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This study investigates the characteristics of wind speed in two synoptic weather stations in Niger. Hence, three hourly wind data including wind speed and direction from 2009 to 2019 were used. Prior to the analysis, the dataset was pre‐processed to remove corrupted and irrelevant data. Statistical analysis was conducted on the dataset to understand the variability of the wind speed and wind direction at the two synoptic stations. The results showed that the highest prevailing wind is recorded in the Agadez region with average wind speeds ranging from [3; 6] m/s and [6; 10] m/s at 10 m altitude. The dominant directions are the East from September to May, then the West from June to August. At the Tahoua station, the prevailing winds have average speeds also belonging to [3; 6] m/s and [6; 10] m/s at 10 m altitude, but the dominant directions are East and East‐North‐East from October to April, then West and South‐West from May to September. These findings are useful for the effective planning of a wind energy project in Niger as they provide useful insight regarding the wind characteristics in two windy regions in Niger. [ABSTRACT FROM AUTHOR]

The Editors and Staff of Earth and Space Science thank the reviewers whose selfless work has significantly contributed to the publication process of papers highlighting the best research in geophysics, planetary, and space science in 2023. Peer‐reviewing is a demanding and thankless job. It is however an essential component of the scientific process, requiring the highest standards of integrity and rigor. Reviewers check data and procedures and test reproducibility of methods and results; they share their expertise to verify that the interpretations and conclusions of a paper are consistent with assumptions and existing knowledge. Without this essential work it would not be possible to trust in the scientific process. Publication of papers in a multidisciplinary journal such as Earth and Space Science, that highlights methods, instruments, data and algorithms, relies directly on the expertise of its reviewers to verify and vouch for the quality of the papers that are published. We are indebted to all our reviewers and are delighted to acknowledge them publicly in this Editorial. Plain Language Summary: The Editors and Staff of Earth and Space Science acknowledge the importance of hundreds of peer reviewers who contributed to the scientific rigor of the papers published in the journal. The Editors wish to publicly recognize the 926 reviewers who gave selflessly of their time and expertise in 2023. Key Points: The editors thank the 2023 peer reviewers [ABSTRACT FROM AUTHOR]

Townsend's hypothesis states that turbulence near a wall can be divided into an active part that transports momentum, and an inactive part that does not, and that these two kinds of turbulence do not interact. Active turbulence is generated by wind shear and has properties that scale on local parameters of the flow, while inactive turbulence is the product of energetic processes remote from the surface and scales on outer-layer parameters. Both kinds of motion can be observed in the atmospheric surface layer, so Monin–Obukhov similarity theory, which is framed in terms of local parameters only, can apply only to active motions. If Townsend's hypothesis were wrong, so that active and inactive motions do interact in some significant way, then transport processes near the ground would be sensitive to outer-layer parameters such as boundary-layer depth, and Monin–Obukhov theory would fail. Experimental results have shown that heat transport near the ground does depend on processes in the outer layer. We propose a mechanism for this whereby inactive motions initiate active, coherent ejection/sweep structures that carry much of the momentum and heat. We give evidence that the inactive motions take the form of streak patterns of faster and slower air, and argue that these are induced by the pressure effects of large eddies passing overhead. The streak pattern includes regions where faster streams of air overtake and engulf slower-moving streaks. Transverse vortices form across the spines of the streaks at these places and some of them develop into horseshoe vortices. These horseshoe vortices grow rapidly and are rotated forward in the sheared flow so they soon contact the ground, squirting the air confined between the legs of the horseshoe vortex outwards as a forceful ejection. This model is consistent with a wide range of results from the field and laboratory experiments. Heat transport is significantly affected, so undermining the dimensional assumptions of Monin–Obukhov similarity theory. [ABSTRACT FROM AUTHOR]

