What is the concentration footprint of a tall tower?

摘要: Studies that have attempted to estimate sources and sinks of trace gases such as CO2 with inverse calculations unanimously identify the lack continental stations a prime obstacle. Continental traditionally been avoided because difficulty interpretation due large time-variability substance mixing ratios. Large variability is caused by proximity strongly variable in space time complicated airflow within lowermost 100–200 m planetary boundary layer. To address need for overcome problems associated them, National Oceanic Atmospheric Administration Climate Monitoring Diagnostics Laboratory started 1992 measure other on tall television transmission towers [Bakwin et al., 1995]. An essential question connection these tower measurements area around from which fluxes substantially contribute observed short-term gas We present here simple data back trajectory-based method fraction explained localized flux Wisconsin dependence its location relative (the concentration “footprint”). find timescale over imprint surface air parcels before arrival at are still discernible ratio variations order 1.5 days. Based this characteristics parcel trajectories, we infer spatial extent footprint 106 km2, or roughly tenth United States. This encouraging evidence may be useful global inversions also implications monitoring anthropogenic substances regional scales.