Abstract Across networks of cold weather sites, eddy covariance measurements of ecosystem fluxes commonly indicate carbon uptake throughout winter, a problem that has been linked to open-path infrared gas analyzer (IRGA) self-heating. Though there is no definitive consensus about this phenomenon, the de facto correction for the prevalent LI-7500 is the methodology of Burba et al. (2008) (B08), which predicts self-heating from IRGA surface temperatures and boundary layers. In this paper we examine the validity of this model compared to an updated correction by conducting field studies with the LI-7500 and an IRGA designed by the National Oceanic and Atmospheric Administration (NOAA). Both types of sensors were instrumented to measure sensible heat flux within the instrument path and temperatures of key instrument surfaces. We test hypotheses that (1) considerable IRGA self-heating occurs at a cold, windy, high elevation, mountainous field site, (2) unwarranted boundary layer adjustment terms defined in B08 reduce the bottom and top surface heat fluxes by an order of magnitude, and (3) the weighted sum of the surface heat fluxes should be proportional to their surface area contribution to the IRGA measurement volume. We detected more sensible heat flux within the LI7500 path than outside of it (statistical slopes between 0.95 to 1.3 and offsets between 0 and 35 W m−2) with the largest discrepancies occurring during the day and in winter. The NOAA IRGA has a similar structure to the LI-7500, but with flat surfaces that do not warrant the boundary layer adjustment terms in B08. Bayesian analyses indicated the bottom and top surface heat flux weightings from B08 are improbable and an order of magnitude too large. For the LI-7500, when the boundary layer adjustment terms were omitted the B08 weightings were also improbable; by including these terms and using the new weightings, self-heating estimates were reasonable only because the bottom and top sensible heat fluxes became negligible. We conclude that it is likely the B08 self-heating correction has two errors that roughly cancel out at our field site; this should not generally be expected. The new formulation emphasizes the role of the spar in self-heating, which should be taken into consideration for all cold-weather installations regardless of how the IRGA is mounted.

中文翻译：

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开路红外气体分析仪自热校正的新视角

摘要 在寒冷天气站点网络中，生态系统通量的涡流协方差测量通常表明整个冬季的碳吸收，这一问题与开路红外气体分析仪 (IRGA) 自加热有关。尽管对此现象没有明确的共识，但对普遍存在的 LI-7500 的实际修正是 Burba 等人的方法。(2008) (B08)，根据 IRGA 表面温度和边界层预测自热。在本文中，我们通过使用 LI-7500 和美国国家海洋和大气管理局 (NOAA) 设计的 IRGA 进行实地研究，来检验该模型与更新的校正相比的有效性。两种类型的传感器都用于测量仪器路径内的显热通量和关键仪器表面的温度。我们检验了以下假设：(1) 在寒冷、多风、高海拔、多山的野外场地发生相当大的 IRGA 自热，(2) B08 中定义的无根据的边界层调整项将底部和顶部表面热通量降低了一个数量级, (3) 表面热通量的加权总和应与其表面积对 IRGA 测量体积的贡献成正比。我们在 LI7500 路径内检测到比其外更多的显热通量（统计斜率在 0.95 到 1.3 之间，偏移在 0 到 35 W m-2 之间），最大的差异发生在白天和冬天。NOAA IRGA 具有与 LI-7500 类似的结构，但其平面不保证 B08 中的边界层调整条款。贝叶斯分析表明来自 B08 的底部和顶部表面热通量权重是不可能的，并且一个数量级太大。对于 LI-7500，当省略边界层调整项时，B08 权重也不太可能；通过包括这些项并使用新的权重，自热估计是合理的，因为底部和顶部显热通量变得可以忽略不计。我们得出的结论是，B08 自热修正很可能有两个错误，在我们的现场现场大致抵消了；这通常不应该被预料到。新配方强调了翼梁在自热中的作用，无论 IRGA 如何安装，所有寒冷天气安装都应考虑到这一点。当省略边界层调整项时，B08 权重也不太可能；通过包括这些项并使用新的权重，自热估计是合理的，因为底部和顶部显热通量变得可以忽略不计。我们得出的结论是，B08 自热修正很可能有两个错误，在我们的现场现场大致抵消了；这通常不应该被预料到。新配方强调了翼梁在自热中的作用，无论 IRGA 如何安装，所有寒冷天气安装都应考虑到这一点。当省略边界层调整项时，B08 权重也不太可能；通过包括这些项并使用新的权重，自热估计是合理的，因为底部和顶部显热通量变得可以忽略不计。我们得出的结论是，B08 自热修正很可能有两个错误，在我们的现场现场大致抵消了；这通常不应该被预料到。新配方强调了翼梁在自热中的作用，无论 IRGA 如何安装，所有寒冷天气安装都应考虑到这一点。我们得出的结论是，B08 自热修正很可能有两个错误，在我们的现场现场大致抵消了；这通常不应该被预料到。新配方强调了翼梁在自热中的作用，无论 IRGA 如何安装，所有寒冷天气安装都应考虑到这一点。我们得出的结论是，B08 自热修正很可能有两个错误，在我们的现场现场大致抵消了；这通常不应该被预料到。新配方强调了翼梁在自热中的作用，无论 IRGA 如何安装，所有寒冷天气安装都应考虑到这一点。