共查询到20条相似文献，搜索用时 31 毫秒
1.
The Sun provides the main energy input to the terrestrial atmosphere, and yet the impact of solar variability on long-term changes remains a controversial issue. Direct radiative forcing is the most studied mechanism. Other much weaker mechanisms, however, can have a significant leverage, but the underlying physics is often poorly known. We review the main mechanisms by which solar variability may impact the terrestrial atmosphere on time scales ranging from days to millennia. This includes radiative forcing, but also the effect of interplanetary perturbations and energetic particle fluxes, all of which are eventually driven by the solar magnetic field. 相似文献
2.
Doklady Earth Sciences - 相似文献
3.
Paul Poli 《Comptes Rendus Geoscience》2010,342(4-5):357-369
Measurements of the atmosphere by satellite were first collected in the 1960s. However, it was not until the mid-1990s that these observations were translated into systematic improvements of numerical weather forecasts. We present here the data and methodology of data assimilation that enabled this achievement. Data assimilation is essentially a filtering processing that exploits the (assumed) known error statistical properties of the observations and of the underlying numerical model in which data are assimilated. It is also a process which corrects the state of the numerical model with physical observations of the real world. This part relies on (assumed) known physical laws to relate meteorological quantities (such as temperature, humidity, pressure, and wind) to observables. Atmospheric data collected by satellite all come from the interaction of electromagnetic waves with the atmosphere. Satellite data assimilation has greatly supported the progress in numerical weather prediction and holds promises for climate studies, for example via reanalysis. 相似文献
4.
Uwe Radok 《International Journal of Earth Sciences》1981,70(2):703-724
Alfred Wegener initiated the study of the free polar atmosphere with more than 100 kite and tether balloon soundings to above 3000 m at Danmarkshavn, North Greenland, during 1906–09. From this beginning polar aerology advanced through a series of similar point studies to the first full upper air network during the IGY (1957/8). While its replacement by satellite remote sensing is gradually taking shape, the accumulated polar information has been thoroughly analyzed; a series of comprehensive accounts is referenced. The aspects singled out for this review are themes that would have been of special interest to Wegener — the surface energy balance and the polar inversion, the katabatic winds and snow drift, and the aerosols of the polar atmosphere.
Zusammenfassung Alfred Wegener begann das Studium der freien Polaratmosphäre mit über 100 Drachen- und Fesselballonaufstiegen auf Höhen über 3000 m bei Danmarkshavn in Nordgrönland während der Jahre 1906–1909. Von diesem Anfang entwickelte sich die Polaraerologie durch eine Reihe ähnlicher Lokalstudien bis zum ersten vollständigen Beobachtungsnetz der freien Atmosphäre während des IGY (1956–8). Während des allmählichen Ersatzes dieses Systems durch Fernmessungen von Satelliten aus wurde die angesammelte Polarinformation gründlich analysiert; eine Reihe von umfassenden Berichten wird angeführt. Die hier behandelten Studien wären für Wegener von besonderem Interesse gewesen, da sie die Energiebilanz der Oberfläche und die Polarinversion, den katabatischen Wind und das Schneetreiben, und das Aerosol der Polaratmosphäre betreffen.
Résumé C'est Alfred Wegener qui a commencé l'étude de l'atmosphère polaire par des sondages à l'aide de cerfs-volants et de ballons attachés jusqu'à une hauteur de 3000 m. à Danmarks-Havn au Groenland nord, de 1906 à 1909. Après ce début l'aérologie polaire se développa sur la base d'études locales jusqu'à l'établissement d'un premier réseau de stations d'observations pendant l'année géophysique internationale 1957–58. La recherche exposée ici aurait probablement intéressé Wegener car elle se rapporte à la balance énergétique de surface et à l'inversion polaire, aux vents katabatiques, à le chasse neige et aux aérosols de l'atmosphère polaire.
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5.
