Dr. Jonathan Pleim

Dr. Jonathan Pleim is a physical scientist with over 40 years of experience in air quality and meteorological model development, including 35 years at EPA’s Office of Research and Development. He is a lead developer of several components of the Weather and Research and Forecast (WRF) model, including the Pleim-Xiu Land Surface Model and the Asymmetric Convective Model version 2 planetary boundary layer scheme, both of which have been widely adopted by the air quality modeling community.  He also developed key components of EPA’s Community Multiscale Air Quality (CMAQ) model, such as the M3Dry dry deposition model, the bi-directional ammonia flux model, and an updated aerosol dry-deposition scheme. In his final years at EPA, he began developing the Urban Asymmetric Convective Model (UACM), a new high-resolution urban air quality modeling system that explicitly represents three-dimensional building morphology across both the meteorological and chemical components of WRF-CMAQ. Since leaving EPA, he has continued this work independently, evaluating UACM for New York City at sub-kilometer resolution and building international collaborations with institutions in France and universities in Taiwan. The UACM has direct applications to air quality regulation, environmental justice, and urban heat-stress assessment in the communities most affected by these challenges.

This project proposes to continue the development, evaluation, and application of the Urban Asymmetric Convective Model (UACM), a high-resolution urban meteorology and air quality modeling system that extends EPA’s WRF-CMAQ by explicitly representing 3D building morphology consistently across both meteorological and chemical components.  The UACM represents urban environments as a matrix of street canyons where shading and multiple reflections of short wave and long wave radiation are calculated along with the blocking and shear effects of building walls on wind and turbulence.  The result is a better representation of the urban heat island and more realistic representation of the urban boundary layer.  Evaluation of WRF-CMAQ runs using the UACM for New York City at 0.444-km grid resolution shows substantially better nighttime temperatures (improved urban heat-island representation) and elimination of large nighttime/early-morning PM2.5 overpredictions. The work includes refining algorithms for broader adaptability across various cities, publishing the NYC evaluation journal article, and pursuing collaborations to apply the model to cities in the US and abroad.  The code will be released via public GitHub, with results presented at AGU 2026. The project aims to give agencies and communities urgently needed tools for air quality regulation, environmental justice, and urban heat-stress.