Height Interval Research Articles

Composition, Community Structure and Vertical Distribution of Epiphytic Ferns on Bamboo Species In Bogor Botanic Gardens, Indonesia

Ecological study of epiphytic ferns growing on bamboo species in Bogor Botanic Gardens, a man-made ecosystem located in a wet lowland area was carried out. The 350 phorophytes of 35 bamboo clumps belonging to 9 species and 3 genera were observed. Each culm was divided into intervals of 1 m from ground level to a height of 3 m. A total of 1984 individuals belonging to 12 species, nine genera, and six families of epiphytic ferns were recorded, with the highest species richness in Polypodiaceae (7 spp.). Dendocalamus giganteus Munro was the best host for epiphytic ferns (9 spp.). Two dominant species, Asplenium nidus L. and Davallia denticulata (Burm.f.) Mett. ex Kuhn with the same frequency value (97.14%), and relative species abundance of 31.49 individuals per clump and 14.94 individuals per clump, showed the highest Importance Value Index (IVI) of 83.19 and 54.00%, respectively. The first one-meter level of bamboo culms hosted all the species. Pyrrosia piloselloides (L.) Price was the only species that grew until the highest intervals of height with a decreasing frequency from the bottom. Bangladesh J. Bot. 50(4): 1095-1107, 2021 (December)

ON RANDOM EXPECTED VALUES VARIATIONS OF TRIBOLOGY PARAMETERS IN HUMAN HIP JOINT SURFACES

This paper presents recent progress in the knowledge concerning the stochastic theory of bio- hydrodynamic lubrication with a phospholipids bilayer. On the basis of experimental measurements and analytical solutions, the research concerns the determination of the random expectancy values of load carrying capacity, the friction coefficient, and synovial fluid dynamic variations. After numerous measurements, it directly follows that the random density function of the gap height in the human joint usually indicates a disorderly increases and decreases in the height. Such irregular gap height variations have an important influence on the random synovial bio-fluid dynamic viscosity. This finally leads to the friction coefficient and cartilage wear changes of cooperating bio- surfaces. The main topic of this paper relates to the expectancy values of the tribology parameters localized inside the variable stochastic standard deviation intervals of the human joint gap height. The results obtained finally indicate the influence of the random roughness and growth of living biological cartilage surfaces on the expectancy values of the synovial fluid dynamic viscosity, load carrying capacity and friction forces in human hip joints.

Evaluation of Pavement Runoff and Driving Safety on Highway Curve Segment

Runoff depth distribution on the concave and circular curve sections is obtained from a two-dimensional numerical simulating model in order to analyze the temporal and spatial variation of the pavement runoff on the curve section. The two-dimensional model verified by the field data can depict the alignment of pavement more accurately as compared to the empirical equation and a one-dimensional model. The runoff on the concave section and circular curve section is compared for the free water drainage and centerline drainage. Results show that a two-dimensional model is essential for the analysis of the centerline drainage. The runoff depth can be controlled by a reasonable curb height and location interval. The drainage type affects the variation of the runoff depth on the nearside lane, and the maximum water depth can be up to more than 80 mm on the concave section and nearly 60 mm on the circular curve section under centerline drainage. Besides the existing hydroplaning results, the runoff depth difference of the wheel trace should be considered to evaluate driving safety. Sideslip will occur when the depth difference becomes more than 6 mm under condition that the runoff depth is less than the tread depth (7 mm). When the runoff depth is more than the tread depth, sideslip will occur once the depth difference exceeds 4 mm.

An Adaptive Non-Uniform Vertical Stratification Method for Troposphere Water Vapor Tomography

Global Navigation Satellite System (GNSS) water vapor tomography provides a four-dimensional (4-D) distribution of water vapor in the atmosphere for weather monitoring. It has developed into a widely used technique in numerical weather prediction (NWP). Vertical stratification is essential in discretizing the tomographic region. Traditional discretization methods divide the tomographic area into regular voxels with an equal height interval, which ignores the dynamic exponential distribution of water vapor. In recent years, non-uniform stratification methods have been widely validated by tomographic experiments. However, such experiments have not proposed a specific calculation method for stratification thickness. Therefore, in this paper, we introduced an adaptive non-uniform stratification method that follows the exponential distribution of water vapor in the tomographic region and presented the process of iterative calculation to acquire the optimal stratification interval. The proposed approach was applied based on the exponential decreasing trend in water vapor with increasing altitude. Moreover, it could adaptively calculate the interval of stratification height according to water vapor content. The tomographic experiments were performed using Global Positioning System (GPS) data from 19 ground-based stations in the Hong Kong Satellite Positioning Reference Station Network (SatRef) from 1 to 31 August 2019. The results indicated that, compared to the traditional stratification method, the root mean square error derived from the proposed approach was reduced by 0.26 g/m3. Additionally, severe weather can negatively affect the accuracy of the tomographic results. The results also showed that the accuracy of the tomographic results was reduced with increasing altitude. Moreover, the performance of the tomographic water vapor fields below 3000 m was improved by the proposed approach.