Zbigniew Jaworowski Maria Bysiek Ludwika Kownacka 《Geochimica et cosmochimica acta》1981,45(11):2185-2199
Concentrations of 137Cs, 210Pb, 226Ra, U, V, Pb, Cd and Hg have been measured in firn and ice deposited during the past three decades in accumulation zones of glaciers and also in pre-industrial glacier ice collected in Spitsbergen, Northern Norway, Alaska, Southern Norway, Alps, Himalayas, Ruwenzori, Peruvian Andes, and at King George Island in Antarctica. Except for Hg, the geographical distribution of mean concentrations of 226Ra, U and stable heavy metals in contemporary ice is not uniform, with the lowest concentrations found in Northern Norway, Alaska and Antarctica, and the highest in continental locations at equatorial and middle latitudes. We did not find evidence of changes in rate of metal deposition during the last three decades, as compared with pre-industrial period, however, our samples of pre-industrial ice might be contaminated in part by contemporary fallout migrating from the exposed surface of old parts of glaciers into the deeper ice layers. Using the data on annual injections of 137Cs into the global atmosphere and mean global concentrations of radionuclides and heavy metals found in contemporary ice the global annual flows of 226Ra, 210Pb, U,V, Pb, Cd and Hg were estimated as 6.6 kCi, 485 kCi, 12kt, 4870kt, 590 kt, 180 kt and 190 kt, respectively. These estimates are 1–2 orders of magnitude higher than estimates based on primary paniculate emissions. The anthropogenic contribution is a small fraction of the flows, which are dominated by natural processes leading to enrichment of metals in airborne dust. 相似文献
6.
The structures called Whitney gathers in the catastrophe theory are not unusual among the various types of chromospheric Hα filaments and coronal helmets. They result from a projection of smooth surfaces onto a plane of the sky. The apices of the helmets can be described as gathers of the surface B r = 0 in the corona (where B r is the magnetic field). Near the limb, Hα filaments are frequently observed as similar types of structures. A model of the B r = 0 surface with sources located inside the Sun (∫ Bds = 0) is constructed here in this context. Gathers and folds of this surface are shown to be possible in relatively simple fields. Our model computations are supported by the available observational data. 相似文献
7.
The recent theoretical studies on the formation and evolution of the atmosphere and oceans of the Earth are reviewed. Impact degassing during accretion of the Earth would probably generate an impact-induced steam atmosphere on the proto-Earth. At the end of accretion, the steam atmosphere became unstable and condensed to form the proto-ocean with almost the present mass of ocean. The steam atmosphere would have thus evolved to the proto-CO2 atmosphere during the earliest history of the Earth because CO in the proto-atmosphere may be photochemically converted to CO2. However, CO2 in the proto-atmosphere has decreased with time through the global carbon cycle which may have stabilized the terrestrial environment against an increase in the solar luminosity. The continental growth during Hadean and Archean would therefore have a significant influence on the carbon cycle and the surface temperature. It is also suggested that the continental growth is a necessary condition for the terrestrial environment to evolve to the present state. Both the impact degassing and the subsequent continuous degassing are suggested to have played a major role in the formation and evolution of the atmosphere and ocean. In particular, most of N2 may have been produced by the impact degassing during accretion, and the contribution of the subsequent continuous degassing is at most 10% for N2. As a consequence, after the CO2 level decreased to less than 1 bar, the atmosphere may have been at about 1 bar and composed mainly of N2 for most of the subsequent history of the Earth. 相似文献
8.
A detailed model is presented of methane photochemistry in the primitive terrestrial atmosphere along with speculation about its interpretation. Steady-state CH4 mixing ratios of 10−6–10−4 could have been maintained by a methane source of about 1011 cm−2 s−1, which is comparable to the modern biogenic methane production rate. In the absence of a source, methane would have disappeared in <104 years, being either oxidized, or polymerized into more complex hydrocarbons. The source strength needed to maintain a steady CH4 mixing ratio and the degree to which methane could have polymerized to form higher hydrocarbons depend upon the amount of CO2 present in the early atmosphere. The dependence on H2 is much weaker. Infrared absorption by methane, and especially by other hydrocarbon species, may have supplemented the greenhouse warming due to carbon dioxide. A radiative model is needed to establish this effect quantitatively. The destruction of the methane greenhouse early in the Proterozoic may have triggered the Huronian glaciation.These calculations also suggest that atmospheres rich in both CO2 and CH4 may be photochemically unstable with respect to conversion to CO. 相似文献
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10.
