Methane, Carbon Monoxide and Methylchloroform in the Southern Hemisphere

Fraser, Paul J.; Hyson, P.; Rasmussen, R. A.; Crawford, Anna; Khalil, M. A. K.

doi:10.1007/978-94-009-3909-7_12

Cited by 25 publications

(35 citation statements)

References 44 publications

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“…Several systematic investigations begun since 1978 have found an average increase in concentration of between one and two percent per year, with a majority being closer to the lower end of the range. Most of these measurements have been made in the troposphere using the method of gas chromatography with a flame ionization detector (Rasmussen and Khalil, 1981a;Fraser et al, 1981;Blake et al, 1982;Khalil and Rasmussen, 1983;Fraser et al, 1984;Blake, 1984;Fraser et al, 1986;Blake and Rowland, 1986). Other measurements have relied upon an optical absorption technique which uses the sun as a source of infrared radiation, and yields an average atmospheric abundance along the entire path length traversed through the atmosphere.…”

Section: Introductionmentioning

confidence: 99%

“…The measured latitudinal distribution of tropospheric methane has provided a key constraint on model calculations of its average atmospheric lifetime, and the distribution of its estimated or postulated source functions Khalil and Rasmussen, 1983;Blake, 1984;Fraser et al, 1986). The distribution used by Khalil and Rasmussen (1983) was determined by measurements at six sites ranging in latitude from 90°S to 71 ° N. The seasonal variation was well determined at some of these sites but not at others.…”

Section: Introductionmentioning

confidence: 99%

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The global distribution of methane in the troposphere

Steele

Fraser

Rasmussen³

et al. 1987

J Atmos Chem

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282

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Methane has been measured in air samples collected at approximately weekly intervals at 23 globally distributed sites in the NOAA/GMCC cooperative flask sampling network. Sites range in latitude from 90" S to 76" N, and at most of these we report 2 years of data beginning in early 1983. All measurements have been made by gas chromatography with a flame ionization detector at the NOAA/GMCC laboratory in Boulder, Colorado. All air samples have been referenced to a single secondary standard of methane-in-air, ensuring a high degree of internal consistency in the data. The precision of measurements is estimated from replicate determinations on each sample as 0.2%. The latitudinal distribution of methane and the seasonal variation of this distribution in the marine boundary layer has been defined in great detail, including a remarkable uniformity in background levels of methane in the Southern Hemisphere. We report for the first time the observation of a complete seasonal cycle of methane at the South Pole. A significant vertical gradient is observed between a sea level and a high altitude site in Hawaii. Globally averaged background concentrations in the marine boundary layer have been calculated for the 2 year-period May 1983-April 1985 inclusive, from which we find an average increase of 12.8 ppb per year, or 0.78% per year when referenced to the globally averaged concentration (1625 ppb) at the mid-point of this period. We present evidence that there has been a slowing down in the methane growth rate.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The global distribution of methane in the troposphere

Steele

Fraser

Rasmussen³

et al. 1987

J Atmos Chem

Self Cite

282

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“…From these results, it seems that not change in a biogenic source but of the interhemispheric trans port contributed to the change of the methane growth rate during the ENSO event. The results from aircraft observations indicated that the transport through the upper troposphere is impor tant for the interhemispheric exchange of the tro pospheric methane between the hemispheres (Fraser et al, 1986;Matsueda et al, 1993). Thus, more observations in the upper troposphere are necessary to better understand the interannual variation of the atmospheric methane cycle due to an ENSO event.…”

Section: Interannual Variation Of Growth Ratementioning

confidence: 99%

“…Etheridge et al, 1992). In the late 1970's, accurate measurements of atmospheric methane started using a gas chromatograph with a flame ionization detector (GC/FID) (Fraser et al, 1986;Khalil and Rasmussen, 1983;Blake and Rowland, 1986;Matsueda et al, 1992). These measurements clearly indicate that atmospheric methane had continued to increase at the rate of about 1%/yr around 1980.…”

Section: Introductionmentioning

confidence: 99%

Atmospheric methane over the North Pacific from 1987 to 1993.

