scholarly journals Attenuation Calibration of an X-Band Weather Radar Using a Microwave Link

2006 ◽  
Vol 23 (3) ◽  
pp. 395-405 ◽  
Author(s):  
A. R. Rahimi ◽  
A. R. Holt ◽  
G. J. G. Upton ◽  
S. Krämer ◽  
A. Redder ◽  
...  
Keyword(s):  
Heavy Rainfall ◽  
Weather Radar ◽  
Ground Truth ◽  
Heavy Rain ◽  
Radar Signal ◽  
Convective Conditions ◽  
Correction Algorithm ◽  
Rain Gauges ◽  
X Band ◽  
Microwave Link

Abstract The attenuation of a radar signal is a serious problem facing meteorologists and hydrologists. In heavy rain, reflectivity information can be completely lost from large portions of a radar scan. The problem is particularly acute for X-band radars. Current methods of correcting for attenuation face many difficulties, mainly because the actual amount of attenuation at any given time is unknown. In this paper a backward-iterative attenuation-correction algorithm is presented that uses the attenuation measured by a microwave link with its receiver collocated with an X-band weather radar in Essen, Germany. Data are also available from a network of rain gauges located in the vicinity of the link path. This network provides a measure of “ground truth” rainfall against which radar estimates can be compared. The results show that the algorithm can recover much of the reflectivity information that is lost due to attenuation of the radar beam. The method is seen to be particularly effective in convective conditions where heavy rainfall can cause severe attenuation.

scholarly journals RadarNet-Sur First Weather Radar Network in Tropical High Mountains

2017 ◽  
Vol 98 (6) ◽  
pp. 1235-1254 ◽  
Author(s):  
Jörg Bendix ◽  
Andreas Fries ◽  
Jorge Zárate ◽  
Katja Trachte ◽  
Rütger Rollenbeck ◽  
...  
Keyword(s):  
El Niño ◽  
Weather Forecasting ◽  
El Nino ◽  
Weather Radar ◽  
Cost Effective ◽  
Radar Signal ◽  
High Mountains ◽  
Radar Network ◽  
X Band ◽  
Southern Ecuador

Abstract Weather radar networks are indispensable tools for forecasting and disaster prevention in industrialized countries. However, they are far less common in the countries of South America, which frequently suffer from an underdeveloped network of meteorological stations. To address this problem in southern Ecuador, this article presents a novel radar network using cost-effective, single-polarization, X-band technology: the RadarNet-Sur. The RadarNet-Sur network is based on three scanning X-band weather radar units that cover approximately 87,000 km2 of southern Ecuador. Several instruments, including five optical disdrometers and two vertically aligned K-band Doppler radar profilers, are used to properly (inter) calibrate the radars. Radar signal processing is a major issue in the high mountains of Ecuador because cost-effective radar technologies typically lack Doppler capabilities. Thus, special procedures were developed for clutter detection and beam blockage correction by integrating ground-based and satelliteborne measurements. To demonstrate practical applications, a map of areas frequently affected by intense rainfall is presented, based on a time series of one radar that has been in operation since 2002. Such information is of vital importance to, for example, infrastructure management because rain-driven landslides are a major issue for road maintenance and safety throughout Ecuador. The presented case study of exceptionally strong rain events during the recent El Niño in March 2015 highlights the system’s practicality in weather forecasting related to disaster management. For the first time, RadarNet-Sur warrants a spatial-explicit observation of El Niño-related heavy precipitation in a transect from the coast to the highlands in a spatial resolution of 500 m.

scholarly journals Joint statistical correction of clutters, spokes and beam height for a radar derived precipitation climatology in southern Germany

2012 ◽  
Vol 16 (11) ◽  
pp. 4101-4117 ◽  
Author(s):  
A. Wagner ◽  
J. Seltmann ◽  
H. Kunstmann
Keyword(s):  
Statistical Analysis ◽  
Cell Tracking ◽  
Weather Radar ◽  
Radar Data ◽  
Small Scale ◽  
Correction Algorithm ◽  
Rain Gauges ◽  
Radar Images ◽  
Statistical Correction ◽  
High Level

