Revised methodology for CO<sub>2</sub> and CH<sub>4</sub> measurements at remote sites using a working standard-gas-saving system
<p>We have revised a calculation method of mole fractions and uncertainties for in situ CO<span class="inline-formula"><sub>2</sub></span> and CH<span class="inline-formula"><sub>4</sub></span> measurements with a working stan...
Saved in:
| Main Authors: | , , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2025-04-01
|
| Series: | Atmospheric Measurement Techniques |
| Online Access: | https://amt.copernicus.org/articles/18/1717/2025/amt-18-1717-2025.pdf |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| Summary: | <p>We have revised a calculation method of mole fractions and uncertainties for in situ CO<span class="inline-formula"><sub>2</sub></span> and CH<span class="inline-formula"><sub>4</sub></span> measurements with a working standard-gas-saving system. It uses on-site compressed air to track the baseline drift of sensors. The Japan–Russia Siberian Tall Tower Inland Observation Network (JR-STATION) is made up of this system, which was installed across nine different sites in Siberia. The system acquires semi-continuous data by alternating between sampling air from multiple altitudes through switched flow paths and recording several minutes of averaged data for each altitude. We estimated the sensor repeatability (<span class="inline-formula"><i>u</i><sub>r</sub></span>) based on the measurement of on-site compressed air. The <span class="inline-formula"><i>u</i><sub>r</sub></span> for CO<span class="inline-formula"><sub>2</sub></span> and CH<span class="inline-formula"><sub>4</sub></span> was mostly around 0.05 ppm and below 5 ppb, respectively. The combined standard uncertainties <span class="inline-formula">(<i>u</i><sub>c</sub>(<i>x</i>))</span> of time-averaged ambient air measurements were sometimes higher than the <span class="inline-formula"><i>u</i><sub>r</sub></span> for each period because the data included atmospheric variability during the measurement period of several minutes. Data users should consider the difference between the <span class="inline-formula"><i>u</i><sub>r</sub></span> and <span class="inline-formula"><i>u</i><sub>c</sub>(<i>x</i>)</span> to select optimal data, depending on their focusing spatial scale. The CO<span class="inline-formula"><sub>2</sub></span> and CH<span class="inline-formula"><sub>4</sub></span> data measured with a non-dispersive infrared (NDIR) analyzer and a tin dioxide sensor (TOS) exhibited good agreement with those measured by cavity ring-down spectroscopy (CRDS).</p> |
|---|---|
| ISSN: | 1867-1381 1867-8548 |