scholarly journals Solar Monitoring of the NEXRAD WSR-88D Network using Operational Scan Data

2021 ◽  
Keyword(s):  
Observation Time ◽  
Noise Power ◽  
Monitoring Method ◽  
Continental Scale ◽  
Weather Radars ◽  
Routine Monitoring ◽  
Geographical Maps ◽  
Scan Data ◽  
One Year ◽  
Differential Reflectivity

Abstract Solar monitoring is a method in which solar interferences, recorded during operational scanning of a radar, are used to monitor antenna pointing, identify signal processor issues, track receiver chain stability, and check the balance between horizontal and vertical polarization receive channels. The method is used by Eumetnet to monitor more than 100 radars in twenty European countries and it has been adopted by many national weather services across the world. NEXRAD is a network of 160 similar S-band weather radars (WSR-88Ds), which makes it most suitable for assessing the capability of the solar monitoring method on a continental scale. The NEXRAD Level-II data contain radial-by-radial noise power estimates. An increase in this estimate is observed when the antenna points close to the sun. Our decoding software extracts these noise power estimates for the horizontal and vertical receive channels (converted to solar flux units) and other relevant metadata, including azimuth, elevation, observation time and radar location. Here we present results of analyzing one year of solar-monitoring data generated by 142 radars from the contiguous United States. We show monitoring results, geographical maps, and statistical outcomes on antenna pointing, solar fluxes, and differential reflectivity biases. We also assess the quality of the radars by defining a Figure of Merit, which is calculated from the solar monitoring results. The results demonstrate that the solar method provides great benefit for routine monitoring and harmonization of national and transnational operational radar networks.

scholarly journals Calibration of radar differential reflectivity using quasi-vertical profiles

2021 ◽  
Author(s):  
Daniel Sanchez-Rivas ◽  
Miguel A. Rico-Ramirez
Keyword(s):  
Weather Radar ◽  
Radar Data ◽  
Vertical Profiles ◽  
Weather Radars ◽  
Precipitation Estimates ◽  
Novel Method ◽  
One Year ◽  
The Uk ◽  
Quantitative Precipitation Estimates ◽  
Differential Reflectivity

Abstract. The differential reflectivity (ZDR) is a crucial weather radar measurement that helps to improve quantitative precipitation estimates using polarimetric weather radars. However, a system bias between the horizontal and vertical channels generated by the radar produces an offset in ZDR. Existing methods to calibrate ZDR measurements rely on vertical observations of ZDR taken in rain, in which ZDR values close to 0 dB are expected. However, not all weather radar systems are capable of producing vertical pointing measurements. In this work, we present and analyse a novel method for correcting and monitoring the ZDR offset using quasi-vertical profiles of polarimetric variables. The method is applied to radar data collected through one year of precipitation events by two operational C-band weather radars in the UK. The proposed method proves effective in achieving the required accuracy of 0.1 dB for the calibration of ZDR as the calibration results are consistent with the traditional method based on vertical profiles. Additionally, the method is independently evaluated using disdrometers located near the radar sites. The results showed a good agreement between disdrometer-derived and radar-calibrated ZDR measurements.

scholarly journals Operational Monitoring of Radar Differential Reflectivity Using the Sun

2010 ◽  
Vol 27 (5) ◽  
pp. 881-887 ◽  
Author(s):  
Iwan Holleman ◽  
Asko Huuskonen ◽  
Rashpal Gill ◽  
Pierre Tabary
Keyword(s):  
The Sun ◽  
Volume Data ◽  
High Quality ◽  
Vertical Polarization ◽  
Monitoring Method ◽  
Daily Monitoring ◽  
Weather Radars ◽  
Radar Antenna ◽  
Differential Reflectivity ◽  
Receiver Bias

