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CO2 air quality urban synthesis and analysis (CO2-AQ USA) project: drivers of urban emissions from past, present, to future

Scientific knowledge of how much, where, and why a city emits greenhouses (GHG) such as CO2 and CH4, and the relationships between emissions of GHGs and air quality-relevant species, is critical for understanding the GHG-air quality nexus in urban regions. This proposal focuses on developing this knowledge to elucidate the benefits of mitigating GHG emissions along with air quality-relevant pollutants.
Gaps in the understanding of urban GHG emissions are starting to be addressed, with
researchers carrying out studies of CO2 and CH4 emissions and cycling in several U.S. cities. This work has been synthesized in an existing NOAA-supported project co-led by PI Lin & CoPI Hutyra?CO2-Urban Synthesis & Analysis (CO2-USA; network. This proposal builds on the foundation of the CO2-USA network to begin to link GHGs and air quality in urban settings. We address the following outstanding science questions, organized in two tiers in terms of the number of cities that would be examined:
Tier 1: Across multiple CO2-USA cities
? How have emissions in GHGs and pollutants changed over time in different U.S. cities?
? How do pollutant emissions from vehicles (principally CO2, CO, and NOx) depend on
ambient temperature and humidity?
? How would emissions of GHG and pollutants change under climate change?
Tier 2: Zooming into Boston and Salt Lake City
? How do emissions of GHG and pollutants vary spatially and temporally in these urban areas?
? What trends over time are revealed by the long data records in these two cities?
? How can co-benefits be realized by reducing emissions of both GHGs and pollutants?
Due to the resources required and the wide scope of proposed project activities, the detailed modeling and measurement elements of the proposal focus on Boston and Salt Lake City, with their low barriers of entry, contrasting characteristics, significant measurement infrastructure, and legacy of work (including the urban biosphere). The two cities differ markedly in size, climate, vegetation, urban form, terrain, infrastructure, and distance to the sea. Boston represents an historic, densely populated East Coast city, while Salt Lake City has the lower density emblematic of the arid West. Studies of these cities will help lay the foundation for investigations of urban domains elsewhere.
The proposed work will have the following tasks for Tier 1:
[1] Compile and publish accessible, uniformly formatted air quality datasets, merged and
harmonized with the existing multi-city GHG datasets developed by the CO2-USA project;
[2] Analyze the merged datasets in different U.S. cities, including assessing emissions trends
and evolving relationships between pollutant and GHG emissions over time;
The proposed work will have the following tasks for Tier 2:
[3] Create high resolution GHG + pollutant emission inventories over multiple years;
[4] Make new multi-scale measurements of GHG and pollutants, from in-situ (stationary +
mobile + relocatable) to ground-based column and satellite remote sensing
[5] Link source regions and emissions to observed data through atmospheric modeling
Synthesis (Tiers 1 and 2):
[6] Combine [1] ? [5] to assess the potential benefits and co-benefits of mitigation efforts.

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