Simultaneous measurements of O sub(3) , CO, and ultrafine aerosol particles (UFP), conducted on board of a Boeing 767-ER passenger aircraft flying from Sri Lanka to Germany (project CARIBIC), are ...used to study two-way cross-tropopause mixing near a subtropical tropopause fold. On the equatorward side of the fold, downward mixing of stratospheric air into the upper troposphere is identified by enhanced concentrations of O sub(3) and super(1) super(4) CO. Very high UFP number concentrations of up to 1.5 x 10 super(4) cm super(-) super(3) (STP) were encountered inside the poleward half of the fold. This accumulation of small particles is explained by recent extensive aerosol nucleation, most likely triggered by the mixing of stratospheric air with tropospheric air injected into the fold. Further, nine particle formation events were observed outside the fold which are attributed to isolated cells of deep convection and to rising air parcels under cyclonic conditions that mix with surrounding air. In the upper troposphere O sub(3) and CO were found to be correlated with high Delta O sub(3) / Delta CO ratios of 0.6 to 1.5. In the fold the correlation was strongly negative with Delta O sub(3) / Delta CO = -3.5; but the high CO mixing ratios of 100 ppb at O sub(3) mixing ratios of 250 ppb point to earlier injection of tropospheric air, in agreement with the UFP measurements.
Fluxes of CO
2
, CH
4
, and N
2
O from forest soils were measured with an enclosed chamber technique between October 1990 and December 1991 in a deciduous forest near Darmstadt, Germany. Flux ...measurements were made before and after the removal of leaves and humus layer from the forest floor, and gas fluxes from the leaves and humus alone were also measured as well as depth profiles of CH
4
, N
2
O, and soil moisture. Except for N
2
O, large seasonal variations were observed with generally higher gas fluxes during the summer. CO
2
and CH
4
fluxes were significantly dependent on changes in ambient temperature, whereas N
2
O fluxes were more affected by soil moisture. A good correlation between CO
2
production and CH
4
uptake was observed, but no relationship was found between N
2
O emissions and either CO
2
or CH
4
fluxes. Depth profiles of the CH
4
mixing ratio in soil air consistently showed an exponential decrease with depth, whereas N
2
O profiles were highly variable and appeared to be related to changes in soil moisture. The manipulated soil experiments indicate that the leaves and the humus layers contribute significantly to the soil-atmosphere exchange of trace gases.
Fluxes of CO sub(2) , CH sub(4) , and N sub(2) O from forest soils were measured with an enclosed chamber technique between October 1990 and December 1991 in a deciduous forest near Darmstadt, ...Germany. Flux measurements were made before and after the removal of leaves and humus layer from the forest floor, and gas fluxes from the leaves and humus alone were also measured as well as depth profiles of CH sub(4) , N sub(2) O, and soil moisture. Except for N sub(2) O, large seasonal variations were observed with generally higher gas fluxes during the summer. CO sub(2) and CH sub(4) fluxes were significantly dependent on changes in ambient temperature, whereas N sub(2) O fluxes were more affected by soil moisture. A good correlation between CO sub(2) production and CH sub(4) uptake was observed, but no relationship was found between N sub(2) O emissions and either CO sub(2) or CH sub(4) fluxes. Depth profiles of the CH sub(4) mixing ratio in soil air consistently showed an exponential decrease with depth, whereas N sub(2) O profiles were highly variable and appeared to be related to changes in soil moisture. The manipulated soil experiments indicate that the leaves and the humus layers contribute significantly to the soil-atmosphere exchange of trace gases.
