Spectroscopically Based Measurements of Atmospheric Nitrogen Dioxide (NO2): Improvements to a Broadband Cavity Enhanced Spectrometer

Air quality and atmospheric composition are of concern to public welfare due to their effects on human health and ecosystems. For this reason, it is imperative to develop accurate analytical instrumentation for measurement of the trace gases and emissions associated with air quality issues. Cavity Enhanced Spectroscopy (CES) has established itself as a reliable and efficient technique for in-situ measurements of atmospheric species in aircraft, ground, and laboratory sampling. This work focuses on improving the precision of the NOAA Airborne Cavity Enhanced Spectrometer (ACES) which employs two broadband light emitting diodes (LEDs) centered at 365nm and 455nm, and high-finesse optical cavities for high sensitivity measurements of light absorption by trace gases. We present a new data reduction method for determining concentrations of NO2, as well as hardware improvements to the instrument. These improvements to the ACES instrument have been made in effort to further the progress of the Fire Influence on Regional to Global Environments Experiment (FIREX), which is studying the impact of biomass burning on climate and air quality. Fires in western North America are an important current air quality issue affecting the concentration of regulated secondary pollutants such as ozone and particulate matter on a continental scale. Nitrogen oxides are one of the key emissions from biomass burning. Improved instrument performance will be a key component of its successful deployment on the research aircraft during the 2019 FIREX field intensive.