The Coplane Analysis Technique for Three-Dimensional Wind Retrieval Using the HIWRAP Airborne Doppler Radar

An attempt is made to simulate a pre-monsoon hailstorm event over Bangladesh using the high-resolution Weather Research and Forecasting (WRF) model. A severe hailstorm event embedded with multi-cell thunderstorm occurred over the North-central region of Bangladesh and adjacent West Bengal state of India on 30 March 2018, which moved towards the South-East direction up to its highest intensity stage during 0900-1030 UTC is selected for the study. The WRF model is used to investigate the dynamical and thermodynamical characteristics of the selected hail producing thunderstorm event. The model is run on a double nested domain at 9 and 3 km horizontal resolutions using the Kain-Fritsch (new Eta) cumulus and Mellor-Yamada Nakanishi and Niino Level 2.5 (MYNN2) planetary boundary layer parameterization schemes. The analysis of the accumulated hail, mean sea level pressure, vertical wind shear, vertical (w) component of wind, relative humidity along with low level wind, convective available potential energy (CAPE) and convective inhibition energy (CINE), rainfall (mm) parameters are investigated. Rainfall is compared with that of observed value. The high amount of relative humidity (>90%), CAPE (>3000 JKg-1) and vertical wind shear (>40 ms-1) help to form severe convective storm which vertically developed upto 150 hPa level. In addition, the high value of w component of winds (~0.4 ms-1) helps updraft process which is favorable for hail formation. The present combination of parameterization schemes of model is found suitable to capture the selected hailstorm event reasonably well, but more similar hailstorm events need to be studied to make any final conclusions. The Dhaka University Journal of Earth and Environmental Sciences, Centennial Special Volume June 2022: 123-130

Generalizing radar interferometry to three‐dimensional space, we present a model which predicts the variation with respect to frequency of the phase of the cross‐spectrum obtained between two separate antennas. The slope of this variation is proportional to the cosine of the angle between the horizontal wind and the interferometer baseline, and inversely proportional to the horizontal wind amplitude. The zero‐frequency phase depends on the horizontal wind speed and direction, on the vertical wind velocity, and on the anisotropy of the backscattered power with respect to the zenith. The model also allows us to predict qualitatively the effects of specularity, beam shape, and random turbulence on the phase versus frequency variation. Assuming a spaced receiver setup with three baselines rotated by 120°, we present an implementation scheme of the radar interferometry technique which yields a three‐dimensional wind estimate and a parameter characterizing the anisotropy of the echo power distribution. Finally, we argue that the radar interferometry horizontal wind measurements will suffer from limitations similar to those of the so‐called apparent velocity as both techniques are related by Fourier transform, and that the vertical wind component will be unbiaised by anisotropy in the backscattered power.

The effect of the thermospheric vertical neutral wind on vertical total electron content (vTEC) variations including longitudinal anomaly, remaining winter anomaly, mid-latitude summer night anomaly, and semiannual anomaly is studied at mid-latitude regions around zero magnetic declination at midnight during high solar activity. By using the principal component analysis (PCA) numerical technique, this work studies the spatial and temporal variations of the ionosphere at midnight over mid-latitude regions during 2000–2002. PCA is applied to a time series of global vTEC maps produced by the International Global Navigation Satellite System (GNSS) Service. Four regions were studied in particular, each located at mid-latitude and approximately centered at zero magnetic declination, with two in the northern hemisphere and two in southern hemisphere, and all are located near and far from geomagnetic poles in each case. This technique provides an effective method to analyze the main ionospheric variabilities at mid-latitudes. PCA is also applied to the vTEC computed using the International Reference Ionosphere (IRI) 2012 model, to analyze the capability of this model to represent ionospheric variabilities at mid-latitude. Also, the Horizontal Wind Model 2007 (HWM07) is used to improve our climatology interpretation, by analyzing the relationship between vTEC and thermospheric wind, both quantitatively and qualitatively. At midnight, the behavior of mean vTEC values strongly responds to vertical wind variation, experiencing a decrease of about 10–15% with the action of the positive vertical component of the field-aligned neutral wind lasting for 2 h in all regions except for Oceania. Notable results include: a significant increase toward higher latitudes during summer in the South America and Asia regions, associated with the mid-latitude summer night anomaly, and an increase toward higher latitudes in winter in the North America and Oceania regions, highlighting the remnant effect of the winter anomaly. Finally, the longitudinal variations of east–west differences, named longitudinal anomaly, show maximum values in March for North America, in December for South America and Oceania, and are not shown for Asia. Our results show that at mid-latitudes regions, the IRI model represents midnight ionospheric mean values with a similar spatial distribution, but the values are always lower than those obtained by GNSS. The differences between IRI and GNSS results include: the longitudinal anomaly is characterized by a stronger semiannual variation in both North America and South America, with a maximum in the equinoxes, while for the Asian region, the behavior is almost constant throughout the years, and finally, there is an absence of the winter anomaly remnant.

