Sources and sinks of CO2 at regional scales remain poorly understood. Part of the difficulty is our limited knowledge regarding the impacts of synoptic-scale weather (particularly cyclones at mid-latitudes) on terrestrial CO2 emission and atmospheric transport of CO2. About 10 years ago, the Vegetation Photosynthesis and Respiration Model (VPRM) was coupled into the Weather Research and Forecasting (WRF) model to simulate "weather aware" biospheric CO2 fluxes and subsequent transport. Such an online-coupling system (referred to as WRF-VPRM) can facilitate investigation of the impacts of weather on CO2.Ten years have passed, however, WRF-VPRM was barely evaluated over the contiguous United States. The Atmospheric Carbon and Transport-America (ACT-America) mission obtained comprehensive airborne and ground-based measurements of CO2 and meteorological variables over the eastern United States, providing an excellent dataset for evaluation of WRF-VPRM. In this study, atmospheric CO2 concentrations from the Carbon Tracker global simulations are used as boundary conditions for WRF-VPRM simulations with a resolution of 12 km over the contiguous United States for year 2016 and the downscaled CO2 is evaluated using the ACT-America measurements. Initial results show that WRF-VPRM reasonably simulates the diurnal and seasonal variation of CO2 fluxes and concentrations. The downscaling also successfully captures the passages of mid-latitude cyclones and shows interesting contrast of CO2 across fronts. Analysis of these WRF-VPRM downscaling results could help examine the sources and sinks of CO2 over the contiguous United States.WRF-VPRM was also used to investigate the CO2 fluxes, concentrations, and its budget in the Northeast China.