Seasonal and Synoptic Patterns of CO2 Distribution in the North American Continental Boundary Layer

Open Access
Ricciardi, Michelle Elizabeth
Graduate Program:
Master of Science
Document Type:
Master Thesis
Date of Defense:
July 07, 2011
Committee Members:
  • Ken Davis, Thesis Advisor
  • Kenneth James Davis, Thesis Advisor
  • Regional CO2 Distribution; North America CO2; Boun
The increasly dense global CO2 measurement network is expanding, enabling us to capture local fluctuations of CO2 across North America. For this study, continuous CO2 mixing ratio data are gathered across the North American continent in the United States and Southern Canada at 36 land-based measurement sites in 2008. These towers are further divided into two categories in order to distinguish those with a possible urban influence from their environment. Flask measurements obtained along 30°N latitude in the Pacific Ocean and between 3 and 8 km above ground level (agl) at 15 North American aircraft sites are used to estimate boundary layer conditions in the marine boundary layer (MBL) and free troposphere (FT), respectively. MBL and FT CO2 mixing ratios, as well as reliable daytime observations from the highest land-based measurement levels, have been averaged for each day of the year and clearly reveal five distinct seasonal patterns. The sites are separated into regions according to similarities in phasing, amplitude, and seasonal patterns of CO2 mixing ratios: East, Southeast, Mid-Continent, Northwest, and West. An estimate of the CO2 mixing ratio per day for each region is computed by taking the mean of the daily average of all sites in the region for each day of the year. When the results are compared across regions, low regional variability is found during the periods of January to April and October to December. The Mid-Continental Region is characterized by a large decrease in CO2 during the summer months while the Southeast and West are characterized by low yearly variability. A decrease in CO2 is observed during the same time period in the East and Northwest, but the drawdown in the Eastern Region is slightly larger and more significant than that in the Northwest. An analysis of synoptic weather events and regional variance reveals an association between CO2 mixing ratios and frontal systems. Regional variance tends to be larger in the presence of fronts than in the absence of fronts and CO2 mixing ratios are more apt to be higher ahead of frontal systems than behind them. Seasonal patterns of CO2 mixing ratios and their relationship to synoptic weather systems provide insight into the location and mechanisms of sources and sinks in the temperate biosphere of the north latitude ecosystems.