Abstract A method for the daily monitoring of the differential reflectivity bias for polarimetric weather radars is presented. Sun signals detected in polar volume data produced during operational scanning of the radar are used. This method is an extension of that for monitoring the weather radar antenna pointing at low elevations and the radar receiving chain using the sun. This “online” method is ideally suited for routine application in networks of operational radars. The online sun monitoring can be used to check the agreement between horizontal and vertical polarization lobes of the radar antenna, which is a prerequisite for high-quality polarimetric measurements. By performing both online sun monitoring and rain calibration at vertical incidence, the differential receiver bias and differential transmitter bias can be disentangled. Results from the polarimetric radars in Trappes (France) and Bornholm (Denmark), demonstrating the importance of regular monitoring of the differential reflectivity bias, are discussed. It is recommended that the online sun-monitoring method, preferably in combination with rain calibration, is routinely performed on all polarimetric weather radars because accurate calibration is a prerequisite for most polarimetric algorithms.

The Investigation of Fluorine Induced Novel Probe Marker Discoloration

2018 ◽  
Author(s):  
W.F. Hsieh ◽  
Henry Lin ◽  
Vincent Chen ◽  
Irene Ou ◽  
Y.S. Lou
Keyword(s):  
Electric Field ◽  
Dark Field ◽  
Inspection System ◽  
Automated Inspection ◽  
Stress Tests ◽  
Auger Analysis ◽  
Corrosion Film ◽  
Scan Data ◽  
Thickness Variations ◽  
One Year

Abstract This paper describes the investigation of donut-shaped probe marker discolorations found on Al bondpads. Based on SEM/EDS, TEM/EELS, and Auger analysis, the corrosion product is a combination of aluminum, fluorine, and oxygen, implying that the discolorations are due to the presence of fluorine. Highly accelerated stress tests simulating one year of storage in air resulted in no new or worsening discolorations in the affected chips. In order to identify the exact cause of the fluorine-induced corrosion, the authors developed an automated inspection system that scans an entire wafer, recording and quantifying image contrast and brightness variations associated with discolorations. Dark field TEM images reveal thickness variations of up to 5 nm in the corrosion film, and EELS line scan data show the corresponding compositional distributions. The findings indicate that fluorine-containing gases used in upstream processes leave residues behind that are driven in to the Al bondpads by probe-tip forces and activated by the electric field generated during CP testing. The knowledge acquired has proven helpful in managing the problem.

A Method for Efficient Implementation of a Radial-Based Noise Power Estimator for Weather Radars

2021 ◽  
Author(s):  
Martin Hurtado
Keyword(s):  
Closed Form ◽  
Background Noise ◽  
Computational Cost ◽  
Weather Radar ◽  
Efficient Implementation ◽  
Noise Power ◽  
Free Range ◽  
Weather Radars ◽  
Low Computational Cost

AbstractIn a previous work, a weather radar algorithm with low computational cost has been developed to estimate the background noise power from the data collected at each radial. The algorithm consists of a sequence of steps designed to identify signal-free range volumes which are subsequently used to estimate the noise power. In this paper, we derive compact-closed form expressions to replace the numerical formulations used in the first two steps of the algorithm proposed in the original paper. The goal is to facilitate efficient implementation of the algorithm.

scholarly journals Validation of a Multilag Estimator on NJU-CPOL and a Hybrid Approach for Improving Polarimetric Radar Data Quality

2020 ◽  
Vol 12 (1) ◽  
pp. 180
Author(s):  
Shiqing Shao ◽  
Kun Zhao ◽  
Haonan Chen ◽  
Jianjun Chen ◽  
Hao Huang
Keyword(s):  
Theoretical Analysis ◽  
Correlation Coefficient ◽  
Hybrid Method ◽  
Radar Data ◽  
Noise Power ◽  
Signal Power ◽  
Polarimetric Radar ◽  
Moment Estimation ◽  
Spectrum Width ◽  
Differential Reflectivity

