dual-Doppler Radar Measurements Research Articles

Machine Learning-Based Classification of Human Behaviors and Falls in Restroom via Dual Doppler Radar Measurements.

This study presents a radar-based remote measurement system for classification of human behaviors and falls in restrooms without privacy invasion. Our system uses a dual Doppler radar mounted onto a restroom ceiling and wall. Machine learning methods, including the convolutional neural network (CNN), long short-term memory, support vector machine, and random forest methods, are applied to the Doppler radar data to verify the model’s efficiency and features. Experimental results from 21 participants demonstrated the accurate classification of eight realistic behaviors, including falling. Using the Doppler spectrograms (time–velocity distribution) as the inputs, CNN showed the best results with an overall classification accuracy of 95.6% and 100% fall classification accuracy. We confirmed that these accuracies were better than those achieved by conventional restroom monitoring techniques using thermal sensors and radars. Furthermore, the comparison results of various machine learning methods and cases using each radar’s data show that the higher-order derivative parameters of acceleration and jerk, and the motion information in the horizontal direction are the efficient features for behavior classification in a restroom. These findings indicate that daily restroom monitoring using the proposed radar system accurately recognizes human behaviors and allows early detection of fall accidents.

Characterizing turbine inflow during a stability transition using dual-Doppler radar measurements

Measurements from two specialized Doppler radars are used to construct a dual-Doppler synthesis of the boundary layer wind flow during an unstable-to-stable transition. Three rotor sweep concepts are inserted into the flow to evaluate turbine inflow variability across the rotor sweeps. One-second turbine inflow forecasts are constructed using an advanced advection correction technique at each rotor grid point allowing for detailed statistical analysis of shear, veer, and turbulence intensity across the three rotor sweeps.

Very short-term probabilistic forecasting of wind power based on dual-Doppler radar measurements in the North Sea

Probabilistic very short-term forecasts of wind farm power can provide valuable information for electricity market participants, especially in power systems with high penetration of wind energy. Recently, the first dual-Doppler radar measurements of an offshore wind farm have become available. A probabilistic very short-term forecasting model of wind power is proposed using observed wind speeds and directions from a dual-Doppler radar system. Predictive wind speed distributions are derived from three-dimensional dual-Doppler observations covering the wind farm and its vicinity. To estimate the power generated by the wind turbines, a power curve constructed with dual-Doppler observations is used. A forecasting horizon of five minutes is evaluated. Results show an improved performance of a deterministic radar-based forecast of power versus the benchmarks persistence and climatology, and also a high potential for a wind power probabilistic forecast.

Dual-Doppler radar analysis of a near-shore line-shaped convective system on 27 July 2011, Korea: a case study

In the summer rainy season, the Korean Peninsula is frequently influenced by severe weather phenomena such as floods and rain-induced landslides. A band-shaped precipitation system associated with unstable atmospheric conditions occurred over northwest Korea on 27 July 2011. This precipitation system produced heavy rainfall over the Seoul metropolitan area, which received over 80 mm h−1 of rainfall and suffered 70 weather-related fatalities. To investigate the precipitation system, we used diverse meteorological data of environmental condition and estimated three-dimensional wind field from dual-Doppler radar measurements of vertical air motion. Environmental conditions included high equivalent potential temperature (θe) of over 355 K at low levels, and low θe of under 330 K at middle levels, causing vertical instability. Furthermore, a pressure trough was located to the northwest of Korea, favouring the development of the band-shaped precipitation system. The tip of the band-shaped precipitation system was made up of line-shaped convective systems (LSCSs) that caused flooding and landslides, and the LSCSs were continuously enhanced by merging between new cells and the pre-existing cell. The position of merging moved from the coast to offshore areas and influenced the positioning of the regions of enhanced convection. In turn, this affected the roughness of the convective cell and the internal structure of the enhanced convective regions. Onshore, the convective area was higher than in offshore areas because of strong convergence (≤−4×10−4 s−1) at low levels caused by friction over land. The strong convergence generated strong updraft (≥4 m s−1) that influenced the height of the convective area. The convective region offshore was wider than that onshore because of weak convergence (≥−2.2×10−4 s−1) at low levels. Updraft in offshore areas was weak (≤3 m s−1) compared with onshore, resulting in a lower and wider convective area. Spatial variations in surface roughness result in different structural features and profiles of divergence within LSCSs, even if they originate in the same convective region.

