Jiachen Zhang

Research Summary

Our overarching research objective is to better understand the interactions between climate, air pollution, and society, as well as to pursue engineering methods and policy measures to tackle climate change and air pollution. We use computational models and big data to assess the impacts of energy, transportation, and land use policies on urban climate, air quality, public health. and environmental justice.


The topics that we are particularly interested are listed below:

1. Investigate the effects of urban land use and property modifications as a means to mitigate urban heat and lower temperatures

Adopting highly reflective “cool” coatings on buildings can help cities mitigate heat and adapt to climate change. Using a regional meteorology model (WRF) and an air quality model (WRF-Chem), I led the first study that systematically compared the regional climate and air quality impacts of adopting solar reflective “cool roofs” and “cool walls.” I also developed a statistical approach to analyze an earth system model’s (CESM) output and resolved the discrepancies among past studies on the global climate impact of “cool roofs.” Leveraging my WRF-Chem modeling expertise, I will mentor PhD students to study the effectiveness and impacts of other heat mitigation strategies (e.g., planting trees and changing building orientation) and develop a framework to evaluate which strategies would work best for different cities and communities. We are also conducting measurements in three elementary schools to assess the effects of cool pavements.

2. Assess the effectiveness of policies aimed at reducing greenhouse gas emissions in the energy and transportation sectors and associated effects on air quality, health, and equity

The energy and transportation sectors are two of the largest contributors to CO2 emissions, causing global climate change. I believe an interdisciplinary approach is essential to developing innovative solutions to reduce their emissions. During my postdoc, I developed emissions inventories for multiple future energy supply and consumption scenarios, based on the outputs of energy demand and capacity models from collaborators at the National Renewable Energy Laboratory (NREL). My findings ultimately helped the City of Los Angeles set its 100% renewable energy goals. At CARB, I led multiple projects related to the transportation sector, including analyzing big data from ride-hauling companies (e.g., Uber), projecting zero-emission vehicle (ZEV) market share using the California Energy Commission’s consumer choice models, and developing California’s official emissions model for vehicles (EMFAC).
My group develops an integrated modeling system coupling emissions, air quality, and travel demand models, as well as work with professors in other disciplines to study the effectiveness of different strategies in achieving air quality, climate, public health, and equity goals.

3. Improving the simulation for long-range transport of black carbon aerosols, ozone, and per- and polyfluoroalkyl substances (PFAS) in atmospheric models

Light-absorbing Black Carbon (BC) aerosols in the atmosphere absorbs solar radiation, leading to global warming. Additionally, BC is a component of PM2.5 air pollution, leading to adverse health impacts. Therefore, reducing BC aerosols helps mitigate climate change while improving air quality and public health. I have led and advised students on multiple research projects studying the transport, transformation, and climate impacts of black carbon in the atmosphere, using CESM and a global chemistry transport model (MOZART).

To further improve the representation of black carbon in models, my group will calibrate atmospheric models against satellite and ground-based observations and explore the use of machine learning techniques to complement physically based atmospheric modeling. I am interested in the fate of other air pollutants in the atmosphere. Specifically, I have studied the impact of wildfires on ozone production and mentored students to study the influence of sea temperature on ozone concentrations.

Additionally, I am working with other faculty members to investigate the fate of PFAS in the environment and refine relevant physical and chemical processes in the atmospheric model CMAQ.

4. Investigating the emissions and air quality impact of Wildland-Urban-Interface (WUI) fires

Wildland-urban interface (WUI) fires burn natural biomass and urban materials, emitting hazardous air pollutants. Using the January 2025 Los Angeles fire as a case study, we are developing models to quantify emissions, pollutant fate, and population exposure to toxics in air and soil. We also analyzed hourly PM₂.₅ levels and indoor/outdoor ratios using high-resolution data from co-located indoor and outdoor PurpleAir sensors. Findings will inform strategies to mitigate health risks and protect communities.