For the estimation of weak echo with low signal-to-noise ratio (SNR), a multilag estimator is developed, which has better performance than the conventional method. The performance of the multilag estimator is examined by theoretical analysis, simulated radar data and some specific observed data collected by a C-band polarimetric radar in previous research. In this paper, the multilag estimator is implemented and verified for Nanjing University C-band polarimetric Doppler weather radar (NJU-CPOL) during the Observation, Prediction and Analysis of Severe Convection of China (OPACC) field campaign in 2014. The implementation results are also compared with theoretical analysis, including the estimation of signal power, spectrum width, differential reflectivity, and copolar correlation coefficient. The results show that the improvement of the multilag estimator is little for signal power and differential reflectivity, but significant for spectrum width and copolar correlation coefficient when spectrum width is less than 2 ms−1, which implies a large correlation time scale. However, there are obvious biases from the multilag estimator in the regions with large spectrum width. Based on the performance analysis, a hybrid method is thus introduced and examined through NJU-CPOL observations. All lags including lag 0 of autocorrelation function (ACF) are used for moment estimation in this algorithm according to the maximum usable lag number. A case study shows that this hybrid method can improve moment estimation compared to both conventional estimator and multilag estimator, especially for weak weather echoes. The improvement will be significant if SNR decreases or the biases of noise power in the conventional estimator increase. In addition, this hybrid method is easy to implement on both operational and non-operational radars. It is also expected that the proposed hybrid method will have a better performance if applied to S-band polarimetric radars which have twice the maximum useable lags in the same conditions with C-band radars.

Continental scale acoustic monitoring program: One year of data

2015 ◽  
Vol 137 (4) ◽  
pp. 2220-2220 ◽  
Author(s):  
Samuel L. Denes ◽  
Susan E. Parks ◽  
Leanna Matthews ◽  
Hannah Blair ◽  
Pramod Varshney ◽  
...  
Keyword(s):  
Monitoring Program ◽  
Acoustic Monitoring ◽  
Continental Scale ◽  
One Year

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 Characteristics of the Bright Band Based on Quasi-Vertical Profiles of Polarimetric Observations from an S-Band Weather Radar Network

2020 ◽  
Vol 12 (24) ◽  
pp. 4061
Author(s):  
Jeong-Eun Lee ◽  
Sung-Hwa Jung ◽  
Soohyun Kwon
Keyword(s):  
Signal To Noise Ratio ◽  
Vertical Profiles ◽  
Bright Band ◽  
Weather Radars ◽  
Radar Network ◽  
Temperature Zero ◽  
The Mean ◽  
Microphysical Processes ◽  
Differential Reflectivity ◽  
Self Consistency

Bright band (BB) characteristics obtained via dual-polarization weather radars elucidate thermodynamic and microphysical processes within precipitation systems. This study identified BB using morphological features from quasi-vertical profiles (QVPs) of polarimetric observations, and their geometric, thermodynamic, and polarimetric characteristics were statistically examined using nine operational S-band weather radars in South Korea. For comparable analysis among weather radars in the network, the calibration biases in reflectivity (ZH) and differential reflectivity (ZDR) were corrected based on self-consistency. The cross-correlation coefficient (ρHV) bias in the weak echo regions was corrected using the signal-to-noise ratio (SNR). First, we analyzed the heights of BBPEAK derived from the ZH as a function of season and compared the heights of BBPEAK derived from the ZH, ZDR, and ρHV. The heights of BBPEAK were highest in the summer season when the surface temperature was high. However, they showed distinct differences depending on the location (e.g., latitude) within the radar network, even in the same season. The height where the size of melting particles was at a maximum (BBPEAK from the ZH) was above that where the oblateness of these particles maximized (BBPEAK from ZDR). The height at which the inhomogeneity of hydometeors was at maximum (BBPEAK from the ρHV) was also below that of BBPEAK from the ZH. Second, BB thickness and relative position of BBPEAK were investigated to characterize the geometric structure of the BBs. The BB thickness increased as the ZH at BBBOTTOM increased, which indicated that large snowflakes melt more slowly than small snowflakes. The geometrical structure of the BBs was asymmetric, since the melting particles spent more time forming the thin shell of meltwater around them, and they rapidly collapsed to form a raindrop at the final stage of melting. Third, the heights of BBTOP, BBPEAK, and BBBOTTOM were compared with the zero-isotherm heights. The dry-temperature zero-isotherm heights were between BBTOP and BBBOTTOM, while the wet-bulb temperature zero-isotherm heights were close to the height of BBPEAK. Finally, we examined the polarimetric observations to understand the involved microphysical processes. The correlation among ZH at BBTOP, BBPEAK, and BBBOTTOM was high (>0.94), and the ZDR at BBBOTTOM was high when the BB’s intensity was strong. This proved that the size and concentration of snowflakes above the BB influence the size and concentration of raindrops below the BB. There was no depression in the ρHV for a weak BB. Finally, the mean profile of the ZH and ZDR depended on the ZH at BBBOTTOM. In conclusion, the growth process of snowflakes above the BB controls polarimetric observations of BB.

