1. AQ Emissions Data Considerations and Needs Greg Frost NOAA, University of Colorado Two key kinds of AQ data on chemical species: Emissions and Ambient Levels Emissions = How much is put in to the atmosphere Ambient levels = How much of that species is in the atmosphere Both are measured and modeled Science/Research: Data is critical for understanding atmosphere Measured/modeled emissions: what goes in atmosphere, changes over time Measured/modeled ambient levels: state of atmosphere, changes over time Model driving variables (boundary and initial conditions) Model evaluation (comparisons to observations) Policy/Regulation: Data is critical for policy and regulatory decisions Understanding the current state of the atmosphere Quantifying impacts of changing emissions Emission inventories are fundamentally regulatory and policy instruments Emissions are the lever we can control  Focus on emissions in my (random) thoughts

2. Emissions Considerations  Each of these is species dependent, & differ for AQ and climate data sets Sources Primary: Emitted from point or distributed sources, at surface or elevated Secondary: Produced in atmosphere through chemical reactions Anthropogenic, Biogenic, or Mixed Sectors/processes: e.g. mobile, industry, energy production, agriculture, forests Spatial Global, regional, local Resolution Point & gridded vs area-wide (county, state, nation, world region) Temporal Extent (hourly –> multi-decadal) Resolution Development methodologies Bottom-up inventories Top-down estimates Regional/national/international efforts Scientific research

3. Emissions Issues and Needs (1) Lexicon – Units of data – Name and speciation of pollutants – Regional definitions – Sector and process definitions Completeness – Sources – Spatial – Temporal Multiple values – Different developers – Different methodologies – Different pollutant/sector/region definitions Connection and consistency between data sets – Real changes over time vs methodology changes – Differences between different providers – AQ and climate follow different development paths…hinders understanding of climate-AQ interactions

4. Emissions Issues and Needs (2) Documentation – Inventory development literature difficult to access – Inventory development & analysis often not in peer-reviewed literature Accessibility – Differences between regions, providers – Large complex data sets, specific formats – Public vs proprietary data Communication – Different needs and cultures of regulatory and scientific community – Two-way feedbacks between regulators and scientists difficult Evaluation/Assessment – Comparisons of inventories to observations/models – Reliability of methodologies – Expert assessments – Understanding impacts