing of CI and UCG. When the coastal concave terrain and coastline near the CI are artificially removed or filled by additional mountains, the orographic lifting and the local convergence along the coast correspondingly change, which strongly affects the CI and UCG. From a thermodynamic perspective, the coastal concave terrain plays the role of a local moisture “catcher,” which promotes low-level moistening by blocking water vapor coming from an upstream moist tongue over the ocean. Furthermore, new convection is continuously generated by the lifting of low-level moist southerlies at the leading edges of cold pools that tend to move southeastward because of the blocking coastal mountains. Sensitivity experiments suggest that the MCS becomes weaker and moves more slowly when cold pools are weakened through a reduction of rain-evaporation cooling.

Abundance and distribution of cavity trees and the effect of topography on cavity presence in a tropical rainforest, southwestern China

Cavity trees play a crucial role in maintaining biodiversity in forest ecosystems as they host numerous birds, mammals, and other cavity-dependent organisms. However, studies on the abundance and distribution of cavity trees in tropical forests are much less common than those in temperate forests. Also, how tree characteristics and topographic variables affect cavity presence is less clear in tropical forests. We surveyed 27 745 living trees from 386 species using ground-based observations in a tropical rainforest in southwestern China. The density of cavity trees was 86.3 trees·ha–1, which dramatically exceeded that in temperate forests. The number of cavity trees showed a left-skewed distribution with a peak at 10–20 cm diameter at breast height (DBH). The probability of cavity presence in a tree increased with DBH, although the patterns varied across species and crown positions. Moreover, cavity presence, which is influenced by topography in this tropical forest, decreased from valleys (concave terrain and low elevation) to ridges (convex terrain and high elevation). The results prove for the first time that topography is a good predictor of cavity presence, in addition to tree DBH. Our results demonstrate that the patterns determined for cavity presence in tropical forests of other regions also apply to Asian tropical forests. This study provides guidance on predicting the occurrence of cavity trees in the tropics.

Understanding Mn-nodule distribution and evaluation of related deep-sea mining impacts using AUV-based hydroacoustic and optical data

Abstract. In this study, ship- and autonomous underwater vehicle (AUV)-based multibeam data from the German ferromanganese-nodule (Mn-nodule) license area in the Clarion–Clipperton Zone (CCZ; eastern Pacific) are linked to ground-truth data from optical imaging. Photographs obtained by an AUV enable semi-quantitative assessments of nodule coverage at a spatial resolution in the range of meters. Together with high-resolution AUV bathymetry, this revealed a correlation of small-scale terrain variations (< 5 m horizontally, < 1 m vertically) with nodule coverage. In the presented data set, increased nodule coverage could be correlated with slopes > 1.8∘ and concave terrain. On a more regional scale, factors such as the geological setting (existence of horst and graben structures, sediment thickness, outcropping basement) and influence of bottom currents seem to play an essential role for the spatial variation of nodule coverage and the related hard substrate habitat. AUV imagery was also successfully employed to map the distribution of resettled sediment following a disturbance and sediment cloud generation during a sampling deployment of an epibenthic sledge. Data from before and after the “disturbance” allow a direct assessment of the impact. Automated image processing analyzed the nodule coverage at the seafloor, revealing nodule blanketing by resettling of suspended sediment within 16 h after the disturbance. The visually detectable impact was spatially limited to a maximum of 100 m distance from the disturbance track, downstream of the bottom water current. A correlation with high-resolution AUV bathymetry reveals that the blanketing pattern varies in extent by tens of meters, strictly following the bathymetry, even in areas of only slightly undulating seafloor (<1 m vertical change). These results highlight the importance of detailed terrain knowledge when engaging in resource assessment studies for nodule abundance estimates and defining mineable areas. At the same time, it shows the importance of high-resolution mapping for detailed benthic habitat studies that show a heterogeneity at scales of 10 to 100 m. Terrain knowledge is also needed to determine the scale of the impact by seafloor sediment blanketing during mining operations.