Integration of the VHF wind6profiler data within dual doppler wind synthesis

During the Mesoscale Alpine Programme experiment, three Doppler weather radars and a VHF wind-profiler radar were deployed in the lago Maggiore area. The VHF radar was located in the area scanned by the weather radars. For IOP-2a (September 17–18, 1999), 3-D wind fields were retrieved from dual Doppler weather observations using the MANDOP analysis. In this paper, we present the impact on the reconstruction of the wind field when VHF wind-profiler radar data are used as an additional constraint among dual Doppler-radar measurements. The interest of VHF radar data is related to observations at the upper limit of, and above, the convective cell; and to the vertical wind measurements, not measured by Doppler weather radars. The experiment consists to integrate the horizontal wind, or the vertical wind and both of them in the retrieval. For each case, the difference between the reference and the new wind-field is computed. The positive effect of including VHF wind measurements in the upper layers, above 5km, is demonstrated in that it helps to get a better conditioning of the system, especially along the radar base line, which is the classical “hard region” for retrieving the three-dimensional wind field in a dual Doppler-radar configuration.

Structure and Evolution of Winter Cyclones in the Central United States and Their Effects on the Distribution of Precipitation. Part V: Thermodynamic and Dual-Doppler Radar Analysis of a Squall Line Associated with a Cold Front Aloft

Abstract On 8–9 March 1992, a long-lived squall line traversed the state of Kansas, producing hail and damaging winds. It was shown previously that this squall line was part of a synoptic-scale rainband 2000 km in length that was associated with a cold front aloft (CFA). The present study is concerned with the detailed mesoscale structure of this squall line and its relationship to the CFA. Examination of synoptic-scale cross sections based on rawinsonde ascents, and a mesoscale cross section of winds derived from dual-Doppler radar measurements, shows that the squall line was exactly coincident with the “nose” of the CFA. The dual-Doppler analysis also shows that the inflow of air to the squall line was elevated, drawing in air from the potentially unstable layer within the weak warm frontal–like feature that was being occluded by the CFA. The stability analysis of the air in the pre-squall-line environment shows that when the CFA overtook the surface position of the drytrough, the thermal and moisture s...

The Microphysical Structure and Evolution of Hawaiian Rainband Clouds. Part I: Radar Observations of Rainbands Containing High Reflectivity Cores

Abstract Radar reflectivity factors exceeding 60 dBZ are documented within shallow ( 0°C), summertime tropical rainbands offshore of the island of Hawaii. Dual-Doppler radar measurements from the Hawaiian Rainband Project are used to document the formation, evolution, and kinematic structure of the high reflectivity cores. The authors show that extremely high radar reflectivities (50–60 dBZ) can develop from echo free regions (−20 dBZ) within approximately 15 min and are preceded by 5–9 m s−1 peak updrafts. High reflectivities (>50 dBZ) typically first formed in the middle or upper part of the clouds. Over the next 10–15 min, the mature high reflectivity cores extended vertically through the cloud depth and then collapsed to the surface as the updrafts weakened. A near-upright orientation of most updrafts producing these high reflectivity cores is conceptually consistent with the idea that large raindrops grow in the highest liquid water content while falling through the updraft core. Strong...