François Barlier 《Comptes Rendus Geoscience》2010,342(4-5):301-311
The Earth is surrounded by a layer of relatively thin gas, the mass of which is mainly concentrated in the first kilometres. With an exponential decrease of the density of the atmosphere as a function of altitude, 99.9% of this mass is located in the first 50 km. In addition, the composition of major species is homogeneous up to about 85 km, contrarily to what happens beyond. This is the homosphere. This layer of atmosphere, considered in this special issue, is also that which we breathe and which we unfortunately often pollute. All this justifies considering it as of vital importance, in the most basic sense of the word. However, in studying it, it is not possible to ignore what is happening beyond, from where comes, in particular, solar radiation, just as we cannot ignore what happens below the continents and the oceans, where solar radiation is absorbed, diffused and re-emitted to the top by the Earth's surface as infrared radiation. We must therefore keep in mind what are the layers that surround the homosphere, the importance of observing them and also give some examples of possible interactions which may exist with the surrounding layers; these are the objectives of these introductory remarks. Another general consideration must be made here, concerning the problems, which have existed until the middle of the 20th century, of how to observe the atmosphere in situ at all the altitudes. However, since then, the development of engineering involving balloons, rockets, aircrafts and artificial satellites has revolutionized our knowledge of this observational atmosphere; this is the second message of these remarks. 相似文献
11.
Despite uncertainties in our understanding of early Earth volcanism and atmospheric composition, thermodynamic modelling is able to offer estimates of the global production of reactive trace species (NO, OH, SO3, Cl, Br and I) from early Earth volcanism, and thereby to shed light on processes which may have been different in Earth’s early atmosphere. Model results show that thermal decomposition of magmatic H2O, CO2 and SO2 in high-T mixtures of magmatic and atmospheric gases (at T > 1400 °C) generate high levels of reactive trace gas species. Production of these reactive trace species is insensitive to atmospheric CO2 in mixtures where the atmospheric gas is the minor component and will hence continue during periods of low atmospheric CO2. Fluxes of NO, OH, Cl, Br and I from early Earth volcanism are predicted to exceed those from modern Earth volcanism as the higher temperature of early Earth emissions compensates for lower levels of O2 in the atmosphere, compared to the modern Earth. Under certain conditions, the volcanic NO flux from early Earth volcanism is found to be comparable to other sources of reactive N such as lightning NO and photochemical HCN. This is one possible source of fixed nitrogen which may alleviate any postulated Archean nitrogen crisis. Our thermodynamic model reveals that production of SO3 (a potential precursor for near-source volcanic sulphate and hence ‘primary’ volcanic aerosol) is likely to be significantly lower from early Earth volcanism. Uncertainty in the pathway to near-source sulphate in modern volcanism (i.e., the reaction of SO3 with water or direct emission) introduces a large uncertainty into the production rate of near-source volcanic sulphate on the early Earth. 相似文献
12.
Per Geijer 《Geochimica et cosmochimica acta》1956,10(5-6):304-308
Sedimentary haematite ores of central Sweden give evidence of the existence of an oxidizing atmosphere about 2000 × 106 years ago. This is not consistent with Rankama's conclusions from the unoxidized condition of a diorite conglomerate in Finland. Therefore a (later) Pre-Cambrian conglomerate in northern Sweden has been examined for comparison. Where it is made up of dioritic material no proofs of oxidation can be found, but where the material is mainly iron-ore pebbles, magnetite ore is found to have been completely oxidized to haematite (martite) before being embedded as pebbles in the conglomerate. 相似文献
13.
STEVE KERSHAW 《Geology Today》1990,6(2):55-60
Current problems with the ozone layer and rising carbon dioxide levels have highlighted the importance of the atmosphere, with its delicate balance of gases. In fact, the atmosphere has been changing since the Earth formed. From anoxic beginnings to its current oxygenated state, it has influenced depositional processes on the Earth's surface and helped the development of active, oxygen-breathing life forms that culminated in ourselves. Evidence for changes in the atmosphere is found in the sediments accumulated on the Earth's surface, where fossils are also preserved. In this article the major geological aspects of the atmosphere's evolution are considered; in particular, the role of oxygen is aired. 相似文献
14.
A. A. Vedenov V. A. Koutvitsky S. Koutchmy M. M. Molodensky V. N. Oraevsky 《Astronomy Reports》2000,44(2):112-121
Three-dimensional structures in the solar chromosphere and corona are considered. It is demonstrated that two photoheliograms separated by ～1 day can be used (using computer-graphics methods) to construct a stereo image of the Sun. The algorithm for this is presented and carried out for Hα images of the total disk. A bulge in the equatorial region resulting from the differential rotation of the Sun can be seen in the stereo image. Structures called Whitney pleats in catastrophe theory are observed in the solar corona. Such structures are encountered in prominences. The well-known helmets (or streamers) are pleats of heliospheric plasma sheets. Isophotes for such a sheet and the degree of polarization of the radiation in the pleat are calculated and compared with observational data. 相似文献
15.
