Publication Date:
2018-02-24
Description:
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 ( Z hh ), with or without attenuation correction, from differential reflectivity ( Z dr ), from specific differential phase ( K dp ), or from a combination of Z hh , Z dr and K dp , 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 K dp , while for large values of K dp , both methods using K dp 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 K dp in the model analysis. The humidity increments were found higher in convective regions when correcting for attenuation, or when assimilating K dp . Furthermore, the impact of DPOL observations on precipitation forecasts was found slightly positive for the periods of intense convection.
Print ISSN:
0035-9009
Electronic ISSN:
1477-870X
Topics:
Geography
,
Physics
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