Mesoscale covariance of transport and CO2 fluxes: Evidence from observations and simulations using the WRF-VPRM coupled atmosphere-biosphere model

We developed a modeling system which combines a mesoscale meteorological model, the Weather Research and Forecasting (WRF) model, with a diagnostic biospheric model, the Vegetation Photosynthesis and Respiration (VPRM). The WRF-VPRM modeling system was designed to realistically simulate high-resolution atmospheric CO₂ concentration fields. In the system, WRF takes into account anthropogenic and biospheric CO₂ fluxes and realistic initial and boundary conditions for CO₂ from a global model. The system uses several "tagged" tracers for CO₂ fields from different sources. VPRM uses meteorological fields from WRF and high-resolution satellite indices to simulate biospheric CO₂ fluxes with realistic spatiotemporal patterns. Here we present results from the application of the model for interpretation of measurements made within the CarboEurope Regional Experiment Strategy (CERES). Simulated fields of meteorological variables and CO₂ were compared against ground-based and airborne observations. In particular, the characterization by aircraft measurements turned out to be crucial for the model evaluation. The comparison revealed that the model is able to capture the main observed features in the CO₂ distribution reasonably well. The simulations showed that daytime CO₂ measurements made at coastal stations can be strongly affected by land breeze and subsequent sea breeze transport of CO₂ respired from the vegetation during the previous night, which can lead to wrong estimates when such data are used in inverse studies. The results also show that WRF-VPRM is an effective modeling tool for addressing the near-field variability of CO₂ fluxes and concentrations for observing stations around the globe.