Vertical profiles of biospheric and fossil fuel-derived CO₂ and fossil fuel CO₂ : CO ratios from airborne measurements of Δ¹⁴C, CO₂ and CO above Colorado, USA     

By HEATHER D. GRAVEN †  BRITTON B. STEPHENS  THOMAS P. GUILDERSON  TERESA L. CAMPOS  DAVID S. SCHIMEL  J. ELLIOTT CAMPBELL  RALPH F. KEELING 《Tellus. Series B, Chemical and physical meteorology》2009,61(3):536-546

Measurements of  Δ¹⁴C  in atmospheric CO₂ are an effective method of separating CO₂ additions from fossil fuel and biospheric sources or sinks of CO₂. We illustrate this technique with vertical profiles of CO₂ and  Δ¹⁴C  analysed in whole air flask samples collected above Colorado, USA in May and July 2004. Comparison of lower tropospheric composition to cleaner air at higher altitudes (>5 km) revealed considerable additions from respiration in the morning in both urban and rural locations. Afternoon concentrations were mainly governed by fossil fuel emissions and boundary layer depth, also showing net biospheric CO₂ uptake in some cases. We estimate local industrial CO₂:CO emission ratios using in situ measurements of CO concentration. Ratios are found to vary by 100% and average 57 mole CO₂:1 mole CO, higher than expected from emissions inventories. Uncertainty in CO₂ from different sources was ±1.1 to ±4.1 ppm for addition or uptake of −4.6 to 55.8 ppm, limited by  Δ¹⁴C  measurement precision and uncertainty in background  Δ¹⁴C  and CO₂ levels.  相似文献   

Contributions of carbon cycle uncertainty to future climate projection spread   总被引：2，自引：0，他引：2  

By C. HUNTINGFORD  J. A. LOWE  B. B. B. BOOTH  C. D. JONES  G. R. HARRIS  L. K. GOHAR  P. MEIR 《Tellus. Series B, Chemical and physical meteorology》2009,61(2):355-360

We have characterized the relative contributions to uncertainty in predictions of global warming amount by year 2100 in the C4MIP model ensemble ( Friedlingstein et al., 2006 ) due to both carbon cycle process uncertainty and uncertainty in the physical climate properties of the Earth system. We find carbon cycle uncertainty to be important. On average the spread in transient climate response is around 40% of that due to the more frequently debated uncertainties in equilibrium climate sensitivity and global heat capacity.
This result is derived by characterizing the influence of different parameters in a global climate-carbon cycle 'box' model that has been calibrated against the 11 General Circulation models (GCMs) and Earth system Models of Intermediate Complexity (EMICs) in the C4MIP ensemble; a collection of current state-of-the-art climate models that include an explicit representation of the global carbon cycle.  相似文献   

Is the recent build-up of atmospheric CO₂ over Europe reproduced by models. Part 2: an overview with the atmospheric mesoscale transport model CHIMERE     

By C. AULAGNIER  P. RAYNER  P. CIAIS  R. VAUTARD  L. RIVIER  M. RAMONET 《Tellus. Series B, Chemical and physical meteorology》2010,62(1):14-25

In this issue, Ramonet et al. revealed a positive trend in European, atmospheric CO₂ concentrations relative to a marine, North Atlantic reference baseline, for the years 2001–2006. The observed build up mainly occurred during the cold season where it reaches a 0.8 ppm yr⁻¹ at low-altitude stations to a 0.3 ppm yr⁻¹ at mid-altitude stations. We explore the cause of this build-up using the mesoscale model CHIMERE. We first model the observed trends, using interannually varying fluxes and transport, then suppress the interannual variability in fluxes or aspects of transport to elucidate the cause. The run with no interannual variability in fluxes still matches observed trends suggesting that transport is the major cause. Separate runs varying either boundary layer height or winds show that changes in boundary layer height explain the trends at low-altitude stations within the continents while changes in wind regimes drive changes elsewhere.  相似文献   

Assessment of the soil CO₂ gradient method for soil CO₂ efflux measurements: comparison of six models in the calculation of the relative gas diffusion coefficient     

By NATCHAYA PINGINTHA  MONIQUE Y. LECLERC  JOHN P. BEASLEY Jr.  GENGSHENG ZHANG  CHUCKREE SENTHONG 《Tellus. Series B, Chemical and physical meteorology》2010,62(1):47-58

This paper uses a refined soil gradient method to estimate soil CO₂ efflux. Six different models are used to determine the relative gas diffusion coefficient (ξ). A weighted harmonic averaging is used to estimate the soil CO₂ diffusion coefficient, yielding a better estimate of soil CO₂ efflux. The resulting soil CO₂ efflux results are then compared to the soil CO₂ efflux measured with a soil chamber. Depending on the choice of ξ model used, the estimated soil CO₂ efflux using the gradient method reasonably approximates the efflux obtained using the soil chamber method. In addition, the estimated soil CO₂ efflux obtained by this improved method is well described by an exponential function of soil temperature at a depth of 0.05 m with the temperature sensitivity ( Q ₁₀) of 1.81 and a linear function of soil moisture at a depth of 0.12 m, in general agreement with previous findings. These results suggest that the gradient method is a practical cost-effective means to measure soil CO₂ emissions. Results from the present study suggest that the gradient method can be used successfully to measure soil CO₂ efflux provided that proper attention is paid to the judicious use of the proper diffusion coefficient.  相似文献   

Large-scale atmospheric circulation changes are associated with the recent loss of Arctic sea ice   总被引：21，自引：0，他引：21  