Mathematical Principles of Object 3D Reconstruction by Shape-from-Focus Methods

Shape-from-Focus (SFF) methods have been developed for about twenty years. They able to obtain the shape of 3D objects from a series of partially focused images. The plane to which the microscope or camera is focused intersects the 3D object in a contour line. Due to wave properties of light and due to finite resolution of the output device, the image can be considered as sharp not only on this contour line, but also in a certain interval of height—the zone of sharpness. SSFs are able to identify these focused parts to compose a fully focused 2D image and to reconstruct a 3D profile of the surface to be observed.

Diagnostic Relations between Pressure and Entropy Perturbations for Acoustic and Entropy Modes

Diagnostics and decomposition of atmospheric disturbances in a planar flow are considered and applied to numerical modelling with the direct possibility to use in atmosphere monitoring especially in such strong events which follow magnetic storms and other large scale atmospheric phenomena. The study examines a situation in which the stationary equilibrium temperature of a gas may depend on a vertical coordinate, which essentially complicates the diagnostics. The relations connecting perturbations for acoustic and entropy (stationary) modes are analytically established and led to the solvable diagnostic equations. These equations specify acoustic and entropy modes in an arbitrary stratified gas under the condition of stability. The diagnostic relations are independent of time and specify the acoustic and the entropy modes. They provide the ability to decompose the total vector of perturbations into acoustic and non-acoustic (entropy) parts uniquely at any instant within the total accessible heights range. As a prospective model, we consider the diagnostics at the height interval 120–180 km, where the equilibrium temperature of a gas depends linearly on the vertical coordinate. For such a heights range it is possible to proceed with analytical expressions for pressure and entropy perturbations of gas variables. Individual profiles of acoustic and entropy parts for some data are illustrated by the plots for the pure numerical data against those obtained by the model. The total energy of a flow is determined for both approaches and its vertical profiles are compared.

SEMI-ANALYTICAL METHOD FOR UNSTABLE PRESSURE OF 3D FRACTURE NETWORK

Due to the influence of in-situ stress and fracturing technology, the distribution of hydraulic fracture network in highly deviated wells is complex with different inclined directions, different distribution forms and different penetration degrees. In this paper, the fracture surface is discretized into several rectangular micro elements to realize the effective characterization of fracture morphology. The seepage process is divided into two stages: matrix flow to fracture and fracture flow to wellbore. The numerical solution of unsteady seepage in discrete fracture surface is constructed by using finite difference method, and the analytical solution of unsteady seepage in matrix is constructed by combining closed boundary source function and superposition principle. The solution of the unstable pressure of the 3D fracture network is obtained by coupling the numerical solution of flow in fracture and the analytical solution of flow in matrix. Based on the integral mean value theorem, a solution method of point source and special line source instead of surface source is proposed to solve the seepage in matrix. The feasibility and applicable conditions of this method are analyzed, which can ensure the accuracy of the model and improve the calculation efficiency. The research shows that the point source function area fraction method can accurately solve the bottom hole pressure dynamic of 3D pressure fracture network in the matrix, but the calculation is quite inefficient. The point source and special line source approximate surface source method based on the integral mean value theorem can greatly improve the calculation efficiency, and can achieve higher accuracy when the fracture micro element division is more precise (the dimensionless side length of micro element is less than 0.15). Based on this model, the flow regimes and related sensitivity analysis are analyzed. The results show that the fracture conductivity, fracture dip angle, fracture height and fracture interval have great influence on the typical well test curves of highly deviated wells. Fracture dip angle and fracture interval mainly affect the pressure and pressure derivative curve from linear flow to early radial flow, especially when the fracture height is small, the pressure derivative has backflow phenomenon.

