Radio Acoustic Sounding System Research Articles

INFERENCE VERSUS IMPRINT IN CLIMATE MODELING

A statistical inference method known as ε-machine reconstruction is introduced as a modeling procedure for turbulent transport processes in a climate model. Observational data on the atmospheric boundary layer obtained with a radar wind profiler, a radio-acoustic sounding system, and a Raman lidar system was assembled to construct this type of model for use within the unresolved (sub-grid) scales of a numerical climate model. An ensemble of 500 single-column model runs using the inferred sub-grid turbulent transport models demonstrated comparable performance to an identical ensemble of runs using the standard, eddy-diffusivity parametrizations for the turbulent transport. The primary advantages of the ε-machine models are that they are a less biased modeling framework for complex processes such as turbulent transport, and that they are more memory efficient.

Two-dimensional simulations of wake vortex detection using radio acoustic sounding systems

Two-dimensional simulations of wake vortex detection using radio acoustic sounding systems

A Case Study of the Variational Assimilation of GPS Zenith Delay Observations into a Mesoscale Model

Abstract Results from a case study of the four-dimensional variational assimilation of total zenith delay (TZD) observations from a dense global positioning system (GPS) network into the Pennsylvania State University–National Center for Atmospheric Research Fifth-Generation Mesoscale Model are reported. TZD is made up of the rescaled pressure and precipitable water at the site of the GPS receiver. Profiler-wind and radio acoustic sounding system (RASS) virtual temperature observations are also included in the assimilation experiments. Four experiments are performed. The study targets the 12-h period from 0000 to 1200 UTC 6 December 1997, characterized by the passage of a frontal system that produced intense rainfall over southern California. Forecasts prior to data assimilation underestimate the observed 6- and 12-h accumulated rainfall for most of the domain. The (sole) assimilation of TZD observations is found to have a small but beneficial impact on the short-range precipitation forecast. Measured agai...

Estimation of a Humidity Profile Using Turbulence Echo Characteristics

Abstract This paper is concerned with the development of a new stratosphere–troposphere radar technique for determining a height profile of specific humidity (q) by using characteristics of clear-air echoes in the troposphere. Turbulence echoes have been observed with the middle and upper atmosphere (MU) radar in Shigaraki, Japan (34.8°N, 136.1°E), on 2–6 August 1995 and 29–30 July 1999. Applying the radio acoustic sounding system (RASS) technique to the MU radar, the detailed time–height structure of the virtual temperature was simultaneously measured as well. The volume reflectivity (η) for turbulence echoes mainly depends on the refractive index gradient (M), the Brunt–Vaisala frequency squared (N2), and the turbulence energy dissipation rate (ϵ). Because N2 and ϵ can be estimated from the RASS temperature profiles and the spectral width of a Doppler spectrum of turbulence echoes, respectively, a linear relation between η and M2 can be derived where a proportion constant should be calibrated by referri...

Numerical Simulation of Wake Vortex Detection Using a Radio Acoustic Sounding System

A parallel, two-dimensional Euler, one-dimensional Maxwell code is developed to numerically simulate wake vortex detection using a radio acoustic sounding system. The code is written in Fortran 90 with the message passing interface for parallel implementation. The main dife culty with a time-accurate simulation is the number ofsamplesrequired to resolve theDopplershiftin thescattered electromagneticsignal. Even fora one-dimensional simulation with typical scatterer size, the CPU time required to run the code is far beyond currently available computer resources. Two alternatives that overcome this problem are described. In the e rst, the code is run for a e ctitious speed of light. Second, the governing differential equations are recast in order to remove the carrier frequency and solve only for the frequency shift using an implicit scheme with large time steps. The numerical stability characteristics of the resulting discretized equation with complex coefe cients are shown. The code is run for both the approaches with Taylor and Oseen vortex velocity proe les. Finally, the Abel transform is applied to the outputs of both explicit and implicit schemes, and the wake vortex velocity e eld is retrieved with very good accuracy.

