Role of Advection on the Evolution of Near-Surface Temperature and Wind in Urban-Aware Simulations

Abstract

The role of advection of heat and momentum on the evolution of near-surface temperature and wind is evaluated in urban-aware simulations over Houston under dry conditions on a light-wind day. Two sets of experiments, each consisting of four simulations using different planetary boundary layer (PBL) schemes, were conducted over 48 hours using the default urban scheme (BULK) and the single-layer urban canopy model (SLUCM) available within the Weather Research and Forecasting (WRF) model. We focus on understanding and quantifying the role played by temperature and momentum advection, particularly on the windward and leeward sides of the city. Previous studies have largely ignored any quantitative analysis of impacts from the advection of momentum over an urban area.The horizontal advection of temperature was found to be more important in the BULK because of the larger surface temperature gradient caused by warmer surface temperatures over urban areas than in the SLUCM. An analysis of the momentum budget shows that horizontal advection of zonal and meridional momentum plays a prominent role during the period of peak near-surface winds, and this effect is more pronounced in the windward side of the city. The local tendency in peak winds in the leeward side lags that in the windward side by about 1-2 hours, similar to the lag found in horizontal momentum advection. The sensitivity of the results to different urban and PBL schemes was explored. The results imply that representation and influence of land-use patterns via sophisticated urban parameterizations generates locally driven winds that best resemble observations.

Role of Surface Energy Fluxes in Urban Overheating Under Buoyancy‐Driven Atmospheric Conditions

“…At the urban microscale, horizontal heat and momentum advection manipulate meteorlogical conditions in both the urban boundary layer (air mass above the rooftops) and the urban canopy layer (air mass between the ground and the rooftops), with critical effects on the near‐surface temperature and urban overheating (Brousse et al., 2022; Dinda & Chatterjee, 2022; Ray et al., 2021). Increased surface roughness and thermal properties in cities lead to warmer conditions and reduced wind speed at the near‐surface layer (Grimmond & Oke, 1999a).…”