NACP: Urban Greenhouse Gases across the CO2 Urban Synthesis and Analysis Network

Mitchell, L.; Lin, J. C.; Hutyra, Lucy R.; Sargent, M. R.; Wofsy, S.C.; Miles, N. L.; Richardson, Scott J.; Verhulst, K. R.; Duren, Riley; Rice, A. L.; Cohen, R. C.; Shusterman, Alexis A.; Newman, Sally; Guha, Apratim

doi:10.3334/ornldaac/1743

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“…Afternoon hourly average atmospheric CO 2 observations from 21 surface towers are used to evaluate gridded NEE fluxes (Figures 2 and 3; Table S5; Section S2 in Supporting Information S1). The towers, maintained by a variety of data providers (Karion et al, 2020;Miles et al, 2018;Mitchell et al, 2019;NOAA ESRL, 2019;Richardson et al, 2017), were chosen among potential towers as those primarily sited in non-urban areas, excluding locations with challenging topography (for modeling transport) or large fossil fuel emission influence. Although many of these towers have been previously used in atmospheric inversion studies (especially those denoted as NOAA and EC in Table S5 in Supporting Information S1, e.g., L. Hu et al, 2019), roughly half of them (operated by Earth Networks, denoted as EN-NIST in Table S5 in Supporting Information S1) have not been used before in For (c) and (d), afternoon hours have a thicker line width, with "afternoon" defined as described in the supplemental material.…”

Section: Atmospheric Co 2 Tower Networkmentioning

confidence: 99%

A Modified Vegetation Photosynthesis and Respiration Model (VPRM) for the Eastern USA and Canada, Evaluated With Comparison to Atmospheric Observations and Other Biospheric Models

et al. 2022

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Atmospheric CO2 measurements from a dense surface network can help to evaluate terrestrial biosphere model (TBM) simulations of Net Ecosystem Exchange (NEE) with two key benefits. First, gridded CO2 flux estimates can be evaluated over regional scales, not possible using flux tower observations at discrete locations for model evaluation. Second, TBM ability to explain atmospheric CO2 fluctuations due to the biosphere can be directly tested, an important objective for anthropogenic emissions monitoring using atmospheric observations. Here, we customize the Vegetation Photosynthesis and Respiration Model (VPRM) for an eastern North American domain with strong biological activity upwind of urban areas. Parameters are optimized using flux tower observations from a historical database with sites in (and near) the domain. In addition, the respiration model (originally a linear function of temperature) is modified to account for impacts of changing foliage, non‐linear temperature, and water stress. Flux estimates from VPRM, the Carnegie‐Ames‐Stanford Approach (CASA) model and the Simple Biosphere Model v4 (SiB4), are convolved with footprints from atmospheric transport models for evaluation with CO2 observations at 21 towers in the domain, with roughly half of the towers used here for the first time. Results show that the new respiration model in VPRM helps to correct a growing season sink bias in the atmosphere associated with underestimated summertime respiration using the original model with annual parameters. The new VPRM also better explains fine‐scale atmospheric CO2 variability compared to other TBMs, due to higher resolution diagnostic phenology, the new respiration model, domain‐specific parameters, and high‐quality input data sets.

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