IPCC AR6报告解读：地球能量收支、气候反馈和气候敏感度     

张华  王菲  赵树云  谢冰 《气候变化研究进展》2021,17(6):691-698

文中对IPCC第六次评估报告（AR6）第一工作组（WGI）报告的第七章关于地球能量收支、气候反馈和气候敏感度中的重要内容进行了凝练,并简要总结该方面的最新研究成果和结论。评估显示,自工业革命以来,人类活动造成的有效辐射强迫（ERF）为2.72 [1.96~3.48] W/m²,其中,均匀混合温室气体的贡献为3.32 [3.03~3.61] W/m²,气溶胶的贡献为-1.1 [-1.7~-0.4] W/m²。净的气候反馈参数为-1.16 [-1.81~-0.51] W/(m²∙℃),云仍然是气候反馈整体不确定性的最大来源。平衡态气候敏感度（ECS）和瞬态气候响应（TCR）可用于评估全球平均地表气温对强迫的响应,是衡量全球气候响应的有效手段。ECS和TCR的最佳估计分别为3.0 [2.0~5.0]℃和1.8 [1.2~2.4]℃。  相似文献   

Transports of Nordic Seas water masses and excess SF₆ through Fram Strait to the Arctic Ocean     

Marika Marnela  Bert Rudels  K. Anders Olsson  Leif G. Anderson  Daniel J. Torres  James H. Swift 《Progress in Oceanography》2008,78(1):1-11

To determine the exchanges between the Nordic Seas and the Arctic Ocean through Fram Strait is one of the most important aspects, and one of the major challenges, in describing the circulation in the Arctic Mediterranean Sea. Especially the northward transport of Arctic Intermediate Water (AIW) from the Nordic Seas into the Arctic Ocean is little known. In the two-ship study of the circulation in the Nordic Seas, Arctic Ocean - 2002, the Swedish icebreaker Oden operated in the ice-covered areas in and north of Fram Strait and in the western margins of Greenland and Iceland seas, while RV Knorr of Woods Hole worked in the ice free part of the Nordic Seas. Here two hydrographic sections obtained by Oden, augmented by tracer and velocity measurements with Lowered Acoustic Doppler Current Profiler (LADCP), are examined. The first section, reaching from the Svalbard shelf across the Yermak Plateau, covers the region north of Svalbard where inflow to the Arctic Ocean takes place. The second, western, section spans the outflow area extending from west of the Yermak Plateau onto the Greenland shelf. Geostrophic and LADCP derived velocities are both used to estimate the exchanges of water masses between the Nordic Seas and the Arctic Ocean. The geostrophic computations indicate a total flow of 3.6 Sv entering the Arctic on the eastern section. The southward flow on the western section is found to be 5.1 Sv. The total inflow to the Arctic Ocean obtained using the LADCP derived velocities is much larger, 13.6 Sv, and the southward transport on the western section is 13.7 Sv, equal to the northward transport north of Svalbard. Sulphur hexafluoride (SF₆) originating from a tracer release experiment in the Greenland Sea in 1996 has become a marker for the circulation of AIW. From the geostrophic velocities we obtain 0.5 Sv and from the LADCP derived velocities 2.8 Sv of AIW flowing into the Arctic. The annual transport of SF₆ into the Arctic Ocean derived from geostrophy is 5 kg/year, which is of the same magnitude as the observed total annual transport into the North Atlantic, while the LADCP measurements (19 kg/year) imply that it is substantially larger. Little SF₆ was found on the western section, confirming the dominance of the Arctic Ocean water masses and indicating that the major recirculation in Fram Strait takes place farther to the south.  相似文献   

瞬变电磁晚期场资料的一维反演   总被引：3，自引：0，他引：3       下载免费PDF全文

林长佑  扬世荣  叶剑湘 《地震工程学报》1994,16(2):71-78,95

本文研讨了由垂直磁偶源和水平电偶源所激发的瞬变电磁晚期场的垂直磁场时间偏导数及其视电阻率的性态特征。探讨了其一维反演的某些问题，研制出了对该时间域电磁响应函数的一维实用化反演程序，表明具有较好的使用效果。  相似文献   

