Mineral dust aerosol sources in northern Canada : an investigation using the TROPOMI instrument

Abstract

Mineral dust aerosols (MDAs) are important for climate regulation, but little is known about their sources in high-latitude regions like northern Canada. This thesis investigates the atmospheric distribution and surface sources of MDAs in northern Canada using the satellite-based Tropospheric Monitoring Instrument (TROPOMI). TROPOMI Absorbing Aerosol Index (AAI) and Aerosol Layer Height (ALH) data were used, together with the TROPOMI cloud cover (CLO) and carbon monoxide (CO) products. (Where CO and CLO are low, spurious impacts on AAI due to non-MDA atmospheric components are minimized.) The three main research questions were: (1) What is the distribution of dust in northern Canada, according to TROPOMI? and (1b) What does ALH data imply about the sources of the observed dust distributions? (2) How do TROPOMIderived aerosol products compare to those of other well-characterized satellite instruments, like MODIS and OMI? (3) What are the effects of filtering the TROPOMI aerosol products by the carbon monoxide and cloud products? It was found that frequent observations of AAI values greater than 0.5 were made by TROPOMI in high-latitude regions in 2021, suggesting the presence of absorbing aerosols, likely MDAs. Filtering AAI data by ALH isolated likely local MDAsources, previously uncharacterized in field observations. It was also found that TROPOMI AAI data broadly agrees with MODIS Aerosol Optical Depth (AOD) and OMI AAI data, especially when filtered for positive TROPOMI AAI values and statistically significant correlations. Unexpectedly, filtering AAI data by low CO or CLO did not improve the correlation between TROPOMI and MODIS data, but it also did not eliminate the dust sources isolated by ALH filtering. The findings suggest the presence of significant sources of MDAs in northern Canada, but more observational research is needed to confirm their existence and strength, and thus their impact on climate.