Herman Russchenberg - TU Deft - Observation strategies for severe rain in The Netherlands
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Herman Russchenberg - TU Deft - Observation strategies for severe rain in The Netherlands

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Observation strategies for severe rain in The Netherlands...

Observation strategies for severe rain in The Netherlands
Climate change: What to expect in The Netherlands ?
Rainfall in a changing climate
Extreme rainfall in a metropolis
The field laboratory: CESAR
IDRA – TU Delft IRCTR Drizzle radar
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?)

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Herman Russchenberg - TU Deft - Observation strategies for severe rain in The Netherlands Herman Russchenberg - TU Deft - Observation strategies for severe rain in The Netherlands Presentation Transcript

  • Observation strategies for severe rainin The NetherlandsHerman Russchenberg Delft University of Technology Challenge the future
  • Our Earthis slowly warming
  • The world populationis moving into the cities View slide
  • and gets prone to… severe weather View slide
  • and gets prone to… infrastructure infarcts
  • and gets prone to… heat
  • and gets prone to… air pollution
  • ‘Gets prone’… does not have to mean ‘will experience’
  • The challenge is… to make cities a nice place to live… for 50 % of the world population… summer, spring, autumn and winter
  • Climate change:What to expect in The Netherlands? Source: KNMI
  • Rainfall in a changing climate Higher temperature > more water vapour, warmer sea More rainfall and severe weatherObservations during the 20th century: an increase of 20 % Predictions for the 21st century: more extreme rainfall in the summer more rainfall in the winter
  • Extreme rainfall in a metropolis Randstad: coastal urban conglomerate Larger vulnerability modern society (flooding, transport, communication) Accurate information needed Population: 7 millionIntegrated model-observation warning systems Economy: 4th region of Europe Better understanding rainfall formation Dense infrastructure Detailed observations of microphysics needed
  • Philosophy: composite sat-lo-hi-res model to improve forecasts: street level hourly basis
  • The field laboratory: CESAR
  • IDRA – TU Delft IRCTR Drizzle radar SpecificationsCESAR – Cabauw Experimental Site for Atmospheric Research • 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 beamwidth Reference J. 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 IDRA is mounted on top of the 213 m high Processed and raw data available at: meteorological tower. http://data.3tu.nl/repository/collection:cabauw Courtesy Otto
  • Why FM-CW?• Low transmit power• Flexibility• High resolution possible• Solid stateBut: two antennas needed and more complex processing
  • High resolution rain DR= 1 km observations File name: R2008-4-15/7-30-0Par Number of blocks: 143 DR= 30 m Central Frequency: 9.475000 GHz Frequency Sweep: 5.000000 MHz Sweep time: 409.600006 us Transmitted power: 20.000000 W Polarization: Polarimetric Courtesy: KNMI
  • T S A Odifferential reflectivity (dB) reflectivity (dBZ) Mdiff. propagation phase ( ) differential phase ( )diff. backscatter phase ( ) specific diff. phase ( /km) RDSD D0 (mm) RDSD Nw (mm-1 m-3) Examples of polarimetric X-band radar
  • Impact of polarimetry on estimation of rainfall ratesNo polarimetry Optimum use of polarimetry Courtesy Leijnse
  • 35 GHz Courtesy Leijnse
  • Spectral-polarimetric classification Courtesy Durfournet
  • Development of rain: system plus meteorological model Ice and mixed- phase cloudMelting layerBoundary layerecho drizzle rainfall Courtesy Durfournet
  • Concluding remarks• 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?)