The isotopic composition of carbon monoxide ( super(13)C, super(14)C, super(18)O) and methane ( super(13)C, D) was measured on air samples collected between Vladivostok and Moscow using the ...Trans-Siberian railroad during August 1996. Apart from short term fluctuations in the direct vicinity of sources, continuous measurements of CO and CH sub(4) showed sustained, elevated mixing ratios over several hundreds of kilometers indicating the large scale influencing of traversed air masses by significant sources. Persistent, enhanced CH sub(4) levels were found over the west Siberian lowlands concurrent with significantly depleted delta super(13)C and delta D values. The derived isotopic signature of the CH sub(4) source ( delta super(13)C = -62.5 plus or minus 4.7ppt V-PDB; delta D = -311 plus or minus 14ppt V-SMOW) clearly indicates the dominance of biogenic CH sub(4), with the west Siberian wetlands being the most likely candidate. A second major feature in the data set is the enormous enhancement of CO (up to 1500 nmol/mol) east of Chita, extending over a 2000 km section along the river Amur. The super(14)CO measurements and back trajectory analyses identify biomass burning as the origin of the highly elevated CO. This is further supported by the delta super(18)O(CO) and the delta super(13)C/ delta D signature of the accompanying moderate CH sub(4) enhancement.
The isotopic composition of carbon monoxide (
13
C,
14
C,
18
O) and methane (
13
C, D) was measured on air samples collected between Vladivostok and Moscow using the Trans‐Siberian railroad during ...August 1996. Apart from short term fluctuations in the direct vicinity of sources, continuous measurements of CO and CH
4
showed sustained, elevated mixing ratios over several hundreds of kilometers indicating the large scale influencing of traversed air masses by significant sources. Persistent, enhanced CH
4
levels were found over the west Siberian lowlands concurrent with significantly depleted δ
13
C and δD values. The derived isotopic signature of the CH
4
source (δ
13
C = −62.5±4.7‰ V‐PDB; δD = −311±14‰ V‐SMOW) clearly indicates the dominance of biogenic CH
4
, with the west Siberian wetlands being the most likely candidate. A second major feature in the data set is the enormous enhancement of CO (up to 1500 nmol/mol) east of Chita, extending over a 2000 km section along the river Amur. The
14
CO measurements and back trajectory analyses identify biomass burning as the origin of the highly elevated CO. This is further supported by the δ
18
O(CO) and the δ
13
C/δD signature of the accompanying moderate CH
4
enhancement.
The deployment of measurement equipment in passenger aircraft for the observation of atmospheric trace constituents is described. The package of automated instruments that is installed in a ...one-ton-capacity aircraft freight container positioned in the forward cargo bay of a Boeing 767 ER can register a vast amount of atmospheric data during regular long-distance flights. The air inlet system that is mounted on the fuselage directly below the container comprises an aerosol inlet, a separate inlet for trace-gas sampling, and an air exhaust. All instruments, the central computer, and power supply are mounted in aviation-approved racks that slide into the reinforced container. The current instrument package comprises a fast-response chemiluminescence sensor and a conventional UV absorption detector for O sub(3) ; a gas chromatograph for CO; two condensation nuclei counters for particles larger than 5 and 12 nm; and a 12-canister large-capacity whole air sampler for laboratory trace-gas analysis and isotopic analysis of CO sub(2) , CO, CH sub(4) , and N sub(2) O. First measurement results of the operational Civil Aircraft for Remote Sensing and In Situ Measurements in Troposphere and Lower Stratosphere Based on the Instrumentation Container Concept (CARIBIC) container are reported.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
A method has been developed for measuring N2O concentrations in the air extracted from the bubbles contained in ice cores. The air extraction is performed by cutting the ice into very small pieces ...with a rotating knife, in a controlled atmosphere. The N2O concentrations are measured by gas chromatography. The complete original procedure will be discussed, and the results of the different experimental tests given, with a discussion of the uncertainties. This method has been used to perform about 40 measurements on Antarctic ice samples. Ten air samples from the D57 core date approximately from the beginning of the seventeenth and twentieth centuries. The others were taken from the Dome C core and date from the Holocene and the period around the Last Glacial Maximum. The D57 results are in agreement with those of Pearman and others (1986), leading to a similar pre-industrial N2O level (270-290 ppb volume). Furthermore, our Dome C results suggest that during the Last Glacial Maximum atmospheric N2O content was not drastically different from the recent period.
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