Transient electromagnetic response due to a pair of horizontal conducting sheets in a loop field     

R. Nagendra  I. B. Ramaprasada Rao  Satyanarayan Kabra 《Journal of Earth System Science》1985,94(3):269-277

The transient electromagnetic response due to a pair of horizontal conducting sheets induced by a loop field is obtained. The response characteristics in the three different regions (above the upper sheet, between the two sheets and below the lower sheet) are briefly discussed. In the first and second regions the composite response is characterised by an overburden response asymptote during early times and a target response asymptote during late times. The transition zones are characterised by shoulder-like bends. In the third region, the composite response increases in direct proportion to the induction number, eventually merging with the target response for large values of the induction number.  相似文献   

Transient deformation following the 30 January 1997 dike intrusion at Kīlauea volcano,Hawai’i     

Emily K. Desmarais  Paul Segall 《Bulletin of Volcanology》2007,69(4):353-363

On 30 January 1997 an intrusion on Kīlauea volcano opened a new fissure within the East Rift Zone (ERZ) at Nāpau Crater, 3 km uprift from the ongoing eruptions at Pu’u ’Ō’ō. The fissure eruption lasted 22 h and opened a 5.1 km long, nearly vertical dike 1.9 m, extending from the surface to a depth of 2.4 km (Owen et al. 2000b). During the eruption, the lava pond at Pu’u ’Ō’ō drained, and eruptions ceased there. Pu’u ’Ō’ō eventually refilled in late February and eruptions resumed there on 28 March 1997. Continuous GPS data show a large transient following the 30 January 1997 dike intrusion. After lengthening 40 cm during the initial eruption, the baseline between two stations spanning the ERZ lengthened an additional 10 cm over the following 6 months. A coastal station KAEP also exhibited transient deformation, as it continued to move southward (5 cm) over the same 6-month period. The baseline between two stations spanning Kīlauea’s summit caldera contracted sharply during the eruption, but gradually recovered to slightly longer than its previous length 2 months after the intrusion. We use the extended network inversion filter (McGuire and Segall 2003) to invert continuous GPS data for volume change of a spherical pressure source under Kīlauea’s summit, opening distribution on a nearly vertical dike in the ERZ and potential slip on a decollement 9 km beneath the south flank. Following the 30 January intrusion, rift extension continued below the initial dike intrusion for the duration of the transient. Decollement slip, regardless of its assumed depth, is not required to fit the data. The modeled transient summit reinflation and rift opening patterns under Nāpau crater coincide with changes in observed behavior of Pu’u ’Ō’ō’s lava pond. Rift opening accelerated while Pu’u ’Ō’ō eruptions paused and began to decelerate after the lava pond reappeared nearly a month after the Nāpau eruption. The transient deformation is interpreted as resulting from shallow accommodation of the new dike volume.  相似文献   

夏季乌拉尔地区大气环流持续异常的形成与维持   总被引：2，自引：0，他引：2  

Li Shuanglin  Ji Liren  Lin Wantao 《大气科学进展》2001,18(5):819-830

从天气尺度瞬变涡旋与时间平均基本气流双向相互作用建立异常型的角度，研究了夏季乌拉尔地区大气环流持续异常的形成与维持，首先基于合成分析，研究了持续异常期间的天气尺度瞬变波活动情况，结果表明：正异常时，在上游地区，从北大西洋中部到西欧沿岸，瞬变活动明显增强。负异常过程时相反，该地区瞬变活动减弱。利用线性正压原始方程模式，研究了在合成正异常基本流及7月气候基本流等两种基本流下，正异常时上游异常瞬变活动对异常建立的贡献。结果表明：正异常时，上游增强的瞬变波活动有利于正异常的建立与维持。利用基于线性正压原始方程模式设计的风暴轴模式，研究了时间平均基本流在组织与调控瞬变活动中所起的作用。结果表明：当乌拉尔地区高压脊发展时，有利于瞬变在上游的北大西洋中部到西欧沿岸地区组织起来。脊发展越强，越有利。结合上述两方面的结果，提出了瞬变与行星波双向相互作用的乌拉尔持续正异常形成和自维持机制。  相似文献   