Mesoscale Downdraft Influences on Vertical Vorticity in a Mature Mesoscale Convective System

Abstract The vorticity dynamics of a lower-tropospheric mesovortex within a mature mesoscale convective system (MCS) is investigated with observations from a special sounding network and with dual-Doppler radar measurements. The data show that the vorticity distribution and tendency were dictated by the mesoscale downdraft, which formed within the storm's trailing stratiform region, and not by the mesoscale updraft. At midlevels, preexisting vertical vorticity was amplified by convergence as environmental air overtook the storm from the rear and funneled into the evaporatively cooled mesoscale downdraft. Vertical vorticity within the stratiform region also increased by the twisting of horizontal vorticity associated with a backing wind. The horizontal vorticity vector pointed opposite the velocity vector and tipped into positive vertical vorticity when the Row encountered the mesoscale downdraft. At lower-middle storm levels the twisted vorticity was subsequently amplified by convergence along with preexi...

Multiscale Analysis of a Mature Mesoscale Convective Complex

Abstract A multiscale analysis reveals diverse atmospheric structure and processes within a mesoscale convective complex (MCC) observed during the Oklahoma-Kansas Preliminary Regional Experiment for STORM-Central (PRE-STORM) experiment. This midlatitude system was the second in a series of four MCCs that developed and traveled along a quasi-stationary frontal zone over the central United States on 3–4 June 1985. Objectively analyzed mesoscale upper-air soundings encompassing the MCC are interpreted in tandem with more detailed dual-Doppler radar measurements that disclose the storm's internal airflow and precipitation structure. The mature MCC is found to include a variety of local environments and associated weather, ranging from tornadic thunderstorms to more linear convective bands and widespread chilling rains. A corresponding spectrum of mesoscale ver6cW-motion profiles is documented. These findings are related to previous composite-based portrayals of MCCs, as well as detailed case studies of simple...

Initiation and Evolution of Updraft Rotation within an Incipient Supercell Thunderstorm

Abstract One of the distinguishing characteristics of a supercell thunderstorm is the presence of a rotating updraft. During the past 30 years, various hypotheses have been proposed to explain the initiation and maintenance of rotation. However, attempts to verify the initiation process have been frustrated by the lack of multiple-Doppler radar measurements at the time that the first rotating updraft appears. Discussed in this paper are dual-Doppler radar measurements that successfully captured the initiation and evolution of rotation in the Agawam, Oklahoma, storm of 6 June 1979, which occurred during the storm-scale phase of the Severe Environmental Storms and Mesoscale Experiment (SESAME). The process leading to updraft rotation appears to follow that proposed in 1968 by Fujita and Grandoso, whereby a middle-altitude vorticity couplet formed on the downwind flanks of a strong nonrotating updraft, with cyclonic vertical vorticity on the right-forward flank and anticyclonic vertical vorticity on the left...

Organization and Structure of Clouds and Precipitation on the Mid-Atlantic Coast of the United States. Part IV: Retrieval of the Thermodynamic and Cloud Microphysical Structures of a Frontal Rainband from Doppler Radar Data

Abstract The thermodynamic and cloud structure of a relatively weak wintertime frontal rainband are derived from dual-Doppler radar measurements, soundings and high resolution surface observations, and with a cloud model. These derivations are simplified by the high degree of two-dimensionality and steadiness of the rainband. Water vapor, cloud water, cloud ice, rain, and snow are parameterized in the cloud model, subject to a temperature distribution that is constrained to a dynamical balance. Air temperature is derived from buoyancy, which is retrieved from the airflow assuming momentum and heat balance. The results of the thermodynamic and cloud microphysical retrieval are compared with airborne measurements in the rainband. The analysis indicates that the rainband was driven by a weak cold front aloft (CFA), which made the prefrontal air conditionally symmetrically unstable. The CFA appeared as a midlevel intrusion of cold, dry air on the mesoγ scale. The CFA interacted dynamically with the planetary ...