Predicting Spatial Risk of Wolf-Cattle Encounters on Rugged and Extensive Grazing Lands

Author(s): Clark, Patrick E.; Chigbrow, Joe; Johnson, Douglas E.; Williams, John; Larson, Larry L.; Roland, Tyanne | Abstract: Cattle grazing lands in the mountainous western United States are rugged, complex, and extensive. Terrain, vegetation, and other landscape features vary greatly across space. Risk of wolf-cattle encounters and potential for depredation loss certainly differ spatially as consequence of this variability. Yet, our understanding of this spatial risk is quite poor and this knowledge gap severely hampers our abilities to manage wolf-livestock interactions and mitigate conflicts. During 2009-2011, a research study was conducted at four study areas (USFS cattle grazing allotments) in western Idaho to evaluate and predict risk of wolf-cattle encounters. Each year, a random sample of 10 lactating beef cows from each study area was instrumented with GPS collars that logged positions at 5-minute intervals throughout the summer grazing season. Cattle resource selection was modeled using these GPS data and negative-binomial regression. An existing model was used to classify habitats within the study areas in terms of probability of use by wolves as rendezvous sites. Efficacy of this model was confirmed using scat, telemetry, and rendezvous site data. Spatial overlaps in the predicted selectivity of wolves and cattle were assessed and study area landscapes were then classified into five encounter-risk classes (very low to very high). Concurrent wolf and cattle GPS tracking data were used to document wolf-cattle encounters and thus evaluate the accuracy of this classification. About 94% of observed wolf-cattle encounters occurred within either the high or highest encounter-risk classes. Areas classified to the highest risk class were located on smooth, relatively flat slopes in concave terrain (e.g., stream terrace meadows) but not all were associated with surface water. Having this predictive understanding of where wolf-cattle encounters are most likely to occur will allow livestock producers and wildlife managers to more effectively apply resources, husbandry practices, and mitigation techniques to reduce conflict.

Definition of sampling units begets conclusions in ecology: the case of habitats for plant communities.

In ecology, expert knowledge on habitat characteristics is often used to define sampling units such as study sites. Ecologists are especially prone to such approaches when prior sampling frames are not accessible. Here we ask to what extent can different approaches to the definition of sampling units influence the conclusions that are drawn from an ecological study? We do this by comparing a formal versus a subjective definition of sampling units within a study design which is based on well-articulated objectives and proper methodology. Both approaches are applied to tundra plant communities in mesic and snowbed habitats. For the formal approach, sampling units were first defined for each habitat in concave terrain of suitable slope using GIS. In the field, these units were only accepted as the targeted habitats if additional criteria for vegetation cover were fulfilled. For the subjective approach, sampling units were defined visually in the field, based on typical plant communities of mesic and snowbed habitats. For each approach, we collected information about plant community characteristics within a total of 11 mesic and seven snowbed units distributed between two herding districts of contrasting reindeer density. Results from the two approaches differed significantly in several plant community characteristics in both mesic and snowbed habitats. Furthermore, differences between the two approaches were not consistent because their magnitude and direction differed both between the two habitats and the two reindeer herding districts. Consequently, we could draw different conclusions on how plant diversity and relative abundance of functional groups are differentiated between the two habitats depending on the approach used. We therefore challenge ecologists to formalize the expert knowledge applied to define sampling units through a set of well-articulated rules, rather than applying it subjectively. We see this as instrumental for progress in ecology as only rules based on expert knowledge are transparent and lead to results reproducible by other ecologists.

3-D movement mapping of the alpine glacier in Qinghai-Tibetan Plateau by integrating D-InSAR, MAI and Offset-Tracking: Case study of the Dongkemadi Glacier

Three-dimensional (3-D) movements of the Dongkemadi Glacier in the Qinghai-Tibetan Plateau over 2007–2010 are fully determined by using L-band Advanced Land Observing Satellite (ALOS) Phased Array type L-band Synthetic Aperture Radar (PALSAR) ascending and C-band Environmental Satellite (ENVISAT) Advanced Synthetic Aperture Radar (ASAR) descending acquisitions. In order to yield an optimal 3-D solution, a variance component estimation (VCE) algorithm is applied to weigh the D-InSAR and MAI measurements derived from PALSAR data and the Offset-Tracking measurements from ASAR data under the scheme of weighted least squares adjustment. By exploiting the InSAR measurements themselves to determine the weights iteratively, the presented approach results in an accuracy of centimeter to decimeter per year for all the three velocity vectors. The horizontal component shows that the four main tributary streams in the Dongkemadi Glacier are all flowing from the central area of the glacier to its surroundings, along the steepest slope descent direction and with a rate up to about 5m/yr. The glacier thickening or thinning is resolved from the vertical component by subtracting the down-slope movement. A number of interesting accumulation and ablation areas are also detected, with vertical variations of 1–2m/yr, as a result of the horizontal glacier movement or the existence of concave terrain. This can be used as a good indication of the ice dynamics and the location of the subglacial water in the alpine glacier.

