@article{lu_hawbecker_basu_manuel_2019, title={On Wind Turbine Loads During Thunderstorm Downbursts in Contrasting Atmospheric Stability Regimes}, volume={12}, ISSN={["1996-1073"]}, DOI={10.3390/en12142773}, abstractNote={Severe winds produced by thunderstorm downbursts pose a serious risk to the structural integrity of wind turbines. However, guidelines for wind turbine design (such as the International Electrotechnical Commission Standard, IEC 61400-1) do not describe the key physical characteristics of such events realistically. In this study, a large-eddy simulation model is employed to generate several idealized downburst events during contrasting atmospheric stability conditions that range from convective through neutral to stable. Wind and turbulence fields generated from this dataset are then used as inflow for a 5-MW land-based wind turbine model; associated turbine loads are estimated and compared for the different inflow conditions. We first discuss time-varying characteristics of the turbine-scale flow fields during the downbursts; next, we investigate the relationship between the velocity time series and turbine loads as well as the influence and effectiveness of turbine control systems (for blade pitch and nacelle yaw). Finally, a statistical analysis is conducted to assess the distinct influences of the contrasting stability regimes on extreme and fatigue loads on the wind turbine.}, number={14}, journal={ENERGIES}, author={Lu, Nan-You and Hawbecker, Patrick and Basu, Sukanta and Manuel, Lance}, year={2019}, month={Jul} }
 @article{demarco_basu_2018, title={On the tails of the wind ramp distributions}, volume={21}, ISSN={["1099-1824"]}, DOI={10.1002/we.2202}, abstractNote={AbstractWe analyzed several multiyear wind speed datasets from 4 different geographical locations. The probability density functions of wind ramps from all these sites revealed remarkably similar shapes. The tails of the probability density functions are much heavier than a Gaussian distribution, and they also systematically depend on time increments. Quite interestingly, from a purely statistical standpoint, the characteristics of the extreme ramp‐up and ramp‐down events are found to be almost identical. With the aid of extreme value theory, we describe several other inherent features of extreme wind ramps in this paper.}, number={10}, journal={WIND ENERGY}, author={DeMarco, Adam and Basu, Sukanta}, year={2018}, month={Oct}, pages={892–905} }
 @article{he_basu_2016, title={Extending a surface-layer C-n(2) model for strongly stratified conditions utilizing a numerically generated turbulence dataset}, volume={24}, ISSN={["1094-4087"]}, DOI={10.1364/oe.24.009574}, abstractNote={In Wyngaard et al., 1971, a simple model was proposed to estimate Cn2 in the atmospheric surface layer, which only requires routine meteorological information (wind speed and temperature) as input from two heights. This Cn2 model is known to have satisfactory performance in unstable conditions; however, in stable conditions, the model only covers a relatively short range of atmospheric stabilities which significantly limits its applicability during nighttime. To mitigate this limitation, in this study we construct a new Cn2 model utilizing an extensive turbulence dataset generated by a high-fidelity numerical modeling approach (known as direct numerical simulation). The most distinguishing feature of this new Cn2 model is that it covers a wide range of atmospheric stabilities including the strongly stratified (very stable) conditions. To validate this model, approximately four weeks of Cn2 data collected at the Mauna Loa Observatory, Hawaii are used for comparison, and reasonably good agreement is found between the observed and estimated values.}, number={9}, journal={OPTICS EXPRESS}, author={He, Ping and Basu, Sukanta}, year={2016}, month={May}, pages={9574–9582} }
 @article{wang_basu_2016, title={Using an artificial neural network approach to estimate surface-layer optical turbulence at Mauna Loa, Hawaii}, volume={41}, ISSN={["1539-4794"]}, DOI={10.1364/ol.41.002334}, abstractNote={In this Letter, an artificial neural network (ANN) approach is proposed for the estimation of optical turbulence (Cn2) in the atmospheric surface layer. Five routinely available meteorological variables are used as the inputs. Observed Cn2 data near the Mauna Loa Observatory, Hawaii are utilized for validation. The proposed approach has demonstrated its prowess by capturing the temporal evolution of Cn2 remarkably well. More interestingly, this ANN approach is found to outperform a widely used similarity theory-based conventional formulation for all the prevalent atmospheric conditions (including strongly stratified conditions).}, number={10}, journal={OPTICS LETTERS}, author={Wang, Yao and Basu, Sukanta}, year={2016}, month={May}, pages={2334–2337} }
