scholarly journals ERUO: a spectral processing routine for the MRR-PRO

2021 ◽  
Author(s):  
Alfonso Ferrone ◽  
Anne-Claire Marie Billault-Roux ◽  
Alexis Berne
Keyword(s):  
Continuous Wave ◽  
Doppler Radar ◽  
Doppler Spectrum ◽  
Doppler Velocity ◽  
Spectral Processing ◽  
W Band ◽  
X Band ◽  
Radar Information ◽  
Rain Radar

Abstract. The Micro Rain Radar (MRR) PRO is a K-band Doppler weather radar, using frequency modulated continuous wave (FMCW) signals, developed by Metek Meteorologische Messtechnik GmbH (Metek) as successor to the MRR-2. Benefiting from four datasets collected during two field campaigns in Antarctica and Switzerland, we developed a processing library for snowfall measurements, named ERUO (Enhancement and Reconstruction of the spectrUm for the MRR-PRO), with a two-fold objective. Firstly, the proposed method addresses a series of issues plaguing the radar variables, which include interference lines, power drops at the extremes of the Doppler spectrum and abrupt cutoff of the transfer function. Secondly, the algorithm aims to improve the quality of the final variables, by lowering the minimum detectable equivalent attenuated reflectivity factor and extending the valid Doppler velocity range through antialiasing. The performance of the algorithm has been tested against the measurements of a co-located W-band Doppler radar. Information from a close-by X-Band Doppler dual-polarization radar has been used to exclude unsuitable radar volumes from the comparison. Particular attention has been dedicated to verify the estimation of the meteorological signal in the spectra covered by interferences.

scholarly journals Implementation of polarization diversity pulse-pair technique using airborne W-band radar

2019 ◽  
Vol 12 (1) ◽  
pp. 253-269 ◽  
Author(s):  
Mengistu Wolde ◽  
Alessandro Battaglia ◽  
Cuong Nguyen ◽  
Andrew L. Pazmany ◽  
Anthony Illingworth
Keyword(s):  
Doppler Radar ◽  
Pulse Repetition Frequency ◽  
National Research Council ◽  
Doppler Velocity ◽  
Polarization Diversity ◽  
Pulse Pair ◽  
W Band ◽  
Standard Pulse ◽  
Very High

Abstract. This work describes the implementation of polarization diversity on the National Research Council Canada W-band Doppler radar and presents the first-ever airborne Doppler measurements derived via polarization diversity pulse-pair processing. The polarization diversity pulse-pair measurements are interleaved with standard pulse-pair measurements with staggered pulse repetition frequency, this allows a better understanding of the strengths and drawbacks of polarization diversity, a methodology that has been recently proposed for wind-focused Doppler radar space missions. Polarization diversity has the clear advantage of making possible Doppler observations of very fast decorrelating media (as expected when deploying Doppler radars on fast-moving satellites) and of widening the Nyquist interval, thus enabling the observation of very high Doppler velocities (up to more than 100 m s−1 in the present work). Crosstalk between the two polarizations, mainly caused by depolarization at backscattering, deteriorated the quality of the observations by introducing ghost echoes in the power signals and by increasing the noise level in the Doppler measurements. In the different cases analyzed during the field campaigns, the regions affected by crosstalk were generally associated with highly depolarized surface returns and depolarization of backscatter from hydrometeors located at short ranges from the aircraft. The variance of the Doppler velocity estimates can be well predicted from theory and were also estimated directly from the observed correlation between the H-polarized and V-polarized successive pulses. The study represents a key milestone towards the implementation of polarization diversity in Doppler space-borne radars.

scholarly journals Implementation of Polarization Diversity Pulse Pair Technique using airborne W-band radar

2018 ◽  
Author(s):  
Mengistu Wolde ◽  
Alessandro Battaglia ◽  
Cuong Nguyen ◽  
Andrew L. Pazmany ◽  
Anthony Illingworth
Keyword(s):  
Cross Talk ◽  
Doppler Radar ◽  
Pulse Repetition Frequency ◽  
National Research Council ◽  
Doppler Velocity ◽  
Polarization Diversity ◽  
Pulse Pair ◽  
W Band ◽  
Standard Pulse

