Date of Award

Spring 5-2022

Document Type

Honors Thesis

Degree Name

Bachelor of Science

Department

Atmospheric and Environmental Sciences

Advisor/Committee Chair

Kristen Corbosiero

Abstract

Throughout 2020, ambient air pollution was reduced as a result from limiting anthropogenic activities to mitigate the spread of COVID-19. Not all air pollution is created the same as measurements of particulate matter 2.5 (PM2.5) were generally unaffected by this reduction due to PM2.5s source from wildfires. Despite influences from COVID-19 lockdowns, rises in PM2.5 concentrations can be attributed to the anomalously active wildfire season of 2020. As climate change progresses, these extraordinarily active seasons can be classified as the “new normal”; thus, comprehension of such events are vital. Given the ability of lightning to naturally cause wildfires, there exists a positive feedback loop that exists as convection can be influenced by aerosols. To understand this feedback loop, a proper analysis of the interactions between lightning and wildfires is necessary. Data from the Environmental Protection Agency (EPA) Air Quality System, National Lightning Detection Network (NLDN), and the ERA5 Reanalysis was utilized for a statistical analysis. Airports were carefully chosen to result in 132 correlation coefficients for either PM2.5 concentration or lightning strikes to meteorological variables and month. Planetary boundary layer height (PBLH) had the strongest negative correlation with all but one calculated correlation being negative on the East Coast. Numerical modeling methods were implemented to understand aerosol behavior beyond a statistical scope. Two Weather Research and Forecasting (WRF) model simulations were conducted surrounding the Detroit Metropolitan Wayne County Airport (KDTW) using a 3-km High Resolution Rapid Refresh (HRRR) initialization at 0000 UTC 7 September 2020 to compare model runs with and without the inclusion of NASA’s Goddard Earth Observing System (GEOS) model aerosol data. The difference between the simulations including aerosols to no aerosols showed that PBLH mimicked the frontal structure associated with convection for the case. Positive values indicated that WRF simulations that included aerosols had higher PBLH that were observed behind the cold front. Additional cases must be examined to draw adequate conclusions regarding numerical model output to further confirm the existence of a frontal-based relationship surrounding PBLH.

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