Search Results - (Author, Cooperation:L. P. Steele)

2014-09-12

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

Air Pollutants/chemistry ; Atmosphere/*chemistry ; Chloroform/chemistry ; Computer Simulation ; Hydroxyl Radical/*chemistry ; *Models, Theoretical ; Nitrogen Oxides/chemistry

1476-4687

Nature Archives 1869 - 2009

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

[Auszug] Methane is an important greenhouse gas, and its atmospheric concentration has nearly tripled since pre-industrial times. The growth rate of atmospheric methane is determined by the balance between surface emissions and photochemical destruction by the hydroxyl radical, the major atmospheric ...

Electronic Resource

1476-4687

Nature Archives 1869 - 2009

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

[Auszug] Our data set is based on -10,000 air samples collected between May 1983 and December 1990, through the globalcooperative flask sampling network (Fig. 1) operated by NOAA's Climate Monitoring and Diagnostics Laboratory (CMDL). Fixed sites are sampled roughly weekly, and ship-board samples are ...

Electronic Resource

1573-1472

Springer Online Journal Archives 1860-2000

Geosciences

Physics

Abstract Trawsfynydd Power Station (52.9N, 04.0W) lies in a hilly region in northwest Wales. Certain local effects on the surface wind at the power station are revealed by comparing the surface wind there with the surface wind at Valley (53.3N, 04.5W), a well-exposed coastal site only about 50 km to the northwest. Tentative explanations are given for the occurrence of the observed local effects in terms of nearby topography.

Electronic Resource

1573-0662

Methane ; troposphere ; southern hemisphere ; trend ; annual cycle ; vertical gradient

Springer Online Journal Archives 1860-2000

Chemistry and Pharmacology

Geosciences

Abstract Results of more than 800 new measurements of methane (CH4) concentrations in the Southern Hemisphere troposphere (34–41° S, 130–150° E) are reported. These were obtained between September 1980 and March 1983 from the surface at Cape Grim, Tasmania, through the middle (3.5–5.5 km) to the upper troposphere (7–10 km). The concentration of CH4 increased throughout the entire troposphere over the measurement period, adding further support to the view that CH4 concentrations are currently increasing on a global scale. For data averaged vertically through the troposphere the rate of increase found was 20 ppbv/yr or 1.3%/yr at December 1981. In the surface CH4 data a seasonal cycle with a peak to peak amplitude of approximately 28 ppbv is seen, with the minimum concentration occurring in March and the maximum in September–October. A cycle with the same phase as that seen at the surface, but with a significantly decreased amplitude, is apparent in the mid troposphere but no cycle is detected in the upper tropospheric data. The phase and amplitude of the cycle are qualitatively in agreement with the concept that the major sink for methane is oxidation by hydroxyl radicals. Also presented is evidence of a positive vertical gradient in methane, with a suggestion that the magnitude of this gradient has changed over the period of measurements.

Electronic Resource

1573-0662

Arctic ; atmosphere ; methane ; carbon dioxide ; haze ; correlation ; AGASP

Springer Online Journal Archives 1860-2000

Chemistry and Pharmacology

Geosciences

Abstract Fifty flask air samples were taken during April 1986 from a NOAA WP-3D Orion aircraft which flew missions across a broad region of the Arctic as part of the second Arctic Gas and Aerosol Sampling Program (AGASP II). The samples were subsequently analyzed for both carbon dioxide (CO2) and methane (CH4). The samples were taken in well-defined layers of Arctic haze, in the background troposphere where no haze was detected, and from near the surface to the lower stratosphere. Vertical profiles were specifically measured in the vicinity of Barrow, Alaska to enable comparisons with routine surface measurements made at the NOAA/GMCC observatory. Elevated levels of both methane and carbon dioxide were found in haze layers. For samples taken in the background troposphere we found negative vertical gradients (lower concentrations aloft) for both gases. For the entire data set (including samples collected in the haze layers) we found a strong positive correlation between the methane and carbon dioxide concentrations, with a linear regression slope of 17.5 ppb CH4/ppm CO2, a standard error of 0.6, and a correlation coefficient (r2) of 0.95. This correlation between the two gases seen in the aircraft samples was corroborated by in situ surface measurements of these gases made at the Barrow observatory during March and April 1986. We also find a similar relationship between methane and carbon dioxide measured concurrenty for a short period in the moderately polluted urban atmosphere of Boulder, Colorado. We suggest that the strong correlation between methane and carbon dioxide concentrations reflects a common source region for both, with subsequent long-range transport of the polluted air to the Arctic.

Electronic Resource

1573-0662

Methane ; troposphere ; global distribution ; trend ; seasonal cycle ; latitudinal gradient ; vertical gradient

Springer Online Journal Archives 1860-2000

Chemistry and Pharmacology

Geosciences

Abstract 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.

Electronic Resource

1573-0662

Methane ; nitrogen oxides ; oil production ; emissions

Springer Online Journal Archives 1860-2000

Chemistry and Pharmacology

Geosciences

Abstract In this paper we quantify the CH4, CO2 and NO x emissions during routine operations at a major oil and gas production facility, Prudhoe Bay, Alaska, using the concentrations of combustion by products measured at the NOAA-CMDL observatory at Barrow, Alaska and fuel consumption data from Prudhoe Bay. During the 1989 and 1990 measurement campaigns, 10 periods (called ‘events’) were unambiguously identified where surface winds carry the Prudhoe Bay emissions to Barrow (approximately 300 km). The events ranged in duration from 8–48 h and bring ambient air masses containing substantially elevated concentrations of CH4, CO2 and NO y to Barrow. Using the slope of the observed CH4 vs CO2 concentrations during the events and the CO2 emissions based on reported fuel consumption data, we calculate annual CH4 emissions of (24+/−8)×103 metric tons from the facility. In a similar manner, the annual NO x emissions are calculated to be (12+/−4)×103 metric tons, which is in agreement with an independently determined value. The calculated CH4 emissions represent the amount released during routine operations including leakage. However this quantity would not include CH4 released during non-routine operations, such as from venting or gas flaring.

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