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

2022 ◽  
Vol 14 (1) ◽  
pp. 33-55
Author(s):  
Claudia Acquistapace ◽  
Richard Coulter ◽  
Susanne Crewell ◽  
Albert Garcia-Benadi ◽  
Rosa Gierens ◽  
...  
Keyword(s):  
Spectral Width ◽  
Data Availability ◽  
Trade Wind ◽  
Doppler Velocity ◽  
Ship Motions ◽  
High Temporal Resolution ◽  
Liquid Water Path ◽  
W Band ◽  
The Impact ◽  
Rain Radar

Abstract. As part of the EUREC4A field campaign, the research vessel Maria S. Merian probed an oceanic region between 6 to 13.8∘ N and 51 to 60∘ W for approximately 32 d. 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), 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 hydrometeor vertical velocities and the algorithm created to filter interference patterns in the MRR observations. Radar reflectivity, mean Doppler velocity, spectral width and skewness for W-band and reflectivity, mean Doppler velocity, and rain rate for MRR 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, and DOIs can be found in the data availability section of this publication. Data can be accessed and basic variables can be plotted online via the intake catalog of the online book “How to EUREC4A”.

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 Biases caused by the instrument bandwidth and beam width on simulated brightness temperature measurements from scanning microwave radiometers

2012 ◽  
Vol 5 (6) ◽  
pp. 8085-8130
Author(s):  
V. Meunier ◽  
U. Löhnert ◽  
P. Kollias ◽  
S. Crewell
Keyword(s):  
Water Vapor ◽  
Liquid Water ◽  
Beam Width ◽  
Liquid Water Path ◽  
Water Path ◽  
Antenna Beam ◽  
Atmospheric Propagation ◽  
W Band ◽  
The Impact ◽  
Receiver Bandwidth

Abstract. More so than the traditional fixed radiometers, the scanning radiometer requires a careful design to ensure high quality measurements. Here the impact of the radiometer characteristics (e.g. antenna beam width, receiver bandwidth) and atmospheric propagation (e.g. curvature of the earth and refractivity) on the scanning radiometer measurements are presented. A forward radiative transfer model that includes all these effects to represent the instrument measurements is used to estimate the biases as differences between the measurement with and without these characteristics for three commonly used frequency bands: K, V and W-band. The receiver channel bandwidth errors are not so important in K-band and W-band. Thus, the use of a wider bandwidth to improve detection at low signal-to-noise conditions is acceptable. The impact of the antenna beam width is higher than the receiver bandwidth, but, for V-band where they are of similar importance. Using simple regression algorithms, the effects of the bandwidth and beam width biases in liquid water path, integrated water vapor, and temperature are also examined. The largest errors in liquid water path and integrated water vapor are associated with the beam width errors.

scholarly journals Biases caused by the instrument bandwidth and beam width on simulated brightness temperature measurements from scanning microwave radiometers

2013 ◽  
Vol 6 (5) ◽  
pp. 1171-1187 ◽  
Author(s):  
V. Meunier ◽  
U. Löhnert ◽  
P. Kollias ◽  
S. Crewell
Keyword(s):  
Water Vapour ◽  
Liquid Water ◽  
Beam Width ◽  
Liquid Water Path ◽  
Water Path ◽  
Antenna Beam ◽  
W Band ◽  
Integrated Water Vapour ◽  
The Impact ◽  
Receiver Bandwidth

Abstract. More so than the traditional fixed radiometers, the scanning radiometer requires a careful design to ensure high quality measurements. Here the impact of the radiometer characteristics (e.g., antenna beam width and receiver bandwidth) and atmospheric propagation (e.g. curvature of the Earth and vertical gradient of refractive index) on scanning radiometer measurements are presented. A forward radiative transfer model that includes all these effects to represent the instrument measurements is used to estimate the biases. These biases are estimated using differences between the measurement with and without these characteristics for three commonly used frequency bands: K, V and W-band. The receiver channel bandwidth errors are less important in K-band and W-band. Thus, the use of a wider bandwidth to improve detection at low signal-to-noise conditions is acceptable at these frequencies. The biases caused by omitting the antenna beam width in measurement simulations are larger than those caused by omitting the receiver bandwidth, except for V-band where the bandwidth may be more important in the vicinity of absorption peaks. Using simple regression algorithms, the effects of the bandwidth and beam width biases in liquid water path, integrated water vapour, and temperature are also examined. The largest errors in liquid water path and integrated water vapour are associated with the beam width errors.

scholarly journals Doppler W-band polarization diversity spaceborne radar simulator for wind studies

2018 ◽  
Author(s):  
Alessandro Battaglia ◽  
Ranvir Dhillon ◽  
Anthony Illingworth
Keyword(s):  
Spatial Variability ◽  
Wind Shear ◽  
Vertical Wind Shear ◽  
Vertical Wind ◽  
Doppler Velocity ◽  
Polarization Diversity ◽  
Signal To Noise ◽  
Uniform Beam ◽  
W Band ◽  
The Impact