In this paper, time extension methods, originally designed for clear-sky land surface conditions, are used to estimate high-spatial resolution surface daily longwave (LW) radiation from the instantaneous Global LAnd Surface Satellite (GLASS) longwave radiation product. The performance of four time methods were first tested by using ground based flux measurements that were collected from 141 global sites. Combined with the accuracy of daily LW radiation estimated from the instantaneous GLASS LW radiation, the linear sine interpolation method performs better than the other methods and was employed to estimate the daily LW radiation as follows: The bias/Root Mean Square Error (RMSE) of the linear sine interpolation method were −6.30/15.10 W/m2 for the daily longwave upward radiation (LWUP), −1.65/27.63 W/m2 for the daily longwave downward radiation (LWDN), and 4.69/26.42 W/m2 for the daily net longwave radiation (LWNR). We found that the lengths of the diurnal cycle of LW radiation are longer than the durations between sunrise and sunset and we proposed increasing the day length by 1.5 h. The accuracies of daily LW radiation were improved after adjusting the day length. The bias/RMSE were −4.15/13.74 W/m2 for the daily LWUP, −1.3/27.52 W/m2 for the daily LWDN, and 2.85/25.91 W/m2 for the daily LWNR. We are producing long-term surface daily LW radiation values from the GLASS LW radiation product. [ABSTRACT FROM AUTHOR]

Studying the microclimate of plant canopies has long motivated scientists in various research fields such as agronomy, ecology or silviculture, and almost a century has passed since the first measurements of wind speed in a forest stand were published in the scientific literature. The behaviour of wind in canopies is an essential component of their microclimate, which largely conditions the rate of exchange of heat, water vapour, and other gases and particles of interest with the atmosphere. This review examines the evolution of our understanding of turbulent flow in plant canopies, focussing on the period that covers the last fifty years (1970–2020). We first describe how our knowledge and ideas have evolved since canopy flow became a topic of interest, and show how the 1970s was a pivotal decade in this field. Until then, canopy turbulence was considered to result from the superposition of standard surface-layer turbulence and small-scale turbulence generated in the wakes of plant elements. However, it was progressively found that the flow in plant canopies is dominated by large coherent structures, giving canopy turbulence unique characteristics. We thus describe the particular nature and structure of canopy flows, based on experimental observations accumulated over several decades. We show how canopy turbulence was reconsidered on the basis of a now widely-accepted analogy with a plane mixing layer, and we examine the significance of a key parameter, the "canopy-shear length scale". Investigating the effects of canopy density and atmospheric stability, we then discuss the extent of the mixing-layer analogy and the limits of our current understanding of canopy turbulence. Finally, we review the modelling tools used in this field and show how their development has evolved to date to meet our needs. In conclusion, we present a historical summary of the evolution of this research field and suggest future directions. [ABSTRACT FROM AUTHOR]

The focus of this paper is on aligned fiber-reinforced composites, where fiber centers were randomly distributed in their cross-sections. The volume fractions of fibers were V f = 3 0 % and V f = 5 0 %. Samples were built with the help of the simulated annealing technique according to the chosen Radial Distribution Functions (RDFs). For each sample, the fields of local stresses and heat fluxes were simulated by finite element method. Then, homogenization by volume averaging was performed in order to investigate both the effective mechanical and thermal properties. The effect of RDF shape on elastic and thermal properties was quantified along with the influence of the probability of near neighbors of fibers on the physical properties. The more the fiber distributions deviate from Poisson's Law, the higher the results compared to the lower bound of Hashin–Shtrikman. [ABSTRACT FROM AUTHOR]