 @article{basu_2015, title={A simple approach for estimating the refractive index structure parameter (C-n(2)) profile in the atmosphere}, volume={40}, ISSN={["1539-4794"]}, DOI={10.1364/ol.40.004130}, abstractNote={Utilizing the so-called Thorpe scale as a measure of the turbulence outer scale, we propose a physically-based approach for the estimation of Cn2 profiles in the lower atmosphere. This approach only requires coarse-resolution temperature profiles (a.k.a., soundings) as input, yet it has the intrinsic ability to capture layers of high optical turbulence. The prowess of this computationally inexpensive approach is demonstrated by validations against observational data from a field campaign over Mauna Kea, Hawaii.}, number={17}, journal={OPTICS LETTERS}, author={Basu, Sukanta}, year={2015}, month={Sep}, pages={4130–4133} }
 @article{kiliyanpilakkil_basu_ruiz-columbie_araya_castillo_hirth_burgett_2015, title={Buoyancy effects on the scaling characteristics of atmospheric boundary-layer wind fields in the mesoscale range}, volume={92}, ISSN={["1550-2376"]}, DOI={10.1103/physreve.92.033005}, abstractNote={We have analyzed long-term wind speed time series from five field sites up to a height of 300 m from the ground. Structure function-based scaling analysis has revealed that the scaling exponents in the mesoscale regime systematically depend on height. This anomalous behavior is likely caused by the buoyancy effects. In the framework of the extended self-similarity, the relative scaling exponents portray quasiuniversal behavior.}, number={3}, journal={PHYSICAL REVIEW E}, author={Kiliyanpilakkil, V. P. and Basu, S. and Ruiz-Columbie, A. and Araya, G. and Castillo, L. and Hirth, B. and Burgett, W.}, year={2015}, month={Sep} }
 @article{he_basu_2016, title={Development of similarity relationships for energy dissipation rate and temperature structure parameter in stably stratified flows: a direct numerical simulation approach}, volume={16}, ISSN={["1573-1510"]}, DOI={10.1007/s10652-015-9427-y}, number={2}, journal={ENVIRONMENTAL FLUID MECHANICS}, author={He, Ping and Basu, Sukanta}, year={2016}, month={Apr}, pages={373–399} }
 @article{he_basu_2015, title={Direct numerical simulation of intermittent turbulence under stably stratified conditions}, volume={22}, ISSN={["1607-7946"]}, DOI={10.5194/npg-22-447-2015}, abstractNote={Abstract. In this paper, we simulate intermittent turbulence (also known as bursting events) in stably stratified open-channel flows using direct numerical simulation. Clear signatures of this intriguing phenomenon are observed for a range of stabilities. However, the spatiotemporal characteristics of intermittency are found to be strongly stability dependent. In general, the bursting events are much more frequent near the bottom wall than in the upper-channel region. A steady coexistence of laminar and turbulent flows is detected at various horizontal planes in very stable cases. This spatially intermittent pattern is found to propagate downstream and strongly correlate with the temporal evolution of intermittency. Lastly, a long standing hypothesis by Blackadar (1979), i.e., the strong connection between local stability and intermittent turbulence, is corroborated by this modeling study.}, number={4}, journal={NONLINEAR PROCESSES IN GEOPHYSICS}, author={He, P. and Basu, S.}, year={2015}, pages={447–471} }
 @article{basu_he_2015, title={Estimating Refractive Index Structure Parameter (C-n(2)) Profiles in the Atmosphere: A Wavelet Transform-based Approach}, volume={9614}, ISSN={["1996-756X"]}, DOI={10.1117/12.2188195}, abstractNote={We propose a novel framework for the estimation of C2n in the atmosphere by utilizing an inherent vertical scaling characteristics of the temperature fields. Observations from a field campaign over the Hawaii island are used for rigorous validation. Furthermore, the strength of the proposed approach is demonstrated by direct comparison against an alternative approach based on the so-called Thorpe scale.}, journal={LASER COMMUNICATION AND PROPAGATION THROUGH THE ATMOSPHERE AND OCEANS IV}, author={Basu, Sukanta and He, Ping}, year={2015} }
 @article{kiliyanpilakkil_basu_2015, title={Extended self-similarity of atmospheric boundary layer wind fields in mesoscale regime: Is it real?}, volume={112}, ISSN={["1286-4854"]}, DOI={10.1209/0295-5075/112/64003}, abstractNote={In this letter, we study the scaling properties of multi-year observed and atmospheric model-generated wind time series. We have found that the extended self-similarity holds for the observed series, and remarkably, the scaling exponents corresponding to the mesoscale range closely match the well-accepted inertial-range turbulence values. However, the scaling results from the simulated time series are significantly different.}, number={6}, journal={EPL}, author={Kiliyanpilakkil, V. P. and Basu, S.}, year={2015}, month={Dec} }
