Air-land exchanges of CO2, CH4 and N2O measured by FTIR spectrometry and micrometeorological techniques

D. W T Griffith*, R. Leuning, O. T. Denmead, I. M. Jamie

*Corresponding author for this work

Research output: Contribution to journalArticle

72 Citations (Scopus)

Abstract

Micrometeorological flux-gradient and nocturnal boundary layer methods were combined with Fourier transform infrared (FTIR) spectroscopy for high-precision trace gas analysis to measure fluxes of the trace gases CO2, CH4 and N2O between agricultural fields and the atmosphere. The FTIR measurements were fully automated and routinely obtained a precision of 0.1-0.2% for several weeks during a measurement campaign in October 1995. In flux-gradient measurements, vertical profiles of the trace gases were measured every 30min from the ground to 22m. When combined with independent micrometeorological measurements of water vapour fluxes, trace gas fluxes from the underlying surface could be determined. In the nocturnal boundary layer method the rate of change in mass storage in the 0-22m layer was combined with fluxes measured at 22m to estimate surface fluxes. Daytime fluxes for CO2 were -0.78±0.40 (1σ) mg CO2 m-2s-1. Daytime fluxes of N2O and CH4 were very small and difficult to measure reliably using the flux-gradient technique, despite the high precision of the concentration measurements. Mean daytime flux for N2O was 17±48ng Nm-2s-1, while the corresponding flux for CH4 was 47±410ng CH4m-2s-1. The mean nighttime flux of CO2 estimated using the nocturnal boundary layer method was +0.15±0.05mg CO2m-2s-1, in good agreement with chamber measurements of respiration rates. Nighttime fluxes of CH4 and N2O from the nocturnal boundary layer method were 109±69ng CH4 m-2s-1 and 2±3.2ng Nm-2s-1, respectively, in good agreement with chamber measurements and inventory estimates based on the sheep and cattle stocking rates in the region. The suitability of FTIR-based methods for long term monitoring of spatially and temporally averaged flux measurements is discussed.

Original languageEnglish
Pages (from-to)1833-1842
Number of pages10
JournalAtmospheric Environment
Volume36
Issue number11
DOIs
Publication statusPublished - 2002
Externally publishedYes

Fingerprint Dive into the research topics of 'Air-land exchanges of CO2, CH4 and N2O measured by FTIR spectrometry and micrometeorological techniques'. Together they form a unique fingerprint.

  • Cite this