02 Nov 2023
 | 02 Nov 2023
Status: this preprint is open for discussion.

Assessment of the Webb-Pearman-Leuning Correction Method for Estimating CO2 Flux in a Tropical Coastal Sea

Muhammad Fikri Sigid, Yusri Yusup, Abdulghani Essayah Swesi, Haitem M. Almdhun, and Ehsan Jolous Jamshidi

Abstract. CO2 fluxes in coastal waters are vital for the global carbon cycle. The Eddy Covariance technique was used with open-path gas analyzers to estimate CO2 fluxes. However, these analyzers can lead to overestimation due to water vapor and temperature effects, and the Webb-Pearman-Leuning (WPL) correction method was applied to improve the accuracy of the estimated CO2 flux. This study investigates the application of the WPL correction method on CO2 flux measurements over a tropical coastal sea location. The analysis reveals that the CO2 flux in the coastal waters mainly functions as a sink, with the diel cycle showing smaller flux magnitudes during the day and increased uptake during the night. The application of the WPL correction can result in sign changes of CO2 flux, indicating a shift from a CO2 sink to a CO2 source. These sign changes occur frequently, particularly during afternoon hours, and can significantly impact the implications regarding carbon exchange. The WPL correction parameters, especially those related to temperature and water vapor fluctuations, play crucial roles in influencing the CO2 flux variations. The decrease in dry air molar density and increased vertical wind speed within the correction related to water vapor fluctuations are the major reasons for the sign change of the CO2 flux. Based on the quality flagging of the WPL correction, the non-sign change CO2 fluxes are predominantly considered reliable data, while most of the sign change fluxes should be specially checked.

Muhammad Fikri Sigid et al.

Status: open (until 03 Jan 2024)

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  • RC1: 'Comment on egusphere-2023-2383', Anonymous Referee #1, 19 Nov 2023 reply

Muhammad Fikri Sigid et al.

Muhammad Fikri Sigid et al.


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Short summary
In coastal waters, we investigated CO2 flux using the Webb-Pearman-Leuning correction with Eddy Covariance. The correction frequently caused sign changes, especially in the afternoons, shifting from a CO2 sink to a source. These changes have significant implications for carbon exchange, particularly influenced by correction parameters like temperature and water vapor. Reliable data primarily come from non-sign change fluxes, while sign change fluxes mostly need special scrutiny.