By JAMES E. OVERLAND  MUYIN WANG 《地球，A辑:动力气象学与海洋学》2010,62(1):1-9

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An analysis of regional climate model performance over the tropical Americas. Part I: simulating seasonal variability of precipitation associated with ENSO forcing   总被引：1，自引：0，他引：1  

By ETIENNE TOURIGNY  COLIN G. JONES † 《地球，A辑:动力气象学与海洋学》2009,61(3):323-342

Sea surface temperature (SST) anomalies associated with El Niño/Southern Oscillation (ENSO) constitute a major source of predictability in the tropics. We evaluate the ability of a regional climate model (the Rossby Centre Atmospheric Model; RCA) to downscale SST and large-scale atmospheric anomalies associated with ENSO. RCA is configured over the tropical east Pacific and tropical Americas and runs for the period 1979–2005, using European Centre for Medium-Range Weather Forecasts (ECMWF) lateral and surface boundary conditions. We study the ability of RCA to represent regional patterns of precipitation, with respect to both the climatology and interannual variability associated with ENSO. The latter is achieved by grouping the simulations into El Niño and La Niña composites and studying the delayed response of precipitation to SST forcing in four regions of Central and South America.
In this paper, we concentrate on seasonal mean timescales. We find that RCA accurately simulates the main features of the precipitation climatology over the four regions and also reproduces the majority of the documented regional responses to ENSO forcing. Furthermore, the model captures the variability in precipitation anomalies between different ENSO events. The model exhibits a wet bias over the northern Amazon and slightly overestimates the magnitude of ENSO anomalies over Central America.  相似文献   

Vegetation,fire and climate history of the Lesser Caucasus: a new Holocene record from Zarishat fen (Armenia)          下载免费PDF全文

SÉBASTIEN JOANNIN  ADAM A. ALI  VINCENT OLLIVIER  PAUL ROIRON  ODILE PEYRON  SAMY CHEVAUX  SAMUEL NAHAPETYAN  PETROS TOZALAKYAN  ARKADI KARAKHANYAN  CHRISTINE CHATAIGNER 《第四纪科学杂志》2014,29(1):70-82

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Vegetation–soil water interaction within a dynamical ecosystem model of grassland in semi-arid areas     

XIAODONG ZENG  XUBIN ZENG  SAMUEL S. P. SHEN  ROBERT E. DICKINSON  QING-CUN ZENG 《Tellus. Series B, Chemical and physical meteorology》2005,57(3):189-202

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Measurements of desert dust optical characteristics at Porte au Sahara during SAMUM     

By W. VON HOYNINGEN-HUENE  T. DINTER  A. A. KOKHANOVSKY  J. P. BURROWS  M. WENDISCH  E. BIERWIRTH  D. MÜLLER  M. DIOURI 《Tellus. Series B, Chemical and physical meteorology》2009,61(1):206-215

Main optical characteristics of desert dust, such as phase function and single scattering albedo, have been derived from combinations of sun-/sky-radiometer and satellite measurements during the SAMUM experiment (10 May–10 June 2006) at the site Porte au Sahara (30.237°N, 5.607°W) in South Morocco. Scattering phase functions have been retrieved using combined data of spectral aerosol optical thickness (AOT) and spectral sky brightness in the almucantar, considering non-spherical light scattering. Intercomparisons of modelled top-of-atmosphere (TOA) reflectance with satellite observations of the Medium Resolution Imaging Spectrometer (MERIS) and Scanning Imaging Absorption Spectrometer for Atmospheric Chartography () instrument have been used for the estimation of spectral single scattering albedo. For the radiative transfer calculations scattering phase functions and AOT from ground-based observations have been used. The spectral single scattering albedo ranges from 0.93 in the blue to 0.98 at 753 nm.  相似文献   

Leucocratic and Gabbroic Xenoliths from Hualalai Volcano, Hawai'i   总被引：1，自引：0，他引：1  

SHAMBERGER  PATRICK J.; HAMMER  JULIA E. 《Journal of Petrology》2006,47(9):1785-1808

A diverse range of crustal xenoliths is hosted in young alkalibasalt lavas and scoria deposits (erupted 3–5 ka) at thesummit of Huallai. Leucocratic xenoliths, including monzodiorites,diorites and syenogabbros, are distinctive among Hawaiian plutonicrocks in having alkali feldspar, apatite, zircon and biotite,and evolved mineral compositions (e.g. albitic feldspar, clinopyroxeneMg-number 67–78). Fine-grained diorites and monzodioritesare plutonic equivalents of mugearite lavas, which are unknownat Huallai. These xenoliths appear to represent melt compositionsfalling along a liquid line of descent leading to trachyte—amagma type which erupted from Huallai as a prodigious lava flowand scoria cone at 114 ka. Inferred fractionating assemblages,MELTS modeling, pyroxene geobarometry and whole-rock norms allpoint to formation of the parent rocks of the leucocratic xenolithsat 3–7 kbar pressure. This depth constraint on xenolithformation, coupled with a demonstrated affinity to hypersthene-normativebasalt and petrologic links between the xenoliths and the trachyte,suggests that the shift from shield to post-shield magmatismat Huallai was accompanied by significant deepening of the activemagma reservoir and a gradual transition from tholeiitic toalkalic magmas. Subsequent differentiation of transitional basaltsby fractional crystallization was apparently both extreme—culminatingin >5·5 km³ of trachyte—and rapid, at 2·75x 10⁶ m³ magma crystallized/year. KEY WORDS: geothermobarometry; magma chamber; xenolith; cumulate; intensive parameters  相似文献