Urban Influence on Convection and Precipitation in the Coastal City of Houston, TX

Urban environments significantly modify boundary layer processes through spatial heterogeneities in surface heat and momentum fluxes. These heterogeneities are shaped by variations in building heights and land cover and impact the initiation, development, and evolution of convection, influencing precipitation patterns. The extent of these impacts varies under different synoptic weather conditions such as strong winds, weak winds, coastal marine environments, and low-level jets. This study aims to investigate how these local-scale processes interact with larger-scale weather patterns and affect organized convection in the coastal city of Houston, TX.

We conducted sub-kilometer scale simulations using the Weather Research and Forecasting (WRF) model coupled with the multi-layer BEP-BEM urban canopy model. The simulations featured a 3-D turbulent kinetic energy (TKE) scheme for vertical mixing, dynamically transitioning between large-eddy simulation (LES) and mesoscale parameterizations to address the gray-zone challenge. Two case studies were selected from the TRacking Aerosol Convection interactions ExpeRiment (TRACER): (i) a clear-sky day and (ii) a precipitation event.

Observational datasets from TRACER—including ceilometer-derived boundary layer heights, flux anemometer measurements of heat fluxes, radiosonde soundings, radar reflectivity, and surface meteorological observations—were used for model evaluation. Preliminary results indicate that the LES-based configuration captures spatial heterogeneities in near-surface meteorological fields. However, further analysis is required to understand how urban-induced heterogeneities affect the organization of convection and precipitation development under contrasting synoptic conditions.

This study highlights the need for refined experimental design to reveal the contrasting mechanisms across varying local and large-scale conditions. It also addresses key limitations related to parameterization schemes and grid resolution, offering insights for future improvements in urban weather prediction.