Copyright of Revue Archéologique de Picardie is the property of Revue Archeologique de Picardie and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Landscape discontinuities such as forest edges play an important role in determining the characteristics of the atmospheric flow by generating increased turbulence and triggering the formation of coherent tree-scale structures. In a fragmented landscape, consisting of surfaces of different heights and roughness, the multiplicity of edges may lead to complex patterns of flow and turbulence that are potentially difficult to predict. Here, we investigate the effects of different levels of forest fragmentation on the airflow. Five gap spacings (of length approximately 5 h, 10 h, 15 h, 20 h, 30 h, where h is the canopy height) between forest blocks of length 8.7 h, as well as a reference case consisting of a continuous forest after a single edge, were investigated in a wind tunnel. The results reveal a consistent pattern downstream from the first edge of each simulated case, with the streamwise velocity component at tree top increasing and turbulent kinetic energy decreasing as gap size increases, but with overshoots in shear stress and turbulent kinetic energy observed at the forest edges. As the gap spacing increases, the flow appears to change monotonically from a flow over a single edge to a flow over isolated forest blocks. The apparent roughness of the different fragmented configurations also decreases with increasing gap size. No overall enhancement of turbulence is observed at any particular level of fragmentation. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Forest Research is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Wind-flow dynamics has been extensively studied over horizontally uniform canopies, but agricultural plantations structured in rows such as vineyards have received less attention. Here, the wind flow over a vineyard is studied in neutral stratification from both large-eddy simulation (LES) and in situ measurements. The impact of row structure on the wind dynamics is investigated over a range of wind directions from cross-row to down-row, and a typical range of row aspect ratio (row separation/height ratio). It is shown that the mean flow over a vineyard is similar to that observed in uniform canopies, especially for wind directions from cross-row to diagonal. For down-row winds, the mean flow exhibits noticeable spatial variability across each elementary row-gap pattern, as the wind is channeled in the inter-row. This spatial variability increases with the aspect ratio. With down-row winds the turbulent structures are also more intermittent and generate larger turbulent kinetic energy and momentum flux. The displacement height and roughness length of the vineyard vary with the aspect ratio in a way similar to their variation with canopy density in uniform canopies. Both parameters take smaller values in down-row wind flow, for which the canopy appears more open. The analysis of velocity spectra and autocorrelation functions shows that vineyard canopies share similar features to uniform canopies in terms of turbulent coherent structures, with only minor changes with wind direction. [ABSTRACT FROM AUTHOR]

A simple tree swaying model, valid for windstorm conditions, has been developed for the purpose of simulating the effect of strong wind on the vulnerability of heterogeneous forest canopies. In this model the tree is represented as a flexible cantilever beam whose motion, induced by turbulent winds, is solved through a modal analysis. The geometric nonlinearities related to the tree curvature are accounted for through the formulation of the wind drag force. Furthermore, a breakage condition is considered at very large deflections. A variety of case studies is used to evaluate the present model. As compared to field data collected on three different tree species, and to the outputs of mechanistic models of wind damage, it appears to be able to predict accurately large tree deflections as well as tree breakage, using wind velocity at tree top as a forcing function. The instantaneous response of the modelled tree to a turbulent wind load shows very good agreement with a more complex tree model. The simplicity of the present model and its low computational time make it well adapted to future use in large-eddy simulation airflow models, aimed at simulating the complete interaction between turbulent wind fields and tree motion in fragmented forests. [ABSTRACT FROM AUTHOR]

With the increasing penetration of renewable energy generation into the transmission and distribution networks, the problem of managing growing volumes of variable generation needs to be addressed. Energy storage has the potential to help address this problemby storing commercially useful amounts of energy to be discharged as electricity when required. However, energy storage does not have a universally accepted legal definition because it is provided by somany different technologies, operates on different scales and provides a range of functions. This article argues that the lack of a consistent legal definition poses a challenge for legislators who are trying to pick "winners" to receive legislative support and subsidies or other financial incentives. The failure to support one emerging storage technology, while giving preference to another, will almost inevitably have a "chilling" effect on the research and development and any subsequent commercialisation of that technology. This article further argues that the choice of legal definition also affects the ability of multifunctional energy storage technologies to fully participate in an unbundled electricity market structure. [ABSTRACT FROM AUTHOR]

Forested landscapes often exhibit large spatial variability in vertical and horizontal foliage distributions. This variability may affect canopy-atmosphere exchanges through its action on the development of turbulent structures. Here we investigate in neutral stratification the turbulent structures encountered in a maritime pine forest characterized by a high, dense foliated layer associated with a deep and sparse trunk space. Both stand and edge regions are considered. In situ measurements and the results of large-eddy simulations are used and analyzed together. In stand conditions, far from the edge, canopy-top structures appear strongly damped by the dense crown layer. Turbulent wind fluctuations within the trunk space, where the momentum flux vanishes, are closely related to these canopy-top structures through pressure diffusion. Consequently, autocorrelation and spectral analyses are not quite appropriate to characterize the vertical scale of coherent structures in this type of canopy, as pressure diffusion enhances the actual scale of structures. At frequencies higher than those associated with canopy-top structures, wind fluctuations related to wake structures developing behind tree stems are observed within the trunk space. They manifest themselves in wind velocity spectra as secondary peaks in the inertial subrange region, confirming the hypothesis of spectral short-cuts in vegetation canopies. In the edge region specific turbulent structures develop just below the crown layer, in addition to canopy-top structures. They are generated by the wind shear induced by the sub-canopy wind jet that forms at the edge. These structures provide a momentum exchange mechanism similar to that observed at the canopy top but in the opposite direction and with a lower magnitude. They may develop as in plane mixing-layer flows, with some perturbations induced by canopy-top structures. Wake structures are also observed within the trunk space in the edge region. [ABSTRACT FROM AUTHOR]

