Ground-based Remote Sensing of Carbon Dioxide, Carbon Monoxide and Methane on Ascension Island Using Fourier Transform Infrared Spectroscopy

In May, 2012, a remote sensing observatory for performing ground-based total column measurements was established on Ascension Island (7.93AAdegreeS, 14.39AAdegreeW) in the South Atlantic Ocean. Since then measurements of greenhouse gases such as CO2 and CH4 and other gases are conducted in the framework of the Total Carbon Column Observing Network (TCCON). The time series of the measurements of CO2, CH4 and CO (denoted as XCO2, XCH4 and XCO, respectively) now comprise more than five years. A detailed analysis for all time series is shown here. Other data sets like aircraft profiles and in situ data are also used for interpreting the results. The time series of XCO2 is influenced by fluxes from both hemispheres. For CH4, the main finding is an atypical positive gradient with increasing altiude which can be attributed to transport from the continents and the trade wind inversion occuring around Ascension. The time series of XCO allows the detection of the two biomass burning seasons of the Africa.