Dynamics and Fine Structure of a Microburst

Abstract Details of the structure of a moderate reflectivity microburst were provided by dual-Doppler radar measurements during the Phoenix II convective boundary layer experiment. The dated allowed high resolution of the descending microburst in both time and space. Thermodynamic fields of virtual potential temperature and buoyancy retrieved from the radar measurements indicated that the downdraft was associated with a minimum in virtual potential temperature, rather than coinciding with a maximum in precipitation loading. The physical separation of the downdraft from the reflectivity maximum was especially pronounced during the later stages of the microburst and was partly due to the tilled reflectivity core descending more rapidly than the downdraft. The downdraft corms also descended at a rate slower than the magnitude of the maximum downdraft so that air was continually converging and entraining into the downdraft above the level of its peak value and was detraining and diverging below it. The retrie...

Considerations in Estimating Horizontal Wind Gradients from an Individual Doppler Radar or a Network of Wind Profilers

Applications of Doppler weather radar data to the analysis of wind fields are reviewed. Radial velocity measurements from a single radar are used to estimate horizontal wind vectors within small azimuthal sectors using two different models. One assumes a uniform wind, the other a linear wind within the sector. Errors in wind estimates owing to gradients of wind are derived using harmonic analysis. The radar data analysis techniques are tested on complex wind patterns which were reconstructed from dual-Doppler radar measurements.

Clear-Air Roll Vortices and Turbulent Motions as Detected with an Airborne Gust Probe and Dual-Doppler Radar

Abstract A case-study comparison is made of simultaneous airborne gust probe and dual-Doppler radar measurements of motions associated with roll vortices in the optically clear planetary boundary layer. Inter-comparison of the cross-roll component of motion is emphasized. Some similarities and some differences in the data obtained with the two systems are discussed. Considering the differences in measurement techniques, agreement is good between the independent depictions of the roll structure and quantitative determinations of the intensities and predominant scales of eddy motion. The observed roll vortices fit descriptions and cause-effect relationships from certain models and other observations.

Severe Thunderstorm Internal Structure from Dual-Doppler Radar Measurements

AbstractDual-Doppler radar data were analyzed for three different times during the life cycle of a severe thunderstorm. The thunderstorm developed a double vortex inside as a tornado was generated beneath the cloud.The organized kinematic and precipitation internal structure of the thunderstorm support a theoreticaldouble-vortex thunderstorm model that was developed earlier. The horizontal perturbation and relativewinds, vertical winds, horizontal divergence and vorticity are compared for the three different times ofmeasurement. The measurements and theoretical model provide new explanations of the severe thunderstorm and the relationship of associated tornadoes.

Secondary flow fields in the planetary boundary layer estimated from dual-Doppler radar measurements during snow conditions

Secondary flow fields in the planetary boundary layer estimated from dual-Doppler radar measurements during snow conditions

Internal airflow of a convective storm from dual-Doppler radar measurements

The dual-Doppler radar coplane method of scanning and data reduction has been used to determine the internal airflow and radar reflectivity structure of a convective storm. Cumulus convection growing in a moderately sheared wind environment resulted in a nonsteady, moderate intensity thunderstorm. Precipitation fallout and downward moving air are found downshear of an updraft inclined in the downshear direction. Rapid storm translation, vertical shear of the ambient wind, and slow subcloud ascent of inflow air act to establish this observed draft configuration. The absence of significant cold air outflow and its attendant gust front at the surface is attributed to (i) appreciable inflow of slow moving air into the downdraft at the middle layers and (ii) the fact that the potentially coldest air was located too low to contribute significantly to a deep downdraft circulation.

NSSL Dual-Doppler Radar Measurements in Tornadic Storms: a Preview

Abstract Some results of the first 10 cm dual-Doppler radar measurements in a tornadic storm are presented. A mesoscale, cyclonic circulation confirms proposed single Doppler vortex signature and indicates that the curved reflectivity hook echo is around the periphery of the circulation. The interpolated tornado position is within the mesocyclone where high-variance Doppler velocity spectra suggest strong velocity gradients.