Matsueda¹,

Inoue²,

Ishii³

et al. 1996

Geochem. J.

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Atmospheric methane mixing ratios were measured over the North Pacific during the winter season from 1987 to 1993 to extend our methane record since 1978. The latitudinal distribution of methane mixing ratio showed a north-to-south gradient from mid-latitudes to the equator every year. A sharp mixing ratio gradient often appeared at the boundary between the winter monsoon and the trade wind regions around 20°N. No significant longitudinal gradient was found during the winter season, although methane levels along the equator showed a large difference between the western and eastern Pacific. The overall methane increase rate in the western Pacific was estimated to be 13 ppb/yr on the basis of the long-term record for 15 years from 1978 to 1993. This record indicates that the methane growth rate over this Pacific region was gradually slowing down until 1990, followed by no significant increase in the 1990's. The overall deceleration of the growth rate was more rapid in the middle latitudinal zone (20°N 30°N) than in the lower latitudinal zone (3°N-20°N). This latitudinal difference suggests a rapid reduction of methane emissions from the continental regions. The methane growth rate showed an interannual variation with an increasing trend around 1983 and 1987, which was roughly related to the El Niflo events. It is suggested that the methane growth rate was affected by a change of interhemispheric transport due to the ENSO events. INTRODUCTIONAtmospheric methane is known as an important greenhouse gas that influences the radiative bal ance and climate of the earth by warming the troposphere and cooling the stratosphere. In addi tion, atmospheric methane is closely related to the chemical cycles of carbon monoxide, ozone, and water vapor by reaction with hydroxyl radicals. The main sources of atmospheric methane are es timated to be enteric fermentation, rice paddies, and wetlands (Cicerone and Oremland, 1988;Fung et al., 1991). Methane is also emitted to the at mosphere from natural gas leakage, biomass burning, and termites. On the other hand, the main sink is oxidative reaction with hydroxyl radicals (Levy, 1971). A minor sink is methane oxidation by bacteria in the soil. However, large uncertain ties in global estimation of their sources and sinks still remain (Fung et al., 1991).Ice-core records indicate that methane mixing ratio in the atmosphere has increased by about a factor of two in the last 150 years due to human activity (e.g. Etheridge et al., 1992). In the late 1970's, accurate measurements of atmospheric methane started using a gas chromatograph with a flame ionization detector (GC/FID) (Fraser et al., 1986;Khalil and Rasmussen, 1983;Blake and Rowland, 1986;Matsueda et al., 1992). These measurements clearly indicate that atmospheric methane had continued to increase at the rate of about 1%/yr around 1980. More recently, methane levels have been observed regularly at many re mote sites to globally determine the increasing trend (Steele et al., 1987;Blake and Rowland, 1988;Scheel et al., 1990; Aoki et a...

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“…13 " 21 The emphasis has been on ambient air measurements of CH3CCI3 at a number of monitoring sites over extended time periods as long as seven years. 13 " 19 The global emissions of CH3CCI3 over its entire period of usage also must be estimated. These results are utilized in several tropospheric models ranging from the earlier two-box models 13 …”

Section: Use Of Atmospheric Trend Measurements Of Ch3cci3 and Comentioning

confidence: 99%

Ambient Air Hydroxyl Radical Concentrations: Measurements and Model Predictions

Altshuller

1989

JAPCA

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Methane, Carbon Monoxide and Methylchloroform in the Southern Hemisphere

Cited by 25 publications

References 44 publications

The global distribution of methane in the troposphere

The global distribution of methane in the troposphere

Atmospheric methane over the North Pacific from 1987 to 1993.

Ambient Air Hydroxyl Radical Concentrations: Measurements and Model Predictions

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