herman russchenberg - tu deft - observation strategies for severe rain in the netherlands
DESCRIPTION
Observation strategies for severe rain in The NetherlandsClimate change:What to expect in The Netherlands ?Rainfall in a changing climateExtreme rainfall in a metropolisThe field laboratory: CESAR IDRA – TU Delft IRCTR Drizzle radarClimate change leads to more severe weatherBetter forecasts of rainfall neededExplore feasibility of high-frequency, short range radars in citiesDoppler-polarimetry gives details of microphysics and processesCombine with small scale, cloud resolving modelsRadar should be able to do without ground observations (truth?)TRANSCRIPT
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Challenge the future
DelftUniversity ofTechnology
Observation strategies for severe rainin The Netherlands
Herman Russchenberg
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Our Earthis slowly warming
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The world populationis moving into the cities
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and gets prone to … severe weather
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… infrastructure infarctsand gets prone to
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… heat and gets prone to
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… air pollutionand gets prone to
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‘Gets prone’ … does not have to mean ‘will experience’
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The challenge is
… to make cities a nice place to live
… for 50 % of the world population
… summer, spring, autumn and winter
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Climate change:What to expect in The Netherlands?
Source: KNMI
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More rainfall and severe weather
Rainfall in a changing climate
Higher temperature > more water vapour, warmer sea
Observations during the 20th century: an increase of 20 %
Predictions for the 21st century: more extreme rainfall in the summer
more rainfall in the winter
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Extreme rainfall in a metropolis
Integrated model-observation warning systems
Better understanding rainfall formation Detailed observations of microphysics
needed
Accurate information needed
Larger vulnerability modern society(flooding, transport,
communication)
Randstad: coastal urban conglomerate
Population: 7 millionEconomy: 4th region of EuropeDense infrastructure
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Philosophy: composite sat-lo-hi-resmodel
to improveforecasts:street levelhourly basis
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The field laboratory: CESAR
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IDRA – TU Delft IRCTR Drizzle radar
IDRA is mounted on top of the 213 m high meteorological tower.
CES
AR
– C
abauw
Experi
menta
l Sit
e f
or
Atm
osp
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ese
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Specifications• 9.475 GHz central frequency• FMCW with sawtooth modulation• transmitting alternately horizontal and
vertical polarisation, receiving simultaneously the co- and the cross-polarised component
• 20 W transmission power• 102.4 µs – 3276.8 µs sweep time• 2.5 MHz – 50 MHz Tx bandwidth• 60 m – 3 m range resolution• 1.8° antenna half-power beamwidthReferenceJ. Figueras i Ventura: “Design of a High Resolution X-band Doppler Polarimetric Weather Radar”, PhD Thesis, TU Delft, 2009. (online available at http://repository.tudelft.nl)
Near real-time display:http://ftp.tudelft.nl/TUDelft/irctr-rse/idra
Processed and raw data available at:http://data.3tu.nl/repository/collection:cabauw
Courtesy Otto
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Why FM-CW?
• Low transmit power
• Flexibility
• High resolution possible
• Solid state
But: two antennas needed and more complex processing
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High resolution rainobservations
File name: R2008-4-15/7-30-0Par Number of blocks: 143Central Frequency: 9.475000 GHzFrequency Sweep: 5.000000 MHzSweep time: 409.600006 usTransmitted power: 20.000000 WPolarization: Polarimetric
DR= 1 km
DR= 30 m
Courtesy: KNMI
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reflect
ivit
y (
dB
Z)
diff
ere
nti
al re
flect
ivit
y (
dB
)
diff
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nti
al phase
(°)
diff
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pagati
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hase
(°)
speci
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(°/
km)
diff
. back
scatt
er
phase
(°)
RD
SD
Nw (
mm
-1 m
-3)
RD
SD
D0 (m
m)
Examples of polarimetric X-band radarATMOS
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Impact of polarimetry on estimationof rainfall rates
No polarimetry Optimum use of polarimetry
Courtesy Leijnse
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Courtesy Leijnse
35 GHz
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Spectral-polarimetric classification
Courtesy Durfournet
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Development of rain: system plus meteorological model
Boundary layer echo
drizzle
Melting layer
rainfall
Ice and mixed-phase cloud
Courtesy Durfournet
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• Climate change leads to more severe weather• Better forecasts of rainfall needed• Explore feasibility of high-frequency, short range radars in
cities• Doppler-polarimetry gives details of microphysics and
processes• Combine with small scale, cloud resolving models• Radar should be able to do without ground observations
(truth?)
Concluding remarks