Forest canopies are important components of the terrestrial carbon budget, which has motivated a worldwide effort, FLUXNET, to measure CO2 exchange between forests and the atmosphere. These measurements are difficult to interpret and to scale up to estimate exchange across a landscape. Here we review the effects of complex terrain on the mean flow, turbulence, and scalar exchange in canopy flows, as exemplified by adjustment to forest edges and hills, including the effects of stable stratification. We focus on the fundamental fluid mechanics, in which developments in theory, measurements, and modeling, particularly through large-eddy simulation, are identifying important processes and providing scaling arguments. These developments set the stage for the development of predictive models that can be used in combination with measurements to estimate exchange at the landscape scale. [ABSTRACT FROM AUTHOR]

As forest edges are often associated with wind damage, it may be of interest to modify the edge region in order to reduce wind- induced risks. To this purpose, this study investigates tree vulnerability to wind load downwind from leading edges designed with various treatments: sharp, tapered, sparse, dense, tall and small edges. Using a large- eddy simulation flow model, instantaneous wind and turbulence fields are simulated on either side of each edge. These fields are then used to compute mean and extreme tree bending moments as well as their ratio, the gust factor. The behaviour of these variables downwind from the edge agrees well with previous wind tunnel measurements. The gust factor increases at some distance behind the edge, due to the development of coherent eddy structures generated at the canopy-air interface. Unlike wind gusts in the vicinity of the edge, these structures penetrate deep within the canopy through sweep motions. Tree vulnerability is slightly reduced downwind from tapered, sparse and small edges and enhanced downwind from dense ones. Behind tall edges, the gust factor is reduced in the edge region but enhanced further downstream due to the interaction of the canopy with the wake of the edge treatment. [ABSTRACT FROM AUTHOR]

This study presents a predictive dynamic model developed to analyse the mechanical response of trees submitted to a turbulent airflow. This finite-element model integrates a three-dimensional description of tree architecture and is driven by fluctuating drag forces applied on all parts. For validation purposes, instantaneous wind velocities and wind-induced stem displacements of two trees were recorded in a mature Maritime pine stand (Pinus pinaster) at several heights. The tree geometrical and physical characteristics were measured to describe their architecture. No model parameter was adjusted. Tree motions appear to be driven by wind pulses reflecting turbulence intermittency. No evidence is found for resonant behaviour. In the mean wind direction, the simulated oscillations agree well with the measured time series. The underestimation of tree movement in the cross-stream direction outlines the importance of torque behaviour on the predictive accuracy of the model. The mechanical transfer functions of the modelled trees show vibration peak frequencies very similar to the measured ones. At higher frequencies, the simulated damping appears overestimated, with the set of parameters used. The model provides a sound basis to further investigate the influence of tree aerial architecture and turbulence structure on tree stability to wind. [ABSTRACT FROM AUTHOR]

Sharp heterogeneities in forest structure, such as edges, are often responsible for wind damage. In order to better understand the behaviour of turbulent flow through canopy edges, large-eddy simulations (LES) have been performed at very fine scale (2 m) within and above heterogeneous vegetation canopies. A modified version of the Advanced Regional Prediction System (ARPS), previously validated in homogeneous conditions against field and wind-tunnel measurements, has been used for this purpose. Here it is validated in a simple forest-clearing-forest configuration. The model is shown to be able to reproduce accurately the main features observed in turbulent edge flow, especially the “enhanced gust zone” (EGZ) present around the canopy top at a few canopy heights downwind from the edge, and the turbulent region that develops further downstream. The EGZ is characterized by a peak in streamwise velocity skewness, which reflects the presence of intense intermittent wind gusts. A sensitivity study of the edge flow to the forest morphology shows that with increasing canopy density the flow adjusts faster and turbulent features such as the EGZ become more marked. When the canopy is characterized by a sparse trunk space the length of the adjustment region increases significantly due to the formation of a sub-canopy wind jet from the leading edge. It is shown that the position and magnitude of the EGZ are related to the mean upward motion formed around canopy top behind the leading edge, caused by the deceleration in the sub-canopy. Indeed, this mean upward motion advects low turbulence levels from the bottom of the canopy; this emphasises the passage of sudden strong wind gusts from the clearing, thereby increasing the skewness in streamwise velocity as compared with locations further downstream where ambient turbulence is stronger. [ABSTRACT FROM AUTHOR]