Comparison of atmospheric boundary layer soundings by a metric and a decimetric RASS

The vertical thermal profile of the lower atmosphere can be remotely measured by the Radio Acoustic Sounding System (RASS). A RASS operating at the acoustic wavelength λa ∼ 1 m was designed and developed twenty years ago. It is suitable for monitoring the temperature profile of the lower troposphere and has been utilised for studies of the atmospheric boundary layer in different conditions and for the application of control strategies to air pollution emissions. The acoustic antenna is composed by 9 folded horns covering an area of 7x7 m2; the two radar antennas are composed by arrays of dipoles with square reflector of 2.8x2.8 m2 for each antenna. Therefore the metric RASS can be utilised only in a settled station. Recently we have designed and developed a decimetric RASS (λa = 0.34 m) with smaller antennas, which can be used as a mobile system. It can be housed and carried by a trailer. As it is known, increasing the sounding frequency gives a decreasing of the sounding range. Comparisons of results obtained by both the metric and the decimetric RASS in different atmospheric conditions are presented and discussed.

RASS time series parametric modeling: A way to overcome the classical Fourier Transform

RASS (Radio Acoustic Sounding System) is designed in order to remotely measure atmospheric temperature profiles by combining acoustic and radar techniques. Usually, RASS data are processed with the same signal processing algorithms as for wind profiling: using the classical Fourier analysis. In order to improve the accuracy of the temperature estimates, this paper proposes to take into account RASS time series characteristics. A parametric approach is studied and AutoRegressive modeling is shown to give better temperature estimation than the usual Fourier Transform based algorithm.

Fluctuating Effective Centers of the Targets of Acoustic and Radio-Acoustic Atmospheric Sounding Systems

Fluctuating Effective Centers of the Targets of Acoustic and Radio-Acoustic Atmospheric Sounding Systems

A monostatic radio-acoustic sounding system used as an indoor remote temperature profiler

Radar-acoustic sounding systems (RASS) generally employ a bistatic scheme with the radar source and receiver placed symmetrically beside the acoustic radiator. This paper presents a novel method for combining the acoustic and the electromagnetic waves which reduces complexity, size, and cost of the system and enhances portability. Other advantages of the new monostatic approach are that only one hf-antenna is needed and that no dead zone exists in front of the system. Three possible solutions for realizing a monostatic system are taken into account. The first approach uses a dielectric plate to redirect the acoustic wave. By the second solution, the electromagnetic wave is directed into the ultrasonic propagation by a wire grid. Another possibility is to use a composite antenna array made up of acoustic and electromagnetic sources. As no frequency limits exist for the monostatic RASS, it is possible to employ the usual RASS frequencies at 915 MHz or 1290 MHz for the electromagnetic wave. Measurements show that a maximum distance of 30 m can be reached with an uncertainty of /spl plusmn/5 mm at 10 GHz for ranging measurements and /spl plusmn/0.5 K for temperature profiling.

A brief history of the development of wind-profiling or MST radars

Abstract. The history of the development of the wind-profiling or MST radar technique is reviewed from its inception in the late 1960s to the present. Extensions of the technique by the development of boundary-layer radars and the radio-acoustic sounding system (RASS) technique to measure temperature are documented. Applications are described briefly, particularly practical applications to weather forecasting, with data from networks of radars, and scientific applications to the study of rapidly varying atmospheric phenomena such as gravity waves and turbulence.Key words: Meteorology and atmospheric dynamics (instruments and techniques) · Radio science (remote sensing; instruments and techniques)

A brief history of the development of wind-profiling or MST radars

<strong class="journal-contentHeaderColor">Abstract.</strong> The history of the development of the wind-profiling or MST radar technique is reviewed from its inception in the late 1960s to the present. Extensions of the technique by the development of boundary-layer radars and the radio-acoustic sounding system (RASS) technique to measure temperature are documented. Applications are described briefly, particularly practical applications to weather forecasting, with data from networks of radars, and scientific applications to the study of rapidly varying atmospheric phenomena such as gravity waves and turbulence.<br><br><b>Key words: </b>Meteorology and atmospheric dynamics (instruments and techniques) · Radio science (remote sensing; instruments and techniques)

