Adjustment of rainfall estimates from weather radars using in-situ stormwater drainage sensors

Malte Ahm

Publikation: Bog/antologi/afhandling/rapportPh.d.-afhandlingForskning

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Resumé

Emnet for denne Ph.D.-afhandling er justering af vejrradar regnestimater til afløbsteknisk anvendelse ved brug af afstrømningsmålere i afløbssystemet. Ved brug af vejrradarer er det muligt at måle regnen med den stedslige og tidslige opløsning, som ønskes for avanceret afløbsteknisk modellering af distribuerede afløbssystemer. Det er nødvendigt at anvende data, som repræsenterer den stedslige og tidslige variabilitet af regnen, for at kunne modellere regnafstrømning korrekt i distribuerede afløbssystemer samt anvende realtidsstyring til at styre disse distribuerede systemer.

Vejrradarer måler regnen indirekte i atmosfæren, hvilket giver nogle udfordringer i forhold til at anvende vejrradardataene i afløbstekniske sammenhænge. Der kan oftest observeres afvigelser mellem det radarmålte regn i atmosfæren og hvad der måles ved jordoverflade. Vejrradardata er derfor ofte justeret til regnmålere for bedre at repræsentere regnen ved overflade. Når de justerede vejrradardata anvendes til afløbsteknisk modellering, observeres der oftest afvigelser mellem den estimerede regnafstrømning og den målte regnafstrømning. I afløbstekniske sammenhænge er det mere vigtigt at kunne estimere regnafstrømning, og derved flow og vandstande i kritiske punkter af afløbssystemet, end det er at kunne estimere regnen korrekt ved overflade. Det giver derfor mening at undersøge muligheden for at justere vejrradardata til afstrømningsmålinger for at forbedre forudsigelsen af flow og vandstanden.

Dette Ph.D.-studie har undersøgt, hvordan målinger af regnafstrømning kan anvendes til at justere vejrradarer. To justeringsmetoder baseret på afstrømningsmålinger er blevet udviklet. Metoderne er baseret på to traditionelle radar-regnmåler justeringsmetoder. Den første metode er baseret på Z-R forholdet, som beskriver forholdet mellem radar refleksivitet (Z) og radar regnintensitet (R). Et Z-Q forhold blev udviklet, som beskriver forholdet mellem radar refleksivitet (Z) og radar regnafstrømning (Q). Den anden metode er baseret på en radarregnmåler bias justering (mean field bias adjustment). En radar-regnafstrømning bias justering blev udviklet. Den anden metode er mindre beregningstung og nemmere at implementere for et større komplekst opland. Det er ikke nødvendigt at bruge en afstrømningsmodel til at beskrive forholdet mellem regn og regnafstrømning ved anvendelse af den anden metode.

De to justeringsmetoder baseret på afstrømningsmålinger blev testet under praktiske forhold ved brug af to forskellige oplande. Begge metoder præsterede på samme niveau som radar-regnmåler justeringsmetoderne. Sammenligningen var baseret på radar estimeret og målt regnafstrømning. Niveauet faldt dog for regnmåler justeringsmetoderne, hvis de kun blev baseret på regnmålere uden for oplandet. Dette Ph.D.-studie har vidst, at det er muligt at justere vejrradarer ved brug af regnafstrømningsmålinger.

Den største udfordring ved at bruge justeringsmetoder baseret på regnafstrømning er at lukke massebalancen for regnafstrømningen. Hvis oplandet indeholder overløbsbygværker, bassiner, pumper ol. kan dette være meget besværligt. En stor del af Ph.D.-studiet er brugt på at udvikle metoder til at lukke massebalancen. En lukket massebalancen er også vigtig for præcis kalibrering af afløbstekniske modeller anvendt til analyse og realtidsstyring. En del af arbejdet i dette studie kan derfor også anvendes til at forbedre kalibreringen af afløbstekniske modeller.
OriginalsprogEngelsk
Udgivelses stedAalborg
ForlagDepartment of Civil Engineering, Aalborg University
Antal sider166
StatusUdgivet - 2015
NavnDCE Thesis
Nummer73
ISSN1901-7294

Fingeraftryk

stormwater
radar
drainage
sensor
weather
rainfall
runoff
urban drainage
gauge
mass balance
in situ
water level
catchment
reflectivity
method
calibration
rain
atmosphere
transfer function