 @article{nunalee_horvath_basu_2015, title={High-resolution numerical modeling of mesoscale island wakes and sensitivity to static topographic relief data}, volume={8}, ISSN={["1991-9603"]}, DOI={10.5194/gmd-8-2645-2015}, abstractNote={Abstract. Recent decades have witnessed a drastic increase in the fidelity of numerical weather prediction (NWP) modeling. Currently, both research-grade and operational NWP models regularly perform simulations with horizontal grid spacings as fine as 1 km. This migration towards higher resolution potentially improves NWP model solutions by increasing the resolvability of mesoscale processes and reducing dependency on empirical physics parameterizations. However, at the same time, the accuracy of high-resolution simulations, particularly in the atmospheric boundary layer (ABL), is also sensitive to orographic forcing which can have significant variability on the same spatial scale as, or smaller than, NWP model grids. Despite this sensitivity, many high-resolution atmospheric simulations do not consider uncertainty with respect to selection of static terrain height data set. In this paper, we use the Weather Research and Forecasting (WRF) model to simulate realistic cases of lower tropospheric flow over and downstream of mountainous islands using the default global 30 s United States Geographic Survey terrain height data set (GTOPO30), the Shuttle Radar Topography Mission (SRTM), and the Global Multi-resolution Terrain Elevation Data set (GMTED2010) terrain height data sets. While the differences between the SRTM-based and GMTED2010-based simulations are extremely small, the GTOPO30-based simulations differ significantly. Our results demonstrate cases where the differences between the source terrain data sets are significant enough to produce entirely different orographic wake mechanics, such as vortex shedding vs. no vortex shedding. These results are also compared to MODIS visible satellite imagery and ASCAT near-surface wind retrievals. Collectively, these results highlight the importance of utilizing accurate static orographic boundary conditions when running high-resolution mesoscale models.
                    }, number={8}, journal={GEOSCIENTIFIC MODEL DEVELOPMENT}, author={Nunalee, C. G. and Horvath, A. and Basu, S.}, year={2015}, pages={2645–2653} }
 @article{he_nunalee_basu_minet_vorontsov_fiorino_2015, title={Influence of heterogeneous refractivity on optical wave propagation in coastal environments}, volume={127}, ISSN={["1436-5065"]}, DOI={10.1007/s00703-015-0391-3}, number={6}, journal={METEOROLOGY AND ATMOSPHERIC PHYSICS}, author={He, Ping and Nunalee, Christopher G. and Basu, Sukanta and Minet, Jean and Vorontsov, Mikhail A. and Fiorino, Steven T.}, year={2015}, month={Dec}, pages={685–699} }
 @article{he_basu_2015, title={Mesoscale Modeling of Optical Turbulence (C-n(2)) Utilizing a Novel Physically-based Parameterization}, volume={9614}, ISSN={["1996-756X"]}, DOI={10.1117/12.2188227}, abstractNote={In this paper, we propose a novel parameterization for optical turbulence (C2n) simulations in the atmosphere. In this approach, C2n is calculated from the output of atmospheric models using a high-order turbulence closure scheme. An important feature of this parameterization is that, in the free atmosphere (i.e., above the boundary layer), it is consistent with a well-established C2n formulation by Tatarskii. Furthermore, it approaches a Monin-Obukhov similarity-based relationship in the surface layer. To test the performance of the proposed parameterization, we conduct mesoscale modeling and compare the simulated C2n values with those measured during two field campaigns over the Hawaii island. A popular regression-based approach proposed by Trinquet and Vernin (2007) is also used for comparison. The predicted C2n values, obtained from both the physically and statistically-based parameterizations, agree reasonably well with the observational data. However, in the presence of a large-scale atmospheric phenomenon (a breaking mountain wave), the physically-based parameterization outperforms the statistically-based one.}, journal={LASER COMMUNICATION AND PROPAGATION THROUGH THE ATMOSPHERE AND OCEANS IV}, author={He, Ping and Basu, Sukanta}, year={2015} }
