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Toshitaka Tsuda – One of the best experts on this subject based on the ideXlab platform.
retrieval of temperature profiles using radio Acoustic Sounding system rass with the equatorial atmosphere radar ear in west sumatra indonesiaEarth Planets and Space, 2018Co-Authors: Ina Juaeni, Hiroyuki Hashiguchi, Hiraku Tabata, Toshitaka TsudaAbstract:
The radio Acoustic Sounding system (RASS) with the equatorial atmosphere radar (EAR) at Koto Tabang, Indonesia was adapted to test the effects of the Acoustic source location and Acoustic frequency range on the continuous measurement of height profiles of temperature in the tropical troposphere. We installed the Acoustic transmitting system by using six high-power horn speakers and four subwoofers. We developed a three-dimensional ray-tracing method of Acoustic waves to predict the shape of Acoustic wavefronts, accounting for the effects of the background winds on Acoustic wave propagation. Then, we selected the appropriate antenna beam directions for EAR that satisfy the Bragg condition between the radar and Acoustic wave propagation vectors. We carried out eight campaign observations in 2016, testing the performance of EAR–RASS. We found that the location and Acoustic frequency range affected the RASS echoes. We also tested the compensation method of the background wind velocity with EAR to obtain the true sound speed. We intensively analyzed the RASS results from August 29 to September 3, 2016, when radiosondes were launched 12 times from the EAR site. We successfully retrieved the temperature profiles from RASS from 2 to 6–14 km with time and height resolutions of about 10 min and 150 m, respectively. Some temperature profiles were obtained up to about the tropopause at 17 km, although the observation period was short. During the RASS campaign, we detected a few interesting events regarding temperature variations as well as large perturbations in the three components of wind velocity.
preliminary observation of temperature profiles by radio Acoustic Sounding system rass with a 1280 mhz lower atmospheric wind profiler at gadanki indiaAtmospheric Measurement Techniques Discussions, 2012Co-Authors: T Chandrasekhar V Sarma, P Srinivasulu, Toshitaka TsudaAbstract:
A UHF wind profiler operating at 1280 MHz has been developed at NARL for atmospheric studies in the planetary boundary layer. In order to explore application of radio Acoustic Sounding system (RASS) technique to this profiler, a suitable Acoustic attachment was designed and preliminary experiments were conducted on 27–30 August 2010. Height profiles of virtual temperature, T v , in the planetary boundary layer were derived with 1 μs and 0.25 μs pulse transmission, corresponding to a height resolution of 150 m and about 40 m, respectively. Diurnal variation of T v is clearly recognized, and perturbations of T v are also seen in association with a precipitation event. Simultaneous profiles obtained from the MST Radar-RASS and an onsite 50 m tower demonstrate the capability to continuously profile the atmospheric temperature from near the ground to upper tropospheric altitudes.
observations of temperature profiles by 443 mhz wind profiling radar using a radio Acoustic Sounding system in okinawaJournal of Atmospheric and Solar-Terrestrial Physics, 2011Co-Authors: Tomonori Shinoda, Junichi Furumoto, Shinsuke Satoh, Seiji Nagai, Yasuhiro Murayama, Toshitaka TsudaAbstract:
Abstract The present study is devoted to developing a radio Acoustic Sounding system (RASS) for the 443 MHz wind profiling radar (443 MHz WPR) installed at the Ogimi Wind Profiler Facility of the National Institute of Information and Communications Technology (NICT) in Okinawa, Japan. We used four fixed horns attached to the sides of the 443 MHz WPR antenna. Additional 15 portable horn speakers were also installed to transmit Acoustic waves at frequencies of 900–1050 Hz, which is suitable for the 443 MHz WPR with RASS (443 MHz WPR/RASS) observation. We also developed the software to switch active speakers adaptively by considering the real-time raytracing results of Acoustic wavefronts. In the software, four fixed speakers are always activated and several portable speakers are selectively used in order to efficiently obtain strong RASS echoes. Aiming at unmanned operation of the 443 MHz WPR/RASS, a remote control and monitoring system for 443 MHz WPR/RASS observation and a data processing system to derive virtual temperature profiles were developed. Virtual temperature profiles obtained using the 443 MHz WPR/RASS were evaluated by comparison with the data from radiosondes launched from the radar site in 2006.
Turker Ince – One of the best experts on this subject based on the ideXlab platform.
Early forest fire detection using radio-Acoustic Sounding systemSensors, 2009Co-Authors: Yasar Guneri Sahin, Turker InceAbstract:
Automated early fire detection systems have recently received a significant amount of attention due to their importance in protecting the global environment. Some emergent technologies such as ground-based, satellite-based remote sensing and distributed sensor networks systems have been used to detect forest fires in the early stages. In this study, a radio-Acoustic Sounding system with fine space and time resolution capabilities for continuous monitoring and early detection of forest fires is proposed. Simulations show that remote thermal mapping of a particular forest region by the proposed system could be a potential solution to the problem of early detection of forest fires.
