Analysis of the pkt correction for direct co 2 flux measurements over the ocean
Eddy covariance measurements of air-sea CO2 fluxes can be affected by cross-sensitivities of the CO2 measurement to water vapour, resulting in order-of-magnitude biases. Well-established causes for these biases are (i) cross-sensitivity of the broadband non-dispersive infrared sensors due to band-br...
Published in: | Atmospheric Chemistry and Physics |
---|---|
Main Authors: | , , , , |
Format: | Article in Journal/Newspaper |
Language: | unknown |
Published: |
Copernicus GmbH
2014
|
Subjects: | |
Online Access: | http://hdl.handle.net/10379/12371 https://doi.org/10.5194/acp-14-3361-2014 |
id |
ftnuigalway:oai:aran.library.nuigalway.ie/:10379/12371 |
---|---|
record_format |
openpolar |
spelling |
ftnuigalway:oai:aran.library.nuigalway.ie/:10379/12371 2023-06-11T04:17:04+02:00 Analysis of the pkt correction for direct co 2 flux measurements over the ocean Landwehr, S. Miller, S. D. Smith, M. J. Saltzman, E. S. Ward, B. 2014-04-04 http://hdl.handle.net/10379/12371 https://doi.org/10.5194/acp-14-3361-2014 unknown Copernicus GmbH Atmospheric Chemistry and Physics Landwehr, S. Miller, S. D.; Smith, M. J.; Saltzman, E. S.; Ward, B. (2014). Analysis of the pkt correction for direct co 2 flux measurements over the ocean. Atmospheric Chemistry and Physics 14 (7), 3361-3372 1680-7324 http://hdl.handle.net/10379/12371 doi:10.5194/acp-14-3361-2014 Attribution-NonCommercial-NoDerivs 3.0 Ireland https://creativecommons.org/licenses/by-nc-nd/3.0/ie/ air-sea exchange gas-exchange wind-speed open-path turbulence heat temperature platforms system flow Article 2014 ftnuigalway https://doi.org/10.5194/acp-14-3361-2014 2023-05-28T18:05:34Z Eddy covariance measurements of air-sea CO2 fluxes can be affected by cross-sensitivities of the CO2 measurement to water vapour, resulting in order-of-magnitude biases. Well-established causes for these biases are (i) cross-sensitivity of the broadband non-dispersive infrared sensors due to band-broadening and spectral overlap (commercial sensors typically correct for this) and (ii) the effect of air density fluctuations (removed by determining the dry air CO2 mixing ratio). Another bias related to water vapour fluctuations has recently been observed with open-path sensors, attributed to sea salt build-up and water films on sensor optics. Two very different approaches have been used to deal with these water vapour-related biases. Miller et al. (2010) employed a membrane drier to physically eliminate 97% of the water vapour fluctuations in the sample air before it entered a closed-path gas analyser. Prytherch et al. (2010a) employed the empirical (Peter K. Taylor, PKT) post-processing correction to correct open-path sensor data. In this paper, we test these methods side by side using data from the Surface Ocean Aerosol Production (SOAP) experiment in the Southern Ocean. The air-sea CO2 flux was directly measured with four closed-path analysers, two of which were positioned down-stream of a membrane dryer. The CO2 fluxes from the two dried gas analysers matched each other and were in general agreement with common parameterisations. The flux estimates from the un-dried sensors agreed with the dried sensors only during periods with low latent heat flux (<= 7 W m(-2)). When latent heat flux was higher, CO2 flux estimates from the un-dried sensors exhibited large scatter and an order-of-magnitude bias. Applying the PKT correction to the flux data from the un-dried analysers did not remove the bias when compared to the data from the dried gas analyser. The results of this study demonstrate the validity of measuring CO2 fluxes using a pre-dried air stream and show that the PKT correction is not valid for the ... Article in Journal/Newspaper Southern Ocean National University of Ireland (NUI), Galway: ARAN Southern Ocean Atmospheric Chemistry and Physics 14 7 3361 3372 |
institution |
Open Polar |
collection |
National University of Ireland (NUI), Galway: ARAN |
op_collection_id |
ftnuigalway |
language |
unknown |
topic |
air-sea exchange gas-exchange wind-speed open-path turbulence heat temperature platforms system flow |