3D MSSD: A multilayer spatial structure 3D object detection network for mobile LiDAR point clouds

Point cloud-based object detection is vital and essential for many real-world applications, such as autonomous driving and robot vision. The PointPillars model has achieved the efficient detection of objects in front of a vehicle. However, the algorithm does not consider the spatial structures semantic information stored in the three-dimensional point cloud for a given spatial structure, thus leading to missed or false detections for objects with complex spatial structures or singular structures. We propose an approach based on PointPillars, which considers the spatial structure characteristics of 3D point clouds to enhance the detection accuracy. First, based on the specified range of the z-axis coordinates, the entire point cloud scene is divided into several layers so that the point cloud areas in the same height interval form one layer. Data from several layers are obtained. Second, the point clouds of several layers are processed with Pillar Feature Net to obtain several pseudoimages. Each pseudoimage represents the semantic information from the corresponding level of the point cloud. Third, the obtained pseudoimages from each level are merged with the pseudoimages of the entire scene to obtain a feature map with spatial structure characteristics. We apply a Region Proposal Network, and an object detection operator processes the feature map and obtains the result of object detection. Experiments show that the proposed method has a highly accurate detection effect for objects with complex spatial structures. In addition, the proposed method does not erroneously detect objects with similar semantic information after vertical dimension projection.

NATURAL REGENERATION AND ARTIFICIAL THINNING FOR EARLY FOREST RESTORATION ON A PERMANENTLY CLOSED SKI SLOPE

: In recent decades, numerous ski resorts in Japan have had to close due to financial difficulties. Forest restoration on these abandoned ski slopes is necessary for landscape management and to prevent avalanches and landslides. However, forest restoration activities are hindered by the scarcity of nutrients due to topsoil removal at the time of ski slope construction. In this study, the effect of thinning on alleviating competition for soil nutrients was examined. The study site was located on Mt. Tateshina in central Japan. The study site's ski slope was closed permanently in 1997, and the first natural regeneration of larch occurred in 1998. Chubu Regional Forest Office performed artificial thinning in 2003. Two thinned, nine un-thinned quadrat plots in 2016 were established and measured the total height and diameter at all living and dead trees' breast height. Tree-ring analysis of nine sample trees in each of the un-thinned and thinned plots at 1 m height intervals was performed to clarify tree growth. The un-thinned field had a high tree density, small tree size, and numerous dead trees, suggesting the existence of severe competition. Conversely, the thinned plot was characterized by a lower tree density, large tree size, and fewer dead trees. According to the tree-ring analysis, artificial thinning improved the survival rate and smaller trees' growth rate. It was concluded that the artificial thinning of natural forests on ski slopes is useful for accelerating tree growth and early forest development.

Multitemporal Landslide Inventory and Activity Analysis by Means of Aerial Photogrammetry and LiDAR Techniques in an Area of Southern Spain

This paper deals with the use of aerial photogrammetry and LiDAR techniques to analyze landslide activity over a long time span—just over 32 years. The data correspond to several aerial surveys (1984, 1996, 2001, 2005, 2009, 2010, 2011, 2013 and 2016) covering an area of about 50 km2 along highway A-44, near Jaén (Southern Spain). An ad hoc combined photogrammetric and LiDAR aerial survey of 2010 was established as the reference flight. This flight was processed by means of direct orientation methods and iterative adjustments between both data sets. Meanwhile, historical flights available in public geographical data servers were oriented by transferring ground control points from the reference flight. Then, digital surface models (DSMs) and orthophotographs were generated, as well as the corresponding differential models (DoDs), which, after the application of filters and taking into account the estimated uncertainty of ± 1 m, allowed us to identify true changes on the ground surface. This analysis, complemented by photointerpretation, led us to obtain a landslide multitemporal inventory in the study area that was analyzed in order to characterize the landslide type, morphology and activity. Three basic typologies were identified: rock falls–collapses, slides and flows. These types present different morphometric properties (area, perimeter and height interval) and are associated with different conditions (height, slope, orientation and lithology). Moreover, a set of monitoring areas, common for the different flights, was also used to analyze the activity throughout the study period. Thus, some more active periods were identified (2009–2010, 2010–2011, 2011–2013 and 1996–2001) among other less active ones (1984–1996, 2001–2005, 2005–2009 and 2013–2016), which are related to rainy events and dry years, respectively.

