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根据行星探测的资料,综合分析了水星、金星、地球(包括月球)、火星的大气层和水体的发育特征,对比了金星、火星的大气层与水体同地球的差异。类地行星质量小、体积小、密度大、旋转慢、卫星少甚至没有、挥发性元素较类木行星少、距离太阳较近,早期残留的原始大气层已经被早期太阳在金牛变星阶段的强烈太阳风所驱赶,加上巨大而频繁的撞击作用,使原始大气层被驱赶殆尽。现在的大气层是次生的,是由行星内部的去气作用形成的。类地行星的大气层、水体的发育和表生作用的特征与行星的质量大小(表征行星内部能量的大小和构造活动的强烈及持续时间)及行星与太阳的距离等因素有关。在类地行星中,地球和金星质量最大,逃逸速度最大,可将更多的气体“束缚”在它们表面,因此它们的大气有着复杂的组成和较大的密度。火星质量较小,逃逸速度不到地球的一半,在漫长的演化历史中,大气逐渐逸散进入太空,大气密度变得很稀薄。水星质量更小,而且最靠近太阳,不仅太阳风的驱赶作用强烈,而且表面温度高,气体分子的热运动更加剧烈,加剧了大气的逸散,所以水星的大气层极为稀薄,并且主要为太阳风成分。月球质量最小,几乎没有大气层,更没有水体的发育。行星的热演化历史对大气层和水体发育具有重要的制 相似文献
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论大气二氧化碳温室效应的饱和度 总被引：4，自引：0，他引：4
利用最新版本的大气分子吸收光谱资料HITRAN2000，用精确的逐线积分算法，计算了大气CO2浓度变化后产生的辐射强迫。在此基础上，研究了CO2温室效应的饱和度以及影响CO2辐射强迫的各种因子。主要结论如下：地面温度愈高，一般辐射强迫也愈大，但辐射强迫并不完全取决于地面温度，它还受大气温度廓线的强烈影响；研究的 6种模式大气中，吸收带重叠对热带大气的CO2辐射强迫影响最大，对亚极冬季大气的影响最小；与长波辐射强迫相比，短波辐射强迫的贡献很小；CO2的温室效应在15μm带中心等波段确实已经达到饱和，但在其它（15μm带两翼，10μm，5.2μm带等）波段远未达到饱和，在最近的将来也不会达到饱和。 相似文献
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气候变化对陆地水循环影响研究的问题 总被引：29，自引：5，他引：24
简要地回顾了现存的由气候情景驱动水文模型研究气候变化对陆地水循环影响的方法。指出这种单向连接方法很难将气候变暖及人类活动引起的陆地水循环变化反馈给大气。这既影响对降雨的预测精度,又不能正确地描写陆地水循环的变化。近10年来气候学家对大气环流模型中陆面过程模型的改进以及水文气候学家对大尺度水文模型研究所取得的进展,展现了它们之间的互补性,以及未来用水文-气候耦合模型方法研究气候变化与人类活动对陆地水循环影响及水资源预测的可能性。 相似文献
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The planet's radiation budget includes practically all energy exchange between the Sun, the Earth, and space, and so is a fundamental factor of climate. The terms of this budget, observable only from space, are determined from sampled direct measurements of the solar and terrestrial radiation fields. On the contrary, however, it should be remembered that energy exchange between the Earth's surface and its atmosphere involves not only radiative but also non-radiative energy fluxes. Nevertheless, only observations from space can provide satisfactory global coverage of the different energy fluxes that determine climate at the Earth's surface, by way of indirect retrievals of radiative fluxes at the surface and at different heights in the atmosphere. We describe the methods, applied to measurements made with a variety of instruments on board different artificial satellites, that have led to our present knowledge of the Earth's radiation budget (ERB) at the “top of the atmosphere”: global annual mean values of the ERB terms, its annual cycle, its geographical structure, and its variations. We know that solar irradiance, averaged over the globe and the year, varies by only 0.1% with the solar activity cycle; we also know that planetary (Bond) albedo is close to 0.3, that the global annual mean emission of thermal infrared radiation to space is close to 240 Wm?2, and that these terms exhibit a weak but well determined annual cycle. We also know that cloud cover plays a major role in the radiation budget, both in the “shortwave” domain (global SW “cloud radiative forcing” –50 Wm?2) and in the “longwave” domain (+20 Wm?2), thus a net forcing of –30 Wm?2. Successive satellite missions give consistent results for the shape, the phase, and the amplitude of the annual cycle of the planetary radiation balance. However, the different estimates of its annual mean absolute value remain uncertain, not differing significantly from zero, although generally excessively positive. We also rapidly review the methods used to determine the surface radiation budget as well as that of the atmosphere. For the planetary (TOA) radiation budget, we examine to what extent interannual variations and interdecadal trends have been or could be detected. We conclude with a review of projects under way. We also discuss priorities for future efforts, considering in particular, on the one hand (Ringer, 1997), the need to better quantify the factors that govern climate sensitivity to modifications of the atmosphere's radiative properties, on the other hand, the importance of monitoring the evolution of the present disequilibrium situation. 相似文献
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D. N. Rachkovskii 《Astronomy Reports》2013,57(10):766-777
A new derivation of the matrix equations of radiative transfer in a magnetic field is presented, which is based on the classical approach of M. Born and V.E. Stepanov. Convenient vector relations making it possible to formulate the radiative-transfer equations in an arbitrary coordinate system and choose a convenient system of Stokes parameters are presented. The cases of the solar atmosphere and a stellar atmosphere with a dipolar magnetic field are presented as examples. The use of the radiative-transfer equations written in terms of two main oscillation components (the method of V.E. Stepanov) can lead to crude errors when the complex nature of the absorption coefficients is taken into account. 相似文献
