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ABSTRACT The use of acoustic Doppler current profilers (ADCP) for discharge measurements and three-dimensional flow mapping has increased rapidly in recent years and has been primarily driven by advances in acoustic technology and signal processing. Recent research has developed a variety of methods for processing data obtained from a range of ADCP deployments and this paper builds on this progress by describing new software for processing and visualizing ADCP data collected along transects in rivers or other bodies of water. The new utility, the Velocity Mapping Toolbox (VMT), allows rapid processing (vector rotation, projection, averaging and smoothing), visualization (planform and cross-section vector and contouring), and analysis of a range of ADCP-derived datasets. The paper documents the data processing routines in the toolbox and presents a set of diverse examples that demonstrate its capabilities. The toolbox is applicable to the analysis of ADCP data collected in a wide range of aquatic environments and is made available as open-source code along with this publication. Published 2012. This article is a U.S. Government work and is in the public domain in the USA. [ABSTRACT FROM AUTHOR]

Abstract: A methodology for using RF Doppler data for spin-axis estimation is presented. The NASA Radiation Belt Storm Probes (RBSP) mission, a dual-spacecraft mission planned for a 2012 launch, will yield valuable insights into the physical dynamics and processes of the Earth''s radiation belts, particularly those that produce hazardous space weather effects and those that can affect solar system exploration. Both spacecraft have on-board Sun sensors that, in conjunction with magnetometer data, provide the required data to determine the attitude. However, the quality of the magnetometer measurements is compromised at higher altitudes because of a weaker magnetic field and also during solar storms because of variations in the Earth''s magnetic field. Each spacecraft''s on-board S-band radio frequency (RF) system includes a JHU/APL Frontier Radio transceiver, which provides a coherent downlink signal used for Doppler navigation. The RF system also includes two low-gain antennas offset from the spin axis with boresights parallel to the spin and anti-spin axes. Due to the spin of the spacecraft, a Doppler-induced modulation is present on the downlink carrier. Once the orbit determination is performed and the Doppler signal is analyzed, this modulation, or spin signature, is apparent. This spin signature can be used to accurately determine the spin rate, spin phase, and, in conjunction with Sun sensor data, the spin axis orientation. This provides a level of system redundancy with the magnetometer for attitude determination. The Sun sensor provides the angle from the spin axis to the Sun vector; the amplitude of spin signature on the Doppler data provides the instantaneous aspect angle from the spin axis to the ground station. These two measurements establish the spin axis direction. This paper describes the established theory and a method for processing the spin signature and determining the spin axis as applicable to the RBSP spacecraft. Further, RF-related errors on the Doppler carrier frequency measurement are characterized and related to the error in the spin axis orientation determination. Finally, this paper introduces the concept of attitude determination by processing the Doppler spin signature data alone over a period of time that encompasses a sufficient change to the spin axis/ground station aspect angle. This provides a further level of redundancy in the event of a failed Sun sensor. Results from processing actual data from a current mission are given. [Copyright &y& Elsevier]

Observations of semidiurnal currents from high-frequency radio Doppler current meters and moored acoustic Doppler current profilers (ADCPs) in the Kauai Channel, Hawaii, are described and compared with two primitive equation numerical models of the tides. The Kauai Channel, separating the islands of Oahu and Kauai, is a site of strong internal tide generation by the barotropic tides flowing over Kaena Ridge, the subsurface extension of Oahu. The nature and impacts of internal tide generation in the Kauai Channel were intensively studied during the 2002–03 near-field component of the Hawaii Ocean Mixing Experiment. Comparisons of observed coherent (i.e., phase locked to the astronomical forcing) M2 and S2 surface currents with model predictions show good agreement for the phases, indicating propagation of internal tides away from the ridge. Although the predicted M2 and S2 surface currents are similar (except for their magnitudes), as expected for internal waves at periods closer to each other (12.4 and 12 h, respectively) than to the inertial period (33 h), the observed M2 and S2 surface currents differ significantly. The S2 kinetic energy pattern resembles the predicted pattern. In contrast, the observed structure and magnitude of the more important M2 kinetic energy pattern differs significantly from the model predictions. The models predict a band of enhanced M2 surface kinetic energy 30–40 km from the ridge axis, corresponding to the first surface reflection of internal tide beams generated on the ridge flanks. The beams are clearly observed by the moored ADCPs, albeit with weaker amplitudes than predicted. Observations at the surface show an area of enhanced kinetic energy that is 10–20 km farther away from the ridge than predicted, with weaker magnitude. Observed M2 surface currents also exhibit apparent seasonal variability, with magnitudes weaker in spring 2003 than in fall 2002. Complex-demodulated semidiurnal currents exhibit significant temporal variability in amplitude and phase, not only because of the interference between semidiurnal constituents (e.g., the spring–neap cycle) but also on shorter and irregular time scales. The result is that ∼20% of semidiurnal energy is incoherent with astronomical forcing. Furthermore, the temporal variability is not spatially coherent; the spatial patterns of semidiurnal kinetic energy resemble those predicted by the numerical models during the strongest spring tides but differ from them at other times. As a result, M2 and S2 kinetic energy patterns phase locked to the astronomical forcing differ from each other. Some features of the observed spatial pattern and amplitude modulations can be qualitatively reproduced by a simple analytical model of the effects of homogeneous barotropic background currents on internal tide beams. [ABSTRACT FROM AUTHOR]

