Observed features of salinity bias with negative pressure dependency for measurements by SBE 41CP and SBE 61 CTD sensors on deep profiling floats
Observed features of salinity bias with negative pressure dependency for measurements by SBE 41CP and SBE 61 CTD sensors on deep profiling floats
复制标题
深剖面浮标上 SBE 41CP 和 SBE 61 CTD 传感器测量的盐度偏差与负压依赖性的观测特征
DOI：
10.1016/j.pocean.2021.102686
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发表时间：
2021
影响因子：
4.1
通讯作者：
B. King
中科院分区：
文献类型：
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作者：
Taiyo Kobayashi;Kanako Sato;B. King
SBE 41CP和SBE 61电导率-温度-深度（CTD）传感器在深水浮子上测量的盐度，通过与部署时的船载CTD铸造进行比较，在验证温度和压力不太可能存在偏差后进行评估。含盐量偏倚与负压相关，表示为asΔS=ΔSoffset+ap×pressureandap< 0，即使在第一个剖面中也被统计地识别出来。对于SBE 61传感器，平均依赖系数为- 0.54 × 10−6dbar - 1andΔSoffsetwas略为正（+0.8 × 10−3）。SBE 41CP传感器的结果显示出更严重的依赖性：平均分别为apandΔSoffsetwere−1.80 × 10−6dbar−1和−0.012。两种传感器的负性均有统计学意义。对于SBE 41CP，具有fresherΔSoffsettended的传感器具有较小的边框。SBE 41CP的新鲜盐度偏差随着时间的推移而向盐水倾斜，主要是becauseΔSoffsetbecame更少的新鲜，并且速率递减。长期以来，大多数传感器都期望稳定，但有时会在前几个配置文件中增加到特定值。同时，对于SBE 61传感器，这些指标在较长时期内似乎相当稳定。大多数Argo浮子具有SBE 41/41CP CTD传感器，这是深水浮子的原始CTD模型。对383个Argo浮标数据的分析并没有发现盐度对压力的显著依赖性。综上所述，SBE 41CP和SBE 61 CTD传感器在目前的状态下，由于盐度偏差，通常不能满足deep Argo的盐度目标精度。本研究表明，通过以下改进，两种CTD传感器几乎可以达到目标精度：对传感器进行高压老化处理，对压力老化传感器进行精确校准，以及适当的压力抵消因子（CPcor； SBE 41CP为- 12.6 × 10 - 8dbar−1，SBE 61为- 11.0 × 10 - 8dbar−1）。这些操作可以大大减少由压力依赖性、海面偏移及其随时间变化引起的盐度偏差。
The salinity measured by SBE 41CP and SBE 61 conductivity-temperature-depth (CTD) sensors on deep floats was evaluated by comparison with shipboard CTD casts at deployment, after temperature and pressure were verified as unlikely to be biased. Salinity biases with a negative pressure dependency, expressed asΔS=ΔSoffset+ap×pressureandap< 0, were identified statistically even in the first profiles. For SBE 61 sensors, the average dependency coefficientapwas −0.54 × 10−6dbar−1andΔSoffsetwas slightly positive (+0.8 × 10−3). The results for SBE 41CP sensors showed a more severe dependency:apandΔSoffsetwere −1.80 × 10−6dbar−1and −0.012 on average, respectively. Theapnegativity was statistically significant for both sensors. For SBE 41CP, sensors with a fresherΔSoffsettended to have a smallerap. The fresh salinity bias found for SBE 41CP changed toward saline over time, mainly becauseΔSoffsetbecame less fresh with a decreasing rate. Stableapfor a long time was expected for the majority of sensors, but sometimesapincreased to a specific value within the first several profiles. Meanwhile, for SBE 61 sensors, these indicators seemed fairly stable for a longer period. Most Argo floats had the SBE 41/41CP CTD sensor, which was the original CTD model for deep floats. An analysis of data from 383 Argo floats did not identify a statistically significant pressure dependency for salinity. Conclusively, the SBE 41CP and SBE 61 CTD sensors on deep floats, in their present states, generally did not meet the target accuracy of Deep Argo for salinity due to the salinity bias. The present study suggests that both CTD sensors could almost achieve the target accuracy by the following improvements: aging treatment with high pressure on the sensor, accurate calibration of pressure-aged sensors, and a suitable canceling factor for pressure (CPcor; −12.6 × 10−8dbar−1for SBE 41CP and −11.0 × 10−8dbar−1for SBE 61). These operations can greatly reduce the salinity biases derived from the pressure dependency, the offset at the sea surface, and their changes over time.