Abstract. This work describes the implementation of polarization diversity on the National Research Council Canada W-band Doppler radar and presents the first-ever airborne Doppler measurements derived via polarization diversity pulse pair processing. The polarization diversity pulse pair measurements are interleaved with standard pulse pair measurements with staggered pulse repetition frequency; this allows a better understanding of the strengths and drawbacks of polarization diversity, a methodology that has been recently proposed for wind-focussed Doppler radar space missions. Polarization diversity has the clear advantage of making possible Doppler observations of very fast de-correlating media (as expected when deploying Doppler radars on fast moving satellites) and of widening the Nyquist interval, thus enabling the observation of very high Doppler velocities (up to more than 100 m/s in present work). Cross-talk between the two polarizations, mainly caused by depolarization at backscattering deteriorated the quality of the observations by introducing ghost echoes in the power signals and by increasing the noise level in the Doppler measurements. In the different cases analyzed during the field campaigns, the regions affected by cross-talk were generally associated with highly depolarized surface returns and depolarization of backscatter from hydrometeors located at short ranges from the air craft. The variance of the Doppler velocity estimates can be well predicted from theory and were also estimated directly from the observed correlation between the H-polarized and V-polarized successive pulses. The study represents a key milestone towards the implementation of polarization diver sity in Doppler space-borne radars.

A W-Band Radar–Radiometer System for Accurate and Continuous Monitoring of Clouds and Precipitation

2017 ◽  
Vol 34 (11) ◽  
pp. 2375-2392 ◽  
Author(s):  
Nils Küchler ◽  
Stefan Kneifel ◽  
Ulrich Löhnert ◽  
Pavlos Kollias ◽  
Harald Czekala ◽  
...  
Keyword(s):  
Continuous Wave ◽  
Doppler Radar ◽  
External Source ◽  
Automatic Regulation ◽  
Doppler Velocity ◽  
Liquid Water Path ◽  
Vertical Column ◽  
Range Resolution ◽  
Transmitter Power ◽  
W Band

AbstractA new 94-GHz frequency-modulated continuous wave (FMCW) Doppler radar–radiometer system [Jülich Observatory for Cloud Evolution (JOYCE) Radar–94 GHz (JOYRAD-94)] is presented that is suitable for long-term continuous observations of cloud and precipitation processes. New features of the system include an optimally beam-matched radar–radiometer; a vertical resolution of up to 5 m with sensitivities down to −62 dBZ at 100-m distance; adjustable measurement configurations within the vertical column to account for different observational requirements; an automatic regulation of the transmitter power to avoid receiver saturation; and a high-powered blowing system that prevents hydrometeors from adhering to the radome. JOYRAD-94 has been calibrated with an uncertainty of 0.5 dB that was assessed by observing a metal sphere in the radar’s far field and by comparing radar reflectivities to a collocated 35-GHz radar. The calibrations of the radar receiver and the radiometric receiver are performed via a two-point calibration with liquid nitrogen. The passive channel at 89 GHz is particularly useful for deriving an estimate of the liquid water path (LWP). The developed retrieval shows that the LWP can be retrieved with an RMS uncertainty (not including potential calibration offsets) of about ±15 g m−2 when constraining the integrated water vapor from an external source with an uncertainty of ±2 kg m−2. Finally, a dealiasing method [dual-radar dealiasing method (DRDM)] for FMCW Doppler spectra is introduced that combines measurements of two collocated radars with different measurement setups. The DRDM ensures high range resolution with a wide unambiguous Doppler velocity range.

scholarly journals Measurements and Simulations of Nadir-Viewing Radar Returns from the Melting Layer at X and W Bands

2009 ◽  
Vol 48 (11) ◽  
pp. 2215-2226 ◽  
Author(s):  
Liang Liao ◽  
Robert Meneghini ◽  
Lin Tian ◽  
Gerald M. Heymsfield
Keyword(s):  
Water Content ◽  
Doppler Radar ◽  
Tropical Rainfall Measuring Mission ◽  
Dielectric Constants ◽  
Doppler Velocity ◽  
Regional Study ◽  
Melting Layer ◽  
Bright Band ◽  
W Band ◽  
X Band

