Geophysical hazards produced by deep convection can pose significant threats to urban populations and there may be reciprocal feedback from the urban land use to deep convection. Here, we investigate this feedback in: 1) Dallas-Fort Worth (DFW) which is a relatively isolated urban area surrounded by grassland, and 2) Northeast (NE) urban corridor from Washington D.C. to Boston which has one of the largest urban aggregates in the US. Using cloud-resolving simulations with the Weather Research and Forecasting model and an ensemble of microphysical schemes we quantify the degree to which historical storylines are modified by changing atmospheric conditions (in pseudo-global warming simulations based on projections from E3SM) and changing land-use land-cover.  Extending DFW from 0 to 8 times the current urban extent generally has only a modest impact on rainfall rates, hail probability and vertical velocities and the sign of change is strongly dependent on the microphysics scheme used. Simulations where the urban extent of the NE corridor is quadrupled indicate that for these 13 storyline events, there is generally a reduction of rainfall rates over the urban area. Thus, consistent with simulations performed at lower resolution by Gao and Bukovsky (2023), while expansion of the urban area may increase the exposed population, the geophysical hazard is slightly reduced. In contrast to expectations based on Clausius–Clapeyron and climatological simulations which indicate increased precipitation over urban areas in the NE, preliminary results suggest that rainfall rates over the urban corridor during these storyline events are further suppressed in coupled LULC change and PGW experiments.

Gao J., Bukovsky M.S. (2023): Urban land patterns can moderate population exposures to climate extremes over the 21st century. Nat Commun 14, 6536.