Weather Radar and Hydrology Edited by

7

Urban hydrology and water management applications
Advances in the application of radar data to urban hydrology Hans-Reinhard Verworn			595
What is a proper resolution of weather radar precipitation estimates for urban drainage modelling? Jesper E. Nielsen, Michael R. Rasmussen & Søren Thorndahl			601
The flooding potential of convective rain cells Efrat Morin & Hagit Yakir			607
Analysis of different quantitative precipitation forecast methods for runoff and flow prediction in a small urban area Alma Schellart, Sara Liguori, Stefan Krämer, Adrian Saul & Miguel Rico-Ramirez			614
On comparing NWP and radar nowcast models for forecasting of urban runoff S. Thorndahl, T. Bøvith, M. R. Rasmussen & R. S. Gill			620
Decision support for urban drainage using radar data of HydroNET-SCOUT Arnold Lobbrecht, Thomas Einfalt, Leanne Reichard & Irene Poortinga			626
Radar-based pluvial flood forecasting over urban areas: Redbridge case study Li-Pen Wang, Nuno Simões, Miguel Rico-Ramirez, Susana Ochoa, Joao Leitão & Čedo Maksimović			632
A new FEH rainfall depth-duration-frequency model for hydrological applications Elizabeth J. Stewart, David G. Morris, David A. Jones & Cecilia Svensson			638
Use of weather radar by the water industry in Scotland Steven J. Cole, Dominic McBennett, Kevin B. Black & Robert J. Moore			644
Impact of Z-R relationship on flow estimates in central São Paulo Roberto V. Calheiros & Ana M. Gomes			650
Derivation of seasonally-specific Z-R relationships for NEXRAD radar for a sparse raingauge network Samuel H. Rendon, Baxter E. Vieux & Chandra S. Pathak			655
Weather radar to predict bathing water quality Murray Dale & Ruth Stidson			661
Key word index			667

Weather Radar and Hydrology

(Proceedings of a symposium held in Exeter, UK, April 2011) (IAHS Publ. 351, 2012), 3-8.

Weather radar for hydrology – the UK experience and prospects for the future
Malcolm Kitchen

Met Office, Fitzroy Rd, Exeter EX1 3PB, UK

[e-mail]
Abstract The national weather radar network in the UK has now been operational for a quarter of a century. It was established by a consortium of agencies to provide a real-time rainfall monitoring capability. Today those same agencies, and their successors, are still involved in the maintenance and development of this national infrastructure on behalf of the wider stakeholders. An attempt is made here to identify some lessons that have been learnt along the way, and suggest how the benefit to hydrology can be increased in the next 25 years.

Key words weather radar; rainfall; refractivity


Weather Radar and Hydrology

(Proceedings of a symposium held in Exeter, UK, April 2011) (IAHS Publ. 351, 2012), 9-14

EUMETNET OPERA Radar Data Centre: providing operational, homogeneous European radar rainfall composites
Stuart Matthews¹, pascale dupuy², ROBERT SCOVELL¹,
ANTOINE KERGOMARD², BERNARD URBAN², ASKO HUUSKONEN³,
ALISON SMITH¹ & Nicolas Gaussiat¹

1 Met Office, FitzRoy Road, Exeter EX1 3PB, UK

[e-mail]

2 Météo France, 42, avenue Corriolis, 31057 Toulouse, France

3 Finnish Meteorological Institute, PO Box 503, 00101-Helsinki, Finland
Abstract The main objective of the third EIG EUMENET OPERA Programme is the development and operational running of a European Radar Data Centre (Odyssey). Odyssey, which went live in January 2011, has the ability to ingest raw polar volume radar products from almost 200 operational weather radars operated by European National Meteorological Services. Composites of rain-rate, maximum reflectivity and hourly accumulations are produced every 15 min at 2 km resolution. Odyssey’s algorithms have been designed to process data in a consistent way, allowing Odyssey to generate homogenous radar products for the whole European domain. Shared operational capability across two centres, Météo France and the Met Office, provides high levels of operational resilience. It is anticipated that these new Odyssey products should improve flood forecasting capability (especially for large river basins, e.g. the Danube, Elbe and Rhine) in their own right or by helping produce more accurate short range NWP forecast products.

