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30
Correcting propagation effects in C-band polarimetric radar observations of tropical convection using differential propagation phase
- Jnl appl. Met
, 2000
"... A propagation correction algorithm utilizing the differential propagation phase ( � dp) was developed and tested on C-band polarimetric radar observations of tropical convection obtained during the Maritime Continent Thunderstorm Experiment. An empirical procedure was refined to estimate the mean co ..."
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Cited by 22 (7 self)
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A propagation correction algorithm utilizing the differential propagation phase ( � dp) was developed and tested on C-band polarimetric radar observations of tropical convection obtained during the Maritime Continent Thunderstorm Experiment. An empirical procedure was refined to estimate the mean coefficient of proportionality a (b) in the linear relationship between � dp and the horizontal (differential) attenuation throughout each radar volume. The empirical estimates of these coefficients were a factor of 1.5–2 times larger than predicted by prior scattering simulations. This discrepancy was attributed to the routine presence of large drops [e.g., differential reflectivity Zdr � 3 dB] within the tropical convection that were not included in prior theoretical studies. Scattering simulations demonstrated that the coefficients a and b are nearly constant for small to moderate sized drops (e.g., 0.5 � Zdr � 2 dB; 1 � diameter D0 � 2.5 mm) but actually increase with the differential reflectivity for drop size distributions characterized by Zdr � 2 dB. As a result, large drops 1) bias the mean coefficients upward and 2) increase the standard error associated with the mean empirical coefficients down range of convective cores that contain large drops. To reduce this error, the authors implemented a ‘‘large drop correction’ ’ that utilizes enhanced coefficients a * and b * in large drop cores. Validation of the propagation correction algorithm was accomplished with cumulative rain gauge data and
2001: The use of radar depolarization ratios for estimating shapes of ice hydrometeors
"... An approach is suggested to relate measurements of radar depolarization ratios and aspect ratios of predominant hydrometeors in nonprecipitating and weakly precipitating layers of winter clouds. The trends of elevation angle dependencies of depolarization ratios are first used to distinguish between ..."
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Cited by 11 (4 self)
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An approach is suggested to relate measurements of radar depolarization ratios and aspect ratios of predominant hydrometeors in nonprecipitating and weakly precipitating layers of winter clouds. The trends of elevation angle dependencies of depolarization ratios are first used to distinguish between columnar-type and plate-type particles. For the established particle type, values of depolarization ratios observed at certain elevation angles, for which the influence of particle orientation is minimal, are then used to estimate aspect ratios when information on particle effective bulk density is assumed or inferred from other measurements. The use of different polarizations, including circular, slant-458 linear, and two elliptical polarizations, is discussed. These two elliptical polarizations are quasi-circular and quasi-linear slant-458 linear, and both are currently achievable with the National Oceanic and Atmospheric Administration Environmental Technology Laboratory’s Ka-band radar. In comparison with the true circular and slant-458 linear polarizations, the discussed elliptical polarizations provide a stronger signal in the ‘‘weak’ ’ radar receiver channel; however, it is at the expense of diminished dynamic range of depolarization ratio variations. For depolarization measurements at the radar elevation angles that do not show much sensitivity to particle orientations, the available quasi-circular polarization provides a better depolarization contrast between nonspherical and spherical particles than does the available quasi-linear slant-458polarization. The use of the
2008: A polarimetric radar forward operator for model evaluation
- J. Appl. Meteor. Climatol
"... A polarimetric radar forward operator has been developed as a tool for the systematic evaluation of microphysical parameterization schemes in high-resolution numerical weather prediction (NWP) models. The application of such a forward operator allows a direct comparison of the model simulations to p ..."
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Cited by 4 (0 self)
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A polarimetric radar forward operator has been developed as a tool for the systematic evaluation of microphysical parameterization schemes in high-resolution numerical weather prediction (NWP) models. The application of such a forward operator allows a direct comparison of the model simulations to polar-imetric radar observations. While the comparison of observed and synthetic reflectivity gives information on the quality of quantitative precipitation forecasts, the information from the polarimetric quantities allows for a direct evaluation of the capacity of the NWP model to realistically describe the processes involved in the formation and interactions of the hydrometeors and, hence, the performance of the microphysical parameterization scheme. This information is expected to be valuable for detecting systematic model errors and hence improve model physics. This paper summarizes the technical characteristics of the synthetic polarimetric radar (SynPolRad). Different polarimetric radar quantities are computed from model forecasts using a T-matrix scattering code and ice phase hydrometeors are explicitly considered. To do so, the sensitivities of the scattering processes to the microphysical characteristics of different ice hydrometeors are investigated using sensitivity studies. Furthermore, beam propagation effects are considered, including attenuation and beam bending. The performance of SynPolRad and the consistence of the assumptions made in the derivation of the input parameters are illustrated in a case study. The resulting synthetic quantities as well as hydrometeor classification are compared with observations and are shown to be consistent with the model assumptions. 1.
Validation of TOPEX rain algorithm: Comparison with ground-based radar
- DOI 10.1029/2001JD000872) NYSTUEN, J.A
, 2002
"... Recently-developed algorithms have shown the potential recovery of rainfall information from spaceborne dual-frequency altimeters. Given the long mission achieved with TOPEX and the prospect of several other dual-frequency altimeters we need to validate the altimetrically-derived values so as to fos ..."
