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  • × National Center for Atmospheric Research, Boulder, Colorado, USA
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来源:Atmospheric Measurement Techniques

作者:Yong Han;Larrabee Strow;Jochen Landgraf;等

使用许可:署名(BY)

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来源:Biogeosciences

作者:M. Manning;S. Nichol;S. E. Mikaloff Fletcher;等

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We present an analysis of a 39-year record of continuous atmosphericCO2 observations made at Baring Head, New Zealand, filtered for steadybackground CO2 mole fractions during southerly wind conditions. Wediscuss relationships between variability in the filtered CO2 timeseries and regional to global carbon cycling. Baring Head is well situatedto sample air that has been isolated from terrestrial influences over theSouthern Ocean, and experiences extended episodes of strong southerly windswith low CO2 variability. The filtered Baring Head CO2 recordreveals an average seasonal cycle with amplitude of 0.95 ppm that is 13%smaller and 3 weeks earlier in phase than that at the South Pole. Seasonalvariations in a given year are sensitive to the timing and magnitude of thecombined influences of Southern Ocean CO2 fluxes and terrestrial fluxesfrom both hemispheres. The amplitude of the seasonal cycle varies throughoutthe record, but we find no significant long-term seasonal changes withrespect to the South Pole. Interannual variations in CO2 growth rate inthe Baring Head record closely match the El Niño-Southern Oscillation,reflecting the global reach of CO2 mole fraction anomalies associatedwith this cycle. We use atmospheric transport model results to investigatecontributions to seasonal and annual-mean components of the observedCO2 record. Long-term trends in mean gradients between Baring Head andother stations are predominately due to increases in Northern Hemispherefossil-fuel burning and Southern Ocean CO2 uptake, for which thereremains a wide range of future estimates. We find that the postulated recent reduction in the efficiency of Southern Oceananthropogenic CO2 uptake, as a result of increased zonal winds, is too small to be detectableas significant differences in atmospheric CO2 between mid to high latitude SouthernHemisphere observing stations.

    来源:Biogeosciences

    作者:M. Manning;S. Nichol;S. E. Mikaloff Fletcher;等

    使用许可:署名(BY)

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    来源:Atmospheric Chemistry and Physics

    作者:M. Riese;L. Hoffmann;F. Stroh;等

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    来源:Atmospheric Chemistry and Physics

    作者:H. Worden;V. Payne;M. Lee;等

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    Tropical fires represent a highly uncertainsource of atmospheric methane (CH4) because of the variability of fireemissions and the dependency of the fire CH4 emission factors (g kg−1 drymatter burned) on fuel type and combustion phase. In this paper we use newobservations of CH4 and CO in the free troposphere from the AuraTropospheric Emission Sounder (TES) satellite instrument to placeconstraints on the role of tropical fire emissions versus microbialproduction (e.g. in wetlands and livestock) during the (October) 2006 ElNiño, a time of significant fire emissions from Indonesia. We first comparethe global CH4 distributions from TES using the GEOS-Chem model. Wefind a mean bias between the observations and model of 26.3 ppb CH4that is independent of latitude between 50° S and 80° N, consistent with previous validation studies of TES CH4 retrievalsusing aircraft measurements. The slope of the distribution of CH4versus CO as observed by TES and modeled by GEOS-Chem is consistent (withinthe TES observation error) for air parcels over the Indonesian peat fires,South America, and Africa. The CH4 and CO distributions are correlatedbetween R = 0.42 and R= 0.46, with these correlations primarily limitedby the TES random error. Over Indonesia, the observed slope of 0.13(ppb ppb−1) ±0.01, as compared to a modeled slope of 0.153 (ppb ppb−1)±0.005 and an emission ratio used within the GEOS-Chem model ofapproximately 0.11 (ppb ppb−1), indicates that most of the observed methaneenhancement originated from the fire. Slopes of 0.47 (ppb ppb−1) ±0.04and 0.44 (ppb ppb−1) ±0.03 over South America and Africa show that themethane in the observed air parcels primarily came from microbial-generatedemissions. Sensitivity studies using GEOS-Chem show that part of theobserved correlation for the Indonesian observations and most of theobserved correlations over South America and Africa are a result oftransport and mixing of the fire and nearby microbial-generated emissionsinto the observed air parcels. Differences between observed and modeledCH4 distributions over South America and southern Africa indicate thatthe magnitude of the methane emissions for this time period are inconsistentwith observations even if the relative distribution of fire versus bioticemissions are consistent. This study shows the potential for estimation ofCH4 emissions over tropical regions using joint satellite observationsof CH4 and CO.

      来源:Atmospheric Chemistry and Physics

      作者:M. Riese;L. Hoffmann;F. Stroh;等

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      This paper presents a set of observations and analyses of trace gascross sections in the extratropical upper troposphere/lower stratosphere(UTLS). The spatially highly resolved (≈0.5 km vertically and12.5 km horizontally) cross sections of ozone (O3), nitric acid(HNO3), and peroxyacetyl nitrate (PAN), retrieved from the measurements ofthe CRISTA-NF infrared limb sounder flown on the Russian M55-Geophysica,revealed intricate layer structures in the region of the subtropicaltropopause break. The chemical structure in this region shows an intertwinedstratosphere and troposphere. The observed filaments in all discussed tracegases are of a spatial scale of less than 0.8 km vertically and about200 km horizontally across the jet stream. Backward trajectory calculationsconfirm that the observed filaments are the result of a breaking Rossby wavein the preceding days. An analysis of the trace gas relationships between PANand O3 identifies four distinct groups of air mass: polluted subtropicaltropospheric air, clean tropical upper-tropospheric air, the lowermoststratospheric air, and air from the deep stratosphere. The tracerrelationships further allow the identification of tropospheric,stratospheric, and the transitional air mass made of a mixture of UT and LSair. Mapping of these air mass types onto the geo-spatial location in thecross sections reveals a highly structured extratropical transition layer(ExTL). Finally, the ratio between the measured reactive nitrogen species(HNO3 + PAN + ClONO2) and O3 is analysed to estimate theinfluence of tropospheric pollution on the extratropical UTLS.In combination, these diagnostics provide the first example of amulti-species two-dimensional picture of the inhomogeneous distribution ofchemical species within the UTLS region. Since Rossby wave breaking occursfrequently in the region of the tropopause break, these observed fine-scalefilaments are likely ubiquitous in the region. The implications of thelayered structure for chemistry and radiation need to be examined, and therepresentation of this structure in chemistry-climate models is discussed.