Use of radar data in ALADIN

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Use of radar data in ALADIN

• Marián Juraek
• marian.jurasek_at_shmu.sk
• Slovak Hydrometeorological Institute

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Use of radar data in ALADIN
EWGLAM/SRNWP/COST717, Lisbon 2003
Contents of presentation

• current work with radar and ALADIN data in
  ALADINs countries
• future Research plan for radar data
  assimilation in ALADIN

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Use of radar data in ALADIN
EWGLAM/SRNWP/COST717, Lisbon 2003
Current status

• assimilation of radar data not yet developed for
  ALADIN
• usage of radar data
• for ALADIN verification
• together with ALADIN in hydrological models
• together with ALADIN in nowcasting application
• all work is done only on national level

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AUSTRIA

• archiving 1h cumulated precipitation from 10
  minutes radar data in lat-lon grid
• archiving precipitation fields based on surface
  observations in the same grid
• mainly used for ALADIN convective rainfall
  forecast visual verification

Use of radar data in ALADIN
EWGLAM/SRNWP/COST717, Lisbon 2003
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AUSTRIA (2)

• first study made for eastern alpine domain
• period summer 2003
• first results
• ALADIN precipitation forecast is not selective
  enough in space
• early bias with regard to the onset of
  precipitation
• in some areas model generates convective
  precipitation on almost every day during the
  summer season

Use of radar data in ALADIN
EWGLAM/SRNWP/COST717, Lisbon 2003
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AUSTRIA (3)
Use of radar data in ALADIN
EWGLAM/SRNWP/COST717, Lisbon 2003
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AUSTRIA (4)
17th August 2003, 17 UTC
Convective cloudiness and precipitation
prognosed by ALADIN
Convective precipitation (hourly rate) prognosed
by ALADIN
Use of radar data in ALADIN
EWGLAM/SRNWP/COST717, Lisbon 2003
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AUSTRIA (5)

• results leaded to the experiments with modified
  trigger functions in the ALADIN deep convection
  scheme.
• larger project connected with integrated flood
  forecasting system will probably start next year
• combination surface precipitation observations,
  radar and ALADIN

Use of radar data in ALADIN
EWGLAM/SRNWP/COST717, Lisbon 2003
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CZECH REPUBLIC

• ALADIN data used for generating radar image
  forecast
• wind field data - crucial point of the radar echo
  prediction
• tested 3 different methods for wind field
  calculation
• COTREC
• Wavelet Transform Decomposition
• ALADIN geopotential field at 700 hPa

Use of radar data in ALADIN
EWGLAM/SRNWP/COST717, Lisbon 2003
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CZECH REPUBLIC (2)

• COTREC
• comparison of two consecutive radar images using
  some similarity criteria
• smoothing of final field
• WAVELET
• similar to COTREC, but radar image is decomposed
  to subspaces using the wavelet transformation
• calculation of decomposition similarity criteria
  at several different detail levels
• smoothing of final field like in COTREC

Use of radar data in ALADIN
EWGLAM/SRNWP/COST717, Lisbon 2003
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CZECH REPUBLIC (3)

• ALADIN
• cloud motion is controlled by air mass flow at
  approx. 3-5 km above sea level
• it corresponds with geopotential at 700 hPA (cca
  3 km)
• ALADIN data interpolated to the image size and to
  the resolution of radar data
• motion field calculated from geostrophical
  approximation

Use of radar data in ALADIN
EWGLAM/SRNWP/COST717, Lisbon 2003
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CZECH REPUBLIC (4)
COTREC
Wind field calculated by COTREC method
Forecasted radar image by COTREC method
Use of radar data in ALADIN
EWGLAM/SRNWP/COST717, Lisbon 2003
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CZECH REPUBLIC (5)
WAVELET
Wind field calculated by WAVELET method
Forecasted radar image by WAVELET method
Use of radar data in ALADIN
EWGLAM/SRNWP/COST717, Lisbon 2003
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CZECH REPUBLIC (6)
ALADIN
Forecasted radar image by ALADIN method
Wind field calculated by ALADIN method
Use of radar data in ALADIN
EWGLAM/SRNWP/COST717, Lisbon 2003
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CZECH REPUBLIC (7)

• Results of comparison
• all methods improve radar information
• for all methods, similar decrease in forecast
  quality with forecast time
• in most cases, the ALADIN method is slightly
  worse
• ALADIN method needs only one radar image
• ALADIN method has the smallest hardware
  requirements

Use of radar data in ALADIN
EWGLAM/SRNWP/COST717, Lisbon 2003
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CZECH REPUBLIC (8)

• Conclusion
• in operational use only COTREC and ALADIN methods
• forecasted radar image generated every 10 minutes
• forecasted for 10 min 20 min ... 90 min

Use of radar data in ALADIN
EWGLAM/SRNWP/COST717, Lisbon 2003
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FRANCE

• study of flood event in southern France from 8th
  to 10th September 2002
• visual verification (comparison) of cumulative
  radar rain with cumulative ALADIN rain forecast
• main goal to see the general evolution of the
  precipitation

Use of radar data in ALADIN
EWGLAM/SRNWP/COST717, Lisbon 2003
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FRANCE (2)
48 h cumulated precipitation measured by radar
48 h cumulated precipitation forecasted by ALADIN
Use of radar data in ALADIN
EWGLAM/SRNWP/COST717, Lisbon 2003
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(No Transcript)
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FRANCE (3)

