Wind prediction modelling and validation using coherent Doppler LIDAR data

A physically-based wind model is applied to determine wind speed and direction and to conduct a model sensitivity analysis. The model is later coupled with a microclimatic model utilizing a novel technique to support short term forecasting at Lake Turkana Wind Fam site, Kenya. Improved statistical comparisons of wind speed and direction are achieved between the model and in situ observations. Coherent Doppler LIDAR observations agreed well with the microclimatic model

A review of progress and applications of pulsed doppler wind LiDARs

Doppler wind LiDAR (Light Detection And Ranging) makes use of the principle of optical Doppler shift between the reference and backscattered radiations to measure radial velocities at distances up to several kilometers above the ground. Such instruments promise some advantages, including its large scan volume, movability and provision of 3-dimensional wind measurements, as well as its relatively higher temporal and spatial resolution comparing with other measurement devices. In recent decades, Doppler LiDARs developed by scientific institutes and commercial companies have been well adopted in several real-life applications. Doppler LiDARs are installed in about a dozen airports to study aircraft-induced vortices and detect wind shears. In the wind energy industry, the Doppler LiDAR technique provides a promising alternative to in-situ techniques in wind energy assessment, turbine wake analysis and turbine control. Doppler LiDARs have also been applied in meteorological studies, such as observing boundary layers and tracking tropical cyclones. These applications demonstrate the capability of Doppler LiDARs for measuring backscatter coefficients and wind profiles. In addition, Doppler LiDAR measurements show considerable potential for validating and improving numerical models. It is expected that future development of the Doppler LiDAR technique and data processing algorithms will provide accurate measurements with high spatial and temporal resolutions under different environmental conditions

2D VAR single Doppler lidar vector retrieval and its application in offshore wind energy

abstract: Remote sensors like Doppler lidars can map the winds with high accuracy and spatial resolution. One shortcoming of lidars is that the radial velocity measured by the lidar does not give a complete picture of the windfield necessitating additional data processing to reconstruct the windfield. Most of the popular vector retrieval algorithms rely on the homogenous wind field assumption which plays a vital role in reducing the indeterminacy of the inverse problem of obtaining Cartesian velocity from radial velocity measurements. Consequently, these methods fail in situations where the flow is heterogeneous e.g., Turbine wakes. Alternate methods are based either on statistical models (e.g., optimal interpolation [1]) or computationally intensive four dimensional variational methods [2]. This study deals with a 2D variational vector retrieval for Doppler lidar that uses the radial velocity advection equation as an additional constraint along with a tangential velocity constraint derived from a new formulation with gradients of radial velocity. The retrieval was applied on lidar data from a wind farm and preliminary analysis revealed that the algorithm was able to retrieve the mean wind field while preserving the small scale flow structure

Cross‐valley vortices in the Inn valley, Austria: Structure, evolution and governing force imbalances

Exchange of momentum and scalars in the mountain boundary layer is achieved through an interaction of meso-to-microscale motions, occurring to varying extents depending on the combined effect of thermally driven as well as dynamically driven forcings. One such motion, known as a secondary circulation, results from a horizontal force imbalance across a curved valley segment, wherein the centrifugal force towards the outside of the valley bend can create a pressure gradient force in the opposite direction. The lack of adequate measurement strategies capable of sampling such motions in curved mountain valleys explains the near-absence of any observational evidence of secondary circulations there. The goal of the CROSSINN (Cross-valley flow in the Inn valley investigated by dual-Doppler lidar measurements) campaign, conducted in a curved segment of the Inn valley, Austria, was to determine the character of the cross-valley flow by means of a coplanar retrieval applied to a multi-Doppler wind lidar configuration. A signature of a secondary circulation, hereafter referred to as a cross-valley vortex, stood out particularly during intense daytime upvalley flow episodes. Vortices were detected on 23 upvalley wind days, with a declining frequency of occurrence from August to October. Nearly all identified vortices were marked by a low-level upvalley jet, a clockwise wind direction turning with height, and a cessation of upvalley flow at the local ridgeline level. The routinely sampled coplanar-retrieved cross-valley wind field enabled the quantification of more advanced parameters based on vorticity, revealing a faster spin rate of the vortex around its streamwise axis given a stronger upvalley flow, and a period of revolution on the order of several tens of minutes. A detailed inspection of the lateral momentum budget and associated uncertainties confirmed the importance of the relationship between the centrifugal and the pressure gradient force for the cross-valley vortex occurrence in a curved valley