We summarize a study of PKS 0920-397 using our 42 ks Chandra observation in conjunction with our ATCA 20GHz image, and HST/ACS F814W and F475W images. We investigate the hypothesis that the jet X–ray emission is due to inverse-Compton (IC) scattering on the cosmic microwave background (CMB) from the same population of relativistic electrons that give rise to the radio emission. To calculate parameters intrinsic to the source, one must finesse the fact that we do not know the true angle of the jet to our line of sight. Typical assumptions are that the Doppler factor equals the bulk Lorentz factor, or that the Lorentz factor takes some fixed numerical value. While giving useful estimates, neither assumption can be exact in general. We try different constraints to determine the jet quantities. It is plausible that the kinetic flux is constant along the jet, prior to a terminal hotspot or lobe, and with minimal bending of the jet. Alternatively, because PKS 0920-397 appears straight in projection on the sky, we might assume the jet maintains a constant angle to our line of sight. Either approach gives bulk Lorentz factors of 6 to 8, with kinetic energy flux of order 1046 erg s-1, and with the jet at an angle 2° to 4° from our line of sight. [ABSTRACT FROM AUTHOR]

In recent years, the Earth System Research Laboratory (ESRL) of the National Oceanic and Atmospheric Administration (NOAA) has developed a space and time mesoscale analysis system (STMAS), which is currently a sequential three-dimensional variational data assimilation (3DVAR) system and is developing into a sequential 4DVAR in the near future. It is implemented by using a multigrid method based on a variational approach to generate grid analyses. This study is to test how STMAS deals with 2D Doppler radar radial velocity and to what degree the 2D Doppler radar radial velocity can improve the conventional (in situ) observation analysis. Two idealized experiments and one experiment with real Doppler radar radial velocity data, handled by STMAS, demonstrated significant improvement of the conventional observation analysis. Because the radar radial wind data can provide additional wind information (even it is incomplete: e.g., missing tangential wind vector), the analyses by assimilating both radial wind data and conventional data showed better results than those by assimilating only conventional data. Especially in the case of sparse conventional data, radar radial wind data can provide significant information and improve the analyses considerably. [ABSTRACT FROM AUTHOR]

The first satellite navigation system called the Navy Navigation Satellite System (NNSS) or TRANSIT was planned in the USA in 1958. It consisted of 5-6 artificial Earth satellites, was set in motion for the USA military in 1964, and in 1967 for civilian purposes. The frequency shift of received radio waves emitted from the satellite and caused by the Doppler effect was measured. The TRANSIT satellite speed of approaching or moving away was derived from that; the TRANSIT satellites emmited also their own coordinates. Then the ship's position was determined by an intersection of three hyperboloids, which were determined from differences of distances in three time intervals. Maintenance of this navigation system was stopped in 1996, but it is still being used in the USA Navy for exploring the ionosphere. Furthermore, results of Doppler measurements in international projects at the Hvar Observatory from 1982 and 1983. This was the first time in Croatia and the former country that the coordinates of the Hvar Observatory were determined in the unique world coordinate system WGS72. The paper ends with a brief representation of the Tsiklon Doppler navigation system produced in the former Soviet Union, and there is a list of some of numerous produced and designed satellite navigation systems. [ABSTRACT FROM AUTHOR]

The article reports on the partnership between Mesoscale and Microscale Meteorology Division (MMM) at the National Center for Atmospheric Research (NCAR), the Korean Meteorological Administration (KMA) and the Seoul National University (SNU) for weather forecasting research in the U.S. They will use the Doppler radar data in the MM5, the Pennsylvania State University/National Center for Atmospheric Research (PSU/NCA) numerical model, with the Weather Research and Forecasting (WRF) 3-dimensional variational (3D-Var) data-assimilation system. Results show that by using the equipment, improvement of rainfall forecasts, the overall pattern of the weather system was better predicted in the summer of 2006 than 2005.

