Enhancing Air Quality Forecasts in City Environments: Characterizing the Impacts of Boundary Layer and Urban Schemes in Numerical Weather Prediction Models

Title: Enhancing Air Quality Forecasts in City Environments: Characterizing the Impacts of Boundary Layer and Urban Schemes in Numerical Weather Prediction Models

Authors: Leo Matak and Mostafa Momen

Department of Civil and Environmental Engineering, University of Houston

Abstract:

At present, urban regions are inhabited by over 3.5 billion people, about half of the world’s population. Projections indicate that this figure is anticipated to rise to above 65% by the mid-century, with a substantial increase to about 90% for the United States (United Nations 2018). This rapid urbanization and global warming can impact air quality in urban areas, which can be harmful to human health and the natural environment. Urban environments can exacerbate human exposure to heat and air pollution due to the urban heat island effect, higher anthropogenic emissions, and convergent air circulations by reduced wind speed. Despite these complexities of urban surfaces, the current numerical weather prediction (NWP) models typically use simplified parameterizations and are not thoroughly tested for air quality forecasting. Hence, the impacts of complex urban environments on air quality predictions are poorly understood.

In this talk, we aim to bridge this knowledge by conducting multiple coupled atmospheric simulations in urban areas. In particular, the Weather Research and Forecasting (WRF) model (Matak and Momen 2023; Li et al. 2023) coupled with Chemistry (WRF-CHEM) will be used to evaluate the impacts of various planetary boundary layer (PBL), and urban schemes on air quality forecasts. Our efforts center on refining the urban scheme parameterization to enhance the accuracy of forecasting not only meteorological variables but also concentrations of aerosols. Our preliminary results indicate that the urban schemes in the WRF-CHEM model overestimate the aerosols compared to the measured data.

We will present some suggested modifications of the urban schemes, which remarkably improved air quality forecasts in urban environments. For example, Fig. 1 (below), shows contours of WRF-CHEM simulations in Houston conducted without an urban scheme (1a), with a multi-layer Building Energy Model coupled with Building Effect Parameterization (BEP + BEM) urban scheme (1b), and with our modified BEP+BEM scheme (1c). The comparison of the particulate matter (pm2.5) concentrations with the observed data (1d) shows that the considered urban scheme exacerbates the forecasts. Our modified urban scheme was able to improve the agreement with the observed data. The contour maps show how this change can greatly influence aerosol dispersion in urban areas. This air quality prediction enhancement is pivotal for providing reliable insights into the intricate interdependencies between urban environments and aerosol dispersion, ultimately contributing to informed decision-making for urban planning, public health interventions, and sustainable development.

References:

Li M, Zhang JA, Matak L, Momen M (2023) The impacts of adjusting momentum roughness length on strong and weak hurricanes forecasts: a comprehensive analysis of weather simulations and observations. Mon Weather Rev. https://doi.org/10.1175/MWR-D-22-0191.1

Matak L, Momen M (2023) The role of vertical diffusion parameterizations in the dynamics and accuracy of simulated intensifying hurricanes. Boundary Layer Meteorology. https://doi.org/10.1007/s10546-023-00818-w

United Nations (2018) World Urbanization Prospects 2018