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The terrestrial water cycle is the mutual transformation of surface and near-surface water, which controls the supply of fresh water resources. It is affected by human activities, solar radiation and gravity, as well as climate and environmental conditions. Inter-basin water transfer, irrigation, crop cultivation and harvesting, exploitation of groundwater water and other human activities lead to the change of spatial and temporal distribution of soil moisture, the underground water level, surface albedo, surface evaporation, as well as water and energy exchange between land surface and atmosphere. Human water use generates important feedback on the climate and changes the processes of the terrestrial water cycle significantly. The spatial and temporal distribution of precipitation in China is uneven. In addition, human activities further exacerbate the fragility of water resources and the contradiction between supply and demand, posing a serious challenge to the sustainable development of social economy. Therefore, understanding the laws and mechanisms of terrestrial water cycle change is very important for water resources utilization and human sustainable development. From the perspective of climate change and human activities, this paper summarized the impact of human activities on terrestrial water cycle and the progress of climate feedback research. It is urgent to consider the evolution of terrestrial water cycle and its climate under the dual impact of natural and human activities, and develop the large-scale land surface hydrological models and climate models with human water use, crop planting and irrigation, lateral groundwater flow. From the perspective of a fully coupled system, we need quantitatively to assess the climate feedback of human water use and its impact on the terrestrial water cycle process, and to explore its mechanism. We need to distinguish the contribution of human water activities and global climate change to the evolution of terrestrial water cycle in the context of climate change, and to propose water resources management strategies to address climate change. 相似文献
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George W Wetherill 《Geochimica et cosmochimica acta》1976,40(11):1297-1317
The total number of Earth-crossing Apollo objects larger than 500 m in radius is estimated to be 600, based on failure of chance rediscovery, lunar crater frequency and completeness-of-search results of Shoemaker, Helin and Gillett. The number of Amor objects (perihelion between 1.0 and 1.3 A.U.) is estimated to be about 500. These estimates are about an order of magnitude higher than those given by previous workers, and these objects appear sufficiently numerous to dominate post-mare lunar and terrestrial cratering (d ≥ 10 km).The terrestrial meteorite and meteorite yield of 100-106 g bodies derived from fragmentation of Apollo objects is re-evaluated using this estimate, together with more recent data on asteroid albedos and on hypervelocity impact. Terrestrial rate of impacts of these fragments at sufficiently low velocities to penetrate the atmosphere is estimated to be ~2 × 108g/yr. This is in the middle of the range of the actual extraterrestrial impact rate based on photographic fireball surveys (Prairie Network), lunar seismometry, and recovery of meteorites. It is likely that most ordinary chondrites are fragments of Apollo objects, provided that these fragments are sufficiently strong to survive atmospheric entry.Possible asteroidal and cometary sources of Apollo objects are reviewed. Several mechanisms for the removal of asteroids into Earth-crossing orbit are qualitatively acceptable, but appear inadequate by at least an order of magnitude to supply the required number. Most Apollo objects are probably the cores of comets which have lost their volatile material by repeated solar evaporation, as proposed by Öpik.The distribution of the component of the Apollo objects' angular momentum perpendicular to the plane of the solar system is tabulated. It is found that considerable non-random clustering of these values exists, for which no adequate explanation is known. 相似文献