spellingShingle |
air-sea exchange gas-exchange wind-speed open-path turbulence heat temperature platforms system flow Landwehr, S. Miller, S. D. Smith, M. J. Saltzman, E. S. Ward, B. Analysis of the pkt correction for direct co 2 flux measurements over the ocean |
topic_facet |
air-sea exchange gas-exchange wind-speed open-path turbulence heat temperature platforms system flow |
description |
Eddy covariance measurements of air-sea CO2 fluxes can be affected by cross-sensitivities of the CO2 measurement to water vapour, resulting in order-of-magnitude biases. Well-established causes for these biases are (i) cross-sensitivity of the broadband non-dispersive infrared sensors due to band-broadening and spectral overlap (commercial sensors typically correct for this) and (ii) the effect of air density fluctuations (removed by determining the dry air CO2 mixing ratio). Another bias related to water vapour fluctuations has recently been observed with open-path sensors, attributed to sea salt build-up and water films on sensor optics. Two very different approaches have been used to deal with these water vapour-related biases. Miller et al. (2010) employed a membrane drier to physically eliminate 97% of the water vapour fluctuations in the sample air before it entered a closed-path gas analyser. Prytherch et al. (2010a) employed the empirical (Peter K. Taylor, PKT) post-processing correction to correct open-path sensor data. In this paper, we test these methods side by side using data from the Surface Ocean Aerosol Production (SOAP) experiment in the Southern Ocean. The air-sea CO2 flux was directly measured with four closed-path analysers, two of which were positioned down-stream of a membrane dryer. The CO2 fluxes from the two dried gas analysers matched each other and were in general agreement with common parameterisations. The flux estimates from the un-dried sensors agreed with the dried sensors only during periods with low latent heat flux (<= 7 W m(-2)). When latent heat flux was higher, CO2 flux estimates from the un-dried sensors exhibited large scatter and an order-of-magnitude bias. Applying the PKT correction to the flux data from the un-dried analysers did not remove the bias when compared to the data from the dried gas analyser. The results of this study demonstrate the validity of measuring CO2 fluxes using a pre-dried air stream and show that the PKT correction is not valid for the ... |
format |
Article in Journal/Newspaper |
author |
Landwehr, S. Miller, S. D. Smith, M. J. Saltzman, E. S. Ward, B. |
author_facet |
Landwehr, S. Miller, S. D. Smith, M. J. Saltzman, E. S. Ward, B. |
author_sort |
Landwehr, S. |
title |
Analysis of the pkt correction for direct co 2 flux measurements over the ocean |
title_short |
Analysis of the pkt correction for direct co 2 flux measurements over the ocean |
title_full |
Analysis of the pkt correction for direct co 2 flux measurements over the ocean |
title_fullStr |
Analysis of the pkt correction for direct co 2 flux measurements over the ocean |
title_full_unstemmed |
Analysis of the pkt correction for direct co 2 flux measurements over the ocean |
title_sort |
analysis of the pkt correction for direct co 2 flux measurements over the ocean |
publisher |
Copernicus GmbH |
publishDate |
2014 |
url |
http://hdl.handle.net/10379/12371 https://doi.org/10.5194/acp-14-3361-2014 |
geographic |
Southern Ocean |
geographic_facet |
Southern Ocean |
genre |
Southern Ocean |
genre_facet |
Southern Ocean |
op_relation |
Atmospheric Chemistry and Physics Landwehr, S. Miller, S. D.; Smith, M. J.; Saltzman, E. S.; Ward, B. (2014). Analysis of the pkt correction for direct co 2 flux measurements over the ocean. Atmospheric Chemistry and Physics 14 (7), 3361-3372 1680-7324 http://hdl.handle.net/10379/12371 doi:10.5194/acp-14-3361-2014 |
op_rights |
Attribution-NonCommercial-NoDerivs 3.0 Ireland https://creativecommons.org/licenses/by-nc-nd/3.0/ie/ |
op_doi |
https://doi.org/10.5194/acp-14-3361-2014 |
container_title |
Atmospheric Chemistry and Physics |
container_volume |
14 |
container_issue |
7 |
container_start_page |
3361 |
op_container_end_page |
3372 |
_version_ |
1768375876548820992 |