Enhanced Accuracy of RASS-Measured Temperatures Due to an Improved Range Correction

Abstract The accuracy of virtual temperature measurements taken by the Radio Acoustic Sounding System (RASS) has been improved essentially by the application of a more precise range correction that takes into account the profile of reflectivity and the range weighting function of the receiver. Especially, the height dependence of the RASS temperature error compared to radiosondes was significantly reduced. The improved range correction was verified with a 1-yr dataset consisting of more than 1000 comparisons of 482- and 1290-MHz wind profiler/RASS with radiosondes observations. Other corrections discussed in the literature accounting for the displacement of the acoustic source, horizontal wind, and turbulence have been neglected because they are usually not significant. After the application of the improved range correction together with the correction of vertical wind as well as more accurate constants in the temperature retrieval, the bias with respect to radiosondes is smaller than 0.3 K and the standa...

RASS - A new remote sensing system for the surveillance of meteorological dispersion / RASS - Ein neues System zur Überwachung der meteorologischen Dispersion.

The combination of acoustic and radio waves called RASS (Radio Acoustic Sounding System) allows ground based measurements of the vertical profiles for temperature, wind and turbulent parameters. The technique uses the scattering of the radio waves at the density fluctuations caused by the acoustic wave field. Compared to SODAR or RADAR techniques which have proven their reliable routine operation in various applications RASS shows no sensitivity to fixed echo, to environmental noise or to precipitation. The height range of the RASS sounding is limited only by the atmospheric absorption of the sound waves and the shift of he acoustic wave with the mean field. Depending on the specific choice of acoustic and radio operation frequencies and the geometric configuration of the antennas RASS can be optimized for profiling in height ranges of some hundreds meter to some kilometer. In view of on-line environmental monitoring at industrial sites RASS allows direct measurements of the profiles of the meteorological parameters for transport and dispersion, atmospheric stability and the formation and decay of inversions.

469ソーダによる大気温度変動の可視化とライダーなどによる都市域の観測

Monitoring of the lower atmosphere is an important part of the investigation of urban meteorology. In recent years, meteorological remote-sensing technology has advanced to the point where monitoring of upper temperature and wind using a ground-based instrument is possible. Echo patterns recorded by sodar (acoustic radar) enable visualization of atmospheric temperature distribution. Layer-type and grounded-type echoes are observed under stable atmospheric conditions or with temperature inversion layers. The RASS (radio acoustic sounding system) uses a Doppler radar to track sound pulses that have been transmitted vertically. The Doppler radar measures the velocity of sound at each altitude, from which the air temperature can be calculated. Simultaneous monitoring results of RASS and sodar echo patterns show good agreement. A mobile RASS was developed to measure the temperature profiles at various places in a city when the urban heat island phenomenon occurs. The observation of an urban area was conducted using lidar (laser radar), the mobile RASS and radio sonde.

Kelvin Waves and Internal Bores in the Marine Boundary Layer Inversion and Their Relationship to Coastally Trapped Wind Reversals

Abstract Detailed observations of a coastally trapped disturbance, or wind reversal, on 10–11 June 1994 along the California coast provide comprehensive documentation of its structure, based on aircraft, wind profiler, radio acoustic sounding system, and buoy measurements. Unlike the expectations from earlier studies based on limited data, which concluded that the deepening of the marine boundary layer (MBL) was a key factor, the 1994 data show that the perturbation was better characterized as an upward thickening of the inversion capping the MBL. As the event propagated over a site, the reversal in the alongshore wind direction occurred first within the inversion and then 3–4 h later at the surface. A node in the vertical structure (defined here as the altitude of zero vertical displacement) is found just above the inversion base, with up to 200-m upward displacements of isentropic surfaces above the node, and 70-m downward displacements below. Although this is a single event, it is shown that the vertic...