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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
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James M.D. Day 《Geology Today》2015,31(1):12-20
The history of the solar system is locked within the planets, asteroids and other objects that orbit the Sun. While remote observations of these celestial bodies are essential for understanding planetary processes, much of the geological and geochemical information regarding solar system heritage comes directly from the study of rocks and other materials originating from them. The diversity of materials available for study from planetary bodies largely comes from meteorites; fragments of rock that fall through Earth's atmosphere after impact‐extraction from their parent planet or asteroid. These extra‐terrestrial objects are fundamental scientific materials, providing information on past conditions within planets, and on their surfaces, and revealing the timing of key events that affected a planet's evolution. Meteorites can be sub‐divided into four main groups: (1) chondrites, which are unmelted and variably metamorphosed ‘cosmic sediments’ composed of particles that made up the early solar nebula; (2) achondrites, which represent predominantly silicate materials from asteroids and planets that have partially to fully melted, from a broadly chondritic initial composition; (3) iron meteorites, which represent Fe‐Ni samples from the cores of asteroids and planetesimals; and (4) stony‐iron meteorites such as pallasites and mesosiderites, which are mixtures of metal and dominantly basaltic materials. Meteorite studies are rapidly expanding our understanding of how the solar system formed and when and how key events such as planetary accretion and differentiation occurred. Together with a burgeoning collection of classified meteorites, these scientific advances herald an unprecedented period of further scientific challenges and discoveries, an exciting prospect for understanding our origins. 相似文献
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Noble gas components in planetary atmospheres and interiors in relation to solar wind and meteorites
We discuss observed xenon isotopic signatures in solar system reservoirs and possible relationships. The predominant trapped
xenon component in ordinary chondrites (OC) is OC-Xe and its isotopic signature differs from Xe in ureilites, in carbonaceous
chondrites, in the atmospheres of Earth and Mars, and in the solar wind. Additional minor Xe components were identified in
type 3 chondrites and in the metal phase of chondrites. The OC-Xe and ureilite signatures are both consistent with varying
mixtures of HL-Xe and slightly mass fractionated solar-type Xe. Xenon in the Martian atmosphere is found to be strongly mass
fractionated by 37.7‰ per amu, relative to solar Xe, favoring the heavy isotopes. Xenon in SNC’s from the Martian mantle show
admixture of solar-type Xe, which belongs to an elementally strongly fractionated component. The origin of the isotopic signatures
of Ne and Xe in the terrestrial atmosphere are discussed in the light of evidence that the Xe isotopic fractionations in the
Martian and terrestrial atmospheres are consistent. However, in the terrestrial atmospheric Xe component excesses are observed
for132Xe and also for129,131Xe, relative to fractionated solar Xe. The suggested chemically fractionated fission Xe component (CFF-Xe) seems to closely
match the above excesses. We discuss models of origin for planetary volatiles and possible processes driving their evolution
to present day compositions. 相似文献
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Andrew P. Roberts Eelco J. Rohling Katharine M. Grant Juan C. Larrasoaña Qingsong Liu 《Quaternary Science Reviews》2011,30(25-26):3537-3541