Electromagnetic radiation, in its passage through the atmosphere, is attenuated by absorption and scattering by atmospheric
gases, dust and aerosols. The most important absorber is water vapour and the most significant parameter in atmospheric absorption
studies is the total precipitable water in the atmosphere. The present paper summarises the results of a study made to compute
the total precipitable water in the atmosphere over India using radiosonde and other data, as part of a programme for the
computation of direct, global and diffuse solar radiation at the ground from the solar constant. Using values of air temperature
and dew point from the ground up to 250 mb at 19 radiosonde stations and surface water vapour mixing ratio values at 105 surface
observatories in India, precipitable water amounts have been computed for 124 stations, for each month and for the whole year.
The paper describes the techniques used to extend the total precipitable water amounts derived from radiosonde data at 19
stations to 124 stations covering the major climatic zones in the country and presents the results in the form of 12 maps
showing the spatial and temporal distribution of total precipitable water over India 相似文献
16.
The precise amount of O2 and O3 in the Earth's prebiological paleoatmosphere has been a topic of considerable discussion in the past. Since the photolysis of H2O and CO2, the prebiological mechanisms to produce O2, depends on the ultraviolet (UV) flux from the Sun, a reliable quantification of the problem requires detailed knowledge of such flux. Using the most recent astronomical observation of young stars from the International Ultraviolet Explorer, as well as a detailed photochemical model of the paleoatmosphere, we find that the amount of O2 in the prebiological paleoatmosphere may have been as much as 106 times greater than previously estimated.Some of the implications of this new value are discussed. 相似文献
17.
Based on a certain analogy between the physical conditions in the region of the upper atmosphere, transitional from the mesosphere
to the lower thermosphere (MLT), and the atmospheric boundary layer (ABL), for the first time for the upper atmosphere we
obtained helicity estimates and analyzed the Ekmantype instability. The performed calculations of the orientation of the formed
periodic structures agree with the experimental data. 相似文献
18.
Why the atmosphere became oxygenated: A proposal 总被引：3，自引：0，他引：3
The increase in the oxidation state of the atmosphere during Earth history is well documented, but not the reasons for this process. The course of atmospheric evolution has been dominated by the effects of photosynthesis and by the composition of volcanic gases. The H2/H2O ratio of volcanic gases has remained essentially constant during most of Earth history. It is here proposed that their CO2/H2O and SO2/H2O ratios have increased with time. A simple model for the degassing and the recycling of CO2, SO2, and H2O can account for many of the major steps in the oxygenation of the atmosphere. 相似文献
19.
Current models predict that the early atmosphere consisted mostly of CO2, N2, and H2O, along with traces of H2 and CO. Such models are based on the assumption that the redox state of the upper mantle has not changed, so that volcanic gas composition has remained approximately constant with time. We argue here that this assumption is probably incorrect: the upper mantle was originally more reduced than today, although not as reduced as the metal arrest level, and has become progressively more oxidized as a consequence of the release of reduced volcanic gases and the subduction of hydrated, oxidized seafloor. Data on the redox state of sulfide and chromite inclusions in diamonds imply that the process of mantle oxidation was slow, so that reduced conditions could have prevailed for as much as half of the earth's history. To be sure, other oxybarometers of ancient rocks give different results, so the question of when the mantle redox state has changed remains unresolved. Mantle redox evolution is intimately linked to the oxidation state of the primitive atmosphere: A reduced Archean atmosphere would have had a high hydrogen escape rate and should correspond to a changing mantle redox state; an oxidized Archean atmosphere should be associated with a constant mantle redox state. The converses of these statements are also true. Finally, our theory of mantle redox evolution may explain why the Archean atmosphere remained oxygen-deficient until approximately 2.0 billion years ago (Ga) despite a probable early origin for photosynthesis. 相似文献
20.
Mikio Shimizu 《Precambrian Research》1976,3(5):463-470
The eddy diffusion coefficient in the primitive upper atmosphere of highly reducing type (CH4H2) is estimated to be of the order of 108 cm2sec?1 or a little less, by solving the dissipation equation of internal gravity waves. Such a strong atmospheric mixing is clearly inconsistent with the previous assumption by McGovern that photochemical equilibrium was established in the upper atmosphere. By taking into account the mixing effect, the exospheric temperature of the highly reducing atmosphere has been computed to be higher than 1300°K. The result indicates that the hypothetical reducing atmosphere might have disappeared, if it existed, in a short time due to the gravitational escape of hydrogen and, consequently, that an anoxygenous but non-reducing atmosphere might be a more plausible environment for the origin of life. 相似文献