scholarly journals Multifrequency radar observations of clouds and precipitation including the G-band

2021 ◽  
Vol 14 (5) ◽  
pp. 3615-3629
Author(s):  
Katia Lamer ◽  
Mariko Oue ◽  
Alessandro Battaglia ◽  
Richard J. Roy ◽  
Ken B. Cooper ◽  
...  
Keyword(s):  
Rayleigh Scattering ◽  
Ideal Liquid ◽  
Melting Behavior ◽  
Ice Crystals ◽  
Triple Frequency ◽  
W Band ◽  
Increased Sensitivity ◽  
Multifrequency Radar ◽  
Differential Reflectivity ◽  
Band Signal

Abstract. Observations collected during the 25 February 2020 deployment of the Vapor In-Cloud Profiling Radar at the Stony Brook Radar Observatory clearly demonstrate the potential of G-band radars for cloud and precipitation research, something that until now was only discussed in theory. The field experiment, which coordinated an X-, Ka-, W- and G-band radar, revealed that the Ka–G pairing can generate differential reflectivity signal several decibels larger than the traditional Ka–W pairing underpinning an increased sensitivity to smaller amounts of liquid and ice water mass and sizes. The observations also showed that G-band signals experience non-Rayleigh scattering in regions where Ka- and W-band signal do not, thus demonstrating the potential of G-band radars for sizing sub-millimeter ice crystals and droplets. Observed peculiar radar reflectivity patterns also suggest that G-band radars could be used to gain insight into the melting behavior of small ice crystals. G-band signal interpretation is challenging, because attenuation and non-Rayleigh effects are typically intertwined. An ideal liquid-free period allowed us to use triple-frequency Ka–W–G observations to test existing ice scattering libraries, and the results raise questions on their comprehensiveness. Overall, this work reinforces the importance of deploying radars (1) with sensitivity sufficient enough to detect small Rayleigh scatters at cloud top in order to derive estimates of path-integrated hydrometeor attenuation, a key constraint for microphysical retrievals; (2) with sensitivity sufficient enough to overcome liquid attenuation, to reveal the larger differential signals generated from using the G-band as part of a multifrequency deployment; and (3) capable of monitoring atmospheric gases to reduce related uncertainty.

scholarly journals First Light Multi-Frequency Observations with a G-band radar

2020 ◽  
Author(s):  
Katia Lamer ◽  
Mariko Oue ◽  
Alessandro Battaglia ◽  
Richard J. Roy ◽  
Ken B. Cooper ◽  
...  
Keyword(s):  
Rayleigh Scattering ◽  
Ideal Liquid ◽  
Melting Behavior ◽  
Ice Crystals ◽  
Triple Frequency ◽  
W Band ◽  
Increased Sensitivity ◽  
Differential Reflectivity ◽  
Ice Water ◽  
Band Signal

Abstract. Observations collected during the 25-February-2020 deployment of the Vapor In-Cloud Profiling Radar at the Stony Brook Radar Observatory clearly demonstrate the potential of G-band radars for cloud and precipitation research, something that until now was only discussed in theory. The field experiment, which coordinated an X-, Ka, W- and G-band radar, revealed that the Ka-G pairing can generate differential reflectivity signal several decibels larger than the traditional Ka-W pairing underpinning an increased sensitivity to smaller amounts of liquid and ice water mass and sizes. The observations also showed that G-band signals experience non-Rayleigh scattering in regions where Ka- and W-band signal don’t, thus demonstrating the potential of G-band radars for sizing sub-millimeter ice crystals and droplets. Observed peculiar radar reflectivity patterns also suggest that G-band radars could be used to gain insight into the melting behavior of small ice crystals. G-band signal interpretation is challenging because attenuation and non-Rayleigh effects are typically intertwined. An ideal liquid-free period allowed us to use triple frequency Ka-W-G observations to test existing ice scattering libraries and the results raise questions on their comprehensiveness. Overall, this work reinforces the importance of deploying radars with 1) sensitivity sufficient to detect small Rayleigh scatters at cloud top in order to derive estimates of path integrated hydrometeor attenuation, a key constraint for microphysical retrievals, 2) sensitivity sufficient to overcome liquid attenuation, to reveal the larger differential signals generated from using G-band as part of a multifrequency deployment, and 3) capable of monitoring atmospheric gases to reduce related uncertainty.