In this paper, we first establish some sufficient and some necessary global optimality conditions for quadratic integer programming problems. Then we present a new local optimization method for quadratic integer programming problems according to its necessary global optimality conditions. A new global optimization method is proposed by combining its sufficient global optimality conditions, local optimization method and an auxiliary function. The numerical examples are also presented to show that the proposed optimization methods for quadratic integer programming problems are very efficient and stable.

Comparison of ionospheric electrical conductances inferred from coincident radar and spacecraft measurements and photoionization models

In situ measurements of the zonal and vertical components of neutral winds and the kinetic temperature being made by the DE‐B Wind and Temperature Spectrometer (WATS) in the upper thermosphere provide the opportunity to gain new knowledge of polar region physics. On the basis of the data we have obtained to date we confirm that the global thermosphere wind distribution is primarily thermally driven over the earth from the mid‐afternoon sector. The velocities range from tens to a few hundred meters per second. However, the polar cap and auroral region wind systems are highly dynamic with velocities as high as 1 km sec−1. They appear as superimposed on the thermally driven wind system. The polar regions' zonal wind patterns appear to be generally in accord with the solar and anti‐solar ion convection patterns previously observed and described by investigators in many publications. In addition we have observed vertical motions with velocity peaks from 100‐250 m/sec−1 that frequently correlate well with peaks in the zonal component. Simultaneously observed exospheric kinetic temperatures show expected values at sub‐auroral latitudes and variations of hundred of degrees in the polar regions. There are apparent correlations with vertical motions, but less obvious correlations with the winds' zonal components.

The influences of horizontal wind gradients on “apparent” and “true” spaced antenna wind estimators are examined within the scope of a linear wind model. It is found that apparent velocity estimators are highly sensitive to horizontal gradients in horizontal wind components. Systematic errors in true velocity estimates increase with the probing radar beam width. For a beam width of ∼6° and realistic values of horizontal wind gradients, systematic errors in true velocity estimates remain less than ∼4 m/s at mesospheric altitudes in the absence of gradients in the vertical wind component.

Improved techniques for measuring horizontal and vertical wind components and state variables on research aircraft are presented. They include a filtering method for correcting ground speed and position Inertial Navigation System data with Global Positioning System data, use of moist-air thermodynamic properties in the true airspeed calculation, postflight calculation of the aircraft vertical velocity, and calibration of airflow attack and sideslip angles from the two air-data systems on each aircraft—a radome gust probe and a pair of fuselage-mounted Rosemount 858Y probes. Winds from the two air-data systems are compared for the National Oceanic and Atmospheric Administration WP-3D aircraft. As an evaluation of these techniques, data from the two aircraft during side-by-side low-level constant-heading runs are compared for mean and turbulent measurements of wind, ambient temperature, and absolute humidity. Small empirical offsets were determined and applied to the two latter scalars as well as to static and dynamic pressures. Median differences between mean horizontal wind components from nine comparisons were within 0.1 ± 0.4 m s−1. Median differences in latent heat and sensible heat fluxes and momentum flux components were 3.5 ± 15 W m−2, 0 ± 2.5 W m−2, and 0 ± 0.015 Pa, respectively.

Abstract. In stratiform rainfall, the melting layer (ML) is often visible in radar observations as an enhanced reflectivity band, the so-called bright band. Despite the ongoing debate on the exact microphysical processes taking place in the ML and on how they translate into radar measurements, both model simulations and observations indicate that the radar-measured ML properties are influenced by snow microphysical processes that take place above it. There is still, however, a lack of comprehensive observations to link the two. To advance our knowledge of precipitation formation in ice clouds and provide new insights into radar signatures of snow growth processes, we have investigated this link. This study is divided into two parts. Firstly, surface-based snowfall measurements are used to develop a new method for identifying rimed and unrimed snow from X- and Ka-band Doppler radar observations. Secondly, this classification is used in combination with multifrequency and dual-polarization radar observations collected during the Biogenic Aerosols – Effects on Clouds and Climate (BAECC) experiment in 2014 to investigate the impact of precipitation intensity, aggregation, riming and dendritic growth on the ML properties. The results show that the radar-observed ML properties are highly related to the precipitation intensity. The previously reported bright band “sagging” is mainly connected to the increase in precipitation intensity. Ice particle riming plays a secondary role. In moderate to heavy rainfall, riming may cause additional bright band sagging, while in light precipitation the sagging is associated with unrimed snow. The correlation between ML properties and dual-polarization radar signatures in the snow region above appears to be arising through the connection of the radar signatures and ML properties to the precipitation intensity. In addition to advancing our knowledge of the link between ML properties and snow processes, the presented analysis demonstrates how multifrequency Doppler radar observations can be used to get a more detailed view of cloud processes and establish a link to precipitation formation.