Key words operational; composite; multinational catchments; homogenous; quality index


Weather Radar and Hydrology

(Proceedings of a symposium held in Exeter, UK, April 2011) (IAHS Publ. 351, 2012). 15-19

Tri-agency radar networks in Korea: where are we heading?
GYUWON LEE¹, SUNG-HWA JUNG¹, JUNG-HOON LEE¹, YO-HAN CHO¹, KWANG-DEUK AHN¹, BOK-HAENG HEO² & CHOONG-KE LEE³

1 Dept. of Astronomy and Atmospheric Sciences, Kyungpook Natl’ University, Deagu, Korea

[e-mail]

2 Weather Radar Center, Korea Meteorological Administration, Seoul, Korea

3 Han Flood Control Office, Ministry of Land, Transport and Maritime Affairs, Seoul, Korea
Abstract Korea has three radar networks operated by three agencies: Korea Meteorological Administration (KMA), Korean Air Force and Flood Control Office. A recent tri-agency agreement opens a new era for common use of data, similar maintenance procedures and operations, and possibly unification of radar types. KMA built the Weather Radar Center (WRC) to facilitate this agreement and expects WRC to be a focal point for the Korean radar networks. We will discuss the current status and future plans for the radar networks. Some advantages of using tri-agency networks are demonstrated through a simulation study. Issues in the current networks and ongoing research to resolve them are discussed in terms of data quality control, radar calibration, etc. The fuzzy logic based algorithm of quality control is developed. The radar reflectivity calibration is performed by intercomparison and with a disdrometer. A new scanning strategy is proposed to optimize the ground rain estimation and wind retrieval in space.

Key words radar networks; Korea; Weather Radar Center; quality control; calibration

Weather Radar and Hydrology

(Proceedings of a symposium held in Exeter, UK, April 2011) (IAHS Publ. 351, 2012), 20-25

Compositing international radar data using a weight-based scheme
THOMAS EINFALT¹ & ARNOLD LOBBRECHT²

1 hydro&meteo GmbH & Co. KG, Breite Str. 6-8, D-23552 Luebeck, Germany

[e-mail]

2 HydroLogic BV, Stadsring 57, 3811 HN Amersfoort, The Netherlands
Abstract In the northeastern part of the Netherlands, the Dutch radars of De Bilt and Den Helder have only limited coverage, while the German Emden radar is just opposite the border. Therefore, hydro&meteo and HydroLogic developed a new radar composite for this part of the Netherlands, starting from the basic polar radar products of both national weather services. The composite should be available in near-real time. The paper presents a case study of an interesting rainfall event, using various filtering and correction algorithms. The result shows very good results when compared with independent raingauges. The independent verification demonstrates that the new composite is similar to the one of the Dutch weather service on average for the Netherlands, and in addition it is much better in the northeastern part of the country, due to the Emden radar data. The algorithms are now ready for use in operational water management.

Key words precipitation; radar; rainfall; composite; raingauge; flood


Weather Radar and Hydrology

(Proceedings of a symposium held in Exeter, UK, April 2011) (IAHS Publ. 351, 2012), 26-32

Estimating weather radar coverage over complex terrain
edwin campos

Argonne National Laboratory, Environmental Science Division, Argonne, Illinois, USA

[e-mail]
Abstract Minimizing terrain blockage is a basic consideration when assessing the efficacy of weather radar sites. A numerical model for simulating surveillance coverage of weather radars in mountain terrains is presented. As input, the simulation uses a high-resolution terrain digital model; weather radar parameters; and radiosonde observations of the vertical profile of temperature, pressure, and vapour mixing ratio. The coverage model is validated using observations from Environment Canada’s C-band weather radar located at Mt Sicker (British Columbia, Canada).

Key words beam propagation; terrain blockage; surveillance area

Weather Radar and Hydrology

(Proceedings of a symposium held in Exeter, UK, April 2011) (IAHS Publ. 351, 2012), 33-38

Evaluation and improvement of C-band radar attenuation correction for operational flash flood forecasting
Stephan Jacobi¹, Maik Heistermann¹ & Thomas Pfaff²

1 Institute for Earth and Environmental Science, University of Potsdam, Karl-Liebknecht-Strasse 24–25, 14476 Potsdam, Germany

[e-mail]

2 Institute of Hydraulic Engineering, University of Stuttgart, Pfaffenwaldring 61, 70569 Stuttgart, Germany
Abstract Signal attenuation is, even for C-band radars, an important reason for underestimating precipitation rates during heavy convective rainfall events. Gate-by-gate simulation of specific attenuation based on the conventional power law relation with fixed parameters is prone to instability with increasing distance from the radar location. Hence Krämer (2008) developed an attenuation correction algorithm which optimizes attenuation parameters iteratively for each beam and time step, dependent on the stability of corrected reflectivity. In cases of very high path-integrated attenuation (PIA) this stability criterion is not sufficient for the rainfall events examined; thus a second criterion based on PIA is introduced and the specific attenuation in cases of low reflectivity is limited. With the objective of verifying operational robustness, the correction approaches are compared with uncorrected radar data for several rainfall events, including the severe flash flood event on the River Starzel, Germany.

