scholarly journals Upgrade of a W-band Gyro-TWA for cloud radar application

2016 ◽  
Author(s):  
W. He ◽  
J.R. Garner ◽  
L. Zhang ◽  
P. McElhinney ◽  
H. Yin ◽  
...  
Keyword(s):  
Cloud Radar ◽  
W Band

scholarly journals Finescale Structure of a Snowstorm over the Northeastern United States: A First Look at High-Resolution HIAPER Cloud Radar Observations

2017 ◽  
Vol 98 (2) ◽  
pp. 253-269 ◽  
Author(s):  
Robert M. Rauber ◽  
Scott M. Ellis ◽  
J. Vivekanandan ◽  
Jeffrey Stith ◽  
Wen-Chau Lee ◽  
...  
Keyword(s):  
United States ◽  
High Performance ◽  
Spectral Width ◽  
The United States ◽  
Environmental Research ◽  
Range Resolution ◽  
Cloud Radar ◽  
W Band ◽  
Linear Depolarization Ratio ◽  
Complex Features

Abstract The newly developed High-Performance Instrumented Airborne Platform for Environmental Research (HIAPER) Cloud Radar (HCR) is an airborne, W-band, dual-polarization, Doppler research radar that fits within an underwing pod on the National Center for Atmospheric Research Gulfstream-V HIAPER aircraft. On 2 February 2015, the HCR was flown on its maiden research voyage over a cyclone along the Northeast coast of the United States. Six straight flight legs were flown over 6 h between the northern tip of Delaware Bay and Bangor, Maine, crossing the rain–snow line, and passing directly over Boston, Massachusetts, which received over 16 in. of snow during the event. The HCR, which recorded reflectivity, radial velocity, spectral width, and linear depolarization ratio with a 0.7° beam, was pointed at nadir from a flight altitude of 12,800 m (42,000 ft). The along-track resolution ranged between 20 and 200 m, depending on range, at aircraft speeds varying between 200 and 275 m s−1. The range resolution was 19.2 m. Remarkably detailed finescale structures were found throughout the storm system, including cloud-top generating cells, upright elevated convection, layers of turbulence, vertical velocity perturbations across the melting level, gravity waves, boundary layer circulations, and other complex features. Vertical velocities in these features ranged from 1 to 5 m s−1, and many features were on scales of 5 km or less. The purpose of this paper is to introduce the HCR and highlight the remarkable finescale structures revealed within this Northeast U.S. cyclone by the HCR.

Measurements of Ocean Surface Backscattering Using an Airborne 94-GHz Cloud Radar—Implication for Calibration of Airborne and Spaceborne W-Band Radars

2005 ◽  
Vol 22 (7) ◽  
pp. 1033-1045 ◽  
Author(s):  
Lihua Li ◽  
Gerald M. Heymsfield ◽  
Lin Tian ◽  
Paul E. Racette
Keyword(s):  
Millimeter Wave ◽  
Cross Section ◽  
Incidence Angle ◽  
Surface Wind ◽  
Ocean Surface ◽  
Regional Study ◽  
Specular Scattering ◽  
Cloud Radar ◽  
W Band ◽  
Low Incidence

Abstract Backscattering properties of the ocean surface have been widely used as a calibration reference for airborne and spaceborne microwave sensors. However, at millimeter-wave frequencies, the ocean surface backscattering mechanism is still not well understood, in part, due to the lack of experimental measurements. During the Cirrus Regional Study of Tropical Anvils and Cirrus Layers-Florida Area Cirrus Experiment (CRYSTAL-FACE), measurements of ocean surface backscattering were made using a 94-GHz (W band) cloud radar on board a NASA ER-2 high-altitude aircraft. This unprecedented dataset enhances our knowledge about the ocean surface scattering mechanism at 94 GHz. The measurement set includes the normalized ocean surface cross section over a range of the incidence angles under a variety of wind conditions. It was confirmed that even at 94 GHz, the normalized ocean surface radar cross section, σo, is insensitive to surface wind conditions near a 10° incidence angle, a finding similar to what has been found in the literature for lower frequencies. Analysis of the radar measurements also shows good agreement with a quasi-specular scattering model at low incidence angles. The results of this work support the proposition of using the ocean surface as a calibration reference for airborne millimeter-wave cloud radars and for the ongoing NASA CloudSat mission, which will use a 94-GHz spaceborne cloud radar for global cloud measurements.

