De-aliasing algorithm Case study (illustration de-aliasing)


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De-aliasing algorithm



Case study (illustration de-aliasing)





DUAL DOPPLER RETRIEVAL Po Valley-radars and terrain analysis



Data Gridding

  • Radar data

    • Polar data
    • 4 elevation angles(deg) 0.5, 1.4, 2.3, 3.2
    • ray resolutions 0.25km x 440 bins, beam width: 0.9 deg


Calculating wind field

  • Three Fundamental Equations:

    • Radial Velocities (from each radar)
    • Mass Continuity


Numerical procedures

  • Iterative method:

  • Boundary conditions:

    • zero vertical velocity on ground
    • zero horizontal velocity gradient on ground (optional: simplify computation w/o loss of accuracy)






Velocity-Azimuth Display (VAD)







The Doppler radar radial wind observation operator

  • Interpolation of the model wind vector to the observation location.

  • Projection of the wind vector on the slanted direction of the radar beam.

  • Broadening of the radar beam: Gaussian averaging kernel.

  • Bending of the radar beam: Snell's law.



One-month (January 2002) comparison of Swedish radial winds and HIRLAM model equivalents

  • Figure: rms difference as a function of measurement range.

  • Rms difference for thinned raw data is significantly higher than for SOs.

  • Method used to deter-mine optimal averaging length scales 10 km for 22 km model)









WP 3: Data assimilation



WP 3: Data assimilation



WP 3: Data assimilation



WP 3: Data assimilation



WP 3: Data assimilation



WP 3: Data assimilation





On-line estimation of error covariances

  • Covariances of innovation vectors (v=y-Hxb):

































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