scholarly journals Observational and Modeling Study of Ice Hydrometeor Radar Dual-Wavelength Ratios

2019 ◽  
Vol 58 (9) ◽  
pp. 2005-2017 ◽  
Author(s):  
Sergey Y. Matrosov ◽  
Maximilian Maahn ◽  
Gijs de Boer
Keyword(s):  
Rayleigh Scattering ◽  
Elevation Angle ◽  
Characteristic Size ◽  
Dual Wavelength ◽  
Spherical Particles ◽  
Nonspherical Particles ◽  
Dual Frequency ◽  
Weather Radars ◽  
W Band ◽  
Differential Reflectivity

AbstractThe influence of ice hydrometeor shape on the dual-wavelength ratio (DWR) of radar reflectivities at millimeter-wavelength frequencies is studied theoretically and on the basis of observations. Data from dual-frequency (Ka–W bands) radar show that, for vertically pointing measurements, DWR increasing trends with reflectivity Ze are very pronounced when Ka-band Ze is greater than about 0 dBZ and that DWR and Ze values are usually well correlated. This correlation is explained by strong relations between hydrometeor characteristic size and both of these radar variables. The observed DWR variability for a given level of reflectivity is as large as 8 dB, which is in part due to changes in mean hydrometeor shape as expressed in terms of the particle aspect ratio. Hydrometeors with a higher degree of nonsphericity exhibit lower DWR values when compared with quasi-spherical particles because of near-zenith reflectivity enhancements for particles outside the Rayleigh-scattering regime. When particle mass–size relations do not change significantly (e.g., for low-rime conditions), DWR can be used to differentiate between quasi-spherical and highly nonspherical hydrometeors because (for a given reflectivity value) DWR tends to increase as particles become more spherical. Another approach for differentiating among different degrees of nonsphericity for larger scatterers is based on analyzing DWR changes as a function of radar elevation angle. These changes are more pronounced for highly nonspherical particles and can exceed 10 dB. Measurements of snowfall spatiotemporally collocated with spaceborne CloudSat W-band radar and ground-based S-band operational weather radars also indicate that DWR values are generally smaller for ice hydrometeors with higher degrees of nonsphericity, which, for the same level of S-band reflectivity, exhibit greater differential reflectivity values.

scholarly journals Determination of ice water content (IWC) in tropical convective clouds from X-band dual-polarization airborne radar

2019 ◽  
Vol 12 (11) ◽  
pp. 5897-5911 ◽  
Author(s):  
Cuong M. Nguyen ◽  
Mengistu Wolde ◽  
Alexei Korolev
Keyword(s):  
Water Content ◽  
Ice Crystals ◽  
Airborne Radar ◽  
Dual Polarization ◽  
Differential Phase ◽  
Convective Clouds ◽  
X Band ◽  
Ice Water Content ◽  
Differential Reflectivity ◽  
Ice Water

Abstract. This paper presents a methodology for ice water content (IWC) retrieval from a dual-polarization side-looking X-band airborne radar. Measured IWC from aircraft in situ probes is weighted by a function of the radar differential reflectivity (Zdr) to reduce the effects of ice crystal shape and orientation on the variation in IWC – specific differential phase (Kdp) joint distribution. A theoretical study indicates that the proposed method, which does not require a knowledge of the particle size distribution (PSD) and number density of ice crystals, is suitable for high-ice-water-content (HIWC) regions in tropical convective clouds. Using datasets collected during the High Altitude Ice Crystals – High Ice Water Content (HAIC-HIWC) international field campaign in Cayenne, French Guiana (2015), it is shown that the proposed method improves the estimation bias by 35 % and increases the correlation by 4 % on average, compared to the method using specific differential phase (Kdp) alone.

