Satellite Formaldehyde to Support Model Evaluation.

Area of Science:

• Atmospheric Chemistry
• Air Quality Modeling
• Remote Sensing

Background:

• Formaldehyde (HCHO) is a hazardous air pollutant and known carcinogen regulated by the U.S. EPA.
• Ground-based monitoring networks provide limited spatial and temporal HCHO data.
• The U.S. EPA Community Multiscale Air Quality (CMAQ) model simulates HCHO for exposure assessments like the National Air Toxics Assessment (NATA).

Purpose of the Study:

• To evaluate the performance of three CMAQ model configurations using satellite HCHO retrievals.
• To assess the models' ability to capture spatial and temporal HCHO variations.
• To identify areas for improvement in HCHO modeling and satellite data synergy for NATA.

Main Methods:

• Utilized satellite HCHO retrievals from the Ozone Monitoring Instrument (OMI) - SAO and QA4ECV products.
• Evaluated three CMAQ model configurations for summer 2011 and 2016 with varying biogenic emissions and chemical mechanisms.
• Compared model outputs with OMI satellite data and surface observations.

Main Results:

• CMAQ configurations generally captured spatial and temporal HCHO patterns but underestimated column HCHO, particularly in the western U.S.
• Monthly correlations between CMAQ and OMI HCHO were higher (r = 0.52 - 0.73) than daily correlations (r = 0.26 - 0.38).
• Models showed better agreement with 24-hour surface observations than afternoon-only, indicating improved daily HCHO accuracy.

Conclusions:

• Satellite HCHO retrievals provide valuable data for evaluating air quality models.
• CMAQ models underestimate HCHO, highlighting the need for improved biogenic emissions and chemical mechanisms, especially in the western U.S.
• Synergistic use of modeling and satellite data can enhance near-surface HCHO estimates for NATA and other applications.