Vertical abundance profiles of hydrocarbons in Titan's atmosphere at 15° S and 80° N retrieved from Cassini/CIRS spectra     

Sandrine Vinatier  Bruno Bézard  Nick A. Teanby  Patrick G.J. Irwin  Conor A. Nixon  F. Michael Flasar 《Icarus》2007,188(1):120-138

Limb spectra recorded by the Composite InfraRed Spectrometer (CIRS) on Cassini provide information on abundance vertical profiles of C₂H₂, C₂H₄, C₂H₆, CH₃C₂H, C₃H₈, C₄H₂, C₆H₆ and HCN, along with the temperature profiles in Titan's atmosphere. We analyzed two sets of spectra, one at 15° S (Tb flyby) and the other one at 80° N (T3 flyby). The spectral range 600-1400 cm⁻¹, recorded at a resolution of 0.5 cm⁻¹, was used to determine molecular abundances and temperatures in the stratosphere in the altitude range 100-460 km for Tb and 170-495 km for T3. Both temperature profiles show a well defined stratopause, at around 310 km (0.07 mbar) and 183 K at 13° S, and 380 km (0.01 mbar) with 207 K at 80° N. Near the north pole, stratospheric temperatures are colder and mesospheric temperatures are warmer than near the equator. C₂H₂, C₂H₆, C₃H₈ and HCN display vertical mixing ratio profiles that increase with height at 15° S and 80° N, consistent with their formation in the upper atmosphere, diffusion downwards and condensation in the lower stratosphere, as expected from photochemical models. The CH₃C₂H and C₄H₂ mixing ratios also increase with height at 15° S. But near the north pole, their profiles present an unexpected minimum around 300 km, observed for the first time thanks to the high vertical resolution of the CIRS limb data. C₂H₄ is the only molecule having a vertical abundance profile that decreases with height at 15° S. At 80° N, it also displays a minimum of its mixing ratio around the 0.1-mbar level. For C₆H₆, an upper limit of 1.1 ppb (in the 0.3-10 mbar range) is derived at 15° S, whereas a constant mixing ratio profile of is inferred near the north pole. At 15° S, the vertical profile of HCN exhibits a steeper gradient than other molecules, which suggests that a sink for this molecule exists in the stratosphere, possibly due to haze formation. All molecules display a more or less pronounced enrichment towards the north pole, probably due, in part, to subsidence of air at the north (winter) pole that brings air enriched in photochemical compounds from the upper atmosphere to lower levels.  相似文献   

Messing with nature? Exploring public perceptions of geoengineering in the UK     

Adam Corner  Karen Parkhill  Nick Pidgeon  Naomi E. Vaughan 《Global Environmental Change》2013,23(5):938-947

Anthropogenic influence on the climate – and possible societal responses to it – offers a unique window through which to examine the way people think about and relate to the natural world. This paper reports data from four, one-day deliberative workshops conducted with members of the UK public during early 2012. The workshops focused on geoengineering – the deliberate, large-scale manipulation of the planetary environment – as one of three possible responses to climate change (alongside mitigation and adaptation). Here, we explore one of the most pervasive and wide-ranging themes to emerge from the workshops: whether geoengineering represented an unprecedented human intervention into ‘nature’, and what the moral consequences of this might be. Using the concept of ‘messing with nature’ as an analytical lens, we explore public perceptions of geoengineering. We also reflect on why ‘messing with nature’ was such a focal point for debate and disagreement, and whether the prospect of geoengineering may reveal new dimensions to the way that people think about the natural world, and their relationship to it.  相似文献   

Skills constraints and the low carbon transition     

Nick Jagger  Tim Foxon  Andy Gouldson 《Climate Policy》2013,13(1):43-57

Achieving a successful transition to a low carbon economy, in the UK and other countries, will require sufficient people with appropriate qualifications and skills to manufacture, install, and operate the low carbon technologies and approaches. The actual numbers and types of skills required are uncertain and will depend on the speed and direction of the transition pathways, but there are reasons to doubt that market mechanisms will deliver the necessary skilled workers in a timely manner. The range of market, government, and governance failures relating to the provision of low carbon skills are examined, particularly for their potential to cause a slower, costlier, and less employment-intensive transition. The potential policy responses to these failures are considered, including standardization of funding for training; formalization of transferable qualifications; legally binding targets for carbon emissions reductions and low carbon technology deployment; framework contracts and agreements between actors in key sectors; licensing and accreditation schemes for key technology sectors; government support for skills academies and training centres; support for first movers in niches; increasing mobility of workers; and providing a clear long-term cross-sectoral framework for a low carbon transition, including skills training.

