How Carbon Dioxide Variability Changes with a Synoptic Weather Event

There would be more carbon dioxide (CO₂) in the atmosphere if it were not for the natural land sink over North America due to photosynthetic activity of plants. This study aims to understand the effects of synoptic weather events on CO₂ variability. It was investigated using the summer of 2010 measurements by first finding the day of frontal passage and then finding the corresponding hour of passage from available near-surface meteorological data. In situ CO₂ measurements were taken from the NOAA towers at WBI (Iowa), with measurements taken at 379 m above ground level (agl), and LEF (Wisconsin), with measurements taken at 396 m agl, to study diurnal cycles and then compare to the observations of the WRF model simulations. Between 1 June 2010 and 30 September 2010 there were nine frontal passages through both tower locations. WBI, which is surrounded by a corn belt, has larger variability around the time of frontal passage with amplitudes on the order of 35-45 ppm. LEF, which is surrounded by a forest, has variability around the time of frontal passage with amplitudes on the order of 15-25 ppm. Two days in August were then compared to the WRF model simulations to understand how well the model can detect the impact of frontal passages on CO₂ variability. The overall characteristics of the diurnal cycle pattern for both towers in the model were similar to the observations. Future studies focusing on measurements at similar geographic locations would help towards understanding the impact of frontal events on CO₂ variability.