Atmospheric Chemistry · Chemical Transport Modeling

Lexie Mae Rhodes

First-year PhD student in the Atmospheric Chemistry Lab at the University of Montana, studying volatile organic compounds (VOCs) and ozone chemistry in complex terrain using GEOS-Chem and field campaign data.

About

I'm a first-year PhD student in atmospheric chemistry at the University of Montana, advised by Dr. Lu Hu. My work focuses on evaluating chemical transport model (CTM) performance for VOCs and ozone in the western United States, with a particular interest in how oxygenated VOC primary and secondary sources hold up under real-world complexity.

My current projects center on Salt Lake City, where the topography, the Great Salt Lake breeze, and a mix of urban and biogenic emissions create a genuinely challenging environment for models. I work primarily with GEOS-Chem Classic and the F0AM box model, drawing on data from field campaigns including SLC-SOS 2024, SAMOZA 2022, and the FROZE 2025 Colorado Front Range campaign.

Before starting my PhD, I studied Chemistry and Biology at William & Mary and researched water quality and ocean acidification at the Virginia Institute for Marine Science.


Affiliations

Atmospheric Chemistry Lab, Department of Chemistry & Biochemistry, University of Montana
Teaching Assistant, Introduction to General Chemistry & Introduction to Organic and Biochemistry

Projects & Methods

Research

Chemical transport modeling, box modeling, and field campaign analysis focused on western US VOCs and ozone chemistry.

Active Projects

SLC-SOS 2024 · Primary

GEOS-Chem Performance for VOCs & Ozone in Salt Lake City

Evaluating GEOS-Chem Classic at 12 km resolution against multi-site observations from the Salt Lake City Summer Ozone Study 2024, the US Summer Ozone Study 2024 (NOAA), and UT-DAQ GC-MS measurements. Key themes include NEI2017 emission inventory biases, biogenic VOC underestimation, and sub-grid heterogeneity across three sites (Red Butte, Hawthorne, UT Tech) that fall within a single model grid cell.

SLC-SOS 2024 · Methods

F0AM Box Modeling of Stationary VOC Data

Applying the Framework for 0-D Atmospheric Modeling (F0AM) to stationary measurements at Red Butte, with wind-regime separation to account for the Great Salt Lake breeze and downslope mountain topology's twice-daily flow reversals.


Methods & Tools

GEOS-Chem Classic — nested high-resolution simulations (12 km North America) on the Hellgate HPC cluster; HEMCO emissions configuration; GEOS-FP meteorology.

F0AM — box modeling with MCM chemistry; multi-day continuous runs; VOC/NOx isopleth sensitivity analysis; OH reactivity extraction.

Coding proficiencies — Python, R, Javascript, MATLAB

Conferences & Talks

Presentations

Conference posters, seminars, and invited talks.

2026

June 2026 · IGC12 · St. Louis, MO · Poster C.9

Evaluating GEOS-Chem Classic Performance on Ozone & VOCs in Salt Lake City at 12 km Resolution

12th International GEOS-Chem Conference. Poster presentation covering anthropogenic VOC evaluation (toluene, benzene, propane), biogenic VOC evaluation (isoprene, MVK/MACR, monoterpenes), and OVOC analysis (formaldehyde, methanol, ethanol, acetone, acetaldehyde) using IDW-composited observations from SLC-SOS 2024.

IGC12 Poster · C.9 Download PDF ↓

Peer-Reviewed Work

Publications

Coming soon!

In Preparation

Coming soon!
Get in Touch

Contact

Feel free to reach out about research, collaborations, or questions about GEOS-Chem and VOC chemistry in the western US.