weather radar rainfall for hydrological hazard risk management - dawei han.pdf · dawei han...
TRANSCRIPT
![Page 1: Weather radar rainfall for hydrological hazard risk management - Dawei Han.pdf · Dawei Han 韩大卫 Department of Civil Engineering University of Bristol, UK Weather radar rainfall](https://reader037.vdocuments.mx/reader037/viewer/2022110112/5ae5c1b67f8b9aee078bfaa7/html5/thumbnails/1.jpg)
Dawei Han 韩大卫
Department of Civil Engineering
University of Bristol, UK
Weather radar rainfall for hydrological hazard risk management
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Floods
Droughts
Debris flows
Hydrological hazards related to rainfall
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How to measure rainfall?
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Rain gauge
Radar
Satellite
Rainfall measurements
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Tipping Bucket gauges
Drop counting gauges
Optical gauges
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Larson and Peck (1974)
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WMO report (1982 by Sevruk) Ground truth ?
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Boscastle flood of 16 August 2004
89 mm rain in 60 min, flood peak of 180 cumecs in 1 hour
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http://www.rmets.org/sites/default/files/pdf/presentation/20100417-allott.pdf
Is the rain gauge network sufficient (in time and space)?
In Boscastle, the 4 nearest daily gauges showed less than 3 mm of rain that day
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No rain Rain
Rainfall is not uniform
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Radar
Satellite
Remote sensing could be the answer (?)
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Source: www2010, Univ. of Illinois
Transmitter
Receiver
NOAA
dDDNDZ )(6
dDDNDR )(67.3
baRZ
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Reflectivity
1.6200Z R
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http://www.srh.noaa.gov/jetstream/doppler/beam_max.htm
Beam Spreading
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http://www.srh.noaa.gov/jetstream/doppler/beam_max.htm
Beam refraction
Overshooting/beam blocking
Earth curvature
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Variation of Reflectivity in the Vertical
Rico-Ramirez, et al (2007), Meteorological Applications, 14: 117-129.
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Range
He
igh
t
Radar
Variation of Reflectivity in the Vertical
rainfall rate at the ground?
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Rain drops falling from the sky
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3D wind field (ECMWF Downscaled by WRF)
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Rain drop sizes
http://rpitt.eng.ua.edu/Class/Erosioncontrol/Module3/Module3_files/image022.jpg
disdrometer
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Displacement of rain drops
and time lags
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Pairing of radar pixels and rain gauges
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Exploration of discrepancy between radar and gauge rainfall estimates driven by wind fields, 2014, Qiang Dai and Dawei Han, Water Resources Research
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3D wind field (ECMWF Downscaled by WRF)
3D wind profiler
(Collaborative study with Dr. Yamamoto) (no validation)
How to configure NWP based on wind profile information?
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Model Sensitivity Analysis and Uncertainty Analysis
wikipedia
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Main error sources with weather radars
1, Hardware error
2, Clutter Errors
3, Screening
4, Attenuation
5, Curvature of the earth
6. Z-R relationship
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Radar rainfall error characteristics?
Ideally, radar rain=true rainfall + Noise
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A new error model for weather radar data
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Multivariate Distributed Ensemble Generator: A new scheme for ensemble radar precipitation estimation over temperate maritime climate, 2014, Qiang Dai, Dawei Han, Migue A. Rico-Ramirez, Prashant K. Srivastava, Journal of Hydrology
Probabilistic radar rainfall nowcasts using empirical and theoretical uncertainty models, 2014, Qiang Dai, Miguel A. Rico-Ramirez, Dawei Han, Tanvir Islam, Sara Liguori, Hydrological Processes,
Journal papers on radar error modelling
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Multivariate Distributed Ensemble Generator (MDEG)
MDEG can adopt different kinds of copula functions to simulate the spatial and temporal correlations.
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Modeling radar-rainfall estimation uncertainties using elliptical and Archimedean copulas with different marginal distributions, 2014, Qiang Dai, Dawei Han, Miguel A. Rico-Ramirez, Tanvir Islam, Hydrological Sciences Journal
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The Thurnham radar
Dual-polarization Radar
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3-D film
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Rain drop shape
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1010log hDR
v
ZZ
Z
Differential Reflectivity
indicator of drop shape
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Rinehart, radar for Meteorologists, 2004
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Raw reflectivity Clutter Corrected Reflectivity
Clutter removal using a Bayes classifier
Clutter = Non-precipitation echoes such as
echoes from the ground, sea, ship, airplanes
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dp
Attenuation Correction
differential phase
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Summary
Both rain gauge and weather radar have their own problems.
It is important to understand the strengths and weaknesses of them.
Integration of both data sources would produce better rainfall
estimation
Data uncertainty is important for assessing hydrological modelling
uncertainty