Impacts of Anthropogenic Climate Change and Urbanization on Derechos – Contrasting Results between Two Case Studies
Derechos, powerful and often destructive windstorms, are known for their capability to cause widespread and extensive damage. Therefore, it is crucial to enhance our understanding of how anthropogenic-induced climate change (ACC) and urban expansion may impact the severity of derecho events for effective disaster preparedness, damage mitigation, and developing well-informed policies. In this study, we conducted WRF model simulations at 1 km grid spacing for two derechos that occurred in the northeastern coastal areas during May 14-15, 2018. The simulations were performed under current conditions and scenarios of either future climate change, urban expansion, or both. The ACC impacts were opposite between the two derechos on May 15 and May 14. The derecho on May 15 strengthened, while the one on May 14 drastically weakened, resulting from significantly different responses in relative humidity to ACC. The effects of urbanization on surface wind speeds, heavy precipitation, and significant severe hail (SSH) are consistent in both cases: they enhance heavy precipitation and SSH but weaken near-surface wind speeds. Compared with the May 14 event, urbanization effects are much stronger for the May 15 event because a larger portion of the storm passes over the urban area.