 @article{park_manuel_basu_2015, title={Toward Isolation of Salient Features in Stable Boundary Layer Wind Fields that Influence Loads on Wind Turbines}, volume={8}, ISSN={["1996-1073"]}, DOI={10.3390/en8042977}, abstractNote={Neutral boundary layer (NBL) flow fields, commonly used in turbine load studies and design, are generated using spectral procedures in stochastic simulation. For large utility-scale turbines, stable boundary layer (SBL) flow fields are of great interest because they are often accompanied by enhanced wind shear, wind veer, and even low-level jets (LLJs). The generation of SBL flow fields, in contrast to simpler stochastic simulation for NBL, requires computational fluid dynamics (CFD) procedures to capture the physics and noted characteristics—such as shear and veer—that are distinct from those seen in NBL flows. At present, large-eddy simulation (LES) is the most efficient CFD procedure for SBL flow field generation and related wind turbine loads studies. Design standards, such as from the International Electrotechnical Commission (IEC), provide guidance albeit with simplifying assumptions (one such deals with assuming constant variance of turbulence over the rotor) and recommend standard target turbulence power spectra and coherence functions to allow NBL flow field simulation. In contrast, a systematic SBL flow field simulation procedure has not been offered for design or for site assessment. It is instructive to compare LES-generated SBL flow fields with stochastic NBL flow fields and associated loads which we evaluate for a 5-MW turbine; in doing so, we seek to isolate distinguishing characteristics of wind shear, wind veer, and turbulence variation over the rotor plane in the alternative flow fields and in the turbine loads. Because of known differences in NBL-stochastic and SBL-LES wind fields but an industry preference for simpler stochastic simulation in design practice, this study investigates if one can reproduce stable atmospheric conditions using stochastic approaches with appropriate corrections for shear, veer, turbulence, etc. We find that such simple tuning cannot consistently match turbine target SBL load statistics, even though this is possible in some cases. As such, when there is a need to consider different stability regimes encountered by a wind turbine, easy solutions do not exist and large-eddy simulation at least for the stable boundary layer is needed.}, number={4}, journal={ENERGIES}, author={Park, Jinkyoo and Manuel, Lance and Basu, Sukanta}, year={2015}, month={Apr}, pages={2977–3012} }
 @article{wang_basu_2016, title={Utilizing the Kantorovich metric for the validation of optical turbulence predictions}, volume={41}, DOI={10.1364/pcdvtap.2015.pm1c.1}, abstractNote={We propose a novel framework for the estimation of Cn2 in the atmosphere. This framework only requires coarse-resolution temperature and pressure profiles as input. Observations from a field campaign over Hawaii are used for validation.}, number={17}, journal={Optics Letters}, author={Wang, Y. and Basu, S.}, year={2016}, pages={4008–4011} }
 @article{he_nunalee_basu_vorontsov_fiorino_2014, title={Current Status and Challenges in Optical Turbulence Simulations in Various Layers of the Earth's Atmosphere}, volume={9224}, ISSN={["1996-756X"]}, DOI={10.1117/12.2063023}, abstractNote={In this study, we present a brief review on the existing approaches for optical turbulence estimation in various layers of the Earth’s atmosphere. The advantages and disadvantages of these approaches are also discussed. An alternative approach, based on mesoscale modeling with parameterized turbulence, is proposed and tested for the simulation of refractive index structure parameter (C2n ) in the atmospheric boundary layer. The impacts of a few atmospheric flow phenomena (e.g., low-level jets, island wake vortices, gravity waves) on optical turbulence are discussed. Consideration of diverse geographic settings (e.g., flat terrain, coastal region, ocean islands) makes this study distinct.}, journal={LASER COMMUNICATION AND PROPAGATION THROUGH THE ATMOSPHERE AND OCEANS III}, author={He, Ping and Nunalee, Christopher G. and Basu, Sukanta and Vorontsov, Mikhail A. and Fiorino, Steven T.}, year={2014} }
 @article{wang_basu_2014, title={Estimation of Optical Turbulence in the Atmospheric Surface Layer from Routine Meteorological Observations An Artificial Neural Network Approach}, volume={9224}, ISSN={["0277-786X"]}, DOI={10.1117/12.2063168}, abstractNote={The focus of this paper is on the estimation of optical turbulence (commonly characterized by C2n ) near the land-surface using routinely measured meteorological variables (e.g., temperature, wind speed). We demonstrate that an artificial neural network-based approach has the potential to be effectively utilized for this purpose. We use an extensive scintillometer-based C2n dataset from a recent field experiment in Texas, USA to evaluate the accuracy of the proposed approach.}, journal={LASER COMMUNICATION AND PROPAGATION THROUGH THE ATMOSPHERE AND OCEANS III}, author={Wang, Yao and Basu, Sukanta}, year={2014} }