Multi-level height maps-based registration method for sparse LiDAR point clouds in an urban scene.

The LiDAR sensor has been widely used for reconstruction in urban scenes. However, the current registration method makes it difficult to find stable 3D point correspondences from sparse and low overlapping LiDAR point clouds. In the urban situation, most of the LiDAR point clouds have a common flat ground. Therefore, we propose a novel, to the best of our knowledge, multi-level height (MH) maps-based coarse registration method. It requires that source and target point clouds have a common flat ground, which is easily satisfied for LiDAR point clouds in urban scenes. With MH maps, 3D registration is simplified as 2D registration, increasing the speed of registration. Robust correspondences are extracted in MH maps with different height intervals and statistic height information, improving the registration accuracy. The solid-state LiDAR Livox Mid-100 and mechanical LiDAR Velodyne HDL-64E are used in real-data and dataset experiments, respectively. Verification results demonstrate that our method is stable and outperforms state-of-the-art coarse registration methods for the sparse case. Runtime analysis shows that our method is faster than these methods, for it is non-iterative. Furthermore, our method can be extended for the unordered multi-view point clouds.

Penggunaan Citra DEMNAS untuk Desain Pola Tanam Alley Cropping pada Lahan Garapan Anggota KPPH Talang Mulya Kabupaten Pesawaran Provinsi Lampung

Talang Mulya KPPH farmers has been applying agroforestry system for their land cultivation, but the cropping pattern applied has not been adapted to its sloping conditions and plant spacing which result on non-optimal yields produce. Alley Cropping pattern consider as the most suitable approach. Current analysis can be carried out using mapping techniques and remote sensing using digital elevation data imagery. The DEMNAS imagery was used in this study, results showed that the mean altitude reached 396.67 masl and land slope reached 20.92% in average. The design of the cropping pattern using 1 meter height intervals shows the results of the number of planting arrays of 31.96 strips with 3,564.96 meters in length which is higher than the land with a height interval of 2 meters which results in a total of 10.6 strips with and 942.97 meter lengths. However, the field of agricultural cultivation that can be formed on land with 1 meter height intervals only reaches 4.94 meters, while at 2 meters height intervals it can reach 16.03 meters.

Heading variations resolve the heading-direction ambiguity in vertical-beam radar observations of insect migration

ABSTRACT Vertical-beam entomological radars provide precise measurements of the body alignment of individual overflying insects but are unable to distinguish which of the two axial directions the insect is heading towards. Insects migrating at altitude typically show common alignment, although with a broad spread. We show here that when observations from multiple individual insects are available, and the insects have airspeeds of about 2 ms–1 or greater, the spread in heading directions allows the heading ambiguity to be resolved (though at the sample rather than the individual level). A vector analysis of radar-measured track direction, track speed, and heading will provide consistent results for all the insects in a sample only when the heading direction is chosen correctly. With the heading then resolved, the analysis can continue to estimation of representative values for the airspeed of the insects in the sample and for the speed and direction of the wind they were flying in. This general approach can be implemented in two different ways, which we term the ‘cluster’ and ‘projection’ methods. When applied to an intense migration of large insects, probably moths, these methods produced highly consistent results from hour to hour and from one 150 m height interval to the next. Simulations show that the methods are not liable to directional bias and reveal when they are rendered ineffective by small sample sizes or low insect airspeeds; they also indicate that the cluster method handles small sample sizes better than the projection method, and its use is therefore recommended. A comparison with two previously proposed methods that use meteorological data to resolve the ambiguity shows that the new methods are more reliable. Use of this objective means of resolving the heading ambiguity will increase confidence in radar-based studies of the orientation behaviour of insect migrants and their responses to cues like sky illumination patterns, the Earth’s magnetic field, and wind.

Model studies on polymer strip reinforced soil retaining walls

Polymer strip (PS) reinforced soil retaining walls (RSRW) are in common use due to the associated construction speed, ease of use, aesthetic appeal and low cost. It is quite significant to estimate the deformation behavior of this types of walls before construction. In this study, firstly, a full-scale field model of PS-RSRW was constructed and instrumented. According to the experimental result, the maximum measured displacements occurred at 30% of the height down from the top of the wall. The maximum tensile loads in the reinforcements were measured at a distance of 40% of the wall height from the face of the wall. Then, a two-dimensional (2D) finite element method (FEM) model was established and calibrated with experimental data from the field model. The predicted displacements of the wall facing showed reasonable agreement with the measured deformations. The reinforcement loads calculated from the validated FEM model were also compared with theoretical methods. Finally, RSRW having different heights were numerically modeled with various combinations of materials utilized for filling and reinforcement. The effects of parameters such as wall height (H), reinforcement length (L) and reinforcement interval (Sv) on the horizontal wall displacement and on the reinforcement loads are investigated through parametric analyses.