scholarly journals A Dual-Frequency Cloud Radar for Observations of Precipitation and Cloud in Tibet: Description and Preliminary Measurements

2021 ◽  
Vol 13 (22) ◽  
pp. 4685
Author(s):  
Juan Huo ◽  
Yongheng Bi ◽  
Bo Liu ◽  
Congzheng Han ◽  
Minzheng Duan
Keyword(s):  
Detection Sensitivity ◽  
The Tibetan Plateau ◽  
Dual Frequency ◽  
Cloud Droplets ◽  
Cloud Radar ◽  
W Band ◽  
The Mean ◽  
The Difference ◽  
One Year ◽  
Different Characteristics

A new dual-frequency Doppler polarimetric cloud radar (DDCR), working at 35-GHz (Ka-band radar, wavelength: 8.6 mm) and 94-GHz (W-band radar, wavelength: 3.2 mm) frequencies, has been in operation at Yangbajing Observatory on the Tibetan Plateau (China) for more than a year at the time of writing. Calculations and field observations show that the DDCR has a high detection sensitivity of −39.2 dBZ at 10 km and −33 dBZ at 10 km for the 94-GHz radar and 35-GHz radar, respectively. The radar reflectivity measured by the two radars illustrates different characteristics for different types of cloud: for precipitation, the attenuation caused by liquid cloud droplets is obviously more serious for the 94-GHz radar than the 35-GHz radar (the difference reaches 40 dB in some cases), and the 94-GHz radar lost signals due to serious attenuation by heavy rainfall; while for clouds dominated by ice crystals where the attenuation significantly weakens, the 94-GHz radar shows better detection ability than the 35-GHz radar. Observations in the Tibetan region show that the 35-GHz radar is prone to missing cloud near the edge, such as the cloud-top portion, resulting in underestimation of the cloud-top height (CTH). Statistical analysis based on one year of observations shows that the mean CTH measured by the 94-GHz radar in the Tibetan region is approximately 600 m higher than that measured by the 35-GHz radar. The analysis in this paper shows that the DDCR, with its dual-frequency design, provides more valuable information than simpler configurations, and will therefore play an important role in improving our understanding of clouds and precipitation in the Tibetan region.

The NASA/GSFC 94 GHz Airborne Solid State Cloud Radar System (CRS)

2021 ◽  
Author(s):  
Matthew L. Walker McLinden ◽  
Lihua Li ◽  
Gerald M. Heymsfield ◽  
Michael Coon ◽  
Amber Emory
Keyword(s):  
Solid State ◽  
Digital Technology ◽  
Direct Relationship ◽  
Radar System ◽  
Digital Receiver ◽  
Internal Loop ◽  
Nasa Goddard Space ◽  
Cloud Radar ◽  
W Band ◽  
Reflectarray Antenna

AbstractThe NASA/Goddard Space Flight Center’s (GSFC’s) W-band (94 GHz) Cloud Radar System (CRS) has been comprehensively updated to modern solid-state and digital technology. This W-band (94 GHz) radar flies in nadir-pointing mode on the NASA ER-2 high-altitude aircraft, providing polarimetric reflectivity and Doppler measurements of clouds and precipitation. This paper describes the design and signal processing of the upgraded CRS. It includes details on the hardware upgrades (SSPA transmitter, antenna, and digital receiver) including a new reflectarray antenna and solid-state transmitter. It also includes algorithms, including internal loop-back calibration, external calibration using a direct relationship between volume reflectivity and the range-integrated backscatter of the ocean, and a modified staggered-PRF Doppler algorithm that is highly resistant to unfolding errors. Data samples obtained by upgraded CRS through recent NASA airborne science missions are provided.

