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Abstract. Due to its remote location and extreme weather conditions, atmospheric in situmeasurements are rare in the Southern Ocean. As a result, aerosol–cloudinteractions in this region are poorly understood and remain a major source ofuncertainty in climate models. This, in turn, contributes substantially topersistent biases in climate model simulations such as the well-known positiveshortwave radiation bias at the surface, as well as biases in numericalweather prediction models and reanalyses. It has been shown in previousstudies that in situ and ground-based remote sensing measurements across theSouthern Ocean are critical for complementing satellite data sets due to theimportance of boundary layer and low-level cloud processes. These processesare poorly sampled by satellite-based measurements and are often obscured bymultiple overlying cloud layers. Satellite measurements also do not constrainthe aerosol–cloud processes very well with imprecise estimation of cloudcondensation nuclei. In this work, we present a comprehensive set of ship-basedaerosol and meteorological observations collected on the 6-weekSouthern Ocean Ross Sea Marine Ecosystem and Environment voyage(TAN1802) voyage of RV Tangaroa across the Southern Ocean, from Wellington, New Zealand, tothe Ross Sea, Antarctica. The voyage was carried out from 8 February to21 March 2018. Many distinct, but contemporaneous, data sets were collectedthroughout the voyage. The compiled data sets include measurements from arange of instruments, such as (i) meteorological conditions at the sea surfaceand profile measurements; (ii) the size and concentration of particles; (iii)trace gases dissolved in the ocean surface such as dimethyl sulfide andcarbonyl sulfide; (iv) and remotely sensed observations of low clouds. Here,we describe the voyage, the instruments, and data processing, and provide a briefoverview of some of the data products available. We encourage the scientificcommunity to use these measurements for further analysis and model evaluationstudies, in particular, for studies of Southern Ocean clouds, aerosol, andtheir interaction. The data sets presented in this study are publiclyavailable at https://doi.org/10.5281/zenodo.4060237 (Kremser et al., 2020). 

Abstract. Large-scale climatic forcing is impactingoceanic biogeochemical cycles and is expected to influence the water-columndistribution of trace gases, including methane and nitrous oxide. Our abilityas a scientific community to evaluate changes in the water-column inventoriesof methane and nitrous oxide depends largely on our capacity to obtain robustand accurate concentration measurements that can be validated acrossdifferent laboratory groups. This study represents the first formalinternational intercomparison of oceanic methane and nitrous oxidemeasurements whereby participating laboratories received batches of seawatersamples from the subtropical Pacific Ocean and the Baltic Sea. Additionally,compressed gas standards from the same calibration scale were distributed tothe majority of participating laboratories to improve the analytical accuracyof the gas measurements. The computations used by each laboratory to derivethe dissolved gas concentrations were also evaluated for inconsistencies(e.g., pressure and temperature corrections, solubility constants). Theresults from the intercomparison and intercalibration provided invaluableinsights into methane and nitrous oxide measurements. It was observed thatanalyses of seawater samples with the lowest concentrations of methane andnitrous oxide had the lowest precisions. In comparison, while the analyticalprecision for samples with the highest concentrations of trace gases wasbetter, the variability between the different laboratories was higher:36% for methane and 27% for nitrous oxide. In addition, thecomparison of different batches of seawater samples with methane and nitrousoxide concentrations that ranged over an order of magnitude revealed theramifications of different calibration procedures for each trace gas.Finally, this study builds upon the intercomparison results to developrecommendations for improving oceanic methane and nitrous oxide measurements,with the aim of precluding future analytical discrepancies betweenlaboratories.