• space-time interpolation of precipitation fields
• pattern matching applied on radar data
• attempt to prepare radar data for non-visual
  verification
• radar data space filtered to ALADIN resolution
  (cca 10 km)
• spectral study of radar and ALADIN precipitation

Use of radar data in ALADIN
EWGLAM/SRNWP/COST717, Lisbon 2003
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FRANCE (4)

• result of spectral study forecast error is like
  white noise, no difference between frontal and
  convective precipitation
• spectral filtering used for separating large-
  from small scale precipitation
• discrepancy between radar and model data
  separated to
• large scale scaling error
• large scale geometrical deformation error
• small scale residual

Use of radar data in ALADIN
EWGLAM/SRNWP/COST717, Lisbon 2003
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FRANCE (5)

• Computation of optimal deformation operator
• correlation method - numerically too expensive,
  already for 200 x 200 points field
• incremental variational technique
• highly non-quadratic pattern matching cost
  function
• problem with optimisation if good first guess
  not available

Use of radar data in ALADIN
EWGLAM/SRNWP/COST717, Lisbon 2003
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HUNGARY

• radar and ALADIN data as input for hydrological
  model DIWA (DIstributed WAtershed) running
  outside of Hungarian Meteorological Service
• input for model
• ALADIN precipitation forecast
• ALADIN min/max temperature
• ECMWF forecasts ( as ALADIN ensemble)
• calibrated 12 h cumulated precipitation from
  radar measurements

Use of radar data in ALADIN
EWGLAM/SRNWP/COST717, Lisbon 2003
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HUNGARY (2)
Example of calibrated 12h radar precipitation
Use of radar data in ALADIN
EWGLAM/SRNWP/COST717, Lisbon 2003
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Example of hydrological model simulation
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HUNGARY (3)
Verification of 72 h hydrological model
forecast over 110 days period
Use of radar data in ALADIN
EWGLAM/SRNWP/COST717, Lisbon 2003
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Conclusion of first part

• none radar data assimilation to ALADIN
• usage of radar data together with ALADIN data is
  not coordinated
• only some applications on national level

Use of radar data in ALADIN
EWGLAM/SRNWP/COST717, Lisbon 2003
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Research Plan

• in June 2003 prepared proposal of workplan for
  research of radar data assimilation for ALADIN
• radar data - essential for mesoscale assimilation
• available radar data
• reflectivity
• instantaneous rainrate
• cumulated rainfall
• doppler wind , wind shear, turbulence
• vertical wind profile
• quantities from multiple polarisation measurements

Use of radar data in ALADIN
EWGLAM/SRNWP/COST717, Lisbon 2003
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Which radar data?

• each has advantages and disadvantages
• not all available on all radar sites
• reflectivity seems to be available on most
  European sites
• not common form of data
• PPI images
• volume data

Use of radar data in ALADIN
EWGLAM/SRNWP/COST717, Lisbon 2003
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The philosophy

• learning from satellites
• remote sensing process is complex and nonlinear
• we should assimilate quantity close to measured
  (reflectivity instead of rainrate)
• derived quantities contain hardly correctable
  errors
• observation operator for simulation of
  reflectivity for each radar
• development of system for radar data against
  model data monitoring

Use of radar data in ALADIN
EWGLAM/SRNWP/COST717, Lisbon 2003
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The philosophy (2)

• biases and big errors cannot be handled by
  3D/4D-Var
• software for detection and removal of corrupted
  data
• study of space- and time structure of biases
  between simulated and observed data for bias
  correction
• each radar processed independently
• thinning of too dense data consistently with the
  resolution of the analyses

Use of radar data in ALADIN
EWGLAM/SRNWP/COST717, Lisbon 2003
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The philosophy (3)

• very accurate modelling of physical process of
  observation
• precisely interpolating / averaging model
  variables along the radar beam path
• physical part of observation operator should be
  prepared by radar specialists
• observation operator should relatively
  independent from model

Use of radar data in ALADIN
EWGLAM/SRNWP/COST717, Lisbon 2003
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Things To Do

• get samples of very good quality radar
  reflectivity data
• get idea of fields needed to simulate
  reflectivity
• get simple (to start with) reflectivity
  simulation formulae
• specify obs. operator by list of necessary model
  fields, information about observation

Use of radar data in ALADIN
EWGLAM/SRNWP/COST717, Lisbon 2003
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Things To Do (2)

• carefully specify the technical implementation of
  previous things
• implement radar data into the ODB processing
• implement direct interpolation of model fields
• convert model field to the reflectivity, compute
  and store difference with observation
• study monitoring statistics

Use of radar data in ALADIN
EWGLAM/SRNWP/COST717, Lisbon 2003
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Things To Do (3)

• code tangent linear and adjoint of obs. operator
• simulate one radar pixel
• study the impact of reflectivity assimilation to
  forecast
• run several cycles of data assimilation to see
  the cumulative effect
• retune preprocessing and analysis parameters

Use of radar data in ALADIN
EWGLAM/SRNWP/COST717, Lisbon 2003
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Closure

• lot of work for next years
• big challenge for all aladinists

Use of radar data in ALADIN
EWGLAM/SRNWP/COST717, Lisbon 2003
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Thank You for your attention!

• marian.jurasek_at_shmu.sk

Use of radar data in ALADIN
EWGLAM/SRNWP/COST717, Lisbon 2003