A new, computationally efficient semi-Lagrangian advection (SLA) scheme was used to simulate an idealized supercell storm using WRF coupled with spectral (bin) microphysics (SBM). SLA was developed to make complicated microphysical schemes more computationally accessible to cloud-resolving models. The SLA is a linear combination of semi-Lagrangian schemes of the first and the second order. It has relatively low numerical diffusion, a high level of mass conservation accuracy, and preserves the sum of multiple advected variables. In addition to idealized tests, comparisons were made with standard WRF higher-order, nonlinear advection schemes. Tests of the SLA were performed using different values of weighting coefficients g for the combination of the first- and second-order components. The results of SLA on grids of 1 km, 500 m, and 250magree well with those of the standardWRFadvection schemes, with results most similar to simulations with 250-m grid spacing. At the same time, the advectionCPU time required by the SLA was 2.2-3 times shorter than the WRF advection schemes. The speed-up occurred in part because of the utilization of the same advection matrix for the advection of all hydrometeor mass bins. The findings of this work support the hypothesis that cloud microphysical simulation is more sensitive to the choice of microphysics than to the choice of advection schemes, thereby justifying the use of computationally efficient lower-order linear schemes.
Bibliographical noteFunding Information:
Acknowledgments. This research was supported by the Israel Science Foundation (Grant 2027/17) and the Office of Science (BER). Partial support for this work comes from Grants DE-SC008811, DE-SC0014295, DE-AC0576RL01830, and ASR DE-FOA-1800 from the U.S. Department of Energy Atmospheric System Research Program. We express our gratitude to Dr. J. Fan for her interest in the study.
© 2021 American Meteorological Society.
- Cloud resolving models
- Model comparison
- Numerical analysis/modeling