Understanding processes leading to surface gusts by modeling windstorms at very high resolution – WINDGUST

The methodology is based on «seamless« simulations of extratropical cyclones with the Meso-NH atmospheric model jointly developed at LAERO and CNRM. Such simulations require high resolution over large domains to capture both fine-scale features and mesoscale dynamics, as well as advanced physical parameterizations and coupling with various surface models to capture complex interactions. The project will benefit from decades of Meso-NH model developments in both physics and high-performance computing. A novel methodology to identify coherent structures based on Lagrangiantrajectories will be extended to track small-scale features in the huge data from high-resolution simulations.

The main outcomes will be:
1. A better understanding of processes leading to surface gusts
2. A modeling framework to accurately represent windstorms
3. A conceptual model for error growth in extratropical cyclones

Altogether, the project will contribute to improving forecasts of severe windstorms thus prevent casualties and damages. Beyond the scientific outcomes of process understanding, it will set the degree of complexity that is required to represent windstorms in operational models for numerical weather prediction. Additionally, the high-resolution simulation outputs produced by the project may serve as a reference dataset for the development of physical and statistical parameterizations.

Escobar, J., Wautelet, P., Pianezze, J., Pantillon, F., Dauhut, T., Barthe, C., and Chaboureau, J.-P. (2024): Porting the Meso-NH atmospheric model on different GPU architectures for the next generation of supercomputers (version MESONH-v55-OpenACC), EGUsphere [preprint], doi.org/10.5194/egusphere-2024-2879 HAL anr.hal.science/hal-04728112v1

Lfarh, W., Pantillon, F., Chaboureau, J.-P., & Brumer, S. (2024). Impact of surface turbulent fluxes on the formation of roll vortices in a Mediterranean windstorm. Journal of Geophysical Research: Atmospheres, 129, e2023JD040191. doi.org/10.1029/2023JD040191 HAL anr.hal.science/hal-04252989v2

Doiteau, B., Pantillon, F., Plu, M., Descamps, L., and Rieutord, T. (2024): Systematic evaluation of the predictability of different Mediterranean cyclone categories, Weather Clim. Dynam., 5, 1409–1427, doi.org/10.5194/wcd-5-1409-2024 HAL anr.hal.science/hal-04751722v1

Pantillon, F., Davolio, S., Avolio, E., Calvo-Sancho, C., Carrió, D. S., Dafis, S., Gentile, E. S., Gonzalez-Aleman, J. J., Gray, S., Miglietta, M. M., Patlakas, P., Pytharoulis, I., Ricard, D., Ricchi, A., Sanchez, C., and Flaounas, E. (2024): The crucial representation of deep convection for the cyclogenesis of Medicane Ianos, Weather Clim. Dynam., 5, 1187–1205, doi.org/10.5194/wcd-5-1187-2024 HAL anr.hal.science/hal-04744926v1

Lfarh, W., F. Pantillon, and J.-P. Chaboureau, (2023): The Downward Transport of Strong Wind by Convective Rolls in a Mediterranean Windstorm. Mon. Wea. Rev., 151, 2801–2817, doi.org/10.1175/MWR-D-23-0099.1 HAL anr.hal.science/hal-04252886v1

Windstorms associated with extratropical cyclones belong to the most destructive natural hazards over Europe. While the synoptic and mesoscale dynamics of extratropical cyclones have been extensively documented, the processes leading to the formation of damaging wind gusts are not well understood and too small scale to be explicitly represented by numerical weather prediction models. On the one hand, the dynamics and predictability of extratropical cyclones are typically investigated using medium-range global forecasts due to the scales involved in space (several thousands of km) and time (several days). On the other hand, the impacts of surface gusts on infrastructure and wind energy production are typically investigated using short-range, local physical or statistical models.

The innovation of WINDGUST is to bridge the gap between the different scales, which are also associated with different research communities. The project will relate the driving mesoscale features with the local formation of wind gusts (downscaling) and local diabatic and surface processes with their impact on the mesoscale dynamics (upscaling).

WINDGUST is structured around three objectives:
1. Characterize the fine-scale processes responsible for the formation of wind gusts
2. Quantify the sensitivity of wind gusts to the representation of surface processes
3. Explore the feedback of local processes on extratropical cyclone dynamics

The methodology is based on "seamless" simulations of extratropical cyclones with the Meso-NH atmospheric model jointly developed at LAERO and CNRM. Such simulations require high resolution over large domains to capture both fine-scale features and mesoscale dynamics, as well as advanced physical parameterizations and coupling with various surface models to capture complex interactions. The project will benefit from decades of Meso-NH model developments in both physics and high-performance computing. A novel methodology to identify coherent structures based on Lagrangian trajectories will be extended to track small-scale features in the huge data from high-resolution simulations.

The main outcomes will be:
1. A better understanding of processes leading to surface gusts
2. A modeling framework to accurately represent windstorms
3. A conceptual model for error growth in extratropical cyclones

Altogether, the project will contribute to improving forecasts of severe windstorms thus prevent casualties and damages. Beyond the scientific outcomes of process understanding, it will set the degree of complexity that is required to represent windstorms in operational models for numerical weather prediction. Additionally, the high-resolution simulation outputs produced by the project may serve as a reference dataset for the development of physical and statistical parameterizations.