Land-use practices such as deforestation or agricultural management may affect regional climate, ecosystems and water resources. The present study investigates the impact of surface heterogeneity on the behaviour of the atmospheric boundary layer (ABL), at a typical spatial scale of 1 km. Large-eddy simulations, using an interactive soil–vegetation–atmosphere surface scheme, are performed to document the structure of the three-dimensional flow, as driven by buoyancy forces, over patchy terrain with different surface characteristics (roughness, soil moisture, temperature) on each individual patch. The patchy terrain consists of striped and chessboard patterns. The results show that the ABL strongly responds to the spatial configuration of surface heterogeneities. The stripe configuration made of two patches with different soil moisture contents generates the development of a quasi- two-dimensional inland breeze, whereas a three-dimensional divergent flow is induced by chessboard patterns. The feedback of such small-scale atmospheric circulations on the surface fluxes appears to be highly non-linear. The surface sensible and latent heat fluxes averaged over the 25-km2 domain may vary by 5% with respect to the patch arrangement. [ABSTRACT FROM AUTHOR]

A wind-tunnel experiment has been used to investigate momentum absorption by rough surfaces with sparse random and clustered distributions of roughness elements. An unusual (though longstanding) method was used to measure the boundary-layer depth δ and friction velocity u * and thence to infer the functional relationship z 0/ h = f(λ) between the normalised roughness length z 0/ h and the roughness density λ (where z 0 is the roughness length and h the mean height of the roughness elements). The method for finding u * is based on fitting the velocity defect in the outer layer to a functional form for the dimensionless velocity-defect profile in a canonical zero-pressure-gradient boundary layer. For the conditions investigated here, involving boundary layers over sparse roughness with strong local heterogeneity, this velocity-defect-law method is found to be more robust than several alternative methods for finding u * ( uw covariance, momentum integral and slope of the logarithmic velocity profile). The experimental results show that, (1) there is general agreement in the relationship z 0/ h = f(λ) between the present experiment with random arrays and other wind-tunnel experiments with regular arrays; (2) the main effect of clustering is to increase the scatter in the z 0/ h = f(λ) relationship, through increased local horizontal heterogeneity; (3) this scatter obscures any trend in the z 0/ h = f(λ) relationship in response to clustering; and (4) the agreement between the body of wind-tunnel data (taken as a whole) and field data is good, though with scatter for which it is likely that a major contribution stems from local horizontal heterogeneity in the field. [ABSTRACT FROM AUTHOR]

The damage caused by windstorms to forest ecosystems is often very heterogeneous. In order to improve the stability of forested landscapes, it is of great importance to identify the factors responsible for this spatial variability. The structure of the landscape itself may play a role, through possible influences of canopy heterogeneities on the development of turbulence. For the purpose of investigating the role of landscape fragmentation on turbulence development, we used a numerical flow model with a k–ε turbulence scheme model, previously validated in simple cases with well-defined surface changes (roughness change and forest edge flow). A series of two- and three-dimensional simulations were performed over a heterogeneous urban forested park in Europe, which was severely damaged in various places by the Lothar windstorm in December 1999. The model shows the development of a region of strong turbulence, resulting from the generation of large wind shear at the top of the canopy. A sensitivity study shows how the location, extension and intensity of the region depend on canopy characteristics such as the leaf density, the nature of the edge or the presence of gaps and clearings. Simulations performed in conditions representative of the windstorm show that the location of the damaged areas corresponds very closely to the regions where the turbulent kinetic energy was above a certain threshold. [ABSTRACT FROM AUTHOR]

