Venue: AGU Fall Meeting 2012
Huilin Chen; Stephen A. Montzka; Arlyn E. Andrews; Colm Sweeney; Andrew R. Jacobson; Gabrielle Petron; Michael Trudeau; Benjamin R. Miller; Anna Karion; Jung Martin; Christoph Gerbig; J Elliott Campbell; Mohammad Abu-Naser; Joseph A. Berry; Ian T. Baker; Thomas Nehrkorn; Janusz Eluszkiewicz; Pieter P. Tans (2012) Assessment of North America photosynthetic uptake of CO2 through simulations of COS in a Lagrangian particle dispersion model framework. AGU Fall Meeting 2012, San Francisco, CA.
Improving our understanding of terrestrial gross carbon fluxes, i.e. gross primary production (GPP) and respiration, plays a key role in evaluating feedbacks and thereby improving our ability to predict future climate. Since GPP can only be directly measured on very small scales, estimates of GPP at regional to global scales are derived only from biospheric model simulations. Recent studies suggest that carbonyl sulfide be a useful tracer to provide constraints on GPP, based on the fact that both COS and CO2 are simultaneously taken up by plants. Here we present an assessment of GPP estimates for North America from the Simple Biosphere (SiB) model, the Carnegie-Ames-Stanford Approach (CASA) model, and the MPI-BGC model through atmospheric transport simulations of COS in a Lagrangian particle dispersion model (LPDM) framework. We evaluate the impacts of boundary condition and soil uptake on the GPP estimates we derive. This study uses measurements of COS and CO2 from the NOAA/ESRL tall tower and aircraft air sampling networks, and LPDM simulations backward in time are used to quantify the contribution from different sources to observed mole fractions.
A measurement over the continent contains information about terrestrial fluxes provided the upwind, or background concentration is known. Hence, the background state is an important part of the observed signal to be simulated. Empirical boundary curtains are built based on observations at the NOAA/ESRL marine boundary layer stations and from aircraft vertical profiles. These curtains are utilized as the lateral boundary conditions for COS and CO2 for the North American model domain. To assess the uncertainty of the background values for observations, we compare calculated background values based on the empirical curtains and two different models that identify where on the curtain the air entered the model domain: WRF-STILT and HYSPLIT-NAM12. Furthermore, the non-GPP related COS fluxes due to anthropogenic emissions and soil uptake need to be sufficiently quantified to reduce the uncertainty of the assessment on GPP estimates. We develop a new soil flux map of COS based on the uptake of molecular hydrogen, which shares a common soil uptake term but lacks a vegetative sink. A comparison of the new soil uptake map with existing soil fluxes from Kettle et al. 2002 and SiB will be presented. Based on the results of forward simulations, we will assess the necessity of performing an inversion to derive optimized GPP fluxes.