18 Oct 2021

18 Oct 2021

Review status: this preprint is currently under review for the journal AMT.

Evaluation of convective cloud microphysics in numerical weather prediction model with dual-wavelength polarimetric radar observations: methods and examples

Gregor Köcher1, Tobias Zinner1, Christoph Knote1,3, Eleni Tetoni2, Florian Ewald2, and Martin Hagen2 Gregor Köcher et al.
  • 1Meteorologisches Institut, Ludwig-Maximilians-Universität, Munich, Germany
  • 2Deutsches Zentrum für Luft- und Raumfahrt, Institut für Physik der Atmosphäre, Oberpfaffenhofen, Germany
  • 3Medizinische Fakultät, Universität Augsburg, Augsburg, Germany

Abstract. The representation of cloud microphysical processes contributes substantially to the uncertainty of numerical weather simulations. In part, this is owed to some fundamental knowledge gaps in the underlying processes due to the difficulty to observe them directly. On the path to close these gaps we present a setup for the systematic characterization of differences between numerical weather model and radar observations for convective weather situations. Radar observations are introduced which provide targeted dual-wavelength and polarimetric measurements of convective clouds with the potential to provide more detailed information about hydrometeor shapes and sizes. A convection permitting regional weather model setup is established using 5 different microphysics schemes (double-moment, spectral bin (FSBM), and particle property prediction (P3)). Observations are compared to hindcasts which are created with a polarimetric radar forward simulator for all measurement days. A cell-tracking algorithm applied to radar and model data facilitates comparison on a cell object basis. Statistical comparisons of radar observations and numerical weather model runs are presented on a dataset of 30 convection days. In general, simulations show too few weak and small-scale convective cells. Contoured frequency by altitude distributions of radar signatures reveal deviations between the schemes and observations in ice and liquid phase. Apart from the P3 scheme, simulated reflectivities in the ice phase are too high. Dual-wavelength signatures demonstrate issues of most schemes to correctly represent ice particle size distributions, producing overly large graupel particles. Comparison of polarimetric radar signatures reveal issues of all schemes except the FSBM to correctly represent rain particle size distributions.

Gregor Köcher et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on amt-2021-299', Toshi Matsui, 31 Oct 2021
  • RC2: 'Comment on amt-2021-299', Anonymous Referee #2, 02 Nov 2021

Gregor Köcher et al.

Model code and software

Source code of methods Gregor Köcher

Gregor Köcher et al.


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Short summary
We present a setup for systematic characterization of differences between numerical weather model and radar observations for convective weather situations. Radar observations providing dual-wavelength and polarimetric variables to infer information about hyrometeor shapes and sizes are compared against simulations using microphysics schemes of varying complexity. Differences are found in ice and liquid phase, pointing towards issues of some schemes in reproducing shapes and size distributions.