scholarly journals Impact of airborne cloud radar reflectivity data assimilation on kilometre-scale numerical weather prediction analyses and forecasts of heavy precipitation events

2019 ◽  
Vol 19 (4) ◽  
pp. 907-926 ◽  
Author(s):  
Mary Borderies ◽  
Olivier Caumont ◽  
Julien Delanoë ◽  
Véronique Ducrocq ◽  
Nadia Fourrié ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Numerical Weather Prediction ◽  
Weather Prediction ◽  
Heavy Precipitation ◽  
Mediterranean Area ◽  
Wind Data ◽  
Cloud Radar ◽  
W Band ◽  
Assimilation System ◽  
Precipitation Events

Abstract. This article investigates the potential of W-band radar reflectivity to improve the quality of analyses and forecasts of heavy precipitation events in the Mediterranean area. The “1D+3DVar” assimilation method, operationally employed to assimilate ground-based precipitation radar data in the Météo-France kilometre-scale numerical weather prediction (NWP) model AROME, has been adapted to assimilate the W-band reflectivity measured by the airborne cloud radar RASTA (Radar Airborne System Tool for Atmosphere) during a 2-month period over the Mediterranean area. After applying a bias correction, vertical profiles of relative humidity are first derived via a 1-D Bayesian retrieval, and then used as relative humidity pseudo-observations in the 3DVar assimilation system of AROME. The efficiency of the 1-D Bayesian method in retrieving humidity fields is assessed using independent in-flight humidity measurements. To complement this study, the benefit brought by consistent thermodynamic and dynamic cloud conditions has been investigated by separately and jointly assimilating the W-band reflectivity and horizontal wind measurements collected by RASTA in the 3 h 3DVar assimilation system of AROME. The data assimilation experiments are conducted for a single heavy precipitation event and then also for 32 cases. Results indicate that the W-band reflectivity has a larger impact on the humidity, temperature and pressure fields in the analyses compared to the assimilation of RASTA wind data alone. Besides, the analyses get closer to independent humidity observations if the W-band reflectivity is assimilated alone or jointly with RASTA wind data. Nonetheless, the impact of the W-band reflectivity decreases more rapidly as the forecast range increases when compared to the assimilation of RASTA wind data alone. Generally, the joint assimilation of the W-band reflectivity with wind data results in the best improvement in the rainfall precipitation forecasts. Consequently, results of this study indicate that consistent thermodynamic and dynamic cloud conditions in the analysis leads to an improvement of both model initial conditions and forecasts. Even though to a lesser extent, the assimilation of the W-band reflectivity alone also results in a slight improvement of the rainfall precipitation forecasts.

scholarly journals Absolute Calibration method for FMCW Cloud Radars

2020 ◽  
Author(s):  
Felipe Toledo ◽  
Julien Delanoë ◽  
Martial Haeffelin ◽  
Jean-Charles Dupont
Keyword(s):  
Field Experiments ◽  
Calibration Method ◽  
Absolute Calibration ◽  
Experimental Setup ◽  
Cloud Radar ◽  
Research And Innovation ◽  
W Band ◽  
Calibration Uncertainty ◽  
Radar Calibration ◽  
The Impact

Abstract. This article presents a new Cloud Radar calibration methodology using solid reference reflectors mounted on masts, developed during two field experiments held in 2018 and 2019 at the SIRTA atmospheric observatory, located in Palaiseau, France, in the framework of the ACTRIS-2 research and innovation program. The experimental setup includes 10 cm and 20 cm triangular trihedral targets installed at the top of 10 m and 20 m masts, respectively. The 10 cm target is mounted on a pan-tilt motor at the top of the 10 m mast to precisely align its boresight with the radar beam. Sources of calibration bias and uncertainty are identified and quantified. Specifically, this work assesses the impact of receiver compression, incomplete antenna overlap, temperature variations inside the radar, clutter and experimental setup misalignment. Setup misalignment is a source of bias previously undocumented in the literature, that can have an impact on the order of tenths of dB in calibration retrievals of W band Radars. A detailed analysis enabled the design of a calibration methodology which can reach a cloud radar calibration uncertainty of 0.3 dB based on the equipment used in the experiment. Among different sources of uncertainty, the two largest terms are due to signal-to-clutter ratio and radar-to-target alignment. The analysis revealed that our 20 m mast setup with an approximate alignment approach is preferred to the 10 m mast setup with the motor-driven alignment system. The calibration uncertainty associated with signal-to-clutter ratio of the former is ten times smaller than for the latter. Cloud radar calibration results are found to be repeatable when comparing results from a total of 18 independent tests. Once calibrated the cloud radar provides valid reflectivity values when sampling mid-tropospheric clouds. Thus we conclude that the method is repeatable and robust, and that the uncertainties are precisely characterized. The method can be implemented under different configurations as long as the proposed principles are respected. It could be extended to reference reflectors held by other lifting devices such as tethered balloons or unmanned aerial vehicles.