Abstract. First results of radar derived climatology have emerged over the last years, as datasets of appropriate extent are becoming available. Usually, these statistics are based on time series lasting up to ten years as continuous storage of radar data was often not achieved before. This kind of climatology demands a high level of data quality. Small deviations or minor systematic under- or overestimations in single radar images become a major cause of error in statistical analysis. Extensive corrections of radar data are a crucial prerequisite for radar derived climatology. We present a new statistical post-correction scheme based on a climatological analysis of seven years of radar data of the Munich weather radar (2000–2006) operated by DWD (German Weather Service). Original radar products are used subject only to corrections within the signal processor without any further corrections on single radar images. The aim of this statistical correction is to make up for the average systematic errors caused by clutter, propagation, or measuring effects but to conserve small-scale natural variations in space. The statistical correction is based on a thorough analysis of the different causes of possible errors for the Munich weather radar. This analysis revealed the following basic effects: the decrease of rain amount as a function of height and distance from the radar, clutter effects such as clutter remnants after filtering, holes by eliminated clutter or shading effects from obstacles near the radar, visible as spokes, as well as the influence of the bright band. The correction algorithm is correspondingly based on these results. It consists of three modules. The first one is an altitude correction which minimises measuring effects. The second module corrects clutter effects and disturbances and the third one realises a mean adjustment to selected rain gauges. Two different sets of radar products are used. The statistical analysis as well as module 1 and module 2 of the correction algorithm are based on frequencies of the six reflectivity levels within the so-called PX product. For correction module 3 and for the validation of the correction algorithm, rain amounts are calculated from the 8-bit so-called DX product. The correction algorithm is created to post-correct climatological or statistical analysis of radar data with a temporal resolution larger than one year. The correction algorithm is used for frequencies of occurrence of radar reflectivities which enables its application even for radar products such as DWD's cell-tracking-product CONRAD. Application (2004–2006) and validation (2007–2009) periods of this correction algorithm with rain gauges show an increased conformity for radar climatology after the statistical correction. In the years 2004 to 2006 the Root-Mean-Square-Error (RMSE) between mean annual rain amounts of rain gauges and corresponding radar pixels decreases from 262 mm to 118 mm excluding those pairs of values where the rain gauges are situated in areas of obviously corrupted radar data. The results for the validation period 2007 to 2009 are based on all pairs of values and show a decline of the RMSE from 322 mm to 174 mm.

scholarly journals Hail storm hazard in urban areas: identification and probability of occurrence by using a single-polarization X-band weather radar

2016 ◽  
Author(s):  
Vincenzo Capozzi ◽  
Errico Picciotti ◽  
Vincenzo Mazzarella ◽  
Giorgio Budillon ◽  
Frank Silvio Marzano
Keyword(s):  
Urban Areas ◽  
Low Cost ◽  
Weather Radar ◽  
Ground Truth ◽  
Liquid Density ◽  
Data Set ◽  
Area Of Interest ◽  
X Band ◽  
Radar Measurements ◽  
Single Polarization

Abstract. This work exploits the potentiality of hail warning, based on single-polarization X-band weather radar measurements and tested on a large and well-documented data set of thunderstorm events in southern Italy near Naples. Even though X-band radars may suffer of two-way path attenuation especially at long ranges, due to their relatively low cost their use is rapidly increasing for short-range applications such as urban environments. To identify hail through radar measurements, two different methodologies have been selected and adapted to X-band data within the study area: one uses the Waldvogel (WAL) approach, whereas the other one uses the Vertically-Integrated Liquid Density (VIL-Density) product. The study aims at developing a Probability-of-Hail (POH) index in order to support hail risk management at urban scales. In order to find the optimal threshold values to discriminate between hail and severe rain, an extensive intercomparison between outcomes of the two methodologies and ground truth observations of hail has been performed, using a 2 x 2 contingency table and statistical scores. The results show that both methods are accurate for hail detection in the area of interest, although VIL-Density product is less satisfactory than WAL method in terms of false alarm ratio. The relationship between the output of these two methodologies and POH has been derived through a heuristic approach, using a third-order polynomial fitting curve. As an example, the POH indexes have been applied for the thunderstorm event occurred on 21 July 2014, proving to be reliable for hail core detection.

scholarly journals Polarimetric Attenuation Correction in Heavy Rain at C Band

2011 ◽  
Vol 50 (1) ◽  
pp. 39-58 ◽  
Author(s):  
Ji-Young Gu ◽  
A. Ryzhkov ◽  
P. Zhang ◽  
P. Neilley ◽  
M. Knight ◽  
...  
Keyword(s):  
Attenuation Correction ◽  
Metropolitan Area ◽  
Hot Spots ◽  
Heavy Rain ◽  
Radar Signal ◽  
Polarimetric Radar ◽  
Correction Algorithm ◽  
Correction Scheme ◽  
Radar Measurements ◽  
Convective Cells