Key words QPE; signal attenuation; attenuation correction; attenuation threshold; flash flood; Starzel, Germany
Weather Radar and Hydrology

(Proceedings of a symposium held in Exeter, UK, April 2011) (IAHS Publ. 351, 2012),39-44

Emission: a simple new technique to correct rainfall estimates from attenuation due to both the radome and heavy rainfall
Robert Thompson¹, Anthony Illingworth¹ & James Ovens²

1 Dept of Meteorology, University of Reading, Reading RG6 6BB, UK

[e-mail]

2 Meteorological Office, Fitzroy Rd, Exeter EX1 3PB, UK
Abstract We present a new technique for correcting errors in radar estimates of rainfall due to attenuation which is based on the fact that any attenuating target will itself emit, and that this emission can be detected by the increased noise level in the radar receiver. The technique is being installed on the UK operational network, and for the first time, allows radome attenuation to be monitored using the increased noise at the higher beam elevations. This attenuation has a large azimuthal dependence but for an old radome can be up to 4 dB for rainfall rates of just 2–4 mm/h. This effect has been neglected in the past, but may be responsible for significant errors in rainfall estimates and in radar calibrations using gauges. The extra noise at low radar elevations provides an estimate of the total path integrated attenuation of nearby storms; this total attenuation can then be used as a constraint for gate-by-gate or polarimetric correction algorithms.

Key words attenuation; emission; radome; rainfall estimation; weather radar
Weather Radar and Hydrology

(Proceedings of a symposium held in Exeter, UK, April 2011) (IAHS Publ. 351, 2012), 45-51

Techniques for improving ground clutter identification
J. C. Nicol¹, A. J. Illingworth¹, T. DARLINGTON² & J. SUGIER²

1 University of Reading, Reading, UK

[e-mail]

2 Met Office, Exeter, UK
Abstract Several radar parameters quantifying signal variability in single-polarisation radar measurements (Power Ratio, PR; Clutter Phase Alignment, CPA; and Absolute Power Difference, APD) are evaluated using Bayes’ theorem in terms of the separation between the returns from ground clutter and precipitation. As these parameters are not independent, the intention is to identify the parameter providing the best separation. It is shown that either PR or CPA, in combination with a radial measure of texture of reflectivity (in dBZ), provides excellent separation of ground clutter and precipitation returns on a gate-by-gate basis. The demonstrated skill in clutter identification is comparable to that only previously reported using dual-polarisation measurements. This approach is well-suited for anomalous propagation as clutter maps are not used. The findings suggest that ground clutter identification is likely to benefit from measurements of PR or CPA, even when dual-polarisation parameters are available.

Key words weather radar; ground clutter; precipitation; Bayes classifier


Weather Radar and Hydrology

(Proceedings of a symposium held in Exeter, UK, April 2011) (IAHS Publ. 351, 2012), 52-57

A probability-based sea clutter suppression method for polarimetric weather radar systems
RONALD HANNESEN & ANDRÉ WEIPERT

Selex-SI GmbH, Gematronik Weather Radar Systems, Raiffeisenstr. 10, 41470 Neuss, Germany

[e-mail]
Abstract Beyond calibration, the mitigation and suppression of clutter signals is still a challenge in radar remote sensing. The weather radar market trend (for aviation and hydrological/meteorological applications) shows explicitly that the decision for polarimetric radar systems is continuously increasing, since the potential capabilities and benefits of dual-polarization radar systems are well known. This publication presents an automatic discrimination method between weather and sea clutter based on multi-parameter polar datasets (Doppler and polarimetric) as well as the generation of a sea clutter probability index. Additionally, a new polar-based clutter type map will be introduced and the suppression of sea clutter signals outlined.

Key words sea clutter; clutter suppression; dual polarization
Weather Radar and Hydrology

(Proceedings of a symposium held in Exeter, UK, April 2011) (IAHS Publ. 351, 2012), 58-63

Design of a clutter modelling algorithm based on SRTM DEM data and adaptive signal processing methods
E. Gonzalez-ramirez¹, M. A. Rico-ramirez², I. Cluckie³,
J. I. De la rosa VARGAS¹ & d. ALANIZ-LUMBRERAS¹

1 Autonomous University of Zacatecas, Zacatecas, Mexico

[e-mail]

2 University of Bristol, Bristol, UK

3 Swansea University, Swansea, UK
Abstract This paper presents an algorithm for clutter modelling based on the radar equation, radar characteristics and digital elevation data. Optimization methods from adaptive signal processing theory were used to calculate the weights of an adaptive linear combiner representing the radar system for clutter modelling. Modelled clutter showed an acceptable precision demanded by applications in meteorology and hydrology for radar rainfall estimation.

