Is friction velocity the most appropriate scale for correcting nocturnal carbon dioxide fluxes?
The use of friction velocity u* as the turbulence scale for correcting eddy-covariance carbon dioxide fluxes in low-mixing conditions is questioned. This is done because u* is, itself, a flux and, therefore, its value is highly dependent on the temporal scale used for the analysis. The multiresoluti...
| Autor principal: | Acevedo, Otávio C. |
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| Outros Autores: | Moraes, Osvaldo Luiz Leal de, Degrazia, Gervásio Annes, Fitzjarrald, David Roy, Manzi, Antônio Ocimar, Campos, José Galúcio |
| Grau: | Artigo |
| Idioma: | English |
| Publicado em: |
Agricultural and Forest Meteorology
2020
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| Acesso em linha: |
https://repositorio.inpa.gov.br/handle/1/18471 |
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oai:repositorio:1-18471 |
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oai:repositorio:1-18471 Is friction velocity the most appropriate scale for correcting nocturnal carbon dioxide fluxes? Acevedo, Otávio C. Moraes, Osvaldo Luiz Leal de Degrazia, Gervásio Annes Fitzjarrald, David Roy Manzi, Antônio Ocimar Campos, José Galúcio Carbon Dioxide Carbon Flux Decomposition Eddy Covariance Nocturnal Activity Respiration Time Series Turbulent Mixing Velocity Brasil South America The use of friction velocity u* as the turbulence scale for correcting eddy-covariance carbon dioxide fluxes in low-mixing conditions is questioned. This is done because u* is, itself, a flux and, therefore, its value is highly dependent on the temporal scale used for the analysis. The multiresolution decomposition is applied to data from three different ecosystems in Brazil, to show that u* is well behaved and related to the turbulent mixing only up to the scale that separates the turbulent mixing from the low-frequency exchange. For larger temporal scales, mesoscale fluxes may induce large variability in the friction velocity, so that time series with low turbulent mixing may show an elevated value for u*, and vice-versa. We propose, as an alternative, the use of σw, the standard-deviation of the vertical velocity fluctuations. It is shown that σw has no variability within the mesoscale range and that, therefore, it is a much better scale to quantify the turbulent exchange than u*. The relationship between the two velocity scales is shown to depend on the scale and to be universal for the scales of the turbulent exchange. It is shown that curves of the turbulent carbon dioxide fluxes as a function of the turbulence scale are smoothed when using the friction velocity. Using σw instead of u* in data filtering procedures has two main consequences: easier determination of the threshold for filtering and larger respiration rates of the series classified as turbulent. The improvement is larger for sites where very stable conditions are common. © 2008 Elsevier B.V. All rights reserved. 2020-06-15T21:55:29Z 2020-06-15T21:55:29Z 2009 Artigo https://repositorio.inpa.gov.br/handle/1/18471 10.1016/j.agrformet.2008.06.014 en Volume 149, Número 1, Pags. 1-10 Restrito Agricultural and Forest Meteorology |
| institution |
Instituto Nacional de Pesquisas da Amazônia - Repositório Institucional |
| collection |
INPA-RI |
| language |
English |
| topic |
Carbon Dioxide Carbon Flux Decomposition Eddy Covariance Nocturnal Activity Respiration Time Series Turbulent Mixing Velocity Brasil South America |
| spellingShingle |
Carbon Dioxide Carbon Flux Decomposition Eddy Covariance Nocturnal Activity Respiration Time Series Turbulent Mixing Velocity Brasil South America Acevedo, Otávio C. Is friction velocity the most appropriate scale for correcting nocturnal carbon dioxide fluxes? |
| topic_facet |
Carbon Dioxide Carbon Flux Decomposition Eddy Covariance Nocturnal Activity Respiration Time Series Turbulent Mixing Velocity Brasil South America |
| description |
The use of friction velocity u* as the turbulence scale for correcting eddy-covariance carbon dioxide fluxes in low-mixing conditions is questioned. This is done because u* is, itself, a flux and, therefore, its value is highly dependent on the temporal scale used for the analysis. The multiresolution decomposition is applied to data from three different ecosystems in Brazil, to show that u* is well behaved and related to the turbulent mixing only up to the scale that separates the turbulent mixing from the low-frequency exchange. For larger temporal scales, mesoscale fluxes may induce large variability in the friction velocity, so that time series with low turbulent mixing may show an elevated value for u*, and vice-versa. We propose, as an alternative, the use of σw, the standard-deviation of the vertical velocity fluctuations. It is shown that σw has no variability within the mesoscale range and that, therefore, it is a much better scale to quantify the turbulent exchange than u*. The relationship between the two velocity scales is shown to depend on the scale and to be universal for the scales of the turbulent exchange. It is shown that curves of the turbulent carbon dioxide fluxes as a function of the turbulence scale are smoothed when using the friction velocity. Using σw instead of u* in data filtering procedures has two main consequences: easier determination of the threshold for filtering and larger respiration rates of the series classified as turbulent. The improvement is larger for sites where very stable conditions are common. © 2008 Elsevier B.V. All rights reserved. |
| format |
Artigo |
| author |
Acevedo, Otávio C. |
| author2 |
Moraes, Osvaldo Luiz Leal de Degrazia, Gervásio Annes Fitzjarrald, David Roy Manzi, Antônio Ocimar Campos, José Galúcio |
| author2Str |
Moraes, Osvaldo Luiz Leal de Degrazia, Gervásio Annes Fitzjarrald, David Roy Manzi, Antônio Ocimar Campos, José Galúcio |
| title |
Is friction velocity the most appropriate scale for correcting nocturnal carbon dioxide fluxes? |
| title_short |
Is friction velocity the most appropriate scale for correcting nocturnal carbon dioxide fluxes? |
| title_full |
Is friction velocity the most appropriate scale for correcting nocturnal carbon dioxide fluxes? |
| title_fullStr |
Is friction velocity the most appropriate scale for correcting nocturnal carbon dioxide fluxes? |
| title_full_unstemmed |
Is friction velocity the most appropriate scale for correcting nocturnal carbon dioxide fluxes? |
| title_sort |
is friction velocity the most appropriate scale for correcting nocturnal carbon dioxide fluxes? |
| publisher |
Agricultural and Forest Meteorology |
| publishDate |
2020 |
| url |
https://repositorio.inpa.gov.br/handle/1/18471 |
| _version_ |
1787143937601830912 |
| score |
11.755432 |