Optimal use of buffer volumes for the measurement of atmospheric gas concentration in multi-point systems
Accurate multi-point monitoring systems are required to derive atmospheric measurements of greenhouse gas concentrations both for the calculation of surface fluxes with inversion transport models and for the estimation of non-turbulent components of the mass balance equation (i.e. advection and stor...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2016-09-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | http://www.atmos-meas-tech.net/9/4665/2016/amt-9-4665-2016.pdf |
| _version_ | 1811191790418526208 |
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| author | A. Cescatti B. Marcolla I. Goded C. Gruening |
| author_facet | A. Cescatti B. Marcolla I. Goded C. Gruening |
| author_sort | A. Cescatti |
| collection | DOAJ |
| description | Accurate multi-point monitoring systems are required to
derive atmospheric measurements of greenhouse gas concentrations both for
the calculation of surface fluxes with inversion transport models and for
the estimation of non-turbulent components of the mass balance equation
(i.e. advection and storage fluxes) at eddy covariance sites. When a single
analyser is used to monitor multiple sampling points, the deployment of
buffer volumes (BVs) along sampling lines can reduce the uncertainty due to
the discrete temporal sampling of the signal. In order to optimize the use
of buffer volumes we explored various set-ups by simulating their effect on
time series of high-frequency CO<sub>2</sub> concentration collected at three Fluxnet
sites. Besides, we proposed a novel scheme to calculate half-hourly weighted
arithmetic means from discrete point samples, accounting for the
probabilistic fraction of the signal generated in the averaging period.
Results show that the use of BVs with the new averaging scheme reduces the
mean absolute error (MAE) up to 80 % compared to a set-up without BVs and up
to 60 % compared to the case with BVs and a standard, non-weighted
averaging scheme. The MAE of CO<sub>2</sub> concentration measurements was observed to
depend on the variability of the concentration field and on the size of BVs,
which therefore have to be carefully dimensioned. The optimal volume size
depends on two main features of the instrumental set-up: the number of
measurement points and the time needed to sample at one point (i.e. line
purging plus sampling time). A linear and consistent relationship was
observed at all sites between the sampling frequency, which summarizes the
two features mentioned above, and the renewal frequency associated with the
volume. Ultimately, this empirical relationship can be applied to estimate
the optimal volume size according to the technical specifications of the
sampling system. |
| first_indexed | 2024-04-11T23:42:52Z |
| format | Article |
| id | doaj.art-01b2ecfb2757420fa23c7b73a6f12c00 |
| institution | Directory Open Access Journal |
| issn | 1867-1381 1867-8548 |
| language | English |
| last_indexed | 2024-04-11T23:42:52Z |
| publishDate | 2016-09-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Measurement Techniques |
| spelling | doaj.art-01b2ecfb2757420fa23c7b73a6f12c002022-12-22T03:56:45ZengCopernicus PublicationsAtmospheric Measurement Techniques1867-13811867-85482016-09-01994665467210.5194/amt-9-4665-2016Optimal use of buffer volumes for the measurement of atmospheric gas concentration in multi-point systemsA. Cescatti0B. Marcolla1I. Goded2C. Gruening3European Commission, Joint Research Centre, Ispra, ItalyFondazione Edmund Mach, IASMA Research and Innovation Centre, Sustainable Agro-ecosystems and Bio-resources Department, San Michele all'Adige (TN), ItalyEuropean Commission, Joint Research Centre, Ispra, ItalyEuropean Commission, Joint Research Centre, Ispra, ItalyAccurate multi-point monitoring systems are required to derive atmospheric measurements of greenhouse gas concentrations both for the calculation of surface fluxes with inversion transport models and for the estimation of non-turbulent components of the mass balance equation (i.e. advection and storage fluxes) at eddy covariance sites. When a single analyser is used to monitor multiple sampling points, the deployment of buffer volumes (BVs) along sampling lines can reduce the uncertainty due to the discrete temporal sampling of the signal. In order to optimize the use of buffer volumes we explored various set-ups by simulating their effect on time series of high-frequency CO<sub>2</sub> concentration collected at three Fluxnet sites. Besides, we proposed a novel scheme to calculate half-hourly weighted arithmetic means from discrete point samples, accounting for the probabilistic fraction of the signal generated in the averaging period. Results show that the use of BVs with the new averaging scheme reduces the mean absolute error (MAE) up to 80 % compared to a set-up without BVs and up to 60 % compared to the case with BVs and a standard, non-weighted averaging scheme. The MAE of CO<sub>2</sub> concentration measurements was observed to depend on the variability of the concentration field and on the size of BVs, which therefore have to be carefully dimensioned. The optimal volume size depends on two main features of the instrumental set-up: the number of measurement points and the time needed to sample at one point (i.e. line purging plus sampling time). A linear and consistent relationship was observed at all sites between the sampling frequency, which summarizes the two features mentioned above, and the renewal frequency associated with the volume. Ultimately, this empirical relationship can be applied to estimate the optimal volume size according to the technical specifications of the sampling system.http://www.atmos-meas-tech.net/9/4665/2016/amt-9-4665-2016.pdf |
| spellingShingle | A. Cescatti B. Marcolla I. Goded C. Gruening Optimal use of buffer volumes for the measurement of atmospheric gas concentration in multi-point systems Atmospheric Measurement Techniques |
| title | Optimal use of buffer volumes for the measurement of atmospheric gas
concentration in multi-point systems |
| title_full | Optimal use of buffer volumes for the measurement of atmospheric gas
concentration in multi-point systems |
| title_fullStr | Optimal use of buffer volumes for the measurement of atmospheric gas
concentration in multi-point systems |
| title_full_unstemmed | Optimal use of buffer volumes for the measurement of atmospheric gas
concentration in multi-point systems |
| title_short | Optimal use of buffer volumes for the measurement of atmospheric gas
concentration in multi-point systems |
| title_sort | optimal use of buffer volumes for the measurement of atmospheric gas concentration in multi point systems |
| url | http://www.atmos-meas-tech.net/9/4665/2016/amt-9-4665-2016.pdf |
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