 @article{nunalee_he_basu_vorontsov_fiorino_2014, title={Impact of Large-Scale Atmospheric Refractive Structures on Optical Wave Propagation}, volume={9224}, ISSN={["1996-756X"]}, DOI={10.1117/12.2063022}, abstractNote={Conventional techniques used to model optical wave propagation through the Earth’s atmosphere typically as- sume flow fields based on various empirical relationships. Unfortunately, these synthetic refractive index fields do not take into account the influence of transient macroscale and mesoscale (i.e. larger than turbulent microscale) atmospheric phenomena. Nevertheless, a number of atmospheric structures that are characterized by various spatial and temporal scales exist which have the potential to significantly impact refractive index fields, thereby resulting dramatic impacts on optical wave propagation characteristics. In this paper, we analyze a subset of spatio-temporal dynamics found to strongly affect optical waves propagating through these atmospheric struc- tures. Analysis of wave propagation was performed in the geometrical optics approximation using a standard ray tracing technique. Using a numerical weather prediction (NWP) approach, we simulate multiple realistic atmospheric events (e.g., island wakes, low-level jets, etc.), and estimate the associated refractivity fields prior to performing ray tracing simulations. By coupling NWP model output with ray tracing simulations, we demon- strate the ability to quantitatively assess the potential impacts of coherent atmospheric phenomena on optical ray propagation. Our results show a strong impact of spatio-temporal characteristics of the refractive index field on optical ray trajectories. Such correlations validate the effectiveness of NWP models as they offer a more comprehensive representation of atmospheric refractivity fields compared to conventional methods based on the assumption of horizontal homogeneity.}, journal={LASER COMMUNICATION AND PROPAGATION THROUGH THE ATMOSPHERE AND OCEANS III}, author={Nunalee, Christopher G. and He, Ping and Basu, Sukanta and Vorontsov, Mikhail A. and Fiorino, Steven T.}, year={2014} }
 @article{nunalee_basu_2014, title={Mesoscale Modeling of Low-Level Jets over the North Sea}, volume={2}, ISBN={["978-3-642-54695-2"]}, ISSN={["2196-7806"]}, DOI={10.1007/978-3-642-54696-9_29}, abstractNote={Contemporary onshore and offshore wind resource assessment frameworks incorporate diverse multi-scale weather predictionmodels (commonly known as mesoscale models) to dynamically downscale global-scale atmospheric fields to regional-scale (i.e., spatial and temporal resolutions of a few kilometers and a few minutes, respectively). These high resolution mesoscale models aim at depicting the expected wind behavior (e.g., wind shear, wind turning, topographically induced flow accelerations) at a particular location or region. Over the years, numerous model sensitivity and intercomparison studies have investigated the strengths and weaknesses of the models’ parameterizations (including, but not limited to, planetary boundary layer turbulence) in capturing realistic flows over land. In contrast, only a handful of modeling studies have focused on coastal and offshore flows (e.g., coastal fronts, internal boundary layers, land breeze - sea breeze circulations, low level jets); thus, our understanding and predictive capability of these flows remain less than desirable. This impairment, in combination with the recent world-wide surge in offshore wind energy development, provides the rationale for this study. We are currently evaluating the performance of the Weather Research and Forecasting (WRF) model, a new-generation mesoscale model, in simulating some of the aforementioned coastal and offshore flow phenomena. In this paper, we focus on low-level jets and compare the WRF model-simulated results against the observational data from the FINO1 meteorological mast in the North Sea.We also discuss the sensitivities of the WRF model-generated offshore wind fields with respect to several planetary boundary layer turbulence schemes.}, journal={WIND ENERGY - IMPACT OF TURBULENCE}, author={Nunalee, Christopher and Basu, Sukanta}, year={2014}, pages={197–202} }
 @article{nunalee_basu_2014, title={On the periodicity of atmospheric von Karman vortex streets}, volume={14}, ISSN={["1573-1510"]}, DOI={10.1007/s10652-014-9340-9}, number={6}, journal={ENVIRONMENTAL FLUID MECHANICS}, author={Nunalee, Christopher G. and Basu, Sukanta}, year={2014}, month={Dec}, pages={1335–1355} }
