Observation strategies for severe rainin The NetherlandsHerman Russchenberg     Delft     University of     Technology    ...
Our Earthis slowly warming
The world populationis moving into the cities
and gets prone to… severe weather
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 weat...
Extreme rainfall in a metropolis                                            Randstad:                                     ...
Philosophy:    composite    sat-lo-hi-res    model    to improve    forecasts:    street level    hourly basis
The field laboratory: CESAR
IDRA – TU Delft IRCTR Drizzle radar                                                                                    Spe...
Why FM-CW?• Low transmit power• Flexibility• High resolution possible• Solid stateBut: two antennas needed and more comple...
High resolution rain                          DR= 1 km    observations                       File name: R2008-4-15/7-30-0P...
T                                                            S                                                            ...
Impact of polarimetry on estimation   of rainfall ratesNo polarimetry     Optimum use of polarimetry                      ...
35 GHz         Courtesy Leijnse
Spectral-polarimetric classification                                Courtesy Durfournet
Development of rain: system plus   meteorological model Ice and mixed- phase cloudMelting layerBoundary layerecho         ...
Concluding remarks• Climate change leads to more severe weather• Better forecasts of rainfall needed• Explore feasibility ...
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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
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

  1. 1. Observation strategies for severe rainin The NetherlandsHerman Russchenberg Delft University of Technology Challenge the future
  2. 2. Our Earthis slowly warming
  3. 3. The world populationis moving into the cities
  4. 4. and gets prone to… severe weather
  5. 5. and gets prone to… infrastructure infarcts
  6. 6. and gets prone to… heat
  7. 7. and gets prone to… air pollution
  8. 8. ‘Gets prone’… does not have to mean ‘will experience’
  9. 9. The challenge is… to make cities a nice place to live… for 50 % of the world population… summer, spring, autumn and winter
  10. 10. Climate change:What to expect in The Netherlands? Source: KNMI
  11. 11. 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
  12. 12. 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
  13. 13. Philosophy: composite sat-lo-hi-res model to improve forecasts: street level hourly basis
  14. 14. The field laboratory: CESAR
  15. 15. 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
  16. 16. Why FM-CW?• Low transmit power• Flexibility• High resolution possible• Solid stateBut: two antennas needed and more complex processing
  17. 17. 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
  18. 18. 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
  19. 19. Impact of polarimetry on estimation of rainfall ratesNo polarimetry Optimum use of polarimetry Courtesy Leijnse
  20. 20. 35 GHz Courtesy Leijnse
  21. 21. Spectral-polarimetric classification Courtesy Durfournet
  22. 22. Development of rain: system plus meteorological model Ice and mixed- phase cloudMelting layerBoundary layerecho drizzle rainfall Courtesy Durfournet
  23. 23. 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?)

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