Impacts of the Phase Shift between Incident Radar Waves on the Polarization Variables from Ice Cloud Particles

2020 ◽  
Vol 37 (8) ◽  
pp. 1423-1436
Author(s):  
Valery Melnikov
Keyword(s):  
Rayleigh Scattering ◽  
Resonance Scattering ◽  
Scattering Media ◽  
Differential Phase ◽  
Additional Information ◽  
Ice Cloud ◽  
Ice Particles ◽  
Polarized Waves ◽  
Cloud Particles ◽  
Differential Reflectivity

ABSTRACTThe impacts of the differential phase of incident radar waves (ψi) on measured differential reflectivity (ZDR), differential phase, and correlation coefficient from ice cloud particles are presented for radars employing simultaneous transmission and reception of orthogonally polarized waves (SHV radar design). The maximal values of ZDR and the differential phase upon scattering (δ) from ice particles are obtained as functions of ψi. It is shown that SHV δ from ice particles can exceed a dozen degrees whereas the intrinsic δ is of a few hundredths of a degree. In melting layers, the δ values from particles obeying the Rayleigh scattering law can be several degrees depending on ψi so that, to explain such δ values, an assumption of resonance scattering is not necessary. The phase δ affects the estimation of specific differential phase (KDP) in icy media and, therefore, the phase δ should be measured. The radar differential phase upon transmission ψt is a part of ψi and, therefore, affects the δ values. A radar capability to alter ψi by varying ψt could deliver additional information about scattering media.

Polarimetric radar variables in snowfall at Ka- and W-band frequency bands: A comparative analysis

2020 ◽  
Author(s):  
Sergey Y. Matrosov
Keyword(s):  
Particle Size ◽  
Rayleigh Scattering ◽  
Size Distributions ◽  
Polarimetric Radar ◽  
Dual Frequency ◽  
Particle Size Distributions ◽  
Band Frequency ◽  
Differential Phase ◽  
Data Matching ◽  
W Band

AbstractDual-frequency millimeter-wavelength radar observations in snowfall are analyzed in order to evaluate differences in conventional polarimetric radar variables such as differential reflectivity, ZDR, specific differential phase shift, KDP, and linear depolarization ratio, LDR, at traditional cloud radar frequencies at Ka- and W-bands (~35 and ~94 GHz, correspondingly). Low radar beam elevation (~5°) measurements were performed at Oliktok Point, Alaska with a scanning fully polarimetric radar operating in the horizontal-vertical polarization basis. This radar has the same gate spacing and very close beam widths at both frequencies, which largely alleviates uncertainties associated with spatial and temporal data matching. It is shown that observed Ka- and W-band ZDR differences are, on average, less than about 0.5 dB and do not have a pronounced trend as a function of snowfall reflectivity. The observed ZDR differences agree well with modeling results obtained using integration over non-spherical ice particle size distributions. For higher signal-to-noise ratios, KDP data derived from differential phase measurements are approximately scaled as reciprocals of corresponding radar frequencies indicating that the influence of non-Rayleigh scattering effects on this variable is rather limited. This result is also in satisfactory agreement with data obtained by modeling using realistic particle size distributions. Observed Ka- and W-band LDR differences are strongly affected by the radar hardware system polarization “leak” and are generally less than 4 dB. Smaller differences are observed for higher depolarizations, where the polarization “leak” is less pronounced. Realistic assumptions about particle canting and the system polarization isolation lead to modeling results that satisfactorily agree with observational dual-frequency LDR data.

Triple-Frequency Radar Reflectivity Signatures of Snow: Observations and Comparisons with Theoretical Ice Particle Scattering Models

2014 ◽  
Vol 53 (4) ◽  
pp. 1080-1098 ◽  
Author(s):  
Mark S. Kulie ◽  
Michael J. Hiley ◽  
Ralf Bennartz ◽  
Stefan Kneifel ◽  
Simone Tanelli
Keyword(s):  
Microwave Remote Sensing ◽  
Valuable Insight ◽  
Particle Scattering ◽  
Dual Frequency ◽  
Modeling Framework ◽  
Microphysical Properties ◽  
Triple Frequency ◽  
W Band ◽  
Retrieval Algorithms ◽  
Wakasa Bay

