Sensors that use ultraviolet (UV) light absorption to measure nitrate in seawater at in situ temperatures require a correction to the calibration coefficients if the calibration and sample temperatures are not identical. This is mostly due to the bromide molecule, which absorbs more UV light as temperature increases. The current correction applied to in situ ultraviolet spectrophotometer (ISUS) and submersible ultraviolet nitrate analyzer (SUNA) nitrate sensors generally follows Sakamoto et al. (2009, Limnol. Oceanogr. Methods 7, 132–143). For waters warmer than the calibration temperature, this correction model can lead to a 1–2 μmol kg⁻¹ positive bias in nitrate concentration. Here we present an updated correction model, which reduces this small but noticeable bias by at least 50%. This improved model is based on additional laboratory data and describes the temperature correction as an exponential function of wavelength and temperature difference from the calibration temperature. It is a better fit to the experimental data than the current model and the improvement is validated using two populations of nitrate profiles from Biogeochemical Argo floats navigating through tropical waters. One population is from floats equipped with ISUS sensors while the other arises from floats with SUNA sensors on board. Although this model can be applied to both ISUS and SUNA nitrate sensors, it should not be used for OPUS UV nitrate sensors at this time. This new approach is similar to that used for OPUS sensors (Nehir et al., 2021, Front. Mar. Sci. 8, 663800) with differing model coefficients. This difference suggests that there is an instrumental component to the temperature correction or that there are slight differences in experimental methodologies.

中文翻译：

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使用原位紫外分光光度计和潜水式紫外硝酸盐分析仪硝酸盐传感器计算海水硝酸盐的更新温度校正

如果校准温度和样品温度不相同，则使用紫外 (UV) 光吸收在原位温度下测量海水中硝酸盐的传感器需要对校准系数进行修正。这主要是由于溴化物分子，随着温度升高，溴化物分子吸收更多的紫外线。当前应用于原位紫外分光光度计（ISUS）和潜水式紫外硝酸盐分析仪（SUNA）硝酸盐传感器的校正通常遵循 Sakamoto 等人的方法。(2009, Limnol. Oceanogr. 方法 7, 132–143)。对于比校准温度高的水体，该校正模型可能导致硝酸盐浓度出现 1–2  μ mol kg ^-1正偏差。在这里，我们提出了一个更新的校正模型，它将这种微小但明显的偏差减少了至少 50%。该改进模型基于额外的实验室数据，并将温度校正描述为波长和与校准温度的温差的指数函数。它比当前模型更适合实验数据，并且使用来自热带水域的生物地球化学 Argo 浮标的两组硝酸盐剖面来验证改进。一组来自配备 ISUS 传感器的浮标，而另一组来自配备 SUNA 传感器的浮标。虽然该模型可以应用于 ISUS 和 SUNA 硝酸盐传感器，但目前不应该用于 OPUS UV 硝酸盐传感器。这种新方法与用于 OPUS 传感器的方法类似（Nehir et al., 2021, Front. Mar. Sci. 8, 663800），但模型系数不同。这种差异表明温度校正存在仪器成分，或者实验方法存在细微差异。