City-scale evaluation of urban ecohydrologic processes on surface energy balances, heat, and humidity

Urban regions substantially modify both surface energy and hydrologic cycles. Despite the linkage between urban hydrology and energy cycles, modern coupled land-atmosphere models do not represent common urban hydrologic features like runoff routing from impervious to pervious surfaces or tree canopy that shades pavements. We compare three urban surface models in the Weather and Research Forecasting model across multiple hydrometeorological events in Milwaukee, Wisconsin: a widely used slab urban model (Noah-MP Bulk Parameterization; Typical), multiple land covers per grid cell (Noah-MP Mosaic; Mosaic), and a model which adds sub-grid water transfers between land cover types (Noah-MP HUE; HUE). Inclusion of urban hydrology and vegetation (HUE) increases albedo and emissivity, reducing available energy in our study region. Ambient soil moisture conditions cause divergent responses in HUE simulations: warming when soil water is limited and cooling when ample soil water is available for evapotranspiration. Comparison against observed 2m air temperature and specific humidity show increased skill in the HUE model simulations, especially compared to the Typical model. Noah-MP HUE presents a stride in understanding how urban hydrology influences city-scale meteorology and a pathway to examine urban hydrologic greening initiatives more wholistically in regional atmospheric models.