Optimizing Dual-Doppler Lidar Measurements of Surface Layer Coherent Structures with Large-Eddy Simulations

Coherent structures are patterns in the wind field of the atmospheric boundary layer. The deployment of two scanning Doppler lidars facilitates the measurement of the horizontal wind field, but the inherent averaging processes complicate an interpretation of the results. To assess the suitability of this technique for coherent structure detection large-eddy simulations are used as a basis for virtual measurements, and the effects of the lidar technique on the wind field structure are analyzed

Optimizing Dual-Doppler Lidar Measurements of Surface Layer Coherent Structures with Large-Eddy Simulations

Coherent structures are patterns in the wind field of the atmospheric boundary layer. The deployment of two scanning Doppler lidars facilitates the measurement of the horizontal wind field, but the inherent averaging processes complicate an interpretation of the results. To assess the suitability of this technique for coherent structure detection large-eddy simulations are used as a basis for virtual measurements, and the effects of the lidar technique on the wind field structure are analyzed

Optimizing Dual-Doppler Lidar Measurements of Surface Layer Coherent Structures with Large-Eddy Simulations

Coherent structures are patterns in the wind field of the atmospheric boundary layer. The deployment of two scanning Doppler lidars facilitates the measurement of the horizontal wind field, but the inherent averaging processes complicate an interpretation of the results. To assess the suitability of this technique for coherent structure detection large-eddy simulations are used as a basis for virtual measurements, and the effects of the lidar technique on the wind field structure are analyzed

Doppler Lidar Vector Retrievals and Atmospheric Data Visualization in Mixed/Augmented Reality

abstract: Environmental remote sensing has seen rapid growth in the recent years and Doppler wind lidars have gained popularity primarily due to their non-intrusive, high spatial and temporal measurement capabilities. While lidar applications early on, relied on the radial velocity measurements alone, most of the practical applications in wind farm control and short term wind prediction require knowledge of the vector wind field. Over the past couple of years, multiple works on lidars have explored three primary methods of retrieving wind vectors viz., using homogeneous windfield assumption, computationally extensive variational methods and the use of multiple Doppler lidars. Building on prior research, the current three-part study, first demonstrates the capabilities of single and dual Doppler lidar retrievals in capturing downslope windstorm-type flows occurring at Arizona’s Barringer Meteor Crater as a part of the METCRAX II field experiment. Next, to address the need for a reliable and computationally efficient vector retrieval for adaptive wind farm control applications, a novel 2D vector retrieval based on a variational formulation was developed and applied on lidar scans from an offshore wind farm and validated with data from a cup and vane anemometer installed on a nearby research platform. Finally, a novel data visualization technique using Mixed Reality (MR)/ Augmented Reality (AR) technology is presented to visualize data from atmospheric sensors. MR is an environment in which the user's visual perception of the real world is enhanced with live, interactive, computer generated sensory input (in this case, data from atmospheric sensors like Doppler lidars). A methodology using modern game development platforms is presented and demonstrated with lidar retrieved wind fields. In the current study, the possibility of using this technology to visualize data from atmospheric sensors in mixed reality is explored and demonstrated with lidar retrieved wind fields as well as a few earth science datasets for education and outreach activities.Dissertation/ThesisDoctoral Dissertation Mechanical Engineering 201