High-resolution WRF/Chem-VPRM simulations of CO2 in the Los Angeles Basin

Accurate representation of the mesoscale transport is imperative for improved estimates of regional and global biospheric CO2 sources and sinks derived from inverse modeling. This can only be addressed with high-resolution mesoscale models that include online transport of CO2 and biosphere-atmosphere exchange fluxes of CO2. We couple WRF/Chem with the Vegetation Photosynthesis and Respiration Model (VPRM) and apply the model to simulate atmospheric CO2 in the Los Angeles Basin during the intensive period of May-June 2010 of the CalNex field experiment. CO2 is treated as passive tracers in the WRF/Chem model. CO2 fields from the GEOS-Chem global model are used for initialization and lateral boundary conditions. Model simulated CO2 concentrations are compared with ground-based measurements at CalNex-LA and aircraft measurements from the NOAA P3B, focusing on the diurnal cycle of CO2 and the effect of land-sea breeze and complex topography on the spatiotemporal gradients of CO2. Additionally, model simulated CO2 columns are compared with Fourier Transform Spectrometer (FTS) column CO2 measurements at Mt. Wilson located at the northern edge of the Los Angeles Basin. Exploratory comparisons with satellite observations of CO2 from GOSAT (Greenhouse Gases Observing SATellite) are also shown.