Abstract The ability of C-band polarimetric radar to account for strong attenuation/differential attenuation is demonstrated in two cases of heavy rain that occurred in the Chicago, Illinois, metropolitan area on 5 August 2008 and in central Oklahoma on 10 March 2009. The performance of the polarimetric attenuation correction scheme that separates relative contributions of “hot spots” (i.e., strong convective cells) and the rest of the storm to the path-integrated total and differential attenuation has been explored. It is shown that reliable attenuation correction is possible if the radar signal is attenuated by as much as 40 dB. Examination of the experimentally derived statistics of the ratios of specific attenuation Ah and differential attenuation ADP to specific differential phase KDP in hot spots is included in this study. It is shown that these ratios at C band are highly variable within the hot spots. Validation of the attenuation correction algorithm at C band has been performed through cross-checking with S-band radar measurements that were much less affected by attenuation. In the case of the Oklahoma storm, a comparison was made between the data collected by closely located C-band and S-band polarimetric radars.

scholarly journals Estimation of Dual Polarization Weather Radar Variables

2018 ◽  
Vol 28 (2) ◽  
pp. 1
Author(s):  
Dalia A. Mahmood
Keyword(s):  
Weather Radar ◽  
Heavy Rain ◽  
Radar Reflectivity ◽  
Dual Polarization ◽  
Differential Phase Shift ◽  
Light Rain ◽  
X Band ◽  
The Difference ◽  
Range Of Values ◽  
Reflectivity Factor

Dual polarization weather radar has now become a widely used as instrument in meteorological offices around the world because of its capability in distinguishing different precipitation type and in improving the accuracy of quantitative precipitation estimation. The aim of this work is to estimate the polarimetry radar variables for radars of different frequency bands and study their behavior with rainfall rates. Calculations of polarimetry radar variables were made on the basis of several assumptions. The results showed that factors at horizontal and vertical polarization, ZH,V, ranges between 20 dBz respectively, and more than 55 dBz for light rain and extreme heavy rain respectively, and radar reflectivity factor at horizontal ZH is greater than radar reflectivity factor at vertical ZV for all rainfall rates. The differential reflectivity, ZDR, also increases with increasing rainfall rates since it is the difference between ZH and Zv. Calculations of specific differential attenuation indicated that X band radars are seriously atten-uated by rain and C band radars are less affected by rain. The specific differential attenuation, S band radars is very small. In addition to this feature, the results showed that the differential phase shift between return signals of horizontal and vertical polarizations for S band radars is much less than those for C and X band radars, and also, the results showed that the co-polarization correlation coefficient for S band the radars is much higher than those of C and X bands. In order to investigate the accuracy of the calculated polarimetric weather radar variables per-formed in this research, real radar measurements were used for this purpose. Results indicated that the range of values for calculated polarimetric radar variables are very consistent with range of values for measured variables

scholarly journals Evaluation of a new X-band weather radar for operational use in south Sweden

2020 ◽  
Vol 81 (8) ◽  
pp. 1623-1635 ◽  
Author(s):  
Seyyed Hasan Hosseini ◽  
Hossein Hashemi ◽  
Ronny Berndtsson ◽  
Nicholas South ◽  
Henrik Aspegren ◽  
...  
Keyword(s):  
Moving Objects ◽  
Weather Radar ◽  
Single Event ◽  
Spatiotemporal Resolution ◽  
Rain Gauges ◽  
X Band ◽  
South Sweden ◽  
New Type ◽  
Hydrological Applications ◽  
Rainfall Estimates

Abstract The performance of a new type of X-band weather radar (WR) for Sweden during a pilot run is studied. Compared to the conventional C-band WRs, the X-band WR covers a smaller area but with a higher spatiotemporal resolution, making it suitable for urban hydrological applications. Rainfall estimations from different elevation angles of the radar (levels) are compared at one-minute and single-event timescales with the observations of several rain gauges at different ranges using hyetographs. In general, the estimations aligned well with observations and the best match appeared for ranges as long as 5–10 km. Seemingly, radar estimations suffered from overshooting of lower lying showers by higher level scans in longer ranges (19–30 km) and from the reflectivity contamination due to moving objects in short ranges (<1 km). Also, the effective range of the radar dropped sharply for the moments when a cloudburst was located over the radar. Although various sources of error could affect the X-band WR rainfall estimates, higher resolution spatiotemporal rainfall monitoring for wider areas will benefit from an integration of data from a network of X-band WRs.