Emneord

  • Nedbørsprognoser
  • Vejrradar
  • Nedbørssensorer

Citer dette

Ahm, M. (2015). Adjustment of rainfall estimates from weather radars using in-situ stormwater drainage sensors. Aalborg: Department of Civil Engineering, Aalborg University. DCE Thesis, Nr. 73
Ahm, Malte. / Adjustment of rainfall estimates from weather radars using in-situ stormwater drainage sensors. Aalborg : Department of Civil Engineering, Aalborg University, 2015. 166 s. (DCE Thesis; Nr. 73).
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title = "Adjustment of rainfall estimates from weather radars using in-situ stormwater drainage sensors",
abstract = "The topic of this Ph.D. thesis is adjustment of weather radar rainfall measurements for urban drainage applications by the use of in-situ stormwater runoff measurements. It is possible to obtain the high spatiotemporal resolution rainfall data desired for advanced distributed urban drainage applications by the use of weather radars. Rainfall data representing the spatiotemporal distribution is a necessity for accurate modelling and real-time control of distributed urban drainage systems.Weather radar measurements are indirect measurements of the rainfall in the atmosphere, which poses some challenges for using the data in urban drainage applications. There are discrepancies between radar-rainfall measured in the atmosphere and the “true” rainfall at ground level. Consequently, radar-rainfall estimates are usually adjusted to rainfall observations at ground level from rain gauges. When radar-rain gauge adjusted data is applied for urban drainage models, discrepancies between radar-estimated runoff and observed runoff still occur. The aim of urban drainage applications is to estimate flow and water levels in critical points in the system. The “true” rainfall at ground level is, therefore, of less importance as long as the estimated flow and water levels are correct. It makes sense to investigate the possibility of adjusting weather radar data to rainfall-runoff measurements instead of rain gauge measurements in order to obtain better predictions of flow and water levels.This Ph.D. study investigates how rainfall-runoff measurements can be utilised to adjust weather radars. Two traditional adjustments methods based on rain gauges were used as the basis for developing two radar-runoff adjustment methods. The first method is based on the ZR relationship describing the relation between radar reflectivity (Z) and radar rainfall rate (R). A Z-Q relationship were developed to describe the relation between radar reflectivity (Z) and radar rainfall runoff (Q). The second method is based on the radar-rain gauge mean field bias adjustment approach. A radar-runoff bias adjustment approach was developed. The second method is less computationally heavy and easier to implement in larger complex urban catchments since the method does not require a runoff model to describe the transfer function between rainfall and runoff.The two radar-runoff adjustment methods were tested under real practical conditions using two different case study sites. Both methods performed similar to the radar-rain gauge adjustment methods when comparing radar predicted rainfall-runoff against observed rainfallrunoff. However, the performance of the radar-rain gauge adjustment methods decreases when only based on rain gauges located outside the given catchment. This Ph.D. study has proved that it is possible to adjust weather radar measurement using measured rainfall-runoff.The main challenge of using radar-runoff adjustment methods is to close the rainfallrunoff mass-balance. In complex combined sewer catchment with CSOs, basins, pumps, etc. it can be very difficult to close the rainfall-runoff mass-balance. A great effort of the Ph.D. project was dedicated to developing methods for closing the rainfall-runoff mass-balance. A closed mass-balance is also important for accurate calibration of the urban drainage models used of the analyses and real-time control. Hence, some of the work performed during this Ph.D. can also be used for improving calibration of urban drainage models.",
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author = "Malte Ahm",
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publisher = "Department of Civil Engineering, Aalborg University",
address = "Denmark",

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Ahm, M 2015, Adjustment of rainfall estimates from weather radars using in-situ stormwater drainage sensors. DCE Thesis, nr. 73, Department of Civil Engineering, Aalborg University, Aalborg.

Adjustment of rainfall estimates from weather radars using in-situ stormwater drainage sensors. / Ahm, Malte.

Aalborg : Department of Civil Engineering, Aalborg University, 2015. 166 s.

Publikation: Bog/antologi/afhandling/rapportPh.d.-afhandlingForskning

TY - BOOK

T1 - Adjustment of rainfall estimates from weather radars using in-situ stormwater drainage sensors