A method is evaluated for estimating the longitudinal dispersion coefficient K from velocities and bathymetry measured with an acoustic Doppler current profiler (ADCP). If shear dispersion controls the mixing, the dispersion coefficient can be estimated from measurements of velocity and depth in a cross section. The dispersion coefficient has typically been measured by costly and time-consuming tracer studies because the velocity field could not be resolved sufficiently before the flow changed. However, ADCP transects, which now are routinely used to measure discharge, provide detailed velocity and bathymetry data quickly. The dispersion coefficient is estimated from ADCP measurements from the United States Geological Survey and compared with estimates from dye studies. Half of the estimates of K fall within 50% of the values from tracer studies, and 85% are within a factor of 3. The ADCP method is at least as accurate as the best empirical formula considered. Both the comparison of field data and an analysis with theoretical velocity profiles suggest that the error in K will be largest when the velocity profile is nearly uniform. [ABSTRACT FROM AUTHOR]

Dual-polarization radar observations of precipitation depend on size–shape relations of raindrops. There are several studies presented in literature dedicated to the investigation of this relation. In this work a new approach of investigating raindrop size–shape relation on short time and spatial scales from radar observations is presented. The presented method is based on the use of dual-polarization Doppler power spectral analysis. By measuring complete Doppler spectra at a sufficiently high elevation angle at two polarization settings, namely, horizontal and vertical, it is possible to retrieve drop size distribution (DSD) parameters, ambient air velocity, spectral broadening, and the slope of the assumed linear dependence of raindrop size–shape relation. This paper is mainly focused on the development of the retrieval algorithm and analysis of its performance. As a part of the proposed method an efficient algorithm for DSD parameter retrieval was developed. It is shown that the DSD parameter retrieval method, which usually requires the solution of five-parameter nonlinear optimization problems, can be simplified to a three-parameter nonlinear least squares problem. Furthermore, the performance of the proposed retrieval technique is illustrated on the dual-polarization measurements collected by the S-band Transportable Atmospheric Radar (TARA) at Cabauw, Netherlands, and by the Colorado State University–University of Chicago–Illinois State Water Survey (CSU–CHILL) radar from Greeley, Colorado. [ABSTRACT FROM AUTHOR]

Presents the first documented large-amplitude cloud radar observations of Kelvin-Helmholtz instability in a Florida tropical anvil. Usability of radar in detecting shear instability in the atmosphere; Invalidity of the frequent assumption that an anvil is a well-mixed layer; Existence of several identifiable weaker shear layers in the anvil and in the Doppler spread.

The feasibility of using an ensemble Kalman filter (EnKF) to retrieve the wind and temperature fields in an isolated convective storm has been tested by applying the technique to observations of the 17 May 1981 Arcadia, Oklahoma, tornadic supercell. Radial-velocity and reflectivity observations from a single radar were assimilated into a nonhydrostatic, anelastic numerical model initialized with an idealized (horizontally homogeneous) base state. The assimilation results were compared to observations from another Doppler radar, the results of dual-Doppler wind syntheses, and in situ measurements from an instrumented tower. Observation errors make it more difficult to assess EnKF performance than in previous storm-scale EnKF experiments that employed synthetic observations and a perfect model; nevertheless, the comparisons in this case indicate that the locations of the main updraft and mesocyclone in the Arcadia storm were determined rather accurately, especially at midlevels. The magnitudes of vertical velocity and vertical vorticity in these features are similar to those in the dual-Doppler analyses, except that the low-level updraft is stronger in the EnKF analyses than in the dual-Doppler analyses. Several assimilation-scheme parameters are adjustable, including the method of initializing the ensemble, the inflation factor applied to perturbations, the magnitude of the assumed observation-error variance, and the degree of localization of the filter. In the Arcadia storm experiments, in which observations of a mature storm were assimilated over a relatively short (47 min) period, the results depended most on the ensemble-initialization method. In the data assimilation experiments, too much northerly storm-relative outflow along the south side of the low-level cold pool eventually developed during the assimilation period. Assimilation of Doppler observations did little to correct temperature errors near the surface in the cold pool. Both observational limitations (poor spatial resolution in the radar data near the ground) and model errors (coarse resolution and uncertainties in the parameterizations of moist processes) probably contributed to poor low-level temperature analyses in these experiments. [ABSTRACT FROM AUTHOR]