Abstract. CloudSat observations are used in combination with collocated ECMWF wind reanalysis to simulate spaceborne W-band Doppler observations from slant-looking radars. The simulator also includes cross-polarization effects which are relevant if the Doppler velocities are derived from polarization diversity pulse pair correlation. A specific conically scanning radar configuration (WIVERN), recently proposed to the ESA-Earth Explorer 10 call that aims to provide global in-cloud winds for data assimilation, is analysed in detail in this study. One hundred granules of CloudSat data are exploited to investigate the impact on Doppler velocity estimates from three specific effects: (1) non-uniform beam filling, (2) wind shear, and (3) cross talk between orthogonal polarization channels induced by hydrometeors and surface targets. Errors associated with non-uniform beam filling constitute the most important source of error and can account for almost 1 m s−1 standard deviation, but this can be reduced effectively to less than 0.5 m s−1 by adopting corrections based on estimates of vertical reflectivity gradients. Wind-shear-induced errors are generally much smaller (~ 0.2 m s−1). A methodology for correcting such errors has been developed based on estimates of the vertical wind shear and the reflectivity gradient. Low signal-to-noise ratios lead to higher random errors (especially in winds) and therefore the correction (particularly the one related to the wind-shear induced error) is less effective at low signal-to-noise ratio. Both errors can be underestimated in our model because the CloudSat data do not fully sample the spatial variability of the reflectivity fields whereas the ECMWF reanalysis may have smoother velocity fields than in reality (e.g. they underestimate vertical wind shear). The simulator allows quantification of the average number of accurate measurements that could be gathered by the Doppler radar for each polar orbit, which is strongly impacted by the selection of the polarization diversity H – V pulse separation, Thv. For WIVERN a selection close to 20 μs (with a corresponding folding velocity equal to 40 m s−1) seems to achieve the right balance between maximizing the number of accurate wind measurements (exceeding 10 % of the time at any particular level in the mid-troposphere), and minimizing aliasing effects in the presence of high winds. The study lays the foundation for future studies towards a thorough assessment of the performance of polar orbiting wide-swath W-band Doppler radars on a global scale. The next generation of scanning cloud radar systems and reanalyses with improved resolution will enable full capture of the spatial variability of the cloud reflectivity and the in-cloud wind fields, thus refining the results of this study.

scholarly journals Monitoring aerosol–cloud interactions at the CESAR Observatory in the Netherlands

2017 ◽  
Vol 10 (5) ◽  
pp. 1987-1997 ◽  
Author(s):  
Karolina Sarna ◽  
Herman W. J. Russchenberg
Keyword(s):  
Remote Sensing ◽  
The Netherlands ◽  
Climate Models ◽  
Cloud Droplet ◽  
Doppler Velocity ◽  
Backscatter Coefficient ◽  
Liquid Water Path ◽  
Data Set ◽  
Aerosol Cloud ◽  
The Impact

Abstract. The representation of aerosol–cloud interaction (ACI) processes in climate models, although long studied, still remains the source of high uncertainty. Very often there is a mismatch between the scale of observations used for ACI quantification and the ACI process itself. This can be mitigated by using the observations from ground-based remote sensing instruments. In this paper we presented a direct application of the aerosol–cloud interaction monitoring technique (ACI monitoring). ACI monitoring is based on the standardised Cloudnet data stream, which provides measurements from ground-based remote sensing instruments working in synergy. For the data set collected at the CESAR Observatory in the Netherlands we calculate ACI metrics. We specifically use attenuated backscatter coefficient (ATB) for the characterisation of the aerosol properties and cloud droplet effective radius (re) and number concentration (Nd) for the characterisation of the cloud properties. We calculate two metrics: ACIr  =  ln(re)/ln(ATB) and ACIN  =  ln(Nd)/ln(ATB). The calculated values of ACIr range from 0.001 to 0.085, which correspond to the values reported in previous studies. We also evaluated the impact of the vertical Doppler velocity and liquid water path (LWP) on ACI metrics. The values of ACIr were highest for LWP values between 60 and 105 g m−2. For higher LWP other processes, such as collision and coalescence, seem to be dominant and obscure the ACI processes. We also saw that the values of ACIr are higher when only data points located in the updraught regime are considered. The method presented in this study allow for monitoring ACI daily and further aggregating daily data into bigger data sets.

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 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 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.

Analysis of the Impact of the Frequency Range of the Tensometer Bridge and Projectile Geometry on the Results of Measurements by the Split Hopkinson Pressure Bar Method

2013 ◽  
Vol 20 (4) ◽  
pp. 555-564 ◽  
Author(s):  
Wojciech Moćko
Keyword(s):  
Test Bench ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Deformation ◽  
Spectral Width ◽  
Hopkinson Pressure Bar ◽  
Computing Environment ◽  
Split Hopkinson ◽  
Pressure Bar ◽  
The Impact ◽  
Bench Model

Abstract The paper presents the results of the analysis of the striker shape impact on the shape of the mechanical elastic wave generated in the Hopkinson bar. The influence of the tensometer amplifier bandwidth on the stress-strain characteristics obtained in this method was analyzed too. For the purposes of analyzing under the computing environment ABAQUS / Explicit the test bench model was created, and then the analysis of the process of dynamic deformation of the specimen with specific mechanical parameters was carried out. Based on those tests, it was found that the geometry of the end of the striker has an effect on the form of the loading wave and the spectral width of the signal of that wave. Reduction of the striker end diameter reduces unwanted oscillations, however, adversely affects the time of strain rate stabilization. It was determined for the assumed test bench configuration that a tensometric measurement system with a bandwidth equal to 50 kHz is sufficient

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