AU - Ahm, Malte

PY - 2015

Y1 - 2015

N2 - The topic of this Ph.D. thesis is adjustment of weather radar rainfall measurements for urban drainage applications by the use of in-situ stormwater runoff measurements. It is possible to obtain the high spatiotemporal resolution rainfall data desired for advanced distributed urban drainage applications by the use of weather radars. Rainfall data representing the spatiotemporal distribution is a necessity for accurate modelling and real-time control of distributed urban drainage systems.Weather radar measurements are indirect measurements of the rainfall in the atmosphere, which poses some challenges for using the data in urban drainage applications. There are discrepancies between radar-rainfall measured in the atmosphere and the “true” rainfall at ground level. Consequently, radar-rainfall estimates are usually adjusted to rainfall observations at ground level from rain gauges. When radar-rain gauge adjusted data is applied for urban drainage models, discrepancies between radar-estimated runoff and observed runoff still occur. The aim of urban drainage applications is to estimate flow and water levels in critical points in the system. The “true” rainfall at ground level is, therefore, of less importance as long as the estimated flow and water levels are correct. It makes sense to investigate the possibility of adjusting weather radar data to rainfall-runoff measurements instead of rain gauge measurements in order to obtain better predictions of flow and water levels.This Ph.D. study investigates how rainfall-runoff measurements can be utilised to adjust weather radars. Two traditional adjustments methods based on rain gauges were used as the basis for developing two radar-runoff adjustment methods. The first method is based on the ZR relationship describing the relation between radar reflectivity (Z) and radar rainfall rate (R). A Z-Q relationship were developed to describe the relation between radar reflectivity (Z) and radar rainfall runoff (Q). The second method is based on the radar-rain gauge mean field bias adjustment approach. A radar-runoff bias adjustment approach was developed. The second method is less computationally heavy and easier to implement in larger complex urban catchments since the method does not require a runoff model to describe the transfer function between rainfall and runoff.The two radar-runoff adjustment methods were tested under real practical conditions using two different case study sites. Both methods performed similar to the radar-rain gauge adjustment methods when comparing radar predicted rainfall-runoff against observed rainfallrunoff. However, the performance of the radar-rain gauge adjustment methods decreases when only based on rain gauges located outside the given catchment. This Ph.D. study has proved that it is possible to adjust weather radar measurement using measured rainfall-runoff.The main challenge of using radar-runoff adjustment methods is to close the rainfallrunoff mass-balance. In complex combined sewer catchment with CSOs, basins, pumps, etc. it can be very difficult to close the rainfall-runoff mass-balance. A great effort of the Ph.D. project was dedicated to developing methods for closing the rainfall-runoff mass-balance. A closed mass-balance is also important for accurate calibration of the urban drainage models used of the analyses and real-time control. Hence, some of the work performed during this Ph.D. can also be used for improving calibration of urban drainage models.

AB - The topic of this Ph.D. thesis is adjustment of weather radar rainfall measurements for urban drainage applications by the use of in-situ stormwater runoff measurements. It is possible to obtain the high spatiotemporal resolution rainfall data desired for advanced distributed urban drainage applications by the use of weather radars. Rainfall data representing the spatiotemporal distribution is a necessity for accurate modelling and real-time control of distributed urban drainage systems.Weather radar measurements are indirect measurements of the rainfall in the atmosphere, which poses some challenges for using the data in urban drainage applications. There are discrepancies between radar-rainfall measured in the atmosphere and the “true” rainfall at ground level. Consequently, radar-rainfall estimates are usually adjusted to rainfall observations at ground level from rain gauges. When radar-rain gauge adjusted data is applied for urban drainage models, discrepancies between radar-estimated runoff and observed runoff still occur. The aim of urban drainage applications is to estimate flow and water levels in critical points in the system. The “true” rainfall at ground level is, therefore, of less importance as long as the estimated flow and water levels are correct. It makes sense to investigate the possibility of adjusting weather radar data to rainfall-runoff measurements instead of rain gauge measurements in order to obtain better predictions of flow and water levels.This Ph.D. study investigates how rainfall-runoff measurements can be utilised to adjust weather radars. Two traditional adjustments methods based on rain gauges were used as the basis for developing two radar-runoff adjustment methods. The first method is based on the ZR relationship describing the relation between radar reflectivity (Z) and radar rainfall rate (R). A Z-Q relationship were developed to describe the relation between radar reflectivity (Z) and radar rainfall runoff (Q). The second method is based on the radar-rain gauge mean field bias adjustment approach. A radar-runoff bias adjustment approach was developed. The second method is less computationally heavy and easier to implement in larger complex urban catchments since the method does not require a runoff model to describe the transfer function between rainfall and runoff.The two radar-runoff adjustment methods were tested under real practical conditions using two different case study sites. Both methods performed similar to the radar-rain gauge adjustment methods when comparing radar predicted rainfall-runoff against observed rainfallrunoff. However, the performance of the radar-rain gauge adjustment methods decreases when only based on rain gauges located outside the given catchment. This Ph.D. study has proved that it is possible to adjust weather radar measurement using measured rainfall-runoff.The main challenge of using radar-runoff adjustment methods is to close the rainfallrunoff mass-balance. In complex combined sewer catchment with CSOs, basins, pumps, etc. it can be very difficult to close the rainfall-runoff mass-balance. A great effort of the Ph.D. project was dedicated to developing methods for closing the rainfall-runoff mass-balance. A closed mass-balance is also important for accurate calibration of the urban drainage models used of the analyses and real-time control. Hence, some of the work performed during this Ph.D. can also be used for improving calibration of urban drainage models.

KW - Rainfall estimates

KW - Weather radars

KW - Drainage sensors

KW - Nedbørsprognoser

KW - Vejrradar

KW - Nedbørssensorer

M3 - Ph.D. thesis

BT - Adjustment of rainfall estimates from weather radars using in-situ stormwater drainage sensors

PB - Department of Civil Engineering, Aalborg University

CY - Aalborg

ER -

Ahm M. Adjustment of rainfall estimates from weather radars using in-situ stormwater drainage sensors. Aalborg: Department of Civil Engineering, Aalborg University, 2015. 166 s. (DCE Thesis; Nr. 73).