@article{he_2016, title={A high order finite difference solver for massively parallel simulations of stably stratified turbulent channel flows}, volume={127}, journal={Computers & Fluids}, author={He, P.}, year={2016}, pages={161–173} } @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{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{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{nunalee_he_basu_minet_vorontsov_2015, title={Mapping optical ray trajectories through island wake vortices}, volume={127}, number={3}, journal={Meteorology and Atmospheric Physics}, author={Nunalee, C. G. and He, P. and Basu, S. and Minet, J. and Vorontsov, M. A.}, year={2015}, pages={355–368} } @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{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{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{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} }