Wind Gusts in a Changing Climate: A Case Study using a Convection Permitting Model (HCLIM)

Abstract

Severe wind gusts pose substantial risks to transmission towers and the electric grid. With the ongoing energy transition and global warming, these risks are likely to increase. Despite this, there is a lack of research specifically focused on wind gusts, particularly in the context of climate change. This thesis investigates how wind gust dynamics respond to climate change by applying a global warming method to two regional climate models. The first model, RACMO, operates at a 12 km resolution with parameterized convection schemes, while the second model, HCLIM, is nested within RACMO and has a higher resolution of 2.5 km, enabling explicit convection resolving. These models are run for a severe wind gust event that has been linked to numerous severe wind reports, with the boundary and initial conditions altered using perturbations to simulate future or past climates. The perturbations applied for this thesis correspond to −1.5 °C, +1.5 °C, and wet and dry +3 °C global warming scenarios. The results indicate a significant increase in both wind gust intensity and extent due to global warming, especially in the +3°C dry scenario. The strongest wind gusts in this scenario highlight the impact of a lower relative humidity, which directly enhances evaporative cooling and likely increases cold pool strength. Wind gust-related parame- ters, such as the rear inflow jet (RIJ), mesovortices, and downward mass transport, show stronger correlations with wind gust intensity than environmental parameters like convec- tive available potential energy (CAPE) and vertical wind shear. These findings emphasize downward mass transport as a key predictor of wind gust intensity, underscoring the role of vertical momentum conversion near the surface. Additionally, mesoscale convective systems (MCSs) in warmer climates tend to ex- hibit delayed peak wind gust intensities and longer lifespans due to enhanced convection and mesovortex formation. These results emphasize the need for further research on wind gust dynamics in future climates to improve forecasting and risk assessments for severe storms.