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.

scholarly journals Airborne Radar Observations of Severe Hailstorms: Implications for Future Spaceborne Radar

2013 ◽  
Vol 52 (8) ◽  
pp. 1851-1867 ◽  
Author(s):  
Gerald M. Heymsfield ◽  
Lin Tian ◽  
Lihua Li ◽  
Matthew McLinden ◽  
Jaime I. Cervantes
Keyword(s):  
High Altitude ◽  
Doppler Radar ◽  
Tropical Rainfall Measuring Mission ◽  
Airborne Radar ◽  
Dual Frequency ◽  
Precipitation Radar ◽  
Ka Band ◽  
Severe Thunderstorms ◽  
Radar Measurements ◽  
Spaceborne Radar

AbstractA new dual-frequency (Ku and Ka band) nadir-pointing Doppler radar on the high-altitude NASA ER-2 aircraft, called the High-Altitude Imaging Wind and Rain Airborne Profiler (HIWRAP), has collected data over severe thunderstorms in Oklahoma and Kansas during the Midlatitude Continental Convective Clouds Experiment (MC3E). The overarching motivation for this study is to understand the behavior of the dual-wavelength airborne radar measurements in a global variety of thunderstorms and how these may relate to future spaceborne-radar measurements. HIWRAP is operated at frequencies that are similar to those of the precipitation radar on the Tropical Rainfall Measuring Mission (Ku band) and the upcoming Global Precipitation Measurement mission satellite's dual-frequency (Ku and Ka bands) precipitation radar. The aircraft measurements of strong hailstorms have been combined with ground-based polarimetric measurements to obtain a better understanding of the response of the Ku- and Ka-band radar to the vertical distribution of the hydrometeors, including hail. Data from two flight lines on 24 May 2011 are presented. Doppler velocities were ~39 m s−1 at 10.7-km altitude from the first flight line early on 24 May, and the lower value of ~25 m s−1 on a second flight line later in the day. Vertical motions estimated using a fall speed estimate for large graupel and hail suggested that the first storm had an updraft that possibly exceeded 60 m s−1 for the more intense part of the storm. This large updraft speed along with reports of 5-cm hail at the surface, reflectivities reaching 70 dBZ at S band in the storm cores, and hail signals from polarimetric data provide a highly challenging situation for spaceborne-radar measurements in intense convective systems. The Ku- and Ka-band reflectivities rarely exceed ~47 and ~37 dBZ, respectively, in these storms.

scholarly journals The Coplane Analysis Technique for Three-Dimensional Wind Retrieval Using the HIWRAP Airborne Doppler Radar

2015 ◽  
Vol 54 (3) ◽  
pp. 605-623 ◽  
Author(s):  
Anthony C. Didlake ◽  
Gerald M. Heymsfield ◽  
Lin Tian ◽  
Stephen R. Guimond
Keyword(s):  
Global Optimization ◽  
Doppler Radar ◽  
Three Dimensional ◽  
Optimization Method ◽  
Vertical Wind ◽  
Wind Component ◽  
Global Optimization Method ◽  
Analysis Technique ◽  
Radar Measurements ◽  
Cross Track

AbstractThe coplane analysis technique for mapping the three-dimensional wind field of precipitating systems is applied to the NASA High-Altitude Wind and Rain Airborne Profiler (HIWRAP). HIWRAP is a dual-frequency Doppler radar system with two downward-pointing and conically scanning beams. The coplane technique interpolates radar measurements onto a natural coordinate frame, directly solves for two wind components, and integrates the mass continuity equation to retrieve the unobserved third wind component. This technique is tested using a model simulation of a hurricane and compared with a global optimization retrieval. The coplane method produced lower errors for the cross-track and vertical wind components, while the global optimization method produced lower errors for the along-track wind component. Cross-track and vertical wind errors were dependent upon the accuracy of the estimated boundary condition winds near the surface and at nadir, which were derived by making certain assumptions about the vertical velocity field. The coplane technique was then applied successfully to HIWRAP observations of Hurricane Ingrid (2013). Unlike the global optimization method, the coplane analysis allows for a transparent connection between the radar observations and specific analysis results. With this ability, small-scale features can be analyzed more adequately and erroneous radar measurements can be identified more easily.