A NOAA P-3 instrumented aircraft observed an intense, fast-moving narrow cold frontal rainband (NCFR) as it approached the California coast on 19 February 2001 during the Pacific Coastal Jets Experiment. Airborne Doppler radar data obtained while the frontal system was well offshore indicated that a narrow ribbon of very high radar reflectivity convective cores characterized the rainband at low levels with echo tops to ∼4–5 km, and pseudo-dual-Doppler analyses showed the low-level convergence of the prefrontal air. The NCFR consisted of gaps of weaker reflectivity and cores of stronger reflectivity along its length, perhaps as a result of hydrodynamic instability along its advancing leading edge. In contrast to some earlier studies of cold frontal rainbands, density-current theory described well the motion of the overall front. The character of the updraft structure along the NCFR varied systematically along the length of the precipitation cores and in the gap regions. The vertical shear of the cross-frontal low-level ambient flow exerted a strong influence on the updraft character, consistent with theoretical arguments developed for squall lines describing the balance of vorticity at the leading edge. In short segments at the northern ends of the cores, the vertical wind shear was strongest with the updrafts and rain shafts more intense, narrower, and more erect or even downshear tilted. At the southern ends of the cores and just north of the gaps, the wind shear weakened with less intense updrafts that tilted upshear and contained a broader band of rainfall. Simulations using the nonhydrostatic nested grid version of the fifth-generation Pennsylvania State University–National Center for Atmospheric Research (PSU–NCAR) Mesoscale Model (MM5) are used to investigate the core and gap regions, focusing on the relationship between the character of the modeled updrafts and the balance between the cold-air-induced vorticity and the prefrontal ambient shear vorticity. The cold air behind the NCFR, which forces new convection along its leading edge, is probably maintained by large-scale advection of cold air plus evaporative cooling processes within the heavy rain region of the NCFR. Observations confirm the model results; that is, that the updraft character depends on the balance of vorticity at the leading edge. Downshear-tilted updrafts imply that convection at the northern ends of cores may weaken with time relative to the frontal segments at the southern ends, because inflow air would be affected by passage through the heavy rain region before ascent. A mechanism for line modification is thus implied. [ABSTRACT FROM AUTHOR]

A phased-array Doppler sonar (PADS) system is described that uses sound at frequencies near 200 kHz to probe an area several hundred meters on a side with 7-20-m spatial resolution, The area can be sampled every second or less with under 2 cm s[SUP-1] rms velocity error per sample, Radial velocity estimates from two or more systems can be combined to produce time series of horizontal velocity vector maps over the irregularly shaped overlapping region, Such extensive and continuous sampling intime and space permits analysis via direct 3D Fourier transformation, for example, producing complete wavenumber frequency spectra, Free waves, bound harmonics, finite-amplitude effects, Doppler shifting by currents, etc., can be smdied, Extended temporal sampling permits investigations into lower-frequency vortical and internal wave modes as well as surface waves, and of the modulation of these by tides. A pair of PADS was deployed as part of SandyDuck, a large collaborative field experiment held in 1997 near Duck, North Carolina. An example drawn from SandyDuck data illustrates use of the technique, demonstrating that both mean flow and oscillatory (wave) motions can be detected. [ABSTRACT FROM AUTHOR]

Focuses on NEXRAD or Next Generation Weather Radar, the modern weather radar system that would replace the conventional system by the early nineteen nineties in the United States. Plan to offer improved severe weather warning and forecasting services for civil and military aviation; Government agencies involved in the development of the system; Capabilities of the existing system; Development of the system based on the Doppler effect.

Provides information on a study which explained the response to local and remote forcing over a narrow continental shelf near a coastal promontory using acoustic Doppler current profiler (ADCP) deployed off Point Sur, California. Instrumentation and data processing of the study; Basic description of the spatial and temporal variability; Spectral characteristics of ADCP; Vertical structure of individual events.

Focuses on research developments of electron and atomic physics in the United States. Application of Electron Cyclotron Resonance ion sources; Measurement of Doppler effect by spectroscopic techniques; Principles of local Lorentz invariance and time-reversal invariance.