M A Shapiro – One of the best experts on this subject based on the ideXlab platform.
radio Acoustic Sounding system rass and wind profiler observations of lower and midtropospheric weather systemsMonthly Weather Review, 1992Co-Authors: Paul J Neiman, Peter T May, M A ShapiroAbstract:
Abstract The National 0ceanic and Atmospheric Administration (NOAA) Wave Propagation Laboratory (WPL) wind profilers and accompanying radio Acoustic Sounding system (RASS) temperature profilers in eastern Colorado jointly measure nearly continuous (≤1 h), high vertical resolution (≤300 m) wind-velocity and virtual-temperature profiles. This study presents NOAA/WPL wind profiler and RASS observations and diagnostics of propagating lower- and midtropospheric weather systems over Colorado. The wind and temperature remote-sensing systems observed wind-velocity and virtual-temperature structures associated with a synoptic-scale trough and embedded fronts, and a propagating short-wave trough and trailing midtropospheric jet-stream-frontal-zone (jet-front) system. Single-station hourly diagnostic calculations of geopotential heights, horizontal virtual potential temperature gradients, thermal advections, vertical velocities gradient Richardson numbers, and cross-frontal isentropic potential vorticity demonstrate…
Philip J Morris – One of the best experts on this subject based on the ideXlab platform.
two dimensional simulations of wake vortex detection using radio Acoustic Sounding systemsAIAA Journal, 2002Co-Authors: Said Boluriaan, Philip J MorrisAbstract:
AparallelcodeisdevelopedtosimulatenumericallywakevortexdetectionusingaradioAcousticSoundingsystem (RASS). The code is written in FORTRAN 90 with the message passing interface for parallel implementation. The numerical simulation solves simultaneously the linearized Euler equations for a nonuniform mean e ow and the Maxwellequationsforanonhomogeneousmedium.Theradartransmitterandreceiverantennasaremodeledusing an array of point sources and a beam-forming technique, respectively. Many features of the RASS are explored using thenumericalsimulation.First,a uniformmeane owisconsidered,and theRASSsimulation isperformedfor two different types of incident Acoustic e eld: a short single-frequency Acoustic pulse and a continuous broadband Acoustic source. Both monostatic and bistatic cone gurations are examined, and their results are compared. Taylor and Oseen vortex velocity proe les are used as samplemodels, and their mean e owe eldsare reconstructed from the backscattered electromagnetic signal using the Abel transform. The effect of radar beam width is also considered, as are the issues of nonaxisymmetric and interacting vortices. I. Introduction T HEcapacity of airports is constrainedseverelyby the airtrafe c control system’ s consideration of aircraft wake vortices. The present Instrument Flight Rules (IFR) restrictions are based on aircraft weight. The “ 3‐ 4‐ 5‐ 6 rule” sets the separation distances of aircraft by categories from small, less than 41,000 lb (18,600 kg), to heavy, greater than 255,000 lb (116,000 kg). These separations are viewed as very conservative. However, because there remains signie cant uncertainty about wake vortex behavior under different atmospheric conditions, there are considerable technological barriers to improvements in terminal area productivity. In an attempt to enhance airport capacity, an aircraft vortex spacing system (AVOSS) has been under development at NASA Langley Research Center. The AVOSS will provide the means to allow air trafe c control to reduce spacing safely in instrument operations when the appropriate weather conditions exist. A key element in AVOSS is the development of a real-time reliable wake vortex detection system (WVDS). A radio Acoustic Sounding system (RASS) is a promising candidate for a WVDS. The basic concept of RASS is based on the tracking of sound waves with radar. When Acoustic waves are transmitted, they produce pressure perturbations, which lead to e uctuations in the atmospheric permittivity. An incident electromagnetic e eldisthenscatteredduetothepermittivityvariationsandgenerates an echo that can be detected by a receiver antenna. The spectrum of this echo shows a Doppler shift proportional to the local speed of sound. However, the backscattered signals are so weak that no measurable signal would be received unless the Bragg condition is satise ed.The Bragg condition is a relationshipbetween the incident electromagnetic and Acoustic wavelengths that ensures a constructive interference between the two waves. The Bragg condition may be written as ¸e D 2¸a sin®
numerical simulation of wake vortex detection using a radio Acoustic Sounding systemAIAA Journal, 2001Co-Authors: Said Boluriaan, Philip J MorrisAbstract:
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.
J W Pomeroy – One of the best experts on this subject based on the ideXlab platform.
determining snow water equivalent by Acoustic SoundingHydrological Processes, 2007Co-Authors: N J Kinar, J W PomeroyAbstract:
The possibility of determining snow water equivalent (SWE) by the use of an Acoustic impulse was assessed at two field locations in Saskatchewan and British Columbia, Canada. These sites represent cold windswept prairie and temperate deep mountain snowcovers. A continuous frequency-swept Acoustic wave was sent into the snowpack and received. Signal processing was then subsequently used to estimate the depth and density of each snow layer by a recursive relationship involving frequency-modulated continuous-wave (FMCW) radar and seismological techniques. From this method, it is also shown that the tortuosity of snow can be estimated. Data collected by gravimetric sampling was used as comparison to the SWE values determined by the use of Acoustic Sounding. The results showed that for the Saskatchewan sites, the correlation between the measured and the modeled values of SWE was 0Ð86, whereas at the British Columbia sites, the correlation was 0Ð78. The difference in the correlations was interpreted as being due to additional Acoustic measurement error at the British Columbia sites caused by higher liquid water contents and more layers in the snowpack. The measured and the modeled SWE for Saskatchewan snowpacks with high liquid water contents were found to be weakly associated with correlations of 0Ð30. The Acoustically-determined values of tortuosity were close to unity (˛ ³ 1), which is in agreement with the values characteristic of snow as a porous substance. Further research is necessary to determine whether this technique can be applied to snow in other environmental conditions. Copyright 2007 John Wiley & Sons, Ltd.