Abstract
In this study, a dual-polarimetric radar observation operator is established and modified for the Taiwan area for the purpose of model verification. A severe squall line case during the Southwest Monsoon Experiment Intensive Observing Period 8 (SoWMEX IOP#8) on 14 June 2008, is selected and examined. Because the operator is adopted from the use of the midlatitude region, sensitivity tests are performed to obtain the optimal setting of the operator in the subtropical region. To accurately capture the dynamic structure of the squall lines, the ensemble-based data assimilation system, which assimilates both radial wind and reflectivity data, is used to obtain the optimal analysis field on the mesoscale for evaluating the performance of model simulation. The characteristics of two microphysics schemes are investigated, and the results obtained using the schemes are compared with the S-band dual-polarimetric radar observations. The horizontal and vertical cross-sections show that the analyses resemble the observations. Both schemes can replicate the polarimetric parameter signature such as ZDR and KDP columns. When comparing model simulation with polarimetric parameters through the drawing of contour frequency by altitude diagrams (CFADs), the results reveal that the single moment microphysics scheme performs better than the double moment scheme in this case. However, the reflectivity field in the stratiform area is more accurately captured when using the double moment scheme. Furthermore, validation with polarimetric variables (ZH, ZDR and KDP) histograms shows underestimation of the KDP field in both schemes. Overall, this study indicates the benefit of assimilating radial wind and reflectivity data for the analyses of severe precipitation systems and the necessity of assimilating polarimetric parameters for the accuracy of microphysical processes, especially complex microphysics schemes in subtropical region.
Highlights
Meteorological radar can make observations of high spatial and temporal resolution, which aid weather surveillance and nowcasting
Radial wind and reflectivity observations are assimilated to ensure the precipitation system is close to reality, and the optimal setting of the PRDS is employed to evaluate the performance of a convection-permitting model when using two microphysics schemes and dual-polarimetric variables
To accurately capture the precipitation system, radar reflectivity and radial wind were assimilated in the WRF model at 3-km resolution
Summary
Meteorological radar can make observations of high spatial and temporal resolution, which aid weather surveillance and nowcasting. 2020, 12, 3004 radar data simulator (PRDS), which can convert the hydrometeor mixing ratio and total number concentration into polarimetric parameters. The meaningful statistical data and low-uncertainty data showed that the combination of the sixth moment and ninth moment outperformed the combination of the zeroth moment and third moment in bulk microphysics schemes These forward operators provided a connection between the model variables and dual parameters. Several studies [30,31,32] have indicated that double-moment schemes can simulate polarimetric signatures such as the ZDR arc and ZDR column in supercells. Radial wind and reflectivity observations are assimilated to ensure the precipitation system is close to reality, and the optimal setting of the PRDS is employed to evaluate the performance of a convection-permitting model when using two microphysics schemes and dual-polarimetric variables.
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