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

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 scat...

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Bibliographic Details
Published in:Geoscientific Model Development 2022-01, Vol.15 (1), p.291-313
Main Authors: Shrestha, Prabhakar, Mendrok, Jana, Pejcic, Velibor, Trömel, Silke, Blahak, Ulrich, Carlin, Jacob T
Format: Article
Language:English
Subjects:
Aggregation
Aircraft
Analysis
Data assimilation
Evaluation
Graupel
Hydrometeors
Ice
Microphysics
Modelling
Moisture content
Numerical prediction
Numerical weather forecasting
Polarimetric radar
Polarimetry
Precipitation
Radar
Rain
Scattering
Simulation
Snow
Superhigh frequencies
Uncertainty
Water content
Weather forecasting
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Summary: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 the critical diameter of particles for ice-to-snow conversion by aggregation (Dice) and the threshold temperature responsible for graupel production by riming (Tgr), 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 (lower magnitude than observation) 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.
ISSN:1991-9603
1991-959X
1991-962X
1991-9603
1991-962X
DOI:10.5194/gmd-15-291-2022