On the meridional circulation and balance of momentum in the Southern Ocean of POP     

Dirk Olbers  Vladimir O. Ivchenko 《Ocean Dynamics》2001,52(2):79-93

 The circulation of the Southern Ocean is studied in the eddy-resolving model POP (Parallel Ocean Program) by an analysis of zonally integrated balances. The TEM formalism (Transformed Eulerian Mean) is extended to include topography and continental boundaries, thus deviations from a zonally integrated state involve transient and standing eddies. The meridional circulation is presented in terms of the Eulerian, eddy-induced, and residual streamfunctions. It is shown that the splitting of the meridional circulation into Ekman and geostrophic transports and the component induced by subgrid and Reynolds stresses is identical to a particular form of the zonally integrated balance of zonal momentum. In this balance, the eddy-induced streamfunctions represent the interfacial form stresses by transient and standing eddies and the residual streamfunction represents the acceleration of the zonal current by density fluxes in a zonally integrated frame. The latter acceleration term is directly related to the surface flux of density and interior fluxes due to the resolved and unresolved eddies. The eddy-induced circulation is extremely vigorous in POP. In the upper ocean a shallow circulation, reversed in comparison to the Deacon cell and mainly due to standing eddies, appears to the north of Drake Passage latitudes, and in the Drake Passage belt of latitudes a deep-reaching cell is induced by transient eddies. In the resulting residual circulation the Deacon cell is largely cancelled and the residual advection of the zonal mean potential density is balanced by diapycnal eddy and subgrid fluxes which are strong in the upper few hundred meters but small in the ocean interior. The balance of zonal momentum is consistent with other eddy-resolving models; a new aspect is the clear identification of density effects in the zonally integrated balance. We show that the wind stress and the stress induced by the residual circulation drive the eastward current, whereas both eddy species result in a braking. Finally, we extend the Johnson–Bryden model of zonal transport to incorporate all relevant terms from the zonal momentum balance. It is shown that wind stress and induction by the residual circulation carry an eastward transport while bottom form stress and the stress induced by standing eddies yield westward components of transport. Received: 26 June 2001 / Accepted: 2 November 2001  相似文献   

The main structure and tectonic features of the Chernorud-Mukhor site on the western shore of Lake Baikal from TEM and SP measurements     

Nikolai Kozhevnikov  Bülent Tezkan   《Journal of Applied Geophysics》1998,39(4):237-250

Transient electromagnetic (TEM), self-potential (SP) and geoelectrical mapping measurements were carried out at the Chernorud-Mukhor site in the Priolkhonje area on the western shore of the Lake Baikal. All measurements were made along several profiles across the main strike of the regional Primorsky fault. TEM measurements were carried out in a time range from a few tens of microseconds to several tens of milliseconds. The most important result of the 1D modelling of TEM soundings is the discovery of nearly horizontal boundaries that divide high resistive overlying and well conducting underlying rocks. The resistivity of the former is in the range from 100 Ωm to 1000 Ωm, while the resistivity of the latter varies from less than 1 Ωm to several tens of Ωm. This good conductive zone could also be verified by geoelectrical mapping using Schlumberger array (AB/2=100 m). Due to high conductivity of the underlying rocks only the upper boundary of the conductive layer could be determined by TEM soundings. A regional SP anomaly with amplitude of about −450 mV has also been observed above the low resistivity zone indicating the electron nature of its conductance. Geologically, the conductive zone is represented by a graphite-bearing layer within the region of archean rocks. Since that layer extends over a large area, it may be used as a key in studying structures and tectonics of the Priolkhonje area. A 1D TEM geoelectric section shows a wide, gently sloping syncline as a probable base structure of the Chernorud-Mukhor site. Neotectonic faults divide the syncline into vertically displaced blocks that form a wide complicated graben with a total amplitude of about 250 m.  相似文献   

