Atmospheric composition measurements for air quality and climate studies

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Motivation: Canada is faced with increasing social and regulatory pressures to reduce greenhouse gas (GHG) emissions in order to avert dangerous anthropogenic interference with the climate system and prevent rapid climate change (CC) in this century. At the same time, the reduction of criteria air contaminant (CAC) emissions remains a priority for preventing and managing deteriorating air quality (AQ), while enforcing the ban on ozone depleting substance (ODS) emissions remains crucial for the recovery of the ozone layer. A continued limiting factor on process-based understanding of the role of the atmosphere in climate change, air quality and ozone layer recovery is the scarcity of dense, precise and long-term observations of atmospheric composition. This proposal seeks a continuation of funding for a comprehensive program of long-term, research-grade observations of atmospheric composition in Halifax for air quality and climate studies, including six short-term objectives (O1-O6). Long-term research program goals: The following science questions express the goals of this research: (G1) To what extent are concentrations and long-term trends of air pollutants controlled by the processes of emission/deposition, chemical transformation and transport? (G2) What role do aerosols play in cloud formation, precipitation, atmospheric radiative transfer, and climate? (G3) What is the influence of air-sea gas exchange on the carbon cycle and atmospheric chemistry? Short-term objectives:  G1-O1: What VOC and GHG emissions are associated with marine shipping activities? G1-O2: How accurate are surface-level concentrations of VOCs derived from satellites? G2-O3: What are the characteristics of aerosols, clouds and planetary boundary layer heights in Halifax? G2-O4: How do observations and models compare on mineral dust in cold-cloud regions? G3-O5: What are the characteristics of coastal ocean and saltmarsh fluxes of GHGs? G3-O6: What are the signatures of reactive gases at the air-sea interface? Impact: O1 and O2 relate to G1 and increase the understanding of air pollutants (marine shipping) and satellite-derived surface mapping of HCHO (atmospheric chemistry), with impacts on human and ecosystem health. O3 and O4 relate to G2 and operationalize a new ground-based measurement of aerosols and clouds (mMPL) while validating an existing and long-term satellite-based one (OSIRIS), with impacts on aerosols-cloud-climate interaction understanding (the largest unknown in weather and climate forecasting). O5 and O6 relate to G3 and develop a new technique for GHG air-sea flux measurement while exploring reactive gas concentration gradients at the air-sea interface, thus reducing uncertainty in tropospheric trace gas oceanic budgets related to oxidative chemistry and the carbon cycle. Long-term, high-quality data sets acquired in the course of this work are critical to air quality and climate studies.