UCLA

This dissertation employs a multi-satellite synergy algorithm and a chemical transport model to investigate atmospheric composition changes and public health impacts resulting from the 2020 wildfires in the Western United States. The study synergizes data from the CrIS and TROPOMI satellite instruments to analyze carbon monoxide (CO) and evaluates how these two instruments sensed CO separately and in synergy. Results indicate significantly higher daily average CO columns in the Western U.S. compared to the Central and Eastern U.S., with TROPOMI revealing higher values near fire sources, suggesting stronger contributions from close-to-surface concentrations. Validation against ground-based TCCON and NDACC's FTIR CO column estimates demonstrated Normalized Mean Error of less than 24% for CrIS and 32% for TROPOMI. The synergy between TROPOMI and CrIS CO columns was evaluated by assessing the elevated smoke plume on September 15, 2020, against a balloon-borne retrieval from AirCore. It was found that even when deviations were present in CrIS's predicted profile, consistency between TROPOMI and CrIS CO columns was maintained for lofted plumes. Overall, this analysis shows that CrIS and TROPOMI provide complementary information on CO, enhancing the understanding of CO distribution during the wildfires.

The dissertation then focuses on a detailed study of fire-specific PM2.5 emissions, employing the GEOS-Chem chemical transport model. This section reveals that the 2020 wildfires resulted in an unprecedented emission of 328 million tons PM2.5 across the Western U.S., far exceeding the total emissions of the previous three years. It highlights that California alone was responsible for 18% of the six-year total PM2.5 emissions in 2020. The study revealed that certain locations in the Western United States experienced prolonged periods of hazardous air quality conditions that exceeded the EPA's 24-hour limits for more than 40 days. In total, there were 492 million person-days of exposure to poor air quality in the Western U.S. in 2020. This study emphasizes the importance of distinguishing between emissions from fire-specific smoke and smoke from multiple sources due to the higher toxicity of wildfire smoke.

The aim of this research is to highlight the importance of understanding the impact of wildfires on the environment and populations, especially considering their increasing frequency and severity.