 @article{basu_nunalee_he_fiorino_vorontsov_2014, title={Reconstructing the Prevailing Meteorological and Optical Environment during the Time of the Titanic Disaster}, volume={9224}, ISSN={["1996-756X"]}, DOI={10.1117/12.2063195}, abstractNote={In this paper, we reconstruct the meteorological and optical environment during the time of Titanic’s disaster utilizing a state-of-the-art meteorological model, a ray-tracing code, and a unique public-domain dataset called the Twentieth Century Global Reanalysis. With high fidelity, our simulation captured the occurrence of an unusually high Arctic pressure system over the disaster site with calm wind. It also reproduced the movement of a polar cold front through the region bringing a rapid drop in air temperature. The simulated results also suggest that unusual meteorological conditions persisted several hours prior to the Titanic disaster which contributed to super-refraction and intermittent optical turbulence. However, according to the simulations, such anomalous conditions were not present at the time of the collision of Titanic with an iceberg.}, journal={LASER COMMUNICATION AND PROPAGATION THROUGH THE ATMOSPHERE AND OCEANS III}, author={Basu, Sukanta and Nunalee, Christopher G. and He, Ping and Fiorino, Steven T. and Vorontsov, Mikhail A.}, year={2014} }
 @article{edwards_basu_bosveld_holtslag_2014, title={The Impact of Radiation on the GABLS3 Large-Eddy Simulation through the Night and during the Morning Transition}, volume={152}, ISSN={["1573-1472"]}, DOI={10.1007/s10546-013-9895-x}, number={2}, journal={BOUNDARY-LAYER METEOROLOGY}, author={Edwards, J. M. and Basu, S. and Bosveld, F. C. and Holtslag, A. A. M.}, year={2014}, month={Aug}, pages={189–211} }
 @article{richardson_basu_holtslag_2013, title={Improving Stable Boundary-Layer Height Estimation Using a Stability-Dependent Critical Bulk Richardson Number}, volume={148}, ISSN={["0006-8314"]}, DOI={10.1007/s10546-013-9812-3}, number={1}, journal={BOUNDARY-LAYER METEOROLOGY}, author={Richardson, H. and Basu, S. and Holtslag, A. A. M.}, year={2013}, month={Jul}, pages={93–109} }
 @article{park_basu_manuel_2014, title={Large-eddy simulation of stable boundary layer turbulence and estimation of associated wind turbine loads}, volume={17}, ISSN={["1099-1824"]}, DOI={10.1002/we.1580}, abstractNote={ABSTRACTStochastic simulation of turbulent inflow fields commonly used in wind turbine load computations is unable to account for contrasting states of atmospheric stability. Flow fields in the stable boundary layer, for instance, have characteristics such as enhanced wind speed and directional shear; these effects can influence loads on utility‐scale wind turbines. To investigate these influences, we use large‐eddy simulation (LES) to generate an extensive database of high‐resolution ( ∼ 10 m), four‐dimensional turbulent flow fields. Key atmospheric conditions (e.g., geostrophic wind) and surface conditions (e.g., aerodynamic roughness length) are systematically varied to generate a diverse range of physically realizable atmospheric stabilities. We show that turbine‐scale variables (e.g., hub height wind speed, standard deviation of the longitudinal wind speed, wind speed shear, wind directional shear and Richardson number) are strongly interrelated. Thus, we strongly advocate that these variables should not be prescribed as independent degrees of freedom in any synthetic turbulent inflow generator but rather that any turbulence generation procedure should be able to bring about realistic sets of such physically realizable sets of turbine‐scale flow variables. We demonstrate the utility of our LES‐generated database in estimation of loads on a 5‐MW wind turbine model. More importantly, we identify specific turbine‐scale flow variables that are responsible for large turbine loads—e.g., wind speed shear is found to have a greater influence on out‐of‐plane blade bending moments for the turbine studied compared with its influence on other loads such as the tower‐top yaw moment and the fore‐aft tower base moment.Overall, our study suggests that LES may be effectively used to model inflow fields, to study characteristics of flow fields under various atmospheric stability conditions and to assess turbine loads for conditions that are not typically examined in design standards. Copyright © 2013 John Wiley & Sons, Ltd.}, number={3}, journal={WIND ENERGY}, author={Park, J. and Basu, S. and Manuel, L.}, year={2014}, month={Mar}, pages={359–384} }