Policy relevance

The article argues for the importance of skills issues for a successful transition to a low carbon economy. It outlines the potential causes of skills shortages, both generic and those specific to low carbon, as well as the probable impact of these types of shortages. By changing existing sectoral and occupational patterns, the transition will disrupt the existing market and government mechanisms to identify and remedy skills shortages in specific sectors. The nature and required pace of the low carbon transition also means that there are pressures that could induce greater skills shortages. These shortages, in turn, could critically delay elements of the transition and increase its cost and duration. The article outlines approaches taken to address these causes of skills shortages, drawing on examples from UK low carbon policy. The article ends with an argument that skills issues need to be more central to transitions debates.  相似文献   

Erratum to: Predicting June Mean Rainfall in the Middle/Lower Yangtze River Basin     

Gill M. MARTIN  Nick J. DUNSTONE  Adam A. SCAIFE  Philip E. BETT 《大气科学进展》2020,37(9):1032-1032

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Surface mean temperature from the observational stations and multiple reanalyses over the Tibetan Plateau     

Yan  Yuping  You  Qinglong  Wu  Fangying  Pepin  Nick  Kang  Shichang 《Climate Dynamics》2020,55(9-10):2405-2419

The Tibetan Plateau (TP), also called the “Third pole”, is sensitive to climate change due to extensive areas at high elevation presently dominated by snow and ice. In this study, observed surface temperature trends at 150 stations over the TP during 1979–2018 are analyzed and compared with surface temperatures from multiple reanalyses (NCEP1, NCEP2, ERA-Interim, MERRA, JRA55). Observed warming at the stations has a mean annual rate of 0.46 °C/decade during 1979–2018. Although all reanalyses underestimate observed temperatures (cold bias), most reproduce much of the inter-decadal variations of surface temperature shown in the observations. Absolute errors of mean surface temperature (reanalysis minus observation) are closely correlated with elevation errors, suggesting that parts of the cold bias can be interpreted by elevation errors of reanalysis. After elevation-temperature correction, about half of the cold bias is typically eliminated, more for both ERA-Interim and JRA55. Compared with the observations, corrected NCEP2 surface temperatures still have larger cold biases, and fail to capture the overall warming over the TP. Since the elevation-temperature correction fails to improve trend magnitudes even when a significant proportion of the bias has been removed, this suggests that a more sophisticated modeling of the lapse rate in each reanalysis is required to realistically model warming trends across complex topography.

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The survivability of phyllosilicates and carbonates impacting Stardust Al foils: Facilitating the search for cometary water          下载免费PDF全文

Penelope J. Wozniakiewicz  Hope A. Ishii  Anton T. Kearsley  John P. Bradley  Mark. C. Price  Mark J. Burchell  Nick Teslich  Mike J. Cole 《Meteoritics & planetary science》2015,50(12):2003-2023

Comet 81P/Wild 2 samples returned by NASA's Stardust mission provide an unequalled opportunity to study the contents of, and hence conditions and processes operating on, comets. They can potentially validate contentious interpretations of cometary infrared spectra and in situ mass spectrometry data: specifically the identification of phyllosilicates and carbonates. However, Wild 2 dust was collected via impact into capture media at ~6 km s^?1, leading to uncertainty as to whether these minerals were captured intact, and, if subjected to alteration, whether they remain recognizable. We simulated Stardust Al foil capture conditions using a two‐stage light‐gas gun, and directly compared transmission electron microscope analyses of pre‐ and postimpact samples to investigate survivability of lizardite and cronstedtite (phyllosilicates) and calcite (carbonate). We find the phyllosilicates do not survive impact as intact crystalline materials but as moderately to highly vesiculated amorphous residues lining resultant impact craters, whose bulk cation to Si ratios remain close to that of the impacting grain. Closer inspection reveals variation in these elements on a submicron scale, where impact‐induced melting accompanied by reducing conditions (due to the production of oxygen scavenging molten Al from the target foils) has resulted in the production of native silicon and Fe‐ and Fe‐Si‐rich phases. In contrast, large areas of crystalline calcite are preserved within the calcite residue, with smaller regions of vesiculated, Al‐bearing calcic glass. Unambiguous identification of calcite impactors on Stardust Al foil is therefore possible, while phyllosilicate impactors may be inferred from vesiculated residues with appropriate bulk cation to Si ratios. Finally, we demonstrate that the characteristic textures and elemental distributions identifying phyllosilicates and carbonates by transmission electron microscopy can also be observed by state‐of‐the‐art scanning electron microscopy providing rapid, nondestructive initial mineral identifications in Stardust residues.  相似文献   

The hydrology of inland valleys in the sub‐humid zone of West Africa: rainfall‐runoff processes in the M'bé experimental watershed     

Mutsa C. Masiyandima  Nick van de Giesen  Sitapha Diatta  Pieter N. Windmeijer  Tammo S. Steenhuis 《水文研究》2003,17(6):1213-1225