scholarly journals A NOVEL W-BAND DUAL-POLARIZED CASSEGRAIN ANTENNA FOR CLOUD RADAR

2016 ◽  
Vol 61 ◽  
pp. 99-103 ◽  
Author(s):  
Bing Yu ◽  
Han Xia ◽  
Xiaoye Chen ◽  
Fei Yang ◽  
Fayu Wan ◽  
...  
Keyword(s):  
Cloud Radar ◽  
Cassegrain Antenna ◽  
W Band ◽  
Dual Polarized

scholarly journals W-Band (95 GHz) Radar Attenuation in Tropical Stratiform Ice Anvils

2019 ◽  
Vol 36 (8) ◽  
pp. 1463-1476 ◽  
Author(s):  
Alain Protat ◽  
Surendra Rauniyar ◽  
Julien Delanoë ◽  
Emmanuel Fontaine ◽  
Alfons Schwarzenboeck
Keyword(s):  
Water Content ◽  
Attenuation Coefficient ◽  
Cloud Microphysics ◽  
Vertical Profiles ◽  
High Attenuation ◽  
Cloud Radar ◽  
Ice Particles ◽  
W Band ◽  
Ice Water Content ◽  
Ice Water

AbstractAttenuation of the W-band (95 GHz) radar signal by atmospheric ice particles has long been neglected in cloud microphysics studies. In this work, 95-GHz airborne multibeam cloud radar observations in tropical stratiform ice anvils are used to estimate vertical profiles of 95-GHz attenuation. Two techniques are developed and compared, using very different assumptions. The first technique examines statistical reflectivity differences between repeated aircraft passes through the same cloud mass at different altitudes. The second technique exploits reflectivity differences between two different pathlengths through the same cloud, using the multibeam capabilities of the cloud radar. Using the first technique, the two-way attenuation coefficient produced by stratiform ice particles ranges between 1 and 1.6 dB km−1 for reflectivities between 13 and 18 dBZ, with an expected increase of attenuation with reflectivity. Using the second technique, the multibeam results confirm these high attenuation coefficient values and expand the reflectivity range, with typical attenuation coefficient values of up to 3–4 dB km−1 for reflectivities of 20 dBZ. The potential impact of attenuation on precipitating-ice-cloud microphysics retrievals is quantified using vertical profiles of the mean and the 99th percentile of ice water content derived from noncorrected and attenuation-corrected reflectivities. A large impact is found on the 99th percentile of ice water content, which increases by 0.3–0.4 g m−3 up to 11-km height. Finally, T-matrix calculations of attenuation constrained by measured particle size distributions, ice crystal mass–size, and projected area–size relationships are found to largely underestimate cloud radar attenuation estimates.

scholarly journals Impact of airborne cloud radar reflectivity data assimilation on kilometre-scale NWP analyses and forecasts of heavy precipitation events

2018 ◽  
Author(s):  
Mary Borderies ◽  
Olivier Caumont ◽  
Julien Delanoë ◽  
Véronique Ducrocq ◽  
Nadia Fourrié ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Data Assimilation ◽  
Heavy Precipitation ◽  
Mediterranean Area ◽  
Radar Reflectivity ◽  
Wind Data ◽  
Cloud Radar ◽  
W Band ◽  
Assimilation System ◽  
Precipitation Events

