Biogeochemical ocean-atmosphere transfers in the Arabian Sea   总被引：2，自引：2，他引：2  

S. Wajih A. Naqvi  Hermann W. Bange  Stuart W. Gibb  Catherine Goyet  Angela D. Hatton  Robert C. Upstill-Goddard 《Progress in Oceanography》2005,65(2-4):116

Transfers of some important biogenic atmospheric constituents, carbon dioxide (CO₂), methane (CH₄), molecular nitrogen (N₂), nitrous oxide (N₂O), nitrate , ammonia (NH₃), methylamines (MAs) and dimethylsulphide (DMS), across the air–sea interface are investigated using published data generated mostly during the Arabian Sea Process Study (1992–1997) of the Joint Global Ocean Flux Study (JGOFS). The most important contribution of the region to biogeochemical fluxes is through the production of N₂ and N₂O facilitated by an acute, mid-water deficiency of dissolved oxygen (O₂); emissions of these gases to the atmosphere from the Arabian Sea are globally significant. For the other constituents, especially CO₂, even though the surface concentrations and atmospheric fluxes exhibit extremely large variations both in space and time, arising from the unique physical forcing and associated biogeochemical environment, the overall significance in terms of their global fluxes is not much because of the relatively small area of the Arabian Sea. Distribution and air–sea exchanges of some of these constituents are likely to be greatly influenced by alterations of the subsurface O₂ field forced by human-induced eutrophication and/or modifications to the regional hydrography.  相似文献   

Passatzirkulation und äquatoriale Westwindzone     

H. Flohn 《Theoretical and Applied Climatology》1951,3(1):3-15

Zusammenfassung Auf Grund der Feststellung einer weitgehenden Unabhängigkeit von Boden- und Höhenwind in Äquatornähe wird das Bestehen einer meridionalen Passatzirkulation innerhalb des Urpassates nachgewiesen. Während in Bodennähe eine Komponente zum (meteorologischen) Äquator weht, kehrt sich diese Richtung oberhalb der Reibungsschicht in 1,5 bis 3,5 km Höhe um. Diese im statistischen Mittel existierende ageostrophische Meridionalzirkulation hat mit der Verteilung der geostrophischen E- bzw. W-Winde (Urpassat, Antipassat) nichts zu tun.Die vertikale und horizontale Verbreitung äquatorialer Westwinde wird beschrieben. Diese wehen beiderseits des Äquators und können daher keinesfalls als übertretende Passate erklärt werden. Ihre Bildung stimmt überein mit einer thermisch bedingten Aufspaltung der innertropischen Konvergenzzone.

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Summary Besides the result of a significant independence of surface and upper winds near the equator the author proves the existence of a meridional trade-wind circulation within the tropical easterlies. While near the surface a component of wind is directed to the (meteorological) equator, we observe shifting in 1,5 to 3,5 kms, above the friction layer. This ageostrophic meridional circulation, existing only in a statistical sense, has no connexion to the distribution of geostrophic zonal winds, i.e. tropical easterlies or antitrades (W).The vertical and horizontal existence of equatorial westerlies is described. They are blowing on both sides of the equator, therefore their explanation as trade-winds crossing the equator must be rectified. Their formation corresponds with a splitting of the intertropical convergence zone.

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Résumé Admettant une indépendance assez large du vent au sol et du vent en altitude au voisinage de l'équateur, l'auteur prouve l'existence d'une circulation méridienne d'alizés à l'intérieur de la zone primordiale de ces derniers. Alors qu'au sol il y a une composante dirigée vers l'équateur météorologique, la direction du vent change au-dessus de la couche de frottement, entre 1,5 et 3,5 km d'altitude. Cette circulation méridienne non géostrophique qui apparaît dans les valeurs moyennes de vent n'a rien à voir avec la distribution des vents géostrophiques d'Est ou d'Ouest (alizés et contre-alizés). L'auteur décrit l'extension verticale et horizontale des vents d'Ouest équatoriaux; ceux-ci soufflent de part et d'autre de l'équateur et ne peuvent donc être considérés comme des alizés débordants. Leur formation est en harmonie avec un partage de la zone de convergence intertropicale d'origine thermique.

