Numerical Evaluation of Observation Algorithm for Sea Surface Remote Sensing by Doppler Radar

2011 ◽  
Author(s):  
Takero Yoshida ◽  
Chang-Kyu Rheem
Keyword(s):  
Remote Sensing ◽  
Fourier Transform ◽  
Microwave Irradiation ◽  
Frequency Analysis ◽  
Doppler Radar ◽  
Sea Surface ◽  
Doppler Spectrum ◽  
Doppler Velocity ◽  
Regular Wave ◽  
The Fourier Transform

Algorithms of sea surface remote sensing are based on changes of Doppler shifts, which are measured by a Doppler radar. Microwave irradiation width on the sea surface and time taken to collect data for frequency analysis influence Doppler spectra. In order to evaluate the influences of these parameters in observing algorithms, a simulation of microwave backscattering from numerical sea surface was done in time domain to obtain Doppler spectra. Doppler spectra have been simulated in the case of various numerical regular waves. In the case of the microwave irradiation width is larger than the wavelength of the numerical regular wave or the Fourier transform time for the frequency analysis is longer than the period of the numerical regular wave, the peak value of Doppler spectra shows the phase velocity of the Bragg resonance wave. The results show the principle of measuring sea surface current. In the case of the microwave irradiation width is smaller than the wavelength of the numerical regular wave or the Fourier transform time is shorter than the period of the numerical regular wave, Doppler spectra vary with the orbital motions of the regular wave. As the result, when the sea surface wavelength is five times or more as long as the microwave irradiation width, the time fluctuations of Doppler velocity which shows a mean value of Doppler spectrum are good agreement with the orbital motions of the numerical regular wave. Also in such condition, the wave height of the sea surface waves can be observed accurately by analyzing the changes of Doppler velocity.

scholarly journals Time series forecasting using amplitude-frequency analysis of STL components

2021 ◽  
Vol 2094 (3) ◽  
pp. 032019
Author(s):  
D G Chkalova
Keyword(s):  
Time Series ◽  
Fourier Transform ◽  
Frequency Analysis ◽  
Software Implementation ◽  
Phase Operator ◽  
Economic Time Series ◽  
Economic Time ◽  
Harmonic Components ◽  
The Fourier Transform ◽  
Forecast Quality

Abstract The problem of economic time series analysis and forecasting using amplitude-frequency analysis of STL decomposition is considered. An amplitude-phase operator was chosen as an apparatus for extraction the series harmonic components, the advantages of which (compared to the Fourier transform) are: calculations speed, result accuracy, simplicity and interpretability of software implementation. The forecast quality was carried out using the MAPE metric. Significantly higher prediction quality was achieved compared to Facebook Prophet forecasting package.

scholarly journals Cirrus Mammatus Properties Derived from an Extended Remote Sensing Dataset

2006 ◽  
Vol 63 (2) ◽  
pp. 712-725 ◽  
Author(s):  
Likun Wang ◽  
Kenneth Sassen
Keyword(s):  
Remote Sensing ◽  
Large Scale ◽  
Doppler Radar ◽  
Three Dimensional ◽  
Remote Sensing Data ◽  
Cloud Base ◽  
Doppler Velocity ◽  
Small Scale ◽  
Length Scales ◽  
Atmospheric Remote Sensing

Abstract The first quantitative and statistical evaluation of cirrus mammatus clouds based on wavelet analysis of remote sensing data is made by analyzing the University of Utah Facility for Atmospheric Remote Sensing (FARS) 10-yr high-cloud dataset. First, a case study of cirrus mammata combining a high-resolution lidar system and a W-band Doppler radar is presented, yielding an assessment of the thermodynamic environment and dynamic mechanisms. Then, 25 cirrus mammatus cases selected from the FARS lidar dataset are used to disclose their characteristic environmental conditions, and vertical and length scales. The results show that cirrus mammata occur in the transition zone from moist (cloudy) to dry air layers with weak wind shear, which suggests that cloud-induced thermal structures play a key role in their formation. Their maximum vertical and horizontal length scales vary from 0.3 to 1.1 km and 0.5 to 8.0 km, respectively. It is also found that small-scale structures develop between the large-scale protuberances. The spectral slopes of the lidar-returned power and mean radar Doppler velocity data extracted from the cirrus cloud-base region further indicate the presence of developed three-dimensional, locally isotropic, homogeneous turbulence generated by buoyancy. Finally, comparisons of anvil and cirrus mammata are made. Although both are generated in a similar environment, cirrus mammata generally do not form fallout fronts like their anvil counterparts, and so do not have their smooth and beautiful outlines.

scholarly journals A Doppler Radar Emulator with an Application to the Detectability of Tornadic Signatures

2007 ◽  
Vol 24 (12) ◽  
pp. 1973-1996 ◽  
Author(s):  
Ryan M. May ◽  
Michael I. Biggerstaff ◽  
Ming Xue
Keyword(s):  
Pulse Propagation ◽  
Doppler Radar ◽  
Doppler Spectrum ◽  
Doppler Velocity ◽  
Advanced Regional Prediction System ◽  
Adaptive Sensing ◽  
Regional Prediction ◽  
Sampling Intervals ◽  
Half Power ◽  
The Impact