Abstract Simulated radar signatures within the melting layer in stratiform rain—namely, the radar bright band—are checked by means of comparisons with simultaneous measurements of the bright band made by the ER-2 Doppler radar (EDOP; X band) and Cloud Radar System (CRS; W band) airborne Doppler radars during the Cirrus Regional Study of Tropical Anvils and Cirrus Layers–Florida-Area Cirrus Experiment (CRYSTAL-FACE) campaign in 2002. A stratified-sphere model, allowing the fractional water content to vary along the radius of the particle, is used to compute the scattering properties of individual melting snowflakes. Using the effective dielectric constants computed by the conjugate gradient–fast Fourier transform numerical method for X and W bands and expressing the fractional water content of a melting particle as an exponential function in particle radius, it is found that at X band the simulated radar brightband profiles are in an excellent agreement with the measured profiles. It is also found that the simulated W-band profiles usually resemble the shapes of the measured brightband profiles even though persistent offsets between them are present. These offsets, however, can be explained by the attenuation caused by cloud water and water vapor at W band. This is confirmed by comparisons of the radar profiles made in the rain regions where the unattenuated W-band reflectivity profiles can be estimated through the X- and W-band Doppler velocity measurements. The brightband model described in this paper has the potential to be used effectively for both radar and radiometer algorithms relevant to the satellite-based Tropical Rainfall Measuring Mission and Global Precipitation Measuring Mission.

scholarly journals Improved Micro Rain Radar snow measurements using Doppler spectra post-processing

2012 ◽  
Vol 5 (4) ◽  
pp. 4771-4808 ◽  
Author(s):  
M. Maahn ◽  
P. Kollias
Keyword(s):  
Continuous Wave ◽  
Doppler Radar ◽  
Low Cost ◽  
Spectral Width ◽  
Noise Removal ◽  
Radar System ◽  
Doppler Velocity ◽  
Full Potential ◽  
Post Processing ◽  
Rain Radar

Abstract. The Micro Rain Radar (MRR) is a compact Frequency Modulated Continuous Wave (FMCW) system that operates at 24 GHz. The MRR is a low-cost, portable radar system that requires minimum supervision in the field. As such, the MRR is a frequently used radar system for conducting precipitation research. Current MRR drawbacks are the lack of a sophisticated post-processing algorithm to improve its sensitivity (currently at +3 dBz), spurious artefacts concerning radar receiver noise and the lack of high quality Doppler radar moments. Here we propose an improved processing method which is especially suited for snow observations and provides reliable values of effective reflectivity, Doppler velocity and spectral width. The proposed method is freely available on the web and features a noise removal based on recognition of the most significant peak. A dynamic dealiasing routine allows observations even if the Nyquist velocity range is exceeded. Collocated observations at 115 days of a MRR and a pulsed 35.2 GHz MIRA35 cloud radar show a very high agreement for the proposed method for snow, if reflectivities are larger than −5 dBz. The overall sensitivity is increased to −14 and −8 dBz, depending on range. The proposed method exploits the full potential of MRR's hardware and substantially enhances the use of Micro Rain Radar for studies of solid precipitation.

scholarly journals Improved Micro Rain Radar snow measurements using Doppler spectra post-processing

2012 ◽  
Vol 5 (11) ◽  
pp. 2661-2673 ◽  
Author(s):  
M. Maahn ◽  
P. Kollias
Keyword(s):  
Continuous Wave ◽  
Doppler Radar ◽  
Low Cost ◽  
Spectral Width ◽  
Noise Removal ◽  
Radar System ◽  
Doppler Velocity ◽  
Full Potential ◽  
Post Processing ◽  
Rain Radar

Abstract. The Micro Rain Radar 2 (MRR) is a compact Frequency Modulated Continuous Wave (FMCW) system that operates at 24 GHz. The MRR is a low-cost, portable radar system that requires minimum supervision in the field. As such, the MRR is a frequently used radar system for conducting precipitation research. Current MRR drawbacks are the lack of a sophisticated post-processing algorithm to improve its sensitivity (currently at +3 dBz), spurious artefacts concerning radar receiver noise and the lack of high quality Doppler radar moments. Here we propose an improved processing method which is especially suited for snow observations and provides reliable values of effective reflectivity, Doppler velocity and spectral width. The proposed method is freely available on the web and features a noise removal based on recognition of the most significant peak. A dynamic dealiasing routine allows observations even if the Nyquist velocity range is exceeded. Collocated observations over 115 days of a MRR and a pulsed 35.2 GHz MIRA35 cloud radar show a very high agreement for the proposed method for snow, if reflectivities are larger than −5 dBz. The overall sensitivity is increased to −14 and −8 dBz, depending on range. The proposed method exploits the full potential of MRR's hardware and substantially enhances the use of Micro Rain Radar for studies of solid precipitation.