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Mit 3 Textabbildungen.  相似文献   

Allgemeine Atmosphärische Zirkulation und Paläoklimatologie     

H. Flohn 《International Journal of Earth Sciences》1952,40(1):153-178

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Late-Pleistocene and mid-Holocene environmental changes in highland valley head areas of Santa Catarina state, Southern Brazil   总被引：1，自引：0，他引：1  

Marcelo A.T. de Oliveira  Hermann Behling  Luiz C.R. Pessenda 《Journal of South American Earth Sciences》2008,26(1):55-67

Low resolution of the continental sedimentary record is a common source of skepticism about the application of geomorphology and sedimentology to Quaternary studies. In spite of this, when supported by independent proxy data, geomorphology and sedimentology may favor palaeo-hydrologic interpretation. This paper associates geomorphologic, stratigraphic, sedimentologic, isotopic, palynologic and geochronologic data. The research was conducted in valley head sites in southern Brazilian highlands, under mild subtropical climate. The results point to environmental changes, the ages of which coincide to Marine Isotopic Stages (MIS) 5b, 3, 2 and 1. Although late-Pleistocene temperatures and precipitation were lower than those of today, the study valley heads seem to have sustained locally wetter environments, which fed shallow soil–water saturated zones. These saturated zones are believed to have expanded during transitions between stadial and interstadial states, contributing to hillslope erosion and sedimentation regardless of the sign of the climatic change. The interior organization of holocenic slope-wash deposits suggests that the mid-Holocene climate was drier than today’s and was under the influence of seasonally contrasting precipitation regimes. The predominance of overland flow-related sedimentary records suggests that an excess of precipitation over evaporation influenced local palaeo-hydrology. This palaeo-hydrologic condition seems to have been recurrent and also explains the alternating periods of pedogenesis and sedimentation.  相似文献   

Socotra Island,Yemen: field survey of the 2004 Indian Ocean tsunami     

Hermann M. Fritz  Emile A. Okal 《Natural Hazards》2008,46(1):107-117

The tsunami of 26th December 2004 severely affected Yemen’s Socotra Island with a death at a distance of 4,600 km from the epicenter of the Magnitude 9.0 earthquake. Yemen allowed a detailed assessment of the far-field impact of a tsunami in the main propagation direction. The UNESCO mission surveyed 12 impacted towns on the north and south shores covering from the east to the west tip of Socotra. The international team members were on the ground in Yemen from 11 to 19 October 2006. The team measured tsunami run-up heights and inundation distances based on the location of watermarks on buildings and eyewitness accounts. Maximum run-up heights were typically on the order of 2–6 m. Each measurement was located by means of global positioning systems (GPS) and photographed. Numerous eyewitness interviews were recorded on video. The tsunami impact on Socotra is compared with other locations along the shores of the Indian Ocean.  相似文献   

Experimental subsolidus phase relations in the system CaCO3–CaMg(CO3)2 up to 6.5 GPa and implications for subducted marbles     

Jörg Hermann  Ulrike Troitzsch  Dean Scott 《Contributions to Mineralogy and Petrology》2016,171(10):84

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Correspondence     

Mrs Kathleen Sherrard  Dr Hermann Jaeger 《Australian Journal of Earth Sciences》2013,60(2):351-352

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Food consumption,diet shifts and associated non-CO2 greenhouse gases from agricultural production     

Alexander Popp  Hermann Lotze-Campen  Benjamin Bodirsky 《Global Environmental Change》2010,20(3):451-462

Today, the agricultural sector accounts for approximately 15% of total global anthropogenic emissions, mainly methane and nitrous oxide. Projecting the future development of agricultural non-CO₂ greenhouse gas (GHG) emissions is important to assess their impacts on the climate system but poses many problems as future demand of agricultural products is highly uncertain. We developed a global land use model (MAgPIE) that is suited to assess future anthropogenic agricultural non-CO₂ GHG emissions from various agricultural activities by combining socio-economic information on population, income, food demand, and production costs with spatially explicit environmental data on potential crop yields. In this article we describe how agricultural non-CO₂ GHG emissions are implemented within MAgPIE and compare our simulation results with other studies. Furthermore, we apply the model up to 2055 to assess the impact of future changes in food consumption and diet shifts, but also of technological mitigation options on agricultural non-CO₂ GHG emissions. As a result, we found that global agricultural non-CO₂ emissions increase significantly until 2055 if food energy consumption and diet preferences remain constant at the level of 1995. Non-CO₂ GHG emissions will rise even more if increasing food energy consumption and changing dietary preferences towards higher value foods, like meat and milk, with increasing income are taken into account. In contrast, under a scenario of reduced meat consumption, non-CO₂ GHG emissions would decrease even compared to 1995. Technological mitigation options in the agricultural sector have also the capability of decreasing non-CO₂ GHG emissions significantly. However, these technological mitigation options are not as effective as changes in food consumption. Highest reduction potentials will be achieved by a combination of both approaches.  相似文献   

Late Quaternary vegetation,climate and fire dynamics inferred from the El Tiro record in the southeastern Ecuadorian Andes     