Terrain forms and spatial variability of soil properties in an area cultivatedwith citrus

The technique of precision agriculture and soil-landscape allows delimiting areas for localized management, allowing a localized application of agricultural inputs and thereby may contribute to preservation of natural resources. Therefore, the objective of this work was to characterize the spatial variability of chemical properties and clay content in the context of soil-landscape relationship in a Latosol (Oxisol) under cultivation of citrus. Soil samples were collected at a depth of 0.0-0.2 m in an area of 83.5 ha planted with citrus, as a 50-m intervals grid, with 129 points in concave terrain and 206 points in flat terrain, totaling 335 points. Values for the variables that express the chemical characteristics and clay content of soil properties were analyzed with descriptive statistics and geostatistical modeling of semivariograms for making maps of kriging. The values of range and kriging maps indicated higher variability in the shape of concave topography (top segment) compared with the shape of flat topography (slope and hillside segments below). The identification of different forms of terrain proved to be efficient in understanding the spatial variability of chemical properties and clay content of soil under cultivation of citrus.

19LBA HPV-associated p16-expression and response to radiobiological modifications of radiotherapy in head and neck cancer: results from the randomised DAHANCA trials

Two successive Baige landslides are presented in this study to investigate the dynamics and emplacement mechanisms. Field survey shows that the deposit characteristics of the first landslide are affected by the extremely fractured rock masses and the complex spatial distribution of lithologies in the source area. This deposit consists of abundant angular megablocks on the surface supported by clasts, with a relatively abundant content of rubble ranging from micrometre to decimetre sizes, and rarely well-preserved original stratigraphic sequence, diapiric structure, and convoluted structure. These sedimentological characteristics imply that a simple differential shear process, induced by compression, is distributed through the entire avalanche masses with low internal disturbance during the emplacement of the first landslide. The three-dimensional discrete element simulations show that: (i) the first landslide reaches its maximum average velocity of 41 m/s in ~28 s and eventually is bulldozed to a halt in the river within ~80 s. (ii) The second landslide is controlled by entrainment, which impedes the avalanche from further accelerating, and simultaneously imparts kinematic energy to the substrate, eventually becoming entirely mobilized and reaching a maximum average velocity of 35 m/s in ~36 s. In the dynamic process of the second landslide, the significant entrainment-induced enlarged volume (its entrainment ratio reaches 3.3) is associated with the steep concave terrain, water-bearing substrate and lower-roughness substrate basal boundary, and overloading-impact-induced erosion is proposed to be the most significant contribution to this entrainment.

Relief shapes and precipitation on the south side of the Alps Part II: Heavy-rain cases during MAP and sensitivity to topography modifications

There are two distinct climatological precipitation maxima on the south side of the Alps and an area of reduced precipitation between them. We tested the impact of meso-beta details of topography on precipitation by simulating 15 cases of heavy precipitation during the Mesoscale Alpine Programme (MAP) special observing period with the MM5 model. Data show that the selected 15 cases are climatologically representative since the precipitation amount for these 15 days shows two climatological precipitation maxima and a drier region between them. We used different idealized topographies of the Alps, as well as the real topography and modifications of the latter at meso-beta scale. The simulations with different idealized topographies show clear influence of supra-regional (scale of some 100 km) convergence upon correct location of the southern Alpine maxima and that the concave terrain shapes at this scale determine the location of the precipitation maxima. The simulations with modified real topography show that (i) in the case of removal of the southwards bulging Trentino Mts. the precipitation maximum concentrates at this modified region; (ii) with removal of the Dinaric Alps the precipitation on the eastern part of the Alps is significantly reduced.