 @article{nunalee_basu_2014, title={Mesoscale modeling of coastal low-level jets: implications for offshore wind resource estimation}, volume={17}, ISSN={["1099-1824"]}, DOI={10.1002/we.1628}, abstractNote={Detailed and reliable spatiotemporal characterizations of turbine hub height wind fields over coastal and offshore regions are becoming imperative for the global wind energy industry. Contemporary wind resource assessment frameworks incorporate diverse multiscale prognostic models (commonly known as mesoscale models) to dynamically downscale global-scale atmospheric fields to regional-scale (i.e., spatial and temporal resolutions of a few kilometers and a few minutes, respectively). These high-resolution model solutions aim at depicting the expected wind behavior (e.g., wind shear, wind veering and topographically induced flow accelerations) at a particular location. Coastal and offshore regions considered viable for wind power production are also known to possess complex atmospheric flow phenomena (including, but not limited to, coastal low-level jets (LLJs), internal boundary layers and land breeze–sea breeze circulations). Unfortunately, the capabilities of the new-generation mesoscale models in realistically capturing these diverse flow phenomena are not well documented in the literature. To partially fill this knowledge gap, in this paper, we have evaluated the performance of the Weather Research and Forecasting model, a state-of-the-art mesoscale model, in simulating a series of coastal LLJs. Using observational data sources we explore the importance of coastal LLJs for offshore wind resource estimation along with the capacity to which they can be numerically simulated. We observe model solutions to demonstrate strong sensitivities with respect to planetary boundary layer parameterization and initialization conditions. These sensitivities are found to be responsible for variability in AEP estimates by a factor of two. Copyright © 2013 John Wiley & Sons, Ltd.}, number={8}, journal={WIND ENERGY}, author={Nunalee, Christopher G. and Basu, Sukanta}, year={2014}, month={Aug}, pages={1199–1216} }
 @article{basu_holtslag_caporaso_riccio_steeneveld_2014, title={Observational Support for the Stability Dependence of the Bulk Richardson Number Across the Stable Boundary Layer}, volume={150}, ISSN={["1573-1472"]}, DOI={10.1007/s10546-013-9878-y}, number={3}, journal={BOUNDARY-LAYER METEOROLOGY}, author={Basu, S. and Holtslag, A. A. M. and Caporaso, L. and Riccio, A. and Steeneveld, G-J}, year={2014}, month={Mar}, pages={515–523} }
 @article{holtslag_svensson_baas_basu_beare_beljaars_bosveld_cuxart_lindvall_steeneveld_et al._2013, title={STABLE ATMOSPHERIC BOUNDARY LAYERS AND DIURNAL CYCLES Challenges for Weather and Climate Models}, volume={94}, ISSN={["1520-0477"]}, DOI={10.1175/bams-d-11-00187.1}, abstractNote={The representation of the atmospheric boundary layer is an important part of weather and climate models and impacts many applications such as air quality and wind energy. Over the years, the performance in modeling 2-m temperature and 10-m wind speed has improved but errors are still significant. This is in particular the case under clear skies and low wind speed conditions at night as well as during winter in stably stratified conditions over land and ice. In this paper, the authors review these issues and provide an overview of the current understanding and model performance. Results from weather forecast and climate models are used to illustrate the state of the art as well as findings and recommendations from three intercomparison studies held within the Global Energy and Water Exchanges (GEWEX) Atmospheric Boundary Layer Study (GABLS). Within GABLS, the focus has been on the examination of the representation of the stable boundary layer and the diurnal cycle over land in clear-sky conditions. For this purpose, single-column versions of weather and climate models have been compared with observations, research models, and large-eddy simulations. The intercomparison cases are based on observations taken in the Arctic, Kansas, and Cabauw in the Netherlands. From these studies, we find that even for the noncloudy boundary layer important parameterization challenges remain.}, number={11}, journal={BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY}, author={Holtslag, A. A. M. and Svensson, G. and Baas, P. and Basu, S. and Beare, B. and Beljaars, A. C. M. and Bosveld, F. C. and Cuxart, J. and Lindvall, J. and Steeneveld, G. J. and et al.}, year={2013}, month={Nov}, pages={1691–1706} }