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 Variability in vertical structure of precipitation with sea surface temperature over the Arabian Sea and the Bay of Bengal as inferred by Tropical Rainfall Measuring Mission precipitation radar measurements

2019 ◽  
Vol 19 (15) ◽  
pp. 10423-10432 ◽  
Author(s):  
Kadiri Saikranthi ◽  
Basivi Radhakrishna ◽  
Thota Narayana Rao ◽  
Sreedharan Krishnakumari Satheesh
Keyword(s):  
Surface Temperature ◽  
Bay Of Bengal ◽  
Wind Shear ◽  
Arabian Sea ◽  
Vertical Structure ◽  
Tropical Rainfall Measuring Mission ◽  
Sea Surface ◽  
Precipitation Radar ◽  
Radar Measurements ◽  
Tropospheric Wind

Abstract. Tropical Rainfall Measuring Mission (TRMM) precipitation radar measurements are used to examine the variation in vertical structure of precipitation with sea surface temperature (SST) over the Arabian Sea (AS) and Bay of Bengal (BOB). The variation in reflectivity and precipitation echo top with SST is remarkable over the AS but small over the BOB. The reflectivity increases with SST (from 26 to 31 ∘C) by ∼1 and 4 dBZ above and below 6 km, respectively, over the AS, while its variation is <0.5 dBZ over the BOB. The transition from shallow storms at lower SSTs (≤27 ∘C) to deeper storms at higher SSTs is strongly associated with the decrease in stability and mid-tropospheric wind shear over the AS. In contrary, the storms are deeper at all SSTs over the BOB due to weaker stability and mid-tropospheric wind shear. At lower SSTs, the observed high aerosol optical depth (AOD) and low total column water (TCW) over AS results in the small cloud effective radius (CER) and weaker reflectivity. As SST increases, AOD decreases and TCW increases, leading to a large CER and high reflectivity. The changes in these parameters with SST are marginal over the BOB and hence the CER and reflectivity. The predominance of collision–coalescence process below the bright band is responsible for the observed negative slopes in the reflectivity over both the seas. The observed variations in reflectivity originate at the cloud formation stage over both the seas, and these variations are magnified during the descent of hydrometeors to the ground.

Modeling the Radar Signature of Raindrops in Aircraft Wake Vortices

2013 ◽  
Vol 30 (3) ◽  
pp. 470-484 ◽  
Author(s):  
Zhongxun Liu ◽  
Nicolas Jeannin ◽  
Francois Vincent ◽  
Xuesong Wang
Keyword(s):  
Traffic Control ◽  
Vortex Flow ◽  
Doppler Radar ◽  
Elevation Angle ◽  
Wake Vortex ◽  
Wake Vortices ◽  
Radar Signature ◽  
Radar Echo ◽  
Aircraft Wake ◽  
Resolution Cell

Abstract The present work is dedicated to the modeling and simulation of the radar signature of raindrops within wake vortices. This is achieved through the computation of the equation of raindrop motion within the wake vortex flow. Based on the inhomogeneous distribution of raindrops within wake vortices, the radar echo model is computed for raindrops in a given resolution cell. Simulated Doppler radar signatures of raindrops within wake vortices are shown to be a potential criterion for identifying wake vortex hazards in air traffic control. The dependence of the radar signature on various parameters, including the radial resolution and antenna elevation angle, is also analyzed.

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

1975 ◽  
Vol 56 (5) ◽  
pp. 524-526 ◽  
Author(s):  
Rodger A. Brown ◽  
Donald W. Burgess ◽  
John K. Carter ◽  
Leslie R. Lemon ◽  
Dale Sirmans
Keyword(s):  
Doppler Radar ◽  
Radar Measurements ◽  
Tornadic Storms ◽  
Dual Doppler Radar
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