Intercomparison of Total Carbon Column Observing Network (TCCON) data from two Fourier transform spectrometers at Lauder, New Zealand

We describe the change in operational instrument for the routine measurement of column-averaged dry-air mole fraction of several greenhouse gases (denoted X-gas) at the Lauder Total Carbon Column Observing Network (TC-CON) site and the steps taken to demonstrate comparability between the two observation systems following a systematic methodology. Further, we intercompare retrieved X-gas values during an intensive intercomparison period during October and November 2018, when both instruments were performing optimally, and on subsequent, less frequent occasions. The average difference between the two observing systems was found to be well below the expected level of uncertainty for TCCON retrievals for all compared species. In the case of X-CO2 the average difference was 0.0264 +/- 0.0465% (0.11 +/- 0.19 mu mol mol(-1)).

Automated summary

This study describes a change in operational instrument for the routine measurement of column-averaged dry-air mole fraction of several greenhouse gases at the Lauder Total Carbon Column Observing Network site, and the steps taken to demonstrate comparability between the two observation systems. The intercomparison found that the average difference between the two observing systems was well below the expected level of uncertainty for TCCON retrievals for all compared species. The study specifically noted that for X-CO2, the average difference was 0.0264 +/- 0.0465% (0.11 +/- 0.19 mu mol mol(-1)).