Bang time and reaction history measurements are fundamental components of diagnosing inertial confinement fusion (ICF) implosions and will be essential contributors to diagnosing attempts at ignition on the National Ignition Facility (NIF). Fusion gammas provide a direct measure of fusion interaction rate without being compromised by Doppler spreading. Gamma-based gas Cherenkov detectors that convert fusion gamma rays to optical Cherenkov photons for collection by fast recording systems have been developed and fielded at Omega. These systems have established their usefulness in illuminating ICF physics in several experimental campaigns. Bang time precision better than 25 ps has been demonstrated, well below the 50 ps accuracy requirement defined by the NIF system design requirements. A comprehensive, validated numerical study of candidate systems is providing essential information needed to make a down selection based on optimization of sensitivity, bandwidth, dynamic range, cost, and NIF logistics. This paper presents basic design considerations arising from the two-step conversion process from γ rays to relativistic electrons to UV/visible Cherenkov radiation. [ABSTRACT FROM AUTHOR]

We report on a search for short-period intensity variations in the green-line (Fe xiv 530.3 nm) emission from the solar corona during the 21 August 2017 total eclipse viewed from Idaho in the United States. Our experiment was performed with a much more sensitive detection system, and with better spatial resolution, than on previous occasions (1999 and 2001 eclipses), allowing fine details of quiet coronal loops and an active-region loop system to be seen. A guided 200-mm-aperture Schmidt–Cassegrain telescope was used with a state-of-the-art CCD camera having 16-bit intensity discrimination and a field-of-view ( 0.43 ∘ × 0.43 ∘ ) that encompassed approximately one third of the visible corona. The camera pixel size was 1.55 arcseconds, while the seeing during the eclipse enabled features of ≈ 2 arcseconds (1450 km on the Sun) to be resolved. A total of 429 images were recorded during a 122.9 second portion of the totality at a frame rate of 3.49 s − 1 . In the analysis, we searched particularly for short-period intensity oscillations and travelling waves, since theory predicts fast-mode magneto-hydrodynamic (MHD) waves with short periods may be important in quiet coronal and active-region heating. Allowing first for various instrumental and photometric effects, we used a wavelet technique to search for periodicities in some 404 , 000 pixels in the frequency range 0.5 – 1.6 Hz (periods 2 seconds to 0.6 seconds). We also searched for travelling waves along some 65 coronal structures. However, we found no statistically significant evidence in either. This negative result considerably refines the limit that we obtained from our previous analyses, and it indicates that future searches for short-period coronal waves may be better directed towards Doppler shifts as well as intensity oscillations. [ABSTRACT FROM AUTHOR]

The article offers insights on the advances made by the National Hurricane Center (NHC) in the U.S. It mentions that the key milestones in hurricane forecasting at the NHC were the advent of microwave frequency observations from satellites, and aircraft, Doppler radar, and global positioning system. It further states that during the previous decades, NCH Hurricane Specialists cut by more than half their annual average errors in weather forecasting.

The article offers news briefs related to science including a method of stone architecture restoration proposed by an industrial engineer, the results of a study on the Doppler effect by scientists from Japan, Sweden, France and the U.S., and the high conductivity of certain bismuth strontium calcium copper oxide (BI2212) region is limited by bubbles formed during fabrication

The local area augmentation system (LAAS) is a proposed satellite-based landing system by the Federal Aviation Administration (FAA) to serve as a navigation aid for commercial aircraft during the approach and landing phase of flight. The LAAS utilizes a special ground-based antenna array called the multipath limiting antenna (MLA) to provide differentially corrected global navigation satellite system (GNSS) data to oncoming aircraft as well as to reduce the largest error contributor to pseudo-range estimates; the ground multipath. The performance of the MLA is characterized in terms of its desired-to-undesired (D/U) gain ratio, phase center variation (PCV) and group delay (GD). A high fidelity antenna model (HFAM) of the MLA is presented that estimates the D/U, PCV, and GD as a function of elevation angle. The model consists of two main components: 1) a microwave feed distribution circuit model created using a circuit simulator, and 2) a radiating structure model developed using a full-wave method of moments (MoM) field solver. The performance of the model was assessed against antenna range measurements. The results of the HFAM show good correlation for the D/U and PCV while a significant bias was observed on the results for the GD. The dependence of the GD on the radiating element's impedance, tuning process, and Doppler frequency shift are demonstrated via simulations. [ABSTRACT FROM AUTHOR]