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by Augros, C., Caumont, O., Ducrocq, V. and Gaussiat, N.
Abstract:
This article describes the results of assimilation experiments of dual-polarization (DPOL) radar observations in AROME model with its 3D-Var assimilation system. The assimilation of dual-polarization observations is derived from the current operational assimilation method for radar reflectivities. It has two steps (1D+3D-Var): Relative humidity pseudo-observations are first retrieved from observed profiles of reflectivity (Zhh), with or without attenuation correction, from differential reflectivity (Zdr), from specific differential phase (Kdp), or from a combination of Zhh, Zdr and Kdp, through a unidimensional (1D) Bayesian inversion. The retrievals are then assimilated in the AROME 3D-Var system. In case of attenuation, the values of the relative humidity profiles retrieved with uncorrected reflectivity were found lower in average than with attenuation-corrected reflectivity or Kdp, while for large values of Kdp, both methods using Kdp produced the profiles with the largest values of relative humidity in convective regions. Assimilation experiments were conducted for two convective cases. They demonstrated the benefit of attenuation correction and of the assimilation of Kdp in the model analysis. The humidity increments were found higher in convective regions when correcting for attenuation, or when assimilating Kdp. Furthermore, the impact of DPOL observations on precipitation forecasts was found slightly positive for the periods of intense convection.
Reference:
Augros, C., Caumont, O., Ducrocq, V. and Gaussiat, N., 2018: Assimilation of radar dual-polarization observations in AROME modelQuarterly Journal of the Royal Meteorological Society.
Bibtex Entry:
@Article{Augros2018,
  Title                    = {Assimilation of radar dual-polarization observations in AROME model},
  Author                   = {Augros, C. and Caumont, O. and Ducrocq, V. and Gaussiat, N.},
  Journal                  = {Quarterly Journal of the Royal Meteorological Society},
  Year                     = {2018},

  Abstract                 = {This article describes the results of assimilation experiments of dual-polarization (DPOL) radar observations in AROME model with its 3D-Var assimilation system. The assimilation of dual-polarization observations is derived from the current operational assimilation method for radar reflectivities. It has two steps (1D+3D-Var): Relative humidity pseudo-observations are first retrieved from observed profiles of reflectivity (Zhh), with or without attenuation correction, from differential reflectivity (Zdr), from specific differential phase (Kdp), or from a combination of Zhh, Zdr and Kdp, through a unidimensional (1D) Bayesian inversion. The retrievals are then assimilated in the AROME 3D-Var system.
In case of attenuation, the values of the relative humidity profiles retrieved with uncorrected reflectivity were found lower in average than with attenuation-corrected reflectivity or Kdp, while for large values of Kdp, both methods using Kdp produced the profiles with the largest values of relative humidity in convective regions.
Assimilation experiments were conducted for two convective cases. They demonstrated the benefit of attenuation correction and of the assimilation of Kdp in the model analysis. The humidity increments were found higher in convective regions when correcting for attenuation, or when assimilating Kdp. Furthermore, the impact of DPOL observations on precipitation forecasts was found slightly positive for the periods of intense convection.},
  Copublication            = {4: 4 Fr},
  Doi                      = {10.1002/qj.3269},
  Owner                    = {hymexw},
  Timestamp                = {2018.04.09},
  Url                      = {https://doi.org/10.1002/qj.3269}
}