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Publication - Professor Simon O'Doherty

    Quantifying the UK's carbon dioxide flux

    An atmospheric inverse modelling approach using a regional measurement network

    Citation

    White, ED, Rigby, M, Lunt, MF, Smallman, TL, Comyn-Platt, E, Manning, AJ, Ganesan, AL, O'Doherty, S, Stavert, AR, Stanley, K, Williams, M, Levy, P, Ramonet, M, Forster, GL, Manning, AC & Palmer, PI, 2019, ‘Quantifying the UK's carbon dioxide flux: An atmospheric inverse modelling approach using a regional measurement network’. Atmospheric Chemistry and Physics, vol 19., pp. 4345-4365

    Abstract

    We present a method to derive atmospheric-observation-based estimates of carbon dioxide (CO2) fluxes
    at the national scale, demonstrated using data from a network of surface
    tall-tower sites across the UK and Ireland over the period 2013–2014. The
    inversion is carried out using simulations from a Lagrangian chemical
    transport model and an innovative hierarchical Bayesian Markov chain Monte
    Carlo (MCMC) framework, which addresses some of the traditional problems
    faced by inverse modelling studies, such as subjectivity in the
    specification of model and prior uncertainties. Biospheric fluxes related to
    gross primary productivity and terrestrial ecosystem respiration are solved
    separately in the inversion and then combined a posteriori to determine net
    ecosystem exchange of CO2. Two different models, Data
    Assimilation Linked Ecosystem Carbon (DALEC) and Joint UK Land Environment Simulator (JULES),
    provide prior estimates for these fluxes. We carry out separate inversions
    to assess the impact of these different priors on the posterior flux
    estimates and evaluate the differences between the prior and posterior
    estimates in terms of missing model components. The Numerical Atmospheric
    dispersion Modelling Environment (NAME) is used to relate fluxes to the
    measurements taken across the regional network. Posterior CO2 estimates
    from the two inversions agree within estimated uncertainties, despite large
    differences in the prior fluxes from the different models. With our method,
    averaging results from 2013 and 2014, we find a total annual net biospheric
    flux for the UK of 8±79 Tg CO2 yr−1 (DALEC prior) and
    64±85 Tg CO2 yr−1 (JULES prior), where negative values represent an
    uptake of CO2. These biospheric CO2 estimates show that annual UK
    biospheric sources and sinks are roughly in balance. These annual mean
    estimates consistently indicate a greater net release of CO2 than the
    prior estimates, which show much more pronounced uptake in summer months.

    Full details in the University publications repository