Tackling oxygen optode drift: Near-surface and in-air oxygen optode measurements on a float provide an accurate in-situ reference
Tackling oxygen optode drift: Near-surface and in-air oxygen optode measurements on a float provide an accurate in-situ reference
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DOI：
10.1175/jtech-d-14-00162.1
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发表时间：
2015-08
影响因子：
2.2
通讯作者：
H. Bittig;A. Körtzinger
中科院分区：
文献类型：
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作者：
H. Bittig;A. Körtzinger
在储存/运输过程中，（某些）氧光学传感器出现了一种尚未解释清楚的漂移现象，因此与工厂/实验室校准出现了显著偏差，这一直是自主氧观测的一个主要障碍。光学传感器漂移似乎是系统性的，主要是由于氧敏感性降低而产生的斜率效应。一小部分原因是发光体寿命缩短，这导致了一个小的正偏移。一个可靠的原位参考对于校正这种漂移至关重要。传统上，这需要基于船舶的参考测量，这对机会性浮标部署带来了一些挑战。本研究提出了一种易于实施的替代方法，即使用安装在10厘米杆上的安德拉（Aanderaa）光学传感器进行近表面/空气中的测量，并将其与更传统的方法（工厂校准、实验室校准和原位部署校准）进行比较。空气中的样本显示出一种取决于水饱和度的系统性偏差，这很可能是由标准高度杆式光学传感器偶尔浸入水中造成的。测量的空气中过饱和度与水中过饱和度的线性回归（利用辅助气象数据来确定饱和度水平）有力地消除了这种偏差，从而提供了一种在仪器整个使用寿命期间都可用的精确（0.2%）且准确（1%）的原位校正方法。
A yet unexplained drift of (some) oxygen optodes during storage/transport and thus significant deviations from factory/laboratory calibrations have been a major handicap for autonomous oxygen observations. Optode drift appears to be systematic and is predominantly a slope effect due to reduced oxygen sensitivity. A small contribution comes from a reduced luminophore lifetime, which causes a small positive offset. A reliable in situ reference is essential to correct such a drift. Traditionally, this called for a ship-based reference cast, which poses some challenges for opportunistic float deployments. This study presents an easily implemented alternative using near-surface/in-air measurements of an Aanderaa optode on a 10-cm stalk and compares it to the more traditional approaches (factory, laboratory, and in situ deployment calibration). In-air samples show a systematic bias depending on the water saturation, which is likely caused by occasional submersions of the standard-height stalk optode. Linear regression of measured in-air supersaturation against in-water supersaturation (using ancillary meteorological data to define the saturation level) robustly removes this bias and thus provides a precise (0.2%) and accurate (1%) in situ correction that is available throughout the entire instrument’s lifetime.