Multitemporal Sentinel-1 and Sentinel-2 Images for Characterization and Discrimination of Young Forest Stands Under Regeneration in Norway

There is a need for mapping of forest areas with young stands under regeneration in Norway, as a basis for conducting tending, or precommercial thinning (PCT), whenever necessary. The main objective of this article is to show the potential of multitemporal Sentinel-1 (S-1) and Sentinel-2 (S-2) data for characterization and detection of forest stands under regeneration. We identify the most powerful radar and optical features for discrimination of forest stands under regeneration versus other forest stands. A number of optical and radar features derived from multitemporal S-1 and S-2 data were used for the class separability and cross-correlation analysis. The analysis was performed on forest resource maps consisting of the forest development classes and age in two study sites from south-eastern Norway. Important features were used to train the classical random forest (RF) classification algorithm. A comparative study of performance of the algorithm was used in three cases: I) using only S-1 features, II) using only S-2 optical bands, and III) using combination of S-1 and S-2 features. RF classification results pointed to increased class discrimination when using S-1 and S-2 data in relation to S-1 or S-2 data only. The study shows that forest stands under regeneration in the height interval for PCT can be detected with a detection rate of 91% and F-1 score of 73.2% in case III as most accurate, while tree density and broadleaf fraction could be estimated with coefficient of determination ( $\text {R}^2$ ) of about 0.70 and 0.80, respectively.

A new bias-correction method for precipitation over complex terrain suitable for different climate states: a case study using WRF (version 3.8.1)

Abstract. This work presents a new bias-correction method for precipitation over complex terrain that explicitly considers orographic characteristics. This consideration offers a good alternative to the standard empirical quantile mapping (EQM) method during colder climate states in which the orography strongly deviates from the present-day state, e.g. during glacial conditions such as the Last Glacial Maximum (LGM). Such a method is needed in the event that absolute precipitation fields are used, e.g. as input for glacier modelling or to assess potential human occupation and according migration routes in past climate states. The new bias correction and its performance are presented for Switzerland using regional climate model simulations at 2 km resolution driven by global climate model outputs obtained under perpetual 1990 and LGM conditions. Comparing the present-day regional climate model simulation with observations, we find a strong seasonality and, especially during colder months, a height dependence of the bias in precipitation. Thus, we suggest a three-step correction method consisting of (i) a separation into different orographic characteristics, (ii) correction of very low intensity precipitation, and (iii) the application of an EQM, which is applied to each month separately. We find that separating the orography into 400 m height intervals provides the overall most reasonable correction of the biases in precipitation. The new method is able to fully correct the seasonal precipitation bias induced by the global climate model. At the same time, some regional biases remain, in particular positive biases over high elevated areas in winter and negative biases in deep valleys and Ticino in winter and summer. A rigorous temporal and spatial cross-validation with independent data exhibits robust results. The new bias-correction method certainly leaves some drawbacks under present-day conditions. However, the application to the LGM demonstrates that it is a more appropriate correction compared to the standard EQM under highly different climate conditions as the latter imprints present-day orographic features into the LGM climate.

Simultaneous ground-based and in situ Swarm observations of equatorial F-region irregularities over Jicamarca

