Tropospheric NO₂ Patterns in Eastern Canada Using the First Year of TEMPO Observations

Area of Science:

• Atmospheric Chemistry and Physics
• Environmental Monitoring
• Remote Sensing

Background:

• Tropospheric nitrogen dioxide (NO2) is a key air pollutant with significant health implications.
• Previous satellite monitoring (e.g., TROPOMI) provided limited diurnal and community-scale insights into NO2 variations.
• The TEMPO instrument offers unprecedented hourly resolution for observing atmospheric pollution.

Purpose of the Study:

• To conduct the first exploratory analysis of NO2 patterns in eastern Canada using TEMPO data.
• To compare TEMPO observations with existing satellite (TROPOMI) and ground-based measurements.
• To identify diurnal trends, pollution hotspots, and under-monitored areas in the region.

Main Methods:

• Analysis of TEMPO data gridded at 0.02°×0.02° from September 2023 to August 2024.
• Comparison of TEMPO NO2 data with TROPOMI and Canadian surface-level regulatory monitor data.
• Assessment of diurnal variations, seasonal trends, and weekday-weekend differences in NO2 concentrations.

Main Results:

• TEMPO identified diurnal NO2 trends and hotspots not detectable by once-daily TROPOMI.
• NO2 in major metropolitan areas, ports, and industrial cities peaked in the early morning.
• Correlations between TEMPO and TROPOMI were lower in Atlantic Canada (Spearman's ρ = 0.41–0.53) compared to the Quebec City-Windsor Corridor (Spearman's ρ = 0.81–0.90).

Conclusions:

• TEMPO provides crucial high-resolution data for understanding NO2 pollution dynamics in eastern Canada.
• The findings reveal temporal variations and under-monitored areas, informing air quality management strategies.
• Future research with multi-year TEMPO data is essential for investigating NO2 sources, transport, and health impacts.