Atmospheric mineral dust aerosols affect Earth’s radiative balance and are an important climate forcing and feedback mechanism. Dust is argued to have played an important role in past natural climate changes through glacial cycles, yet temporal and spatial dust variability remain poorly constrained, with scientific understanding of uncertainties associated with radiative perturbations due to mineral dust classified as “very low”. To advance understanding of the dust cycle, we present a high-resolution dust record from the Red Sea, sourced principally from Arabia, with a precise chronology relative to global sea level/ice volume variability. Our record correlates well with a high-resolution Asian dust record from the Chinese Loess Plateau. Importing our age model from the Red Sea to the Chinese Loess Plateau provides a first detailed millennial-scale age model for the Chinese loess, which has been notoriously difficult to date at this resolution and provides a basis for inter-regional correlation of Chinese dust records. We observe a high baseline of dust emissions from Arabia and China, even through interglacials, with strong superimposed millennial-scale variability. Conversely, the distal EPICA Dome C Antarctic ice core record, which is widely used to calculate the radiative impact of dust variations, appears biased to sharply delineated glacial/interglacial contrasts. Calculations based on this Antarctic dust record will therefore overestimate the radiative contrast of atmospheric dust loadings on glacial/interglacial timescales. Additional differences between Arabian/Asian and circum-Saharan records reveal that climate models could be improved by avoiding ‘global mean’ dust considerations and instead including large-scale regions with different dust source variability. 相似文献
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北江天然径流量的变化特征及其影响因素 总被引：7，自引：1，他引：7
分析了最近45年来北江天然径流量的变化特征，并对其影响因素进行了分析，结果表明：北江天然年径流量具有阶段性特征，1984年后，发生明显变化，持续丰水和持续枯水时段开始变长，年际变化存在21年和11年的周期；锋面低槽形成大暴雨是北江主汛期径流量迅速增加的主要原因；大罗山、石坑崆是北江的两级迎水坡，其形成的多雨中心圈是北江径流量补充的主要来源；厄尔尼诺现象出现的次年北江年径流量普遍增大，拉尼娜现象出现的当年北江径流量普遍增大；太阳黑子的急剧变化，改变了地球的热力系统，对大气环流产生影响，这是太阳黑子影响流域径流量的一个主要原因。 相似文献
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Long term characteristics of solar and galactic cosmic rays, as revealed by the study of their nuclear effects in lunar, meteoritic and terrestrial samples are summarised. The data so far available on radioisotopes, noble gases and tracks, though limited, are consistent with nearly constant fluxes and composition during different epochs over billions of years; one exception is14C activity in the earths atmosphere over the past few hundred years, suggesting a variation in the solar activity. Other small or brief variations, which cannot be ruled out as yet, require better estimation of depth and size dependence of nuclear effects in rocks before they can be attributed to cosmic rays. 相似文献
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USGCRP碳循环研究的最新动向 总被引：5，自引：0，他引：5
碳循环研究是国际全球变化研究的热点之一。根据美国全球变化研究委员会提出的“美国全球变化研究计划”(USGCRP),详细介绍了美国碳循环研究的目标、重点研究计划和行动。USGCRP碳循环研究的主要目标是提供碳源和碳汇的综合评价,其重点在于确定北美洲陆地碳汇的数量、位置和成因,通过设立集成观测、过程研究和建模研究的项目来减少其中的不确定性,并提供北美洲陆地碳汇及其变化的更精确估计。USGCRP将从大气、海洋、陆地和人类因素方面结合适当的研究方法,提供多样化的碳循环时空信息,而且提供必要的北美洲陆地碳汇状态的详细描述。在基本反映美国碳循环研究最新趋势的同时,提出了中国碳循环研究应注意的方向。 相似文献
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太阳系探测的进展与比较行星学的主要科学问题 总被引：1，自引：0，他引：1
回顾了太阳系的探测历程,综合分析了太阳系探测的发展趋势。未来的太阳系探测将以月球与火星探测为主线,适度开展太阳系其他行星及其卫星、小行星和彗星的考察性探测。21世纪将是全面探测太阳系并为人类社会长期可持续发展服务的新时代。随着太阳系探测的进展,通过系统比较地球与类地行星的大气层与水体的形成演化过程、地形地貌与地质构造特征、岩石类型、热历史与内部结构等方面的共性与特性研究,表明行星的质量大小和行星与太阳的距离的相互耦合,制约了行星的形成和演化的复杂过程。比较行星学已成为指导太阳系探测的科学理论体系。 相似文献
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Galactic cosmic rays and solar protons ionize the present terrestrial atmosphere,and the air showers are simulated by well-tested Monte-Carlo simulations,such as PHITS code.We use the latest version of PHITS to evaluate the possible ionization of protoplanetary disks by galactic cosmic rays(GCRs),solar protons,and by supernova remnants.The attenuation length of GCR ionization is updated as 118 g cm~(-2),which is approximately 20% larger than the popular value.Hard and soft possible spectra of solar protons give comparable and 20% smaller attenuation lengths compared with those from standard GCR spectra,respectively,while the attenuation length is approximately 10% larger for supernova remnants.Further,all of the attenuation lengths become 10% larger in the compound gas of cosmic abundance,e.g.128 g cm~(-2) for GCRs,which can affect the minimum estimate of the size of dead zones in protoplanetary disks when the incident flux is unusually high. 相似文献
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利用地球系统模式CESM过去2 000年气候模拟试验结果,探讨了在百年尺度上东亚夏季风降水的时空变化特征及其成因,对于认识百年尺度气候变化规律、区分外强迫因子对东亚季风的影响有着重要的科学意义。研究表明:1东亚夏季风降水与温度基本同相变化,降水存在准100年、准150年和准200年周期。2降水标准化EOF第一模态为由北向南"负—正—负—正"的条带状空间分布,而EOF第二模态基本为全区一致的分布型态。3东亚夏季风降水准100年周期主要受太阳辐射、火山活动和气候系统内部变率的共同影响;准150年周期主要受太阳辐射的影响;准200年周期主要受太阳辐射和火山活动的影响。东亚夏季风降水在温带地区主要受温室气体和土地利用/覆盖的影响;在副热带地区主要受太阳辐射和火山活动的影响;在热带地区主要受太阳辐射、火山活动和气候系统内部变率的影响。 相似文献