Measurements of carbon dioxide on very tall towers: results of the NOAA/CMDL program

Measurements of carbon dioxide (CO2) mixing ratios have been carried out si nce 1992 on a 610-m tall communications tower in North Carolina and since 1 994 on a 447-m tall tower in Wisconsin. The data provide insights into the influence of pollution (fossil fuel combustion), biological exchange, bound ary layer dynamics, and advective transport on CO2 mixing ratios over the c ontinents. In this paper, we provide an overview of the data, describe acce ss to the data, and suggest ways in which these results could be used to im prove simulations of the global carbon cycle. In particular, the data will be very useful to constrain model estimates of covariance between terrestri al ecosystem fluxes of CO2 and diurnal and seasonal variations of planetary boundary layer mixing.