scholarly journals Understanding Heavy Lake-Effect Snowfall: The Vertical Structure of Radar Reflectivity in a Deep Snowband over and downwind of Lake Ontario

2016 ◽  
Vol 144 (11) ◽  
pp. 4221-4244 ◽  
Author(s):  
Dan Welsh ◽  
Bart Geerts ◽  
Xiaoqin Jing ◽  
Philip T. Bergmaier ◽  
Justin R. Minder ◽  
...  
Keyword(s):  
Vertical Velocity ◽  
Doppler Radar ◽  
Lake Ontario ◽  
Radar Reflectivity ◽  
Distribution Data ◽  
W Band ◽  
Lake Effect ◽  
X Band ◽  
Axis Parallel ◽  
Frictional Convergence

Abstract The distribution of radar-estimated precipitation from lake-effect snowbands over and downwind of Lake Ontario shows more snowfall in downwind areas than over the lake itself. Here, two nonexclusive processes contributing to this are examined: the collapse of convection that lofts hydrometeors over the lake and allows them to settle downwind; and stratiform ascent over land, due to the development of a stable boundary layer, frictional convergence, and terrain, leading to widespread precipitation there. The main data sources for this study are vertical profiles of radar reflectivity and hydrometeor vertical velocity in a well-defined, deep long-lake-axis-parallel band, observed on 11 December 2013 during the Ontario Winter Lake-effect Systems (OWLeS) project. The profiles are derived from an airborne W-band Doppler radar, as well as an array of four K-band radars, an X-band profiling radar, a scanning X-band radar, and a scanning S-band radar. The presence of convection offshore is evident from deep, strong (up to 10 m s−1) updrafts producing bounded weak-echo regions and locally heavily rimed snow particles. The decrease of the standard deviation, skewness, and peak values of Doppler vertical velocity during the downwind shore crossing is consistent with the convection collapse hypothesis. Consistent with the stratiform ascent hypothesis are (i) an increase in mean vertical velocity over land; and (ii) an increasing abundance of large snowflakes at low levels and over land, due to depositional growth and aggregation, evident from flight-level and surface particle size distribution data, and from differences in reflectivity values from S-, X-, K-, and W-band radars at nearly the same time and location.

scholarly journals Radar and ground-level measurements of precipitation collected by EPFL during the ICE-POP 2018 campaign in South-Korea

2020 ◽  
Author(s):  
Josué Gehring ◽  
Alfonso Ferrone ◽  
Anne-Claire Billault–Roux ◽  
Nikola Besic ◽  
Kwang Deuk Ahn ◽  
...  
Keyword(s):  
Doppler Radar ◽  
Ground Level ◽  
Two Dimensional ◽  
W Band ◽  
X Band ◽  
Precipitation Type ◽  
École Polytechnique ◽  
Liquid Precipitation ◽  
Polarisation Measurements ◽  
Precipitation Events

Abstract. This article describes a four-month dataset of precipitation and cloud measurements collected during the International Collaborative Experiments for PyeongChang 2018 Olympic and Paralympic winter games (ICE-POP 2018). This paper aims to describe the data collected by the Environmental Remote Sensing Laboratory of the École Polytechnique Fédérale de Lausanne. The dataset includes observations from an X-band dual-polarisation Doppler radar, a W-band Doppler cloud profiler, a multi-angle snowflake camera and a two-dimensional video disdrometer (https://doi.pangaea.de/10.1594/PANGAEA.918315, Gehring et al. (2020a)) . Classifications of hydrometeor types derived from dual-polarisation measurements and snowflake photographs are presented. The dataset covers the period from 15 November 2017 to 18 March 2018 and features nine precipitation events with a total accumulation of 195 mm of equivalent liquid precipitation. This represents 85 % of the climatological accumulation over this period. To illustrate the available data, measurements corresponding to the four precipitation events with the largest accumulation are presented. The synoptic situations of these events were contrasted and influenced the precipitation type and accumulation. The hydrometeor classifications reveal that aggregate snowflakes were dominant and that some events featured significant riming. The combination of dual-polarisation variables and high-resolution Doppler spectra with ground-level snowflake images makes this dataset particularly suited to study snowfall microphysics in a region where such measurements were not available before.