Characterizing the relative role of low-frequency and turbulent processes in the nocturnal boundary layer through the analysis of two-point correlations of the wind components

Computational models and inverse dynamic optimization methods are used to predict in-vivo spinal loading. Spinal force is conventionally predicted using the constant loading path method, which is based on the concept that the physiological directions of the spine loads follow the same path of the spinal curve. However, the global convergence optimization method, in which the instantaneous center of rotation of the joint should be also predicted, is necessary for accurate prediction of joint forces of the human body. In this study, we investigate the joint forces, instantaneous centers of rotation, and muscle forces of the human lumbar spine using both global convergence optimization method and constant loading path method during flexion, upright standing, and extension postures. The joint forces predicted using the constant loading path method were 130%, 234%, and 253% greater than those predicted using the global convergence optimization method for the three postures. The instantaneous centers of rotation predicted using the global convergence optimization method were segment level-dependent and moved anteriorly in the flexion and posteriorly in the extension, whereas those predicted using the constant loading path method moved posteriorly in both the flexion and extension. The data indicated that compared to the global convergence optimization method, the constant loading path method introduces additional constraints to the spinal joint model, and thus, it results in greater joint and muscle forces.

Precise knowledge of winds and temperatures in the middle atmosphere is critical for the localization and characterization of infrasound sources. We present the concept, design, and measurement capabilities of a compact, mobile Doppler lidar system developed at the Leibniz Institute of Atmospheric Physics (IAP). This system, is designed for Doppler-Mie, -Rayleigh, and -resonance measurements in the middle atmosphere.The daylight-capable instrument features a compact volume of about 1 m³ and is engineered for easy deployment as part of an array of lidar units. We highlight recent results, emphasizing collocated, high-resolution measurements of wind and temperature. By employing three to five individual fields of view, the system can measure both horizontal and vertical wind components. Between altitudes of 3 and 25 km, the instrument utilizes the narrowband properties of Mie backscatter, relying solely on aerosol backscatter to achieve precise three-dimensional wind measurements. In this altitude range, a novel method enables the measurement of vertical winds with an accuracy better than 0.5 m/s and a time resolution of just 60 seconds.Above 25 km, winds will be measured using Doppler-Rayleigh and -resonance techniques. Concurrent Rayleigh temperature measurements utilize advanced aerosol correction methods, taking advantage of the instrument's high sensitivity to aerosols.The feasibility of integrating this lidar system into a European lidar array is being investigated within the EULIAA (European Lidar Array for Atmospheric Climate Monitoring) project. The transfer of this technology to industry is currently being developed through the LidarCUBE project.

*† ‡ § An efficient and high-fidelity design approach is proposed by combining global and local optimization methods for wing planform and surface design. For enhanced design results, aerodynamic shape optimization process is carried out via 2-stage with different optimization strategy. In the first stage, global optimization techniques are applied to planform design with a few geometric design variables. In the second stage, local optimization techniques are used for wing surface design with a lot of design variables to maintain a sufficient design space with high DOF (Degree of Freedom) geometric change. For global optimization, meta-modeling techniques such as RS (Response Surface) and Kriging methods are used in conjunction with Genetic Algorithm (GA). For local optimization, a discrete adjoint variable method is used. By the successive combination of global and local optimization techniques, drag minimization is performed for a multi-body aircraft configuration while maintaining the baseline lift and the wing weight at the same time. Through the design process, performances of the test models are remarkably improved in comparison with the single stage design approach. The capability of proposed design framework including wing planform design variables can be evaluated by the drag decomposition method which can provide improvement of induced drag and wave drag, respectively.

A reconsideration on the resolution of phase stability analysis using stochastic global optimization methods: Proposal of a reliable set of benchmark problems

Features of several well-known global and local optimization methods were discussed and their robustness and efficiency were tested on several artificial test functions in Matlab environment. The tested local methods were the interior-point, the quasi-Newton method, Nelder–Mead simplex, the pattern search, the NEWUOA and the BOBYQA methods. The global methods were the genetic algorithm (GA), the simulated annealing (SA), the particle swarm optimization (PSO), and the covariance matrix adaptation evolutionary strategy (CMA-ES) methods (see subsections 2.2 and 2.3 for their details). Furthermore, a novel global optimization method, called FOCusing robusT Optimization with Uncertainty-based Sampling (FOCTOPUS), which proved to be very efficient in the optimization of constrained and highly correlated parameters of combustion kinetic models, was also tested. The test functions were selected in such a way that they had a variety of features: uni-modal and multi-modal, differentiable and non-differentiable, separable and non-separable, low dimensional and high dimensional. The following test functions were used: the 20D Alpine function, the 4D Ackley function, the Cross-in-tray 2D function, the Hartmann-6D function, the Holder table 2D function, the 5D Rastrigin function, the 5D Rosenbrock function, the 4D modified Rosenbrock function, the 20D Zakharov function and a typical 2D multi-modal function. The general conclusion here is that, the global methods performed well on the multi-modal and high-dimensional test functions while the local methods were superior in the case of low-dimensional and uni-modal test functions. For the highly multi-modal test functions, the GA was better than all the other methods. The FOCTOPUS method proved to be inferior to GA for most of the test functions, thus its application cannot be generally recommended.