A study of transient variations in the Earth’s electromagnetic field at equatorial electrojet latitudes in western Africa (Mali and the Ivory Coast)     

J. Vassal  M. Menvielle  Y. Cohen  M. Dukhan  V. Doumouya  K. Boka  O. Fambitakoye 《Annales Geophysicae》1998,16(6):677-697

In the framework of the French-Ivorian participation to the IEEY, a network of 10 electromagnetic stations were installed at African longitudes. The aim of this experiment was twofold: firstly, to study the magnetic signature of the equatorial electrojet on the one hand, and secondly, to characterize the induced electric field variations on the other hand. The first results of the magnetic field investigations were presented by Doumouya and coworkers. Those of the electric field experiment will be discussed in this study. The electromagnetic experiment will be described. The analysis of the electromagnetic transient variations was conducted in accordance with the classical distinction between quiet and disturbed magnetic situations. A morphological analysis of the recordings is given, taking into consideration successively quiet and disturbed magnetic situations, with the results interpreted in terms of the characterization of external and internal sources. Particular attention was paid to the effects of the source characteristics on the induced field of internal origin, and to the bias they may consequently cause to the results of electromagnetic probing of the Earth; the source effect in electromagnetic induction studies. During quiet magnetic situations, our results demonstrated the existence of two different sources. One of these, the S_R^E source, was responsible for most of the magnetic diurnal variation and corresponded to the well-known magnetic signature of the equatorial electrojet. The other source (the S_R*^E source) was responsible for most of the electric diurnal variation, and was also likely to be an ionospheric source. Electric and magnetic diurnal variations are therefore related to different ionospheric sources, and interpreting the electric diurnal variation as induced by the magnetic field diurnal variation is not relevant. Furthermore, the magnetotelluric probing of the upper mantle at dip equator latitudes with the electromagnetic diurnal variation is consequently impossible to perform. In the case of irregular variations, the source effect related to the equatorial electrojet is also discussed. A Gaussian model of equatorial electrojet was considered, and apparent resistivities were computed for two models of stratified Earth corresponding to the average resistive structure of the two tectonic provinces crossed by the profile: a sedimentary basin and a cratonic shield. The apparent resistivity curves were found to depend significantly on both the model used and the distance to the center of the electrojet. These numerical results confirm the existence of a daytime source effect related to the equatorial electrojet. Furthermore, we show that the results account for the observed differences between daytime and night-time apparent resistivity curves. In particular, it was shown that electromagnetic probing of the Earth using the classical Cagniard-Tikhonov magnetotelluric method is impossible with daytime recordings made at dip latitude stations.  相似文献   

瞬变电磁方法在探测煤矿浅层高阻采空区中的应用   总被引：1，自引：0，他引：1  

范涛  王秀臣  李貅  王信文  石亚丁  曾方禄 《西北地质》2010,43(2):156-162

过去在煤矿浅层高阻采空区探测中,普遍认为高密度电法为较好的方法,而瞬变电磁法通常被认为其对低阻反映较灵敏,对高阻反映不灵敏,而很少采用,但我国内蒙、山西等地,地表沟壑纵横,高差较大,不具备高密度电法的施工条件。因此,笔者给出一种在较小线框下进行的瞬变电磁方法,通过配合高发射频率和大发射电流,能够比较清晰的反映出地下高阻目标体,以此说明,针对地形起伏较大,不适合高密度电法施工的地方,小框瞬变电磁方法可以在一定程度上解决煤矿中不含水采空区的物探手段问题。文中参考煤矿不含水采空区埋深较浅的情况,设计了理论模型,正演计算得到的效果良好,对高阻的反映较为灵敏,并在鄂尔多斯地区某煤矿实际应用了该方法,得到的结果与开挖情况相符合,对煤矿生产起到了很好的指导作用,这表明该方法是切实有效的。  相似文献