Inland valleys with wet lowlands are an important water source for farming communities in the sub‐humid zone of West Africa. An inland valley and surrounding contributing watershed area located in the sub‐humid zone near M'bé in central Côte d'Ivoire was instrumented to study surface runoff and base flow mechanisms. Four flumes at different distances down the main stream and more than 100 piezometers were installed. Measurements were taken during two rainfall seasons in 1998 and 1999. Under initial wet conditions, a typical single‐peak hydrograph was observed. Under low antecedent moisture conditions, however, runoff was characterized by a double‐peaked hydrograph. The first peak, which occurred during the storm, was caused by rain falling on the saturated valley bottom. The second peak was delayed by minutes to hours from the first peak and consisted of rain flowing via the subsurface of the hydromorphic zone that surrounds the valley bottom. The duration of the delay was a function of the water table depth in the hydromorphic zone before the storm. The volume of the second peak constituted the largest portion of the stream flow. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

Study of the contact binary AK Herculis: Light-curve analysis and orbital period investigation     

Helen Rovithis-Livaniou  Emma Fragoulopoulou  Nick Sergis  Petros Rovithis  Athanassios Kranidiotis 《Astrophysics and Space Science》2001,275(4):337-348

AK Her is a very interesting contact binary exhibiting variable lightcurves and an obvious O'Connell effect, with max I greater than max II. Inthe present work an extensive study of this system is made covering notonly its light curve analysis, but also its orbital period changes in anattempt to give a definite answer regarding the apsidal motion of AK Her.Photoelectric observations of AK Her, obtained between 1985–1987 at theNational Observatory of Athens Greece, are presented, analysed anddiscussed. The light curve analysis was made with the W-D code and thegeometric and photometric elements of the system were derived. TheO'Connell effect was faced with a two dark spot model. Moreover, theorbital period of the system was examined and two periodicities weredetected. Since the first one corresponds to the time interval for whichobservational data exist and the second was found to be half of the first,it turns out that none of them is true. Two other significant results thatcame from the present analysis are that the orbital period of AK Her doesnot follow a sinusoidal variation and that, from the times of minimumlight at primary and secondary eclipses, it seems that there is no apsidalmotion.  相似文献   

The role of midsummer urban aquifer recharge in stormflow generation using isotopic and chemical hydrograph separation techniques   总被引：1，自引：0，他引：1  

Mandana Meriano  Ken W.F. Howard  Nick Eyles 《Journal of Hydrology》2011,396(1-2):82-93

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Mineralogical and geochemical constraints on the shallow origin, ancient veining, and multi-stage modification of the Lherz peridotite     

Amy J.V. Riches  Nick W. Rogers 《Geochimica et cosmochimica acta》2011,75(20):6160-6182

New major- and trace-element data of bulk-rocks and constituent minerals, and whole-rock Re-Os isotopic compositions of samples from the Lherz Massif, French Pyrenees, reveal complex petrological relationships between the dominant lithologies of lherzolite ± olivine-websterite and harzburgite. The Lherz peridotite body contains elongate, foliation parallel, lithological strips of harzburgite, lherzolite, and olivine-websterite cross-cut by later veins of hornblende-bearing pyroxenites. Peridotite lithologies are markedly bimodal, with a clear compositional gap between harzburgites and lherzolites ± olivine-websterite. Bulk-rock and mineral major-element oxide (Mg-Fe-Si-Cr) compositions show that harzburgites are highly-depleted and result from ∼20-25 wt.% melt extraction at pressures <2 GPa. Incompatible and moderately-compatible trace-element abundances of hornblendite-free harzburgites are analogous to some mantle-wedge peridotites. In contrast, lherzolites ± olivine-websterite overlap estimates of primitive mantle composition, yet these materials are composite samples that represent physical mixtures of residual lherzolites and clinopyroxene dominated cumulates equilibrated with a LREE-enriched tholeiitic melt. Trace-element compositions of harzburgite, and some lherzolite bulk-rocks and pyroxenes have been modified by; (1) wide-spread interaction with a low-volume LREE-enriched melt +/− fluid that has disturbed highly-incompatible elements (e.g., LREEs, Zr) without enrichment of alkali- and Ti-contents; and (2) intrusion of relatively recent, small-volume, hornblendite-forming, basanitic melts linked to modal and cryptic metasomatism resulting in whole-rock and pyroxene Ti, Na and MREE enrichment.Rhenium-Os isotope systematics of Lherz samples are also compositionally bimodal; lherzolites ± olivine-websterite have chondritc to suprachondritic ¹⁸⁷Os/¹⁸⁸Os and ¹⁸⁷Re/¹⁸⁸Os values that overlap the range reported for Earth’s primitive upper mantle, whereas harzburgites have sub-chondritic ¹⁸⁷Os/¹⁸⁸Os and ¹⁸⁷Re/¹⁸⁸Os values. Various Os-model age calculations indicate that harzburgites, lherzolites, and olivine-websterites have been isolated from convective homogenisation since the Meso-Proterozoic and this broadly coincides with the time of melt extraction controlled by harzburgite Os-isotope compositions. The association between harzburgites resulting from melting in mantle-wedge environments and Os-rich trace-phases (laurite-erlichmanite sulphides and Pt-Os-Ir-alloys) suggests that a significant portion of persistent refractory anomalies in the present-day convecting mantle of Earth may be linked to ancient large-scale melting events related to wide-spread subduction-zone processing.  相似文献