Abstract. This article investigates the potential of W-band radar reflectivity to improve the quality of analyses and forecasts of heavy precipitation events in the Mediterranean area. The 1D + 3DVar assimilation method, operationally employed to assimilate ground-based precipitation radar data in the Météo-France kilometre-scale NWP model AROME, has been adapted to assimilate the W-band reflectivity measured by the airborne cloud radar RASTA during a two-month period over the Mediterranean area. After applying a bias correction, vertical profiles of relative humidity are first derived via a 1D Bayesian retrieval, and then used as relative humidity pseudo-observations in the 3DVar assimilation system of AROME. The efficiency of the 1D Bayesian method in retrieving humidity fields is assessed using independent in-flight humidity measurements. To complement this study, the benefit brought by consistent thermodynamic and dynamic cloud conditions has been investigated by assimilating separately and jointly in the 3 h 3DVar assimilation system of AROME the W-band reflectivity and horizontal wind measurements collected by RASTA. The data assimilation experiments are conducted for a single heavy precipitation event, and then for 32 cases. Results indicate that the W-band reflectivity has a larger impact on the humidity, temperature and pressure fields in the analyses, compared to the assimilation of RASTA wind data alone. Besides, the analyses get closer to independent humidity observations if the W-band reflectivity is assimilated alone or jointly with RASTA wind data. Nonetheless, the impact of the W-band reflectivity decreases more rapidly as the forecast range increases, compared to the assimilation of RASTA wind data alone. Generally, the assimilation of the W-band reflectivity jointly with wind data results in the best improvement of the rainfall precipitation forecasts. Consequently, results of this study indicate that consistent thermodynamic and dynamic cloud conditions in the analysis leads to an improvement of both model initial conditions and forecasts. Even though to a less extent, the assimilation of the W-band reflectivity alone also results in a slight improvement of the rainfall precipitation forecasts.

scholarly journals Snowfall rate retrieval for K- and W-band radar measurements designed in Hyytiälä, Finland, and tested at Ny-Ålesund, Svalbard

2020 ◽  
Author(s):  
Sybille Y. Schoger ◽  
Dmitri Moisseev ◽  
Annakaisa von Lerber ◽  
Susanne Crewell ◽  
Kerstin Ebell
Keyword(s):  
Rate Estimate ◽  
Arctic Clouds ◽  
Cloud Radar ◽  
Microwave Radar ◽  
W Band ◽  
Radar Measurements ◽  
Rain Radar ◽  
Good Agreement ◽  
K Band

AbstractTwo power law relations linking equivalent radar reflectivity factor (Ze) and snowfall rate (S) are derived for a Micro Rain Radar (MRR), which operates at K-band, and a W-band cloud radar. For the development of these Ze-S relationships, a dataset of calculated and measured variables is used. Surface-based video-disdrometer measurements were collected during snowfall events over five winters at the high-latitude site in Hyytiälä, Finland. The data from 2014-2018 includes particle size distributions (PSD) and their fall velocities, from which snowflake masses were derived. K- and W-band Ze values are computed using these surface-based observations and snowflake scattering properties as provided by T-matrix and single-particle scattering tables, respectively. The uncertainty analysis shows that the K-band snowfall rate estimation is significantly improved by including the intercept parameter N0 of the PSD calculated from concurrent disdrometer measurements. If N0 is used to adjust the prefactor of the Ze-S relationship, the RMSE of the snowfall rate estimate can be reduced from 0.37 to around 0.11 mmh−1. For W-band, a Ze-S relationship with constant parameters for all available snow events shows a similar uncertainty compared to the method that includes the PSD intercept parameter. To demonstrate the performance of the proposed Ze-S relationships, they are applied to measurements of the MRR and the W-band Microwave Radar for Arctic Clouds at the AWIPEV Arctic research base in Ny-Ålesund, Svalbard. The resulting snowfall rate estimates show a good agreement to in situ snowfall observations while other Ze-S relationships from literature reveal larger differences.

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