 @article{sim_basu_manuel_2012, title={On Space-Time Resolution of Inflow Representations for Wind Turbine Loads Analysis}, volume={5}, ISSN={["1996-1073"]}, DOI={10.3390/en5072071}, abstractNote={Efficient spatial and temporal resolution of simulated inflow wind fields is important in order to represent wind turbine dynamics and derive load statistics for design. Using Fourier-based stochastic simulation of inflow turbulence, we first investigate loads for a utility-scale turbine in the neutral atmospheric boundary layer. Load statistics, spectra, and wavelet analysis representations for different space and time resolutions are compared. Next, large-eddy simulation (LES) is employed with space-time resolutions, justified on the basis of the earlier stochastic simulations, to again derive turbine loads. Extreme and fatigue loads from the two approaches used in inflow field generation are compared. On the basis of simulation studies carried out for three different wind speeds in the turbine’s operating range, it is shown that inflow turbulence described using 10-meter spatial resolution and 1 Hz temporal resolution is adequate for assessing turbine loads. Such studies on the investigation of adequate filtering or resolution of inflow wind fields help to establish efficient strategies for LES and other physical or stochastic simulation needed in turbine loads studies.}, number={7}, journal={ENERGIES}, author={Sim, Chungwook and Basu, Sukanta and Manuel, Lance}, year={2012}, month={Jul}, pages={2071–2092} }
 @article{wiel_moene_jonker_baas_basu_donda_sun_holtslag_2012, title={The Minimum Wind Speed for Sustainable Turbulence in the Nocturnal Boundary Layer}, volume={69}, ISSN={["1520-0469"]}, DOI={10.1175/jas-d-12-0107.1}, abstractNote={AbstractThe collapse of turbulence in the nocturnal boundary layer is studied by means of a simple bulk model that describes the basic physical interactions in the surface energy balance. It is shown that for a given mechanical forcing, the amount of turbulent heat that can be transported downward is limited to a certain maximum. In the case of weak winds and clear skies, this maximum can be significantly smaller than the net radiative loss minus soil heat transport. In the case when the surface has low heat capacity, this imbalance generates rapid surface cooling that further suppresses the turbulent heat transport, so that eventually turbulence largely ceases (positive feedback mechanism). The model predicts the minimum wind speed for sustainable turbulence for the so-called crossing level. At this level, some decameters above the surface, the wind is relatively stationary compared to lower and higher levels. The critical speed is predicted in the range of about 5–7 m s−1, depending on radiative forcing and surface properties, and is in agreement with observations at Cabauw. The critical value appears not very sensitive to model details or to the exact values of the input parameters. Finally, results are interpreted in terms of external forcings, such as geostrophic wind. As it is generally larger than the speed at crossing height, a 5 m s−1 geostrophic wind may be considered as the typical limit below which sustainable, continuous turbulence under clear-sky conditions is unlikely to exist. Below this threshold emergence of the very stable nocturnal boundary layer is anticipated.}, number={11}, journal={JOURNAL OF THE ATMOSPHERIC SCIENCES}, author={Wiel, B. J. H. and Moene, A. F. and Jonker, H. J. J. and Baas, P. and Basu, S. and Donda, J. M. M. and Sun, J. and Holtslag, A. A. M.}, year={2012}, month={Nov}, pages={3116–3127} }
 @article{wiel_basu_moene_jonker_steeneveld_holtslag_2011, title={Comments on "An Extremum Solution of the Monin-Obukhov Similarity Equations"}, volume={68}, ISSN={["0022-4928"]}, DOI={10.1175/2010jas3680.1}, abstractNote={Recently, Wang and Bras (2010, hereafter WB10)postulated an extremum hypothesis (EH) of turbulenttransportintheatmosphericsurfacelayer(ASL).Basedon this hypothesis, they derived a unique solution of thewell-knownMonin–Obukhovsimilaritytheory(MOST)equations.Throughoutthepaper,WB10highlightedthesignificance of EH and associated results. We summa-rize a few of their claims below (mostly in the authors’own words):}, number={6}, journal={JOURNAL OF THE ATMOSPHERIC SCIENCES}, author={Wiel, B. J. H. and Basu, S. and Moene, A. F. and Jonker, H. J. J. and Steeneveld, G. -J. and Holtslag, A. A. M.}, year={2011}, month={Jun}, pages={1405–1408} }
 @article{basu_ruiz-columbie_phillipson_harshan_2010, title={Local scaling characteristics of Antarctic surface layer turbulence}, volume={4}, ISSN={["1994-0416"]}, DOI={10.5194/tc-4-325-2010}, abstractNote={Abstract. Over the past years, several studies have validated Nieuwstadt's local scaling hypothesis by utilizing turbulence observations from the mid-latitude, nocturnal stable boundary layers. In this work, we probe into the local scaling characteristics of polar, long-lived stable boundary layers by analyzing turbulence data from the South Pole region of the antarctic plateau.
                    }, number={3}, journal={CRYOSPHERE}, author={Basu, S. and Ruiz-Columbie, A. and Phillipson, J. A. and Harshan, S.}, year={2010}, pages={325–331} }