Gonadal Function in Survivors After Hodgkin Lymphoma (HL) Treatment within the German Hodgkin Study Group (GHSG) HD13–15 Trials.

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 2636-2636
Author(s):  
Karolin Behringer ◽  
Horst Mueller ◽  
Helen Goergen ◽  
Indra Thielen ◽  
Angelika Eibl ◽  
...  
Keyword(s):  
Menstrual Cycle ◽  
Conflicts Of Interest ◽  
Early Stage ◽  
Observation Time ◽  
Advanced Stage ◽  
Gonadal Function ◽  
Treatment Regimens ◽  
Male Survivors ◽  
One Year ◽  
The Impact

Abstract Abstract 2636 Purpose: To improve fertility advice in HL patients before treatment and counseling during survivorship, detailed information on the impact of chemotherapy is needed. Therefore, we analyzed gonadal function in survivors after treatment of early favorable, early unfavorable and advanced stage HL. Methods: Women <40 years and men <50 years at diagnosis in ongoing remission at least one year after treatment within the GHSG HD13–15 trials were included. Hormone parameters, menstrual cycle, symptoms of hypogonadism, measures to preserve fertility, pregnancies, and offspring were evaluated. Results: A total of 1,323 (55%) of 2,412 contacted female and male survivors were evaluable for the current analysis. In women and men, mean age at fertility assessment was 32 and 38 years and mean observation time from the end of treatment was 46 and 48 months, respectively. Comparison of the participating and non-participating patients qualifying for our analysis showed no relevant differences. Hormone levels correlated significantly with therapy intensity (p<.001). After 6–8 cycles BEACOPP (bleomycin, etoposide, adriamycin, cyclophosphamide, vincristine, procarbazine, prednisone), mean Anti-Muellerian hormone (AMH) levels in females were 0μg/l and 88.8% of males had Follicle-stimulating hormone (FSH) and inhibin B levels corresponding to oligospermia. Furthermore, low birth rates were observed in survivors after advanced-stage treatment within the observation time (women: 6.5%, men: 3.3%). Regular menstrual cycle was reported by >90% of early-stage HL female survivors and time to resumption of menstrual activity was mostly reached within one year. After advanced-stage treatment, menstrual activity was strongly related to age. 82% of women younger than 30 years had a regular cycle, compared to only 45% in the older age group (p<.001) and time to recovery was considerably longer than in early-stage patients. 34% of women >30 years suffered severe menopausal symptoms (3–4 fold more frequently than expected). In contrast, male survivors had mean levels of testosterone within the normal range and reported no increased symptoms of hypogonadism. Conclusions: The present analysis in a large group of female and male HL survivors provides well-grounded information on gonadal toxicity of the currently used treatment regimens. Accordingly, the results allow a risk adapted planning of fertility preservation before therapy and a comprehensive support during survivorship. Disclosures: No relevant conflicts of interest to declare.

Sign in / Sign up

Export Citation Format

Share Document