Development and Initial Results of a Mobile RASS

A mobile RASS (Radio Acoustic Sounding System), which can be loaded onto a truck along with all the other equipment, including the power supply, was developed for atmospheric temperature measurement. Also, since it is necessary to avoid noise pollution in surrounding areas when conducting observations with the mobile RASS, a new method that allows measurement of the temperature profile up to about 200 m using a single acoustic pulse was devised. We discuss the development of a truck-mounted mobile RASS and the results of the first mobile observation conducted at various locations in the Tokyo area.

Measuring Vertical Heat Flux with RASS

A wind‐profiling Doppler radar equipped with a radio acoustic sounding system (RASS) may be used to estimate the vertical profile of the vertical flux of heat in the atmosphere. Simultaneous measurements of the time‐varying temperature and vertical air velocity are combined to give the convective heat flux using the eddy‐correlation method. The accuracy of the estimates depends on the fundamental accuracy of the temperature and vertical velocity measurements. Also, in common with all eddy‐correlation methods, uncertainties are introduced by the need to define a suitable averaging time and to remove trends. A problem unique to RASS is the possible presence of ground and intermittent clutter at close ranges, which can cause errors in the vertical air velocity measurements. These considerations are discussed with particular reference to observations using a UHF radar wind profiler situated in an urban environment, where clutter is a serious problem.

The Role of Acoustic Sounding in a High-Technology Era

This paper presents a brief synopsis of past, current and anticipated progress and problems in the use of acoustic remote sensing for basic and applied research of the lower atmosphere. The potential and reality of the sodar for determination of meteorological parameters and turbulence characteristics is discussed. Sodars’ place alongside other ground-based remote sensors, including radar wind profilers, radioacoustic sounding systems (RASS) and lidars, is elucidated. Areas of atmospheric research where Doppler sodar has certain advantages are described such as cost, sensitivity, spatial and temporal resolution and surface layer measurements. The use of sodar in networks of integrated radar/RASS systems designed to supply uninterrupted monitoring of atmospheric parameters for improvements in forecasts of weather and air quality is demonstrated.

Estimation of turbulence energy dissipation rate and vertical eddy diffusivity with the MU radar RASS

We have conducted RASS (Radio Acoustic Sounding System) observations with the MU (Middle and Upper atmosphere) radar on 28–31 July 1994 at Shigaraki, Japan (34°51′ N, 136°06′ E) and determined the characteristics of turbulence energy dissipation rate ( ε) and vertical eddy diffusivity ( K) in the troposphere and lower stratosphere. We have first examined the accuracy of the Brunt Väisälä frequency squared ( N 2) derived from RASS temperature profiles. Then, ε and K are determined by using N 2 and the Doppler spectral width of turbulence echoes ( σ 2 turb). We found that the structures of ε and K are sometimes affected by the local variations of N 2. We found that sometimes ε became small, even though σ 2 turb was large, because N 2 was small. On the contrary, K was enhanced due to small N 2, although σ 2 turb was small.

Investigation of Turbulent Processes in the Lower Troposphere with Water Vapor DIAL and Radar–RASS

Abstract High-resolution water vapor and wind measurements in the lower troposphere within the scope of the Baltic Sea Experiment (BALTEX) are presented. The measurements were performed during a field campaign with a new water vapor differential absorption lidar (DIAL) system and a radar–radio acoustic sounding system (radar–RASS). The analysis of a continuous 24-h measurement period shows that the resolution and the accuracy of these instruments are capable of measuring profiles of water vapor and vertical wind fluctuation moments up to the second order to investigate turbulent processes in the convective boundary layer. Besides the high-resolution data obtained with each instrument it is their combination that yields a further important variable in the boundary layer: the turbulent latent heat flux measured directly using the eddy correlation method. The results demonstrate that active remote sensing instruments like DIAL and radar–RASS can be routinely applied to provide previously unavailable datasets...