Abstract. Ionospheric irregularities are a common phenomenon in the low-latitude ionosphere. They can be seen in situ as depletions of plasma density, radar plasma plumes, or ionogram spread F by ionosondes. In this paper, we compared simultaneous observations of plasma plumes by the Jicamarca Unattended Long-term Investigations of the Ionosphere and Atmosphere (JULIA) radar, ionogram spread F generated from ionosonde observations installed at the Jicamarca Radio Observatory (JRO), and irregularities observed in situ by Swarm in order to determine whether Swarm in situ observations can be used as indicators of the presence of plasma plumes and spread F on the ground. The study covered the years from 2014 to 2018, as this was the period for which JULIA, Swarm, and ionosonde data sets were available. Overall, the results showed that Swarm's in situ density fluctuations on magnetic flux tubes passing over (or near) the JRO may be used as indicators of plasma plumes and spread F over (or near) the observatory. For Swarm and the ground-based observations, a classification procedure was conducted based on the presence or absence of ionospheric irregularities. There was a strong consensus between ground-based observations of ionospheric irregularities and Swarm's depth of disturbance of electron density for most passes. Cases, where ionospheric irregularities were observed on the ground with no apparent variation in the in situ electron density or vice versa, suggest that irregularities may either be localized horizontally or restricted to particular height intervals. The results also showed that the Swarm and ground-based observations of ionospheric irregularities had similar local time statistical trends with the highest occurrence obtained between 20:00 and 22:00 LT. Moreover, similar seasonal patterns of the occurrence of in situ and ground-based ionospheric irregularities were observed with the highest percentage occurrence at the December solstice and the equinoxes and low occurrence at the June solstice. The observed seasonal pattern was explained in terms of the pre-reversal enhancement (PRE) of the vertical plasma drift. Initial findings from this research indicate that fluctuations in the in situ density observed meridionally along magnetic field lines passing through the JRO can be used as an indication of the existence of well-developed plasma plumes.

Study of concrete pressure in formwork using sensor

Formwork has become wide spread which uses moulds made up of timber or steel in construction. In this research we have used a sensor to find the lateral pressure on formwork which will be cost effective and ensure efficient utilization of materials concerning its loads and deformation. A vertical column formwork is casted and concrete is poured at different intervals of height. At various level of rise of concrete and at various height and also during the setting of concrete the pressure on formwork was recorded in a sensor device and it is compared with theoretical pressure obtained from CIRIA formula.

Association between maternal height and mode of delivery in nulliparous Japanese women.

The primary aim of this study was to examine the association between maternal height and mode of delivery in nulliparous Japanese women. The secondary aim was to examine the association between maternal height and maternal and neonatal morbidities. This retrospective cohort study included women who gave birth at Osaka Women's and Children's Hospital, a tertiary perinatal center in Japan, from January 2015 to December 2017. Nulliparous Japanese women with singleton gestation, who went into labor at term were included in the study. The primary outcome was mode of delivery, and the secondary outcomes were maternal and neonatal morbidities. The relationships between maternal height and the outcomes were evaluated using multivariate logistic regression analysis adjusted for potential confounders. Maternal height was categorized into five groups with 5-cm increments for the analysis. A total of 1593 women were analyzed in this study. Shorter women had higher rate of cesarean delivery (CD) than taller women. There were no significant differences in the rates of operative vaginal delivery, maternal morbidity and neonatal morbidity among the maternal-height groups. The adjusted odds ratios (95% confidential interval) of maternal heights of <150 cm, 150-154 cm, 160-164 cm and ≥165 cm for CD, compared with a maternal height of 155-159 cm, were 3.56 (1.79-7.09), 1.68 (1.06-2.64), 0.63 (0.40-1.00) and 0.57 (0.30-1.01), respectively. Shorter nulliparous Japanese women were more likely to undergo intrapartum CD. However, the rates of maternal and neonatal morbidities in shorter women were similar to those in taller women.

WRF-Simulated Springtime Low-Level Jets over Iowa: Implications for Wind Energy

High-resolution simulations with the Weather Research and Forecasting (WRF) model are analyzed to characterize the frequency, intensity, height, and duration of springtime low-level jets (LLJ) and their implications for wind energy resource assessment and planning in Iowa. The time evolution of short-duration LLJ is analyzed to understand wind behavior around LLJ events and to illustrate their importance for high-frequency (few hours) variability in wind speeds and rotor plane turbulent kinetic energy (TKE). During spring, the LLJ core height has a spatiotemporal mean value of 217 m, but the LLJ depth means it frequently intersects typical wind turbine rotor planes. Nearly one-quarter of LLJ exhibit a maximum within the height interval 50-150 m AGL. LLJ profiles are found to have higher mean wind speeds across typical wind turbine rotor planes than non-LLJ profiles and to exhibit lower values of TKE. LLJ occur under stable stratification (i.e. positive Richardson numbers) and are associated with low TKE and the occurrence of high vertical wind shear. The frequency and duration of LLJ exhibit geospatial variability across Iowa with highest values in the northeast of the state. Analyses of daytime and night-time LLJ indicate topographic variability is an important factor in the development of LLJ.