Key words weather radar; modelling; SRTM; adaptive linear combiner

Weather Radar and Hydrology

(Proceedings of a symposium held in Exeter, UK, April 2011) (IAHS Publ. 351, 2012), 64-68

Radar bright band correction using the linear depolarisation ratio
Anthony Illingworth & Robert Thompson

Dept. of Meteorology, University of Reading, Reading RG6 6BB, UK

[e-mail]
Abstract The enhanced radar return associated with melting snow, “the bright band”, can lead to large overestimates of rain-rates. Most correction schemes rely on fitting the radar observations to a vertical profile of reflectivity (VPR) which includes the bright band enhancement. Observations show that the VPR is very variable in space and time; large enhancements occur for melting snow, but none for the melting graupel in embedded convection. Applying a bright band VPR correction to a region of embedded convection will lead to a severe underestimate of rainfall. We revive an earlier suggestion that high values of the linear depolarisation ratio (LDR) are an excellent means of detecting when bright band contamination is occurring and that the value of LDR may be used to correct the value of reflectivity in the bright band.

Key words bright band; rainfall estimation; weather radar

Weather Radar and Hydrology

(Proceedings of a symposium held in Exeter, UK, April 2011) (IAHS Publ. 351, 2012), 69-74

Determining the vertical profile of reflectivity using radar observations at long range
KATE SNOW¹, ALAN SEED² & GEORGE TAKACS¹

1 University of Wollongong, Department of Engineering Physics, New South Wales 2522, Australia

[e-mail]

2 Centre for Australian Weather and Climate Research, Bureau of Meteorology, GPO Box 1289, Melbourne,
Victoria 3001, Australia
Abstract The Vertical Profile of Reflectivity (VPR) plays an important role when estimating the rain rate at the surface and has been the subject of radar meteorology research for many years. The VPR can either be sampled directly from observations that are close to the radar where the impact of the convolution with the beam pattern can be ignored, or the parameters for a theoretical form for the VPR are estimated using the available observations or climatology. In either case, a significant difficulty arises when a rain band approaches the radar and quantitative precipitation estimates are required before any detailed observations of the VPR at close range are possible. Long range in this context is the range where the height of the lowest elevation angle in the volume scan is greater than the wet bulb freezing level at that time, and therefore only limited information on the shape of the bright band is available. This paper uses a modified version of the VPR model proposed by Fabry (1997) and evaluates strategies to make optimum use of empirical observations, and how estimates for the model parameters could be updated in time. The technique is demonstrated using case studies of widespread rainfall over Sydney and Brisbane, Australia. Comparing the final technique to both the current short range and long range methods indicates that the parameterised VPR is able to provide similar VPR accuracies as the short range, with great improvement on the current long range method, making it suitable for rainfall corrections.

Key words vertical profile; parameterisation; long-range; beam convolution; Australia
Weather Radar and Hydrology

(Proceedings of a symposium held in Exeter, UK, April 2011) (IAHS Publ. 351, 2012),75-80

Development of optimal functional forms of Z-R relationships
RAMESH S. V. TEEGAVARAPU¹ & CHANDRA PATHAK²

1 Department of Civil, Environmental and Geomatics Engineering, Florida Atlantic University, Boca Raton,
Florida 33431, USA

[e-mail]

2 Operations and Hydro Data Management Division, South Florida Water Management District, 3301 Gun Club Road, West Palm Beach, Florida, USA
Abstract Use of appropriate functional reflectivity (Z)–rainfall rate (R) relationships is crucial for accurate estimation of precipitation amounts using radar. The spatial and temporal variability of several storm patterns combined with subjectivity in application of a specific functional Z-R relationship for a particular storm makes this task very difficult. This study evaluates the use of gradient and genetic algorithm-based optimization solvers for optimizing the traditional Z-R functional relationships with constants and coefficients for different storm types and seasons. The Z-R relationships will be evaluated for optimized coefficients and exponents based on training and test data. In order to evaluate the optimal relationships developed as a part of the study, reflectivity data and raingauge data were analysed for a region in south Florida, USA. Exhaustive evaluation of Z-R relationships and their utility in real-time improvement of precipitation estimates with optimization formulations were evaluated in this study.