Three-dimensional Nonhydrostatic Numerical Simulation for the PBL of Open-pit Mine

A high-resolution,nonhydrostatic, three-dimensionalplanetary boundary-layer (PBL) model wasestablished considering the characteristic features of an open-pit mine, which is only (2 km × 2 km) wide and more than 100 m deep. The (E-∈) closure schemes was used in the model. Physical processes such as shortwave radiation of the sun and its uneven distribution on the ground,longwave radiation of earth-atmosphere systems, sensible heat and latent heat and heat flowing into the substrate of the earth, were involved in the model. Using this model PBL structures over this kind of microscale concave terrain (an open-pit mine) were fully studied and numerical experiments on the effects of parameters including H, depth of the mine, α, slope angle of the mine, u, incidcent airflow velocity, and P, indicating shear of the initial velocity, on the PBL were also made. Finally, the evolution process of the PBL was simulated. The results showed that a characteristic and major feature of the PBL is re-circulation, which is greatly influenced by the topography of the mine and the meteorolgical conditions therein. Thermal and mechanical forcing play different but important roles in the evolution process of the PBL.

The numerical simulation on the PBL structure and its evolution over small-scale concave terrain

A high-resolution, nonhydrostatic, three-dimensional diagnostic PBL model over small-scale concave terrain was established in this paper. A two-dimensional prognostic model was developed based on the diagnostic model. The hydrostatic approximation was abandoned and the simple energy (E – e) closure scheme was used in both models. Using the two models, characteristics of PBL structure and its evolution were fully studied. The main characteristic of the PBL is the circulation, and it fairly affects the distribution of the pollutant in the pit.

Frost hazard assessment from local weather and terrain data

Minimum air temperatures were measured at 31 sites in a 170 km 2 region of undulating grazing land on 30 winter nights in 1982. The change in minimum temperature with elevation (d T/d z) could be predicted from mean night-time windspeed, total night-time all-wave radiation loss and the minimum air temperature at an exposed hill site. A multiple regression model is used which includes an interaction term for windspeed and net radiation. Excellent agreement between d T/d z values obtained with the 31 thermometer sites and a seven-site Ross recorder network was observed for 24 nights. The above regression model was then further developed with data for seven Ross recorder sites available for 86 days representing a much wider range of weather conditions. The improved model explains some 75% of the variation in minimum air temperature. Sites in convex terrain were consistently warmer and sites in concave terrain were consistently colder than predicted with the above model. A second relationship was therefore developed which predicts mean departures from the above regressions for individual sites from two simple terrain parameters: slope and catchment area. This regression explains 76% of the variation in the residual values. The combined weather—terrain model has been tested successfully with Ross recorder data from eight sites in 1980 ( n = 246), 10 sites in 1981 ( n = 189) and seven sites in 1982 ( n = 602).

Typical low-tropospheric pressure distributions over and around the Plateau of Tibet

The Laplacian of terrain height over Central Asia correlates well with planetary boundary layer (PBL) pressure perturbations during summer. Low-pressure perturbations favor concave terrain forms, high pressure perturbations appear to go with convex terrain forms. Some of these PBL perturbations have been found to trigger severe weather over Tibet and over eastern China. This observation leads to the speculation that large-scale orographic features may cause the establishment of “severe weather alleys” downwind.

Anticyclonic Activity over South Europe and its Relationship to Orography

This is a study of anticyclonic activity over a past of southern Europe in which several anticyclogenetic areas have been noted. There is also a relationship between cyclonic and anticyclonic activity in this region. We also indicate that there is a very close association between the number of anticyclones and cyclones generated over a given “point” (a square 1° longitude by 1° latitude) and the Laplacian Δz0 = ∂2z0/∂x2 + ∂2z0/∂y2 up to these points. If the height of the earth's orography is denoted by z0 = z0(x,y), then the regions with concave terrain forms are such that Δz0 > 0, and vice versa. The above-mentioned close relationship between the number of anticyclones and cyclones generated and Δz0 is due to vertical motions in the real atmosphere, motions which appear because of the concavity and convexity of the terrain, i.e., because of Δz0. The conclusion drawn is that the vertical velocity component WΔz0, which arises because of Δz0, depends only on the magnitude of the wind velocity |V| but not on its direction, i.e., WΔz00 The value of Δz0 is one of the causes, possibly the most important one, determining whether a given area is cyclogenetic or anticyclogenetic.