X-Band local area weather radar – preliminary calibration results

2002 ◽  
Vol 45 (2) ◽  
pp. 135-138 ◽  
Author(s):  
N.E. Jensen
Keyword(s):  
High Resolution ◽  
Weather Radar ◽  
Cost Effective ◽  
Local Area ◽  
Rain Gauges ◽  
X Band ◽  
Danish Meteorological Institute ◽  
Typical Range ◽  
Meteorological Institute ◽  
Good Calibration

DHI has developed a cost-effective X-Band Local Area Weather Radar (LAWR) with a typical range (radius) of 60 km, 500 × 500 m areal resolution and 253 reflection levels. The development is performed in a co-operation with a number of European partners, including Danish Meteorological Institute. The specifications of the weather radar and preliminary results from the calibration are presented. Good calibration results have been obtained using high-resolution rain gauges.

scholarly journals Joint statistical correction of clutters, spokes and beam height for a radar climatology in Southern Germany

2012 ◽  
Vol 9 (4) ◽  
pp. 4703-4746
Author(s):  
A. Wagner ◽  
J. Seltmann ◽  
H. Kunstmann
Keyword(s):  
Statistical Analysis ◽  
Weather Radar ◽  
Radar Data ◽  
Small Scale ◽  
Correction Algorithm ◽  
Rain Gauges ◽  
Radar Images ◽  
Statistical Correction ◽  
First Results ◽  
High Level

Abstract. Extensive corrections of radar data are a crucial prerequisite for radar derived climatology. This kind of climatology demands a high level of data quality. Little deviations or minor systematic underestimations or overestimations in single radar images become a major cause of error in statistical analysis. First results of radar derived climatology have emerged over the last years, as data sets of appropriate extent are becoming available. Usually, these statistics are based on time series lasting up to ten years as storage of radar data was not achieved before. We present a new statistical post-correction scheme, which is based on seven years of radar data of the Munich weather radar (2000–2006) that is operated by DWD (German Weather Service). The typical correction algorithms for single radar images, such as clutter corrections, are used. Then an additional statistical post-correction based on the results of a climatological analysis from radar images follows. The aim of this statistical correction is to correct systematic errors caused by clutter effects or measuring effects but to conserve small-scale natural variations in space. The statistical correction is based on a thorough analysis of the different causes of possible errors for the Munich weather radar. This robust analysis revealed the following basic effects: the decrease of rain rate in relation to height and distance from the radar, clutter effects such as remaining clutter, eliminated clutter or shading effects from obstacles near the radar, visible as spokes, as well as the influence of the Bright Band. The correction algorithm is correspondingly based on these results. It consists of three modules. The first one is an altitude correction, which minimizes measuring effects. The second module corrects clutter effects and the third one realizes a mean adjustment to selected rain gauges. Two different radar products are used. The statistical analysis as well as module one and module two of the correction algorithm are based on frequencies of occurrence of the so-called PX-product with six reflectivity levels. For correction module 3 and for the validation of the correction algorithm rain rates are calculated from the 8-bit-depth so-called DX-product. An application (2004–2006) and a validation (2007–2009) of this correction algorithm with rain gauges show a much higher conformity for radar climatology after the statistical correction. In the years 2004 to 2006 the Root-Mean-Square-Error (RMSE) decreases from 262 mm to 118 mm excluding those pair of values where the rain gauges are situated in areas of obviously corrupted radar data. The results for the validation period 2007 to 2009 are based on all pairs of values and show a decline of the RMSE from 322 mm to 174 mm.

scholarly journals Attenuation Correction of Weather Radar Reflectivity with Arbitrary Oriented Microwave Link

2017 ◽  
Vol 2017 ◽  
pp. 1-17 ◽  
Author(s):  
Peng Zhang ◽  
Xichuan Liu ◽  
Zhaoming Li ◽  
Zeming Zhou ◽  
Kun Song ◽  
...  
Keyword(s):  
Attenuation Correction ◽  
Real Data ◽  
Radar Reflectivity ◽  
Attenuation Effect ◽  
Rain Gauges ◽  
X Band ◽  
Variation Range ◽  
Microwave Link ◽  
Rain Rates ◽  
Key Parameter

To compensate radar reflectivity for attenuation effect, a new method for attenuation correction of the radar reflectivity using arbitrary oriented microwave link (referred henceforth to as ACML) is developed and evaluated. Referring to the measurement of arbitrary oriented microwave link, the ACML method optimizes the ratio of specific attenuation to specific differential phase which is a key parameter in attenuation correction schemes. The proposed method was evaluated using real data of a dual-polarization X-band radar and measurements of two microwave links during two rainstorm events. The results showed that the variation range of the optimized ratio was overall consistent with the results of the previous studies. After attenuation correction with the optimal ratios, the radar reflectivity was significantly compensated, especially at long distances. The corrected reflectivity was more intense than the reflectivity corrected by the “self-consistent” (SC) method and closer to the reflectivity of a nearby S-band radar. The effectiveness of the method was also verified by comparing the rain rates estimated by the X-band radar with those derived by rain gauges. It is demonstrated that arbitrary oriented microwave link can be adopted to optimize the attenuation correction of radar reflectivity.

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