A finite element model was developed to study the influence of aerial architecture on the structural dynamics of trees. The model combines a complete description of the axes of the aerial architecture of the plant with numerical techniques suitable for dynamic nonlinear analyses. Trees were modeled on the basis of morphological measurements that were previously made on three 4-year-old Pinus pinaster Ait. saplings originating from even-aged stands. Calculated and measured oscillations were compared to evaluate model behavior. The computations allowed the characteristics of the fundamental mode of vibration to be estimated with satisfactory accuracy. Inclusion of a topological description of the aerial system in a mechanical model provided insight into the effect of tree architecture on tree dynamic behavior. Simplifications of the branching pattern in the model led to overestimations of the natural swaying frequency of saplings by 10 to 20%. Inadequate values of stem and root anchorage stiffness resulted in errors of 10 to 20%. Modeling results indicated that aerodynamic drag of needles is responsible for 80% of the damping in the studied trees. Additionally, damping of stem movement is reduced by one half when branch oscillations are not considered. It appears that the efficiency of the dissipative mechanisms depends directly on crown topology. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the influence of aerial architecture on the dynamic characteristics of young maritime pines (Pinus pinaster Ait.) using a mechanistic approach. For this purpose, three 4-year-old saplings with prominent differences in their branching patterns were submitted to free oscillation tests. The tests were carried out with different methods and directions of mechanical loading in order to initiate the movement of each sapling. The oscillations of the different architectural elements, i.e. stem and branches of different topological order, were measured with inclinometers and strain gauges fixed to saplings. Successive pruning of the architectural elements was carried out to evaluate their relative influence on the dynamic characteristics of the trees. The aerial systems were digitized before the mechanical tests in order to use 3D visualization techniques and to make architectural analyses of the crown structure. Two distinct modes of deformation were detected during free oscillations. The natural swaying frequency ranged from 0.6–0.8 Hz for the saplings tested at the same period of the year. The frequency variations were partly explained by the morphological differences of the experimental subjects. The motions of the axes were found to depend on their topology, i.e. the movement of the axes of a given branching order was forced by the movement of their respective bearing axis. The axes of third branching order had a significant and negative effect on the damping of the natural deformation mode. Results point out the major role played by foliage, qualitatively and quantitatively, on the damping of tree motions and on coupling the motions of the crown components. [ABSTRACT FROM PUBLISHER]

Background: Intima-media thickness (IMT) is associated with an increased risk of cardiovascular and cerebral ischemic events, but its correlation with the absolute cardiovascular risk is not known in large populations. The Paroi Artérielle et Risque Cardiovasculaire (PARC) Study is an epidemiological study designed to correlate conventional assessment of cardiovascular risk with the mean IMT of the common carotid. Methods: In the PARC study, 6,416 subjects were enrolled, including 80.7% subjects with cardiovascular risk factors and 19.3% without. A specific methodology was designed to harmonize the acquisition and processing of data at the 283 centers. Interreader agreement on image quality and IMT measurement of the common carotid artery (CCAIMT) was assessed from a random sample of 10% of the PARC study population. Results: The intraclass correlation coefficient was 0.98 (95% CI 0.966–0.985), and the accuracy was high (standard deviation of the error measurement: 0.0185 mm). Conclusions: The reproducibility of the measurements assessed by means of the intraclass correlation coefficient and the accuracy of the CCAIMT measurement obtained in the PARC Study demonstrate the feasibility of large multicenter studies of IMT measurement.Copyright © 2005 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

We describe a wavelet-based technique to determine the spectral turbulent contribution to the vertical flux of sensible heat in a position-wavelength representation. This technique combines a wavelet transform (Morlet wavelet) with conditional sampling. We apply this method to aircraft data collected during a sea-breeze circulation (BEMA97 experiment) with heterogeneous turbulence conditions horizontally and vertically as well. The turbulent fluxes are analysed with the conditional wavelet technique as a function of the wavelength and the horizontal distance. The turbulent processes within the thermal internal boundary layer associated with the sea breeze are clearly identified. The results exhibit the wavelength bands through which the upward flux (originating from the surface) and the downward flux (originating from the top of the boundary layer) are important. [ABSTRACT FROM AUTHOR]