scholarly journals EUREC<sup>4</sup>A's Maria S. Merian ship-based cloud and micro rain radar observations of clouds and precipitation

2021 ◽  
Author(s):  
Claudia Acquistapace ◽  
Richard Coulter ◽  
Susanne Crewell ◽  
Albert Garcia-Benadi ◽  
Rosa T. Gierens ◽  
...  
Keyword(s):  
Spectral Width ◽  
Trade Wind ◽  
Doppler Velocity ◽  
Ship Motions ◽  
High Temporal Resolution ◽  
Liquid Water Path ◽  
W Band ◽  
Online Book ◽  
The Impact ◽  
Rain Radar

Abstract. As part of the EUREC4A field campaign, the research vessel Maria S. Merian probed an oceanic region between 6° N and 13.8° N and 51° W to 60° W for approximately 32 days. Trade wind cumulus clouds were sampled in the trade-wind alley region east of Barbados as well as in the transition region between the trades and the intertropical convergence zone, where the ship crossed some mesoscale oceanic eddies. We collected continuous observations of cloud and precipitation profiles at unprecedented vertical resolution (7–10 m in the first 3000 m) and high temporal resolution (1–3 s) using a W-band radar and micro-rain radar (MRR-PRO), installed on an active stabilization platform to reduce the impact of ship motions on the observations. The paper describes the ship motion correction algorithm applied to the Doppler observations to extract corrected hydrometeors vertical velocities and the algorithm created to filter interference patterns in the MRR-PRO observations. Radar reflectivity, mean Doppler velocity, spectral width and skewness for W-band and attenuated reflectivity, mean Doppler velocity and rain rate for MRR-PRO are shown for a case study to demonstrate the potential of the high resolution adopted. As non-standard analysis, we also retrieved and provided liquid water path (LWP) from the 89 GHz passive channel available on the W-band radar system. All datasets and hourly and daily quicklooks are publically available. Data can be accessed and basic variables can be plotted online via the intake catalog of the online book "How to EUREC4A".

scholarly journals Improved Precipitation Typing using POSS Spectral Modal Analysis

2021 ◽  
Author(s):  
Brian E. Sheppard ◽  
Merhala Thurai ◽  
Peter Rodriguez ◽  
Patrick C. Kennedy ◽  
David R. Hudak
Keyword(s):  
Doppler Radar ◽  
A Priori ◽  
Terminal Velocity ◽  
Doppler Velocity ◽  
Multiple Discriminant Analysis ◽  
Training Set ◽  
Spectral Parameters ◽  
Wind Speeds ◽  
Velocity Models ◽  
X Band

AbstractThe Precipitation Occurrence Sensor System (POSS) is a small X-band Doppler radar that measures the Doppler velocity spectra from precipitation falling in a small volume near the sensor. The sensor records a 2-D frequency of occurrence matrix of the velocity and power at the mode of each spectrum measured during one minute. The centroid of the distribution of these modes, along with other spectral parameters, defines a data vector input to a Multiple Discriminant Analysis (MDA) for classification of the precipitation type. This requires the a priori determination of a training set for different types, particle size distributions (PSDs), and wind speed conditions. A software model combines POSS system parameters, particle scattering cross section, and terminal velocity models, to simulate the real time Doppler signal measured by the system for different PSDs and wind speeds. This is processed in the same manner as the system hardware to produce bootstrap samples of the modal centroid distributions for the MDA training set. MDA results are compared to images from the Multi-Angle-Snowflake-Camera (MASC) at the MASCRAD site near Easton, Colorado, and to the CSU-CHILL X-Band observations from Greeley, Colorado. In the four case studies presented, POSS successfully identified precipitation transitions through a range of types (rain, graupel, rimed dendrites, aggregates, unrimed dendrites). Also two separate events of hail were reported and confirmed by the images.

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