High-frequency attenuation in eddy covariance measurements from the LI-7200 IRGA with various heating and filter configurations – a spectral correction approach

IF 5.6 1区农林科学 Q1 AGRONOMY

Agricultural and Forest Meteorology Pub Date : 2024-11-20 DOI:10.1016/j.agrformet.2024.110312

Jamie Smidt, Luise Wanner, Andreas Ibrom, HaPe Schmid, Matthias Mauder

{"title":"High-frequency attenuation in eddy covariance measurements from the LI-7200 IRGA with various heating and filter configurations – a spectral correction approach","authors":"Jamie Smidt, Luise Wanner, Andreas Ibrom, HaPe Schmid, Matthias Mauder","doi":"10.1016/j.agrformet.2024.110312","DOIUrl":null,"url":null,"abstract":"The use of (en)closed-path Infrared Gas Analysers (IRGA) in the measurement of Eddy Covariance (EC) fluxes results in inadvertent high-frequency tube attenuation due to diffusion and mixing of sampled gas inside the tube. The application of tube heating and installation of particulate filters along the tube length also contributes to high-frequency attenuation. The goal of this research is first, to quantify the attenuation effects of different tube heating and filter configurations on CO2 and H2O fluxes. And second, to present a modified power spectral approach (PSA) based on theoretical power spectra to calculate the effective cut-off frequency fc. Measurements for each experimental configuration were performed at an Integrated Carbon Observation System (ICOS) station equipped with the standard LI-7200 enclosed-path IRGA and Gill HS-50 3D sonic anemometer. Correction factors for each dataset were determined and implemented in post-processing. We found only very small attenuation effects of CO2 fluxes between the examined configurations. In agreement with previous studies, we found attenuation worsens with increasing relative humidity rH, in the fluxes of H2O. As expected, the highest (best) fc for H2O was found in the lowest examined rH class of 45-50 % with the configuration of heating on, no filter. The lowest (worst) fc for H2O was in the highest rH class of 90-95 % with the configuration of heating off with the 7 μm filter. Our results confirm that tube attenuation effects for the standard ICOS setup are negligible for CO2 and small for H2O, depending on tube heating settings and use of particulate filters. We also show that the post-processing of attenuation effects, especially for H2O, could improve the accuracy of long-term EC measurements. We recommend that this novel approach be considered by users of datasets collected with the LI-7200 enclosed-path IRGA.","PeriodicalId":50839,"journal":{"name":"Agricultural and Forest Meteorology","volume":"8 1","pages":""},"PeriodicalIF":5.6000,"publicationDate":"2024-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Agricultural and Forest Meteorology","FirstCategoryId":"97","ListUrlMain":"https://doi.org/10.1016/j.agrformet.2024.110312","RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"AGRONOMY","Score":null,"Total":0}

引用次数: 0

Abstract

The use of (en)closed-path Infrared Gas Analysers (IRGA) in the measurement of Eddy Covariance (EC) fluxes results in inadvertent high-frequency tube attenuation due to diffusion and mixing of sampled gas inside the tube. The application of tube heating and installation of particulate filters along the tube length also contributes to high-frequency attenuation. The goal of this research is first, to quantify the attenuation effects of different tube heating and filter configurations on CO₂ and H₂O fluxes. And second, to present a modified power spectral approach (PSA) based on theoretical power spectra to calculate the effective cut-off frequency fc. Measurements for each experimental configuration were performed at an Integrated Carbon Observation System (ICOS) station equipped with the standard LI-7200 enclosed-path IRGA and Gill HS-50 3D sonic anemometer. Correction factors for each dataset were determined and implemented in post-processing. We found only very small attenuation effects of CO₂ fluxes between the examined configurations. In agreement with previous studies, we found attenuation worsens with increasing relative humidity rH, in the fluxes of H₂O. As expected, the highest (best) f_c for H₂O was found in the lowest examined rH class of 45-50 % with the configuration of heating on, no filter. The lowest (worst) f_c for H₂O was in the highest rH class of 90-95 % with the configuration of heating off with the 7 μm filter. Our results confirm that tube attenuation effects for the standard ICOS setup are negligible for CO₂ and small for H₂O, depending on tube heating settings and use of particulate filters. We also show that the post-processing of attenuation effects, especially for H₂O, could improve the accuracy of long-term EC measurements. We recommend that this novel approach be considered by users of datasets collected with the LI-7200 enclosed-path IRGA.

查看原文本刊更多论文

采用不同加热和滤波器配置的 LI-7200 IRGA 涡度协方差测量中的高频衰减--光谱校正方法

使用（封闭）路径红外气体分析仪（IRGA）测量涡度协方差（EC）通量时，由于采样气体在管内的扩散和混合，会无意中造成管内高频衰减。管道加热和沿管道长度安装微粒过滤器也会造成高频衰减。本研究的目标首先是量化不同管道加热和过滤器配置对 CO2 和 H2O 通量的衰减影响。其次，提出一种基于理论功率谱的改进功率谱方法 (PSA)，以计算有效截止频率 fc。每种实验配置的测量都是在配备了标准 LI-7200 封闭路径 IRGA 和 Gill HS-50 三维声波风速计的综合碳观测系统（ICOS）站上进行的。每个数据集的校正因子都已确定，并在后处理中实施。我们发现，在所研究的配置之间，二氧化碳通量的衰减效应非常小。与之前的研究一致，我们发现随着相对湿度 rH 的增加，H2O 通量的衰减也会加剧。正如我们所预期的那样，H2O 的最高（最佳）fc 出现在相对湿度最低的 45-50% 等级中，配置为加热，无过滤器。在关闭加热和 7 μm 过滤器的配置下，H2O 的 fc 最低（最差），在最高 rH 等级中为 90-95%。我们的结果证实，在标准 ICOS 设置中，根据管道加热设置和微粒过滤器的使用情况，管道衰减对 CO2 的影响可以忽略不计，对 H2O 的影响较小。我们还表明，对衰减效应（尤其是对 H2O 的衰减效应）进行后处理可提高长期导电率测量的准确性。我们建议使用 LI-7200 封闭路径 IRGA 采集数据集的用户考虑采用这种新方法。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

求助全文

约1分钟内获得全文求助全文

来源期刊

Agricultural and Forest Meteorology 农林科学-林学

CiteScore

10.30

自引率

9.70%

发文量

415

审稿时长

69 days

期刊介绍： Agricultural and Forest Meteorology is an international journal for the publication of original articles and reviews on the inter-relationship between meteorology, agriculture, forestry, and natural ecosystems. Emphasis is on basic and applied scientific research relevant to practical problems in the field of plant and soil sciences, ecology and biogeochemistry as affected by weather as well as climate variability and change. Theoretical models should be tested against experimental data. Articles must appeal to an international audience. Special issues devoted to single topics are also published. Typical topics include canopy micrometeorology (e.g. canopy radiation transfer, turbulence near the ground, evapotranspiration, energy balance, fluxes of trace gases), micrometeorological instrumentation (e.g., sensors for trace gases, flux measurement instruments, radiation measurement techniques), aerobiology (e.g. the dispersion of pollen, spores, insects and pesticides), biometeorology (e.g. the effect of weather and climate on plant distribution, crop yield, water-use efficiency, and plant phenology), forest-fire/weather interactions, and feedbacks from vegetation to weather and the climate system.