AbstractAn observation-based study is presented that utilizes aircraft data from the 2003 Wakasa Bay Advanced Microwave Scanning Radiometer Precipitation Validation Campaign to assess recent advances in the modeling of microwave scattering properties of nonspherical ice particles in the atmosphere. Previous work has suggested that a triple-frequency (Ku–Ka–W band) reflectivity framework appears capable of identifying key microphysical properties of snow, potentially providing much-needed constraints on significant sources of uncertainty in current snowfall retrieval algorithms used for microwave remote sensing instruments. However, these results were based solely on a modeling framework. In contrast, this study considers the triple-frequency approach from an observational perspective using airborne radar observations from the Wakasa Bay field campaign. After accounting for several challenges with the observational dataset, such as beam mismatching and attenuation, observed dual-wavelength ratio results are presented that confirm both the utility of a multifrequency approach to snowfall retrieval and the validity of the unique signatures predicted by complex aggregate ice particle scattering models. This analysis provides valuable insight into the microphysics of frozen precipitation that can in turn be applied to more readily available single- and dual-frequency systems, providing guidance for future precipitation retrieval algorithms.

scholarly journals Coincident In-situ and Triple-Frequency Radar Airborne Observations in the Arctic

2021 ◽  
Author(s):  
Cuong M. Nguyen ◽  
Mengistu Wolde ◽  
Alessandro Battaglia ◽  
Leonid Nichman ◽  
Natalia Bliankinshtein ◽  
...  
Keyword(s):  
National Research Council ◽  
Characteristic Size ◽  
The Arctic ◽  
Dual Frequency ◽  
Microphysical Properties ◽  
Triple Frequency ◽  
W Band ◽  
Modelling Studies ◽  
Frequency Ratios

Abstract. This paper describes X-Ka-W-band airborne radar observations and almost perfectly co-located in situ microphysical measurements on board the National Research Council Canada (NRC) Convair-580 aircraft from the Radar Snow Experiment (RadSnowExp). Over 12 hours of flight data with more than 3.4 hours in non-Rayleigh regions for at least one of the radar frequencies provide a unique opportunity for studying the relationship between cloud microphysical properties and radar dual-frequency ratios (DFR). The results from this study are consistent with the main findings of previous modelling studies with specific regions of the DFR plane associated with unique scattering properties of different ice habits, especially in riming conditions. Moreover, the datasets could be used to produce look-up-tables for retrieving cloud bulk density and characteristic size.

scholarly journals Bulk-Density Representations of Branched Planar Ice Crystals: Errors in the Polarimetric Radar Variables

2018 ◽  
Vol 57 (2) ◽  
pp. 333-346 ◽  
Author(s):  
Robert S. Schrom ◽  
Matthew R. Kumjian
Keyword(s):  
Bulk Density ◽  
Cross Sections ◽  
Low Frequency ◽  
Resonance Scattering ◽  
Ice Crystals ◽  
Model Output ◽  
Polarimetric Radar ◽  
Radar Observations ◽  
Aspect Ratios ◽  
W Band

AbstractRecent interest in interpreting polarimetric radar observations of ice and evaluating microphysical model output with these observations has highlighted the importance of accurately computing the scattering of microwave radiation by branched planar ice crystals. These particles are often represented as spheroids with uniform bulk density, reduced from that of solid ice to account for the complex, nonuniform structure of natural branched crystals. In this study, the potential errors that arise from this assumption are examined by comparing scattering calculations of branched planar crystals with those of homogeneous, reduced-density plate crystals and spheroids with the same mass, aspect ratio, and maximum dimension. The results show that this assumption leads to significant errors in backscatter cross sections at horizontal and vertical polarization, specific differential phase (KDP), and differential reflectivity (ZDR), with the largest ZDR errors for ice crystals with the most extreme aspect ratios (<0.01) and effective densities < 250 kg m−3. For example, the maximum errors in X-band ZDR are 4.5 dB for 5.6-mm branched planar crystals. However, substantial errors are present at all weather radar frequencies, with resonance scattering effects at Ka and W band amplifying the low-frequency errors. The implications of these results on the interpretation of polarimetric radar observations and forward modeling of the polarimetric radar variables from microphysical model output are discussed.

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