Abstract A Doppler radar emulator was developed to simulate the expected mean returns from scanning radar, including pulse-to-pulse variability associated with changes in viewing angle and atmospheric structure. Based on the user’s configuration, the emulator samples the numerical simulation output to produce simulated returned power, equivalent radar reflectivity, Doppler velocity, and Doppler spectrum width. The emulator is used to evaluate the impact of azimuthal over- and undersampling, gate spacing, velocity and range aliasing, antenna beamwidth and sidelobes, nonstandard (anomalous) pulse propagation, and wavelength-dependent Rayleigh attenuation on features of interest. As an example, the emulator is used to evaluate the detection of the circulation associated with a tornado simulated within a supercell thunderstorm by the Advanced Regional Prediction System (ARPS). Several metrics for tornado intensity are examined, including peak Doppler velocity and axisymmetric vorticity, to determine the degradation of the tornadic signature as a function of range and azimuthal sampling intervals. For the case of a 2° half-power beamwidth radar, like those deployed in the first integrated project of the Center for Collaborative Adaptive Sensing of the Atmosphere (CASA), the detection of the cyclonic shear associated with this simulated tornado will be difficult beyond the 10-km range, if standard metrics such as azimuthal gate-to-gate shear from a single radar are used for detection.

Spaceborne Doppler Radar Measurements of Rainfall: Correction of Errors Induced by Pointing Uncertainties

2005 ◽  
Vol 22 (11) ◽  
pp. 1676-1690 ◽  
Author(s):  
Simone Tanelli ◽  
Eastwood Im ◽  
Satoru Kobayashi ◽  
Roberto Mascelloni ◽  
Luca Facheris
Keyword(s):  
Doppler Radar ◽  
Sea Surface ◽  
Doppler Spectrum ◽  
Airborne Radar ◽  
Precipitation Radar ◽  
Analysis Technique ◽  
Correction Technique ◽  
Radar Echo ◽  
Radar Measurements ◽  
Nonuniform Beam

Abstract In this paper a sea surface radar echo spectral analysis technique to correct for the rainfall velocity error caused by radar-pointing uncertainty is presented. The correction procedure is quite straightforward when the radar is observing a homogeneous rainfall field. When nonuniform beam filling (NUBF) occurs and attenuating frequencies are used, however, additional steps are necessary in order to correctly estimate the antenna-pointing direction. This new technique relies on the application of the combined frequency–time (CFT) algorithm to correct for uneven attenuation effects on the observed sea surface Doppler spectrum. The performance of this correction technique was evaluated by a Monte Carlo simulation of the Doppler precipitation radar backscatter from high-resolution 3D rain fields (either generated by a cloud resolving numerical model or retrieved from airborne radar measurements). The results show that the antenna-pointing-induced error can, indeed, be reduced by the proposed technique in order to achieve 1 m s−1 accuracy on rainfall vertical velocity estimates.

Ku-Band High-Speed Scanning Doppler Radar for Volcanic Eruption Monitoring

2019 ◽  
Vol 14 (4) ◽  
pp. 630-640
Author(s):  
Masayuki Maki ◽  
Shinobu Takahashi ◽  
Sumiya Okada ◽  
Katsuyuki Imai ◽  
Hiroshi Yamaguchi ◽  
...  
Keyword(s):  
Volcanic Eruption ◽  
High Speed ◽  
Doppler Radar ◽  
Volcanic Eruptions ◽  
Radio Station ◽  
Japan Meteorological Agency ◽  
Doppler Spectrum ◽  
Doppler Velocity ◽  
Eruption Column ◽  
Ku Band

This paper presents the major specifications and characteristics of the Ku-band high-speed scanning Doppler radar for volcano observation (KuRAD) introduced to Kagoshima University in March 2017 as well as the results of a test observation at Sakurajima. KuRAD is a Doppler radar for research with a wavelength of approximately 2 cm and uses a 45 cm diameter Luneberg lens antenna as a transmitting and receiving antenna to observe the development of a volcanic eruption column immediately following eruption at a maximum rotation speed of 40 rpm. The maximum transmitter power is 9.6 W and the maximum observational range is 20 km. Observed data includes radar reflectivity factor, Doppler velocity, and Doppler spectrum width. Another feature of KuRAD is an obtained radio station license for observation of a total of seven active volcanos in Kyushu. To assess the basic performance of KuRAD, we carried out test observations of volcanic eruptions at Sakurajima, Kagoshima Prefecture, Japan and collected a total of 87 eruptions (20 of which are explosive eruptions and 7 of which had 3,000 m or higher eruptive smoke from vents). From the eruption data of Showa vent on May 2, 2017, it was confirmed that KuRAD could monitor the three-dimensional internal structure of a volcanic eruption column immediately following eruption. Eruption data from Minamidake of Sakurajima on March 5, 2018, showed that KuRAD successfully observed the eruptive smoke reaching a height of 4,000 m, although the eruptive smoke was covered with clouds and could not be detected by optical instruments of the Japan Meteorological Agency.

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