Preprints
https://doi.org/10.5194/gmd-2021-188
https://doi.org/10.5194/gmd-2021-188

Submitted as: model evaluation paper 06 Sep 2021

Submitted as: model evaluation paper | 06 Sep 2021

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

Evaluation of the COSMO model (v5.1) in polarimetric radar space – Impact of uncertainties in model microphysics, retrievals, and forward operator

Prabhakar Shrestha1, Jana Mendrok2, Velibor Pejcic1, Silke Trömel1,3, Ulrich Blahak2, and Jacob T. Carlin4,5 Prabhakar Shrestha et al.
  • 1Institute of Geosciences, Meteorology Department, Bonn University, Germany
  • 2Deutscher Wetterdienst, Offenbach, Germany
  • 3Laboratory for Clouds and Precipitation Exploration, Geoverbund ABC/J, Bonn, Germany
  • 4Cooperative Institute for Mesoscale Meteorological Studies, University of Oklahoma, USA
  • 5NOAA/OAR National Severe Storms Laboratory, Norman, Oklahoma, USA

Abstract. Sensitivity experiments with a numerical weather prediction (NWP) model and polarimetric radar forward operator (FO) are conducted for a long-duration stratiform event over northwestern Germany, to evaluate uncertainties in the partitioning of the ice water content and assumptions of hydrometeor scattering properties in the NWP model and FO, respectively. Polarimetric observations from X-band radar and retrievals of hydrometeor classifications are used for comparison with the multiple experiments in radar and model space. Modifying two parameters (Dice and Tgr) responsible for the production of snow and graupel, respectively, was found to improve the synthetic polarimetric moments and simulated hydrometeor population, while keeping the difference in surface precipitation statistically insignificant at model resolvable grid scales. However, the model still exhibited a low bias in simulated polarimetric moments at lower levels above the melting layer (−3 to −13 °C) where snow was found to dominate. This necessitates further research into the missing microphysical processes in these lower levels (e.g., fragmentation due to ice-ice collisions), and use of more reliable snow scattering models to draw valid conclusions.

Prabhakar Shrestha et al.

Status: open (until 01 Nov 2021)

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Prabhakar Shrestha et al.

Prabhakar Shrestha et al.

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Short summary
The article focuses on the exploitation of radar polarimetry for model evaluation of stratiform precipitation. The model exhibited a low bias in simulated polarimetric moments at lower levels above the melting layer where snow was found to dominate. This necessitates further research into the missing microphysical processes in these lower levels (e.g., fragmentation due to ice-ice collisions), and use of more reliable snow scattering models in forward operator to draw valid conclusions.