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Cited by 4 (4 self)
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Recently-developed algorithms have shown the potential recovery of rainfall information from spaceborne dual-frequency altimeters. Given the long mission achieved with TOPEX and the prospect of several other dual-frequency altimeters we need to validate the altimetrically-derived values so as to foster their integration with rain information from different sensors. Comparison with some alternative climatologies shows the bimonthly means for TOPEX to be low. Rather than apply a bulk correction we investigate individual rain events to understand the cause of TOPEX’s underestimation. In this paper we compare TOPEX with near-simultaneous ground-based rain radars based in a number of locations, examining both the detection of rain and the quantitative values inferred. The altimeter-only algorithm is found to flag false rain events in very low wind states (less than 3.8 ms-1); the application of an extra test, involving the liquid water path as sensed by the microwave radiometer, removes the spurious detections. Some false detections of rain also occur at high wind speeds (more than 20 ms-1), where the empirical dual-frequency relationship is less well-defined. In the intermediate range of wind speeds, the TOPEX detections are usually good, with the instrument picking up small-scale variations that cannot be recovered from infra-red or passive microwave techniques. The magnitude of TOPEX's rain retrievals can differ by a factor of
M.,“Assessment of Atmospheric Propagation Effects in SAR Images
- IEEE Transactions on Geoscience and Remote Sensing
, 2009
"... A test case showing a comparison of TerraSAR-X and ground-based weather radar data acquired nearly simultaneously (within the same minute) over New York City. A good agreement between rain-cell signatures in (left) the SAR image and (right) the weather radar image can be observed. ..."
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Cited by 3 (0 self)
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A test case showing a comparison of TerraSAR-X and ground-based weather radar data acquired nearly simultaneously (within the same minute) over New York City. A good agreement between rain-cell signatures in (left) the SAR image and (right) the weather radar image can be observed.
Prediction of signal attenuation due to duststorms using Mie scattering,”
- IIUM Engineering Journal,
, 2010
"... ABSTRACT: The present trend in radio design calls for the use of frequencies above 40 GHz for short links carrying wide-band digital communication signals. In order to utilize the new frequency band efficiently, signal attenuation studies due to duststorms is needed urgently for desert areas. This ..."
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Cited by 2 (0 self)
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ABSTRACT: The present trend in radio design calls for the use of frequencies above 40 GHz for short links carrying wide-band digital communication signals. In order to utilize the new frequency band efficiently, signal attenuation studies due to duststorms is needed urgently for desert areas. This paper presents a mathematical model which has been developed to predict the signal attenuation due to duststorm. The proposed model enables the convenient calculation of the signal path attenuation based on Mie solution of Maxwell's equations for the scattering of electromagnetic wave by dust particles. The predicted values from the proposed mathematical model are compared with the measured values observed in Saudi Arabia and Sudan and show relatively close agreement.
Influence of hydrometeors on InSAR observations
, 2003
"... Repeat-pass synthetic aperture radar interferometry is an important tool for measuring earth surface topography and/or surface deformations. These observations, however, are highly affected by the atmosphere. Therefore, an accurate description of atmospheric distortions is very important to improve ..."
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Cited by 2 (0 self)
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Repeat-pass synthetic aperture radar interferometry is an important tool for measuring earth surface topography and/or surface deformations. These observations, however, are highly affected by the atmosphere. Therefore, an accurate description of atmospheric distortions is very important to improve an accuracy of interferometric measurements. In this paper we discuss influence of hydrometeors on the microwave propagation. On examples of two interferograms we show that there is a strong increase in a propagation delay associated with rain. To validate this observation we have used weather radar measurements to estimate contribution of rain droplets on the propagation path. It is shown that in some cases, a rain induced propagation delay can be of several centimeters.
© Author(s) 2009. This work is distributed under the Creative Commons Attribution 3.0 License. Atmospheric Chemistry and Physics
, 2009
"... Abstract. Airborne measurements in Arctic boundary-layer stratocumulus were carried out near Spitsbergen on 9 April 2007 during the Arctic Study of Tropospheric Aerosol, Clouds and Radiation (ASTAR) campaign. A unique set of co-located observations is used to describe the cloud proper-ties, includin ..."
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Abstract. Airborne measurements in Arctic boundary-layer stratocumulus were carried out near Spitsbergen on 9 April 2007 during the Arctic Study of Tropospheric Aerosol, Clouds and Radiation (ASTAR) campaign. A unique set of co-located observations is used to describe the cloud proper-ties, including detailed in situ cloud microphysical and radia-tion measurements along with airborne and co-located space-borne remote sensing data (CALIPSO lidar and CloudSat radar). CALIPSO profiles indicate cloud top levels at tem-perature between −24◦C and −21◦C. In situ measurements confirm that the cloud-top lidar attenuated backscatter sig-nal along the aircraft trajectory is linked with the presence of liquid water, a common feature observed in Arctic mixed-phase stratocumulus clouds. A low concentration of large ice crystals is also observed up to the cloud top resulting in
with a
"... Backscattering enhancement for Marshall-Palmer distributed rains for a W-band nadir-pointing radar ..."
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Backscattering enhancement for Marshall-Palmer distributed rains for a W-band nadir-pointing radar
~|SAPPROVED FOR PUBLIC RELEASE; DISTRIBUTION UNLIMITED
, 1985
"... California. Lt Paul J. Fordenbacher, BMO/MYES, was the Project Officer in charge. This Final Report has been reviewed and is approved for publication..0,. ..."
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California. Lt Paul J. Fordenbacher, BMO/MYES, was the Project Officer in charge. This Final Report has been reviewed and is approved for publication..0,.
