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. We present a10-year (January 2007–December 2016) time series of continuous in situmeasurements of methane ( CH4 ), carbon monoxide (CO) and nitrousoxide ( N2O ) made by an in situ Fourier transform infrared tracegas and isotope analyser (FTIR) operated at Lauder, New Zealand (45.04 S,169.68 E, 370 m a. m. s. l.). Being the longest continuous deployedoperational FTIR system of this type, we are in an ideal position to performa practical evaluation of the multi-year performance of the analyser. Theoperational methodology, measurement precision, reproducibility, accuracy andinstrument reliability are reported. We find the FTIR has a measurement repeatability of the order of 0.37 ppb(1 σ standard deviation) for CH4 , 0.31 ppb for CO and0.12 ppb for N2O . Regular target cylinder measurements provide areproducibility estimate of 1.19 ppb for CH4 , 0.74 ppb for CO and0.27 ppb for N2O . FTIR measurements are compared to co-locatedambient air flask samples acquired at Lauder since May 2009, which allows along-term assessment of the FTIR data set across annual and seasonalcomposition changes. Comparing FTIR and co-located flask measurements showthat the bias (FTIR minus flask) for CH4 of −1.02 ±  2.61 ppb and CO of −0.43 ±  1.60 ppb are within the GlobalAtmospheric Watch (GAW)-recommended compatibility goals of 2 ppb. The N2O FTIR flask bias of −0.01 ±  0.77 ppb is within the GAW-recommended compatibility goals of 0.1 ppb and should be viewed as aserendipitous result due to the large standard deviation along with knownsystematic differences in the measurement sets. Uncertainty budgets for eachgas are also constructed based on instrument precision, reproducibility andaccuracy. In the case of CH4 , systematic uncertainty dominates,whilst for CO and N2O it is comparable to the random uncertaintycomponent. The long-term instrument stability, precision estimates and flask comparisonresults indicate the FTIR CH4 and CO time series meet the GAWcompatibility recommendations across multiple years of operation (andinstrument changes) and are sufficient to capture annual trends and seasonalcycles observed at Lauder. The differences between FTIR and flask N2O measurements need to be reconciled. Trend analysis of the10-year time series captures seasonal cycles and the secular upward trend of CH4 and N2O . The CH4 and CO time series havethe required precision and accuracy at a high enough temporal resolution tobe used in inversion models in a data-sparse region of the world.

atmospheric measurement techniques

A decade of CH&amp;lt;sub&amp;gt;4&amp;lt;/sub&amp;gt;, CO and N&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;O in situ measurements at Lauder, New Zealand: assessing the long-term performance of a Fourier transform infrared trace gas and isotope analyser