We have conducted an Empirical Orthogonal Function analysis (EOF) of a three dimensional, 2-point velocity covariance field, measured in a wind tunnel. The rate of convergence of the EOF sequence was used as an objective test for the presence of distinct large turbulent structures. We found that in the roughness sublayer (2h > z > 0) the sequence converged much more rapidly than in the lower surface layer (6h > z > 0), 75% of the total velocity variance being captured by the first three of 42 eigenmodes; h is the canopy height. The analysis was extended to three dimensions, where over 50% of the variance and most of the spatial structure of the covariance fields were captured by an even smaller fraction of the total number of eigenmodes. With some relatively weak additional assumptions we were able to construct the velocity field of a `characteristic eddy' or large coherent structure. This consisted of a pair of counter-rotating streamwise vortices centred above the canopy. The sense of rotation of the vortex pair was opposite to that found in the wall region of boundary layers but matched that found in plane mixing layers. A strong gust or sweep motion generated between the vortices was responsible for most of the shear stress carried by the large eddies. The region of significant transport of streamwise momentum by the characteristic eddy is much smaller than the region of coherence of the eddy's velocity field. [ABSTRACT FROM AUTHOR]

We studied modulations of flight activity in European grapevine moth females (EGVM) by individual observations in a wind tunnel. The effect of different factors was analyzed: variation in atmospheric pressure prior to the experiments, time of day, first experience of flight, age, mating, and odor of tansy, which attracts females. The circadian flight activity showed a peak the hour preceding the onset of scotophase and sustained activity occurred during the 6 h around this peak. Females with a flight experience in the tunnel took off more quickly than naive ones (3.9 ± 7.4 vs 20.3 ± 22.8 s). Three-day-old unmated females subjected to negative variations of atmospheric pressure (10 hPa) during the 4 h prior to the experiments increased their duration of flight (12.1 ± 8.7 vs 5.3 ± 3.4 s) compared to those not subjected to variation. One-day-old females were less active than older ones; flight was shorter than in 2-day-old females (2.7 ± 6.7 vs 5.1 ± 9.5 s) and fewer of them took off (28 vs 63%). Mating also affected the flight activity of 2-day-old females; mated females flew longer than virgins (12 ± 16.8 vs 5.1 ± 9.5 s) and took off more quickly (6.5 ± 14.4 vs 19.3 ± 20.1 s). Tansy odor in the tunnel did not significantly affect the flight behavior of virgin females, but it increased the proportion of mated females that initiated flight (87 vs 70%) and duration of flight (11.2 ± 24.4 vs 7.2 ± 13.7 s), and it reduced the latency to takeoff (2.1 ± 7.4 vs 8.1 ± 19.1 s). Flight duration in tansy odor was inversely correlated with the total number of eggs laid during the female's whole life. Our experimental settings did not allow observation of movements directed toward the odor source. [ABSTRACT FROM AUTHOR]

The characteristics of turbulence within a forest are spatially heterogeneous and distinct from those associated with the surface boundary layer. Consequently, the size and probability distribution of ’flux footprints‘ emanating from sources below a forest canopy have the potential to differ from those observed above forests. A Lagrangian random walk model was used to investigate this problem since no analytical solution of the diffusion equation exists. Model calculations suggest that spatial characteristics of ’flux footprint‘ probability distributions under forest canopies are much contracted, compared to those evaluated in the surface boundary layer. The key factors affecting the statistical spread of the ’flux footprint‘, and the position of the peak of its probability distribution, are horizontal wind velocity and the standard deviations of vertical and horizontal velocity fluctuations. Consequently, canopies, which attenuate mean horizontal wind speed, or atmospheric conditions, which enhance vertical velocity fluctuations, will contract flux footprint distributions mostly near the floor of a forest. It was also found that the probability distributions of the ’flux footprint‘ are narrower when horizontal wind velocity fluctuations are considered, instead of the simpler case that considers only vertical velocity fluctuations and mean horizontal wind velocity. [ABSTRACT FROM AUTHOR]

Abstract: Early in the 1940s, in response to a housing crisis compounded of lack of construction during the depression, rural to urban migration, and the relocation of labour to the [...]