Holger Niemann  Hermann Behling 《第四纪科学杂志》2008,23(3):203-212

In order to study the stability and dynamics of mountain rainforest and paramo ecosystems, including the biodiversity of these ecosystems, the Holocene and late Pleistocene climate and fire variability, and human impact in the southeastern Ecuadorian Andes, we present a high‐resolution pollen record from El Tiro Pass (2810 m elevation), Podocarpus National Park. Palaeoenvironmental changes, investigated by pollen, spores and charcoal analysis, inferred from a 127 cm long core spanning the last ca. 21 000 cal. yr BP, indicate that grass‐paramo was the main vegetation type at the El Tiro Pass during the late Pleistocene period. The grass‐paramo was rich in Poaceae, Plantago rigida and Plantago australis, reflecting cold and moist climatic conditions. During the early Holocene, from 11 200 to 8900 cal. yr BP, subparamo and upper mountain rainforest vegetation expanded slightly, indicating a slow warming of climatic conditions during this period. From 8900 to 3300 cal. yr BP an upper mountain rainforest developed at the study site, indicated by an increase in Hedyosmun, Podocarpaceae, Myrsine and Ilex. This suggests a warmer climate than the present day at this elevation. The modern subparamo vegetation became established since 3300 cal. yr BP at El Tiro Pass. Fires, probably anthropogenic origin, were very rare during the late Pleistocene but became frequent after 8000 cal. yr BP. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Stardust-NExT,Deep Impact,and the accelerating spin of 9P/Tempel 1     

Michael J.S. Belton  Karen J. Meech  Steven Chesley  Jana Pittichová  Brian Carcich  Michal Drahus  Alan Harris  Stephen Gillam  Joseph Veverka  Nicholas Mastrodemos  William Owen  Michael F. A’Hearn  S. Bagnulo  J. Bai  L. Barrera  Fabienne Bastien  James M. Bauer  J. Bedient  B.C. Bhatt  Hermann Boehnhardt  H. Zhao 《Icarus》2011,213(1):345-368

The evolution of the spin rate of Comet 9P/Tempel 1 through two perihelion passages (in 2000 and 2005) is determined from 1922 Earth-based observations taken over a period of 13 year as part of a World-Wide observing campaign and from 2888 observations taken over a period of 50 days from the Deep Impact spacecraft. We determine the following sidereal spin rates (periods): 209.023 ± 0.025°/dy (41.335 ± 0.005 h) prior to the 2000 perihelion passage, 210.448 ± 0.016°/dy (41.055 ± 0.003 h) for the interval between the 2000 and 2005 perihelion passages, 211.856 ± 0.030°/dy (40.783 ± 0.006 h) from Deep Impact photometry just prior to the 2005 perihelion passage, and 211.625 ± 0.012°/dy (40.827 ± 0.002 h) in the interval 2006–2010 following the 2005 perihelion passage. The period decreased by 16.8 ± 0.3 min during the 2000 passage and by 13.7 ± 0.2 min during the 2005 passage suggesting a secular decrease in the net torque. The change in spin rate is asymmetric with respect to perihelion with the maximum net torque being applied on approach to perihelion. The Deep Impact data alone show that the spin rate was increasing at a rate of 0.024 ± 0.003°/dy/dy at JD2453530.60510 (i.e., 25.134 dy before impact), which provides independent confirmation of the change seen in the Earth-based observations.The rotational phase of the nucleus at times before and after each perihelion and at the Deep Impact encounter is estimated based on the Thomas et al. (Thomas et al. [2007]. Icarus 187, 4–15) pole and longitude system. The possibility of a 180° error in the rotational phase is assessed and found to be significant. Analytical and physical modeling of the behavior of the spin rate through of each perihelion is presented and used as a basis to predict the rotational state of the nucleus at the time of the nominal (i.e., prior to February 2010) Stardust-NExT encounter on 2011 February 14 at 20:42.We find that a net torque in the range of 0.3–2.5 × 10⁷ kg m² s^?2 acts on the nucleus during perihelion passage. The spin rate initially slows down on approach to perihelion and then passes through a minimum. It then accelerates rapidly as it passes through perihelion eventually reaching a maximum post-perihelion. It then decreases to a stable value as the nucleus moves away from the Sun. We find that the pole direction is unlikely to precess by more than ～1° per perihelion passage. The trend of the period with time and the fact that the modeled peak torque occurs before perihelion are in agreement with published accounts of trends in water production rate and suggests that widespread H₂O out-gassing from the surface is largely responsible for the observed spin-up.  相似文献