Development of the TCWA2 bulk cloud microphysics scheme and its integration with a dual-polarization radar operator for forecasting applications
Tsai, T., Chen, J., Liu, Z., Jiang, S., Kong, R., et al. (2026). Development of the TCWA2 bulk cloud microphysics scheme and its integration with a dual-polarization radar operator for forecasting applications. Geoscientific Model Development, doi:https://doi.org/10.5194/gmd-19-6231-2026
| Title | Development of the TCWA2 bulk cloud microphysics scheme and its integration with a dual-polarization radar operator for forecasting applications |
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| Genre | Article |
| Author(s) | T. Tsai, J. Chen, Zhiquan Liu, S. Jiang, Rong Kong, Y. Wu, Junmei Ban, L. Hsiao, Y. Tang, P. Chang, J. Hong |
| Abstract | This study presents the development and evaluation of TCWA2, a double-moment bulk cloud microphysics scheme designed for weather forecasting that incorporates radar observations at the Taiwan Central Weather Administration. By simplifying the triple-moment NTU microphysics scheme, TCWA2 retains a gamma-type particle size distribution with variable spectral parameters, diagnoses hydrometeor-associated physical properties, revises number sinks due to evaporation loss, and implements theoretically based fall-speed formulations that account for particle density and aspect ratio. To connect bulk microphysics parameterizations with radar-based diagnostics, TCWA2 is coupled with a customized bulk dual-polarization radar operator derived from offline bin-based scattering calculations under the Rayleigh approximation. This integrated microphysics-radar system provides an internally consistent representation linking particle-size distribution characteristics, hydrometeor morphology, sedimentation processes, and bulk radar observables.The intrinsic behavior of TCWA2 is first examined through two-dimensional idealized squall-line simulations in the Weather Research and Forecasting (WRF) model, which produce physically interpretable microphysical structures and coherent polarimetric radar signatures. The scheme is further demonstrated through a proof-of-concept real-case simulation of an afternoon convective event using the Model for Prediction Across Scales (MPAS), with comparisons against observed dual-polarization radar measurements. The joint distributions of radar reflectivity and polarimetric variables show encouraging agreement with observations, with pattern correlations exceeding 0.9 across three altitude layers. These results suggest that TCWA2 can capture key radar-signature characteristics associated with dominant hydrometeor populations and support its potential for future radar-based forecasting applications, while further refinement of ice-phase parameterizations, particle-orientation assumptions, and radar-viewing geometry remains necessary. |
| Publication Title | Geoscientific Model Development |
| Publication Date | Jul 1, 2026 |
| Publisher's Version of Record | https://doi.org/10.5194/gmd-19-6231-2026 |
| OpenSky Citable URL | https://n2t.net/ark:/85065/d71r6w4v |
| OpenSky Listing | View on OpenSky |
| MMM Affiliations | PARC |