Mesoscale circulations over complex terrain in the Valencia coastal region, Spain – Part 2: Modeling COsub2/sub transport using idealized surface fluxes

摘要

Vertical profiles of CO₂ concentration were collected during anintensive summer campaign in a coastal complex-terrain region within theframe of the European Project RECAB (Regional Assessment and Modelling ofthe Carbon Balance in Europe). The region presents marked diurnal mesoscalecirculation patterns. These circulations result in a specific couplingbetween atmospherically transported CO₂ and its surface fluxes. Tounderstand the effects of this interaction on the spatial variability of theobserved CO₂ concentrations, we applied a high-resolution transportsimulation to an idealized model of land biotic fluxes. The regional NetEcosystem Exchange fluxes were extrapolated for different land-use classesby using a set of eddy-covariance measurements. The atmospheric transportmodel is a Lagrangian particle dispersion model, driven by a simulation ofthe RAMS mesoscale model. Our simulations were able to successfullyreproduce some of the processes controlling the mesoscale transport ofCO₂. A semi-quantitative comparison between simulations and dataallowed us to characterize how the coupling between mesoscale transport andsurface fluxes produced CO₂ spatial gradients in the domain. Temporalaverages in the simulated CO₂ field show a covariance between flux andtransport consisting of: 1) horizontally, a CO₂ deficit over land,mirrored by a CO₂ excess over the sea and 2) vertically, the prevalenceof a mean CO₂ depletion between 500 and 2000 m, and a permanentbuild-up of CO₂ in the lower levels.