Bottom-up estimates of fossil and biogenic CO2 for Auckland, New Zealand
Abstract
Urban areas account for 70-80% of global greenhouse gas emissions, yet urban emissions are poorly constrained. Fossil fuel emissions (petrol, natural gas and coal use) in Auckland, New Zealand's largest city, are known mostly from sector activity data and population downscaling of the New Zealand annual total emissions reported to the UNFCCC. Perhaps more importantly, Auckland's biogenic CO2 uptake is almost entirely unknown. Auckland's subtropical climate and relatively low density suggest that the urban/suburban biosphere could be a significant carbon sink. The urban biosphere is very different from that of rural areas, with fluxes affected by impervious surfaces, the types of plants grown and management of urban and suburban landscapes, such as irrigation and fertilisation. These factors can result in substantially different biogenic CO2 fluxes compared to the surrounding rural areas.
We present preliminary "bottom-up" process-based CO2 flux estimates for both biogenic and fossil CO2 for Auckland, at 500 m spatial resolution and hourly time resolution. Existing state-of-the-art bottom-up models are adapted for Auckland, using the Hestia model to downscale fossil fuel CO2 emissions and urbanVPRM to calculate the net biogenic CO2 flux. These estimates are compared and evaluated with "top-down" atmospheric observations of total CO2 and 14CO2, allowing us to partition fossil and biogenic emissions. Observations are in the form of air flask samples covering a variety of environments throughout the Auckland region (the central urban area, established suburbs, new developments, and a mix of demographic areas) and are repeated 4 times per year to capture seasonal variations. This approach will ultimately allow for targeted improvement of the bottom-up CO2 flux products.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.A53F..02K
- Keywords:
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- 0345 Pollution: urban and regional;
- ATMOSPHERIC COMPOSITION AND STRUCTUREDE: 3394 Instruments and techniques;
- ATMOSPHERIC PROCESSESDE: 0428 Carbon cycling;
- BIOGEOSCIENCESDE: 0478 Pollution: urban;
- regional and global;
- BIOGEOSCIENCES