Elemental diffusion and segregation processes in partially ionized solar plasma     

Alexey B. Gorshkov  Vladimir A. Baturin 《Astrophysics and Space Science》2010,328(1-2):171-174

Although diffusion is usually associated with equalizing of the chemical composition, the pressure and temperature gradients inside the Sun cause elemental diffusion segregation. While light hydrogen is flowing up to the solar envelope, helium and heavier elements are settling down to the core. The target of our simulation is an accurate estimation of the settling rate in solar plasma during the course of solar evolution. The rate of helium depletion in the envelope is a key parameter of the solar evolution and depends on position and conditions around the base of the convective mixing zone. The rate of heavy element settling is sensitive to the degree of ionization and interaction with the radiation flux. We estimate the effect of ion ionization on the settling rate for several heavy elements up to iron in the framework of the LTE assumption and the thermodynamic calculation according to SAHA-S EOS.  相似文献   

Links between Arctic sea ice and extreme summer precipi- tation in China：an alternative view     

Petteri Uotila  Alexey Karpechko  Timo Vihma 《极地研究(英文版)》2014,(4)

Potential links between the Arctic sea-ice concentration anomalies and extreme precipitation in China are explored. Associations behind these links can be explained by physical interpretations aided by...  相似文献   

Transient hysteresis of near-surface permafrost response to external forcing     

Alexey V. Eliseev  Pavel F. Demchenko  Maxim M. Arzhanov  Igor I. Mokhov 《Climate Dynamics》2014,42(5-6):1203-1215

Estimates of changes in near-surface permafrost (NSP) area S _p relative to change in globally averaged surface air temperature T _g are made by using the global climate model developed at the A.M. Obukhov Institute of Atmospheric Physics RAS (IAP RAS CM). For ensemble of runs forced by scenarios constructed as return-to-preindustrial continuations of the RCP (Representative Concentration Pathways) scenarios family, a possibility of transient hysteresis in dependence of S _p versus T _g is exhibited: in some temperature range which depends on imposed scenario of external forcing, NSP area is larger, at the same global mean surface air temperature, in a warming climate than in a cooling climate. This hysteresis is visible more clearly for scenarios with higher concentration of greenhouse gases in the atmosphere in comparison to those in which this concentration is lower. Hysteresis details are not sensitive to the type of the prescribed continuation path which is used to return the climate to the preindustrial state. The multiple-valued dependence of S _p on T _g arises due to dependence of soil state in the regions of extra-tropical wetlands and near the contemporary NSP boundaries on sign of external climatic forcing. To study the dependence of permafrost hysteresis on amplitude and temporal scale of external forcing, additional model runs are performed. These runs are forced by idealised scenarios of atmospheric CO₂ content varying, depending on run, with periods from 100 to 1,000 year and with different amplitudes. It is shown that the above-mentioned hysteresis is related to the impact of phase transitions of soil water on apparent inertia of the system as well as to the impact of soil state on atmospheric hydrological cycle and radiation transfer in the atmosphere.  相似文献   

An Integrated Study to Analyze Salt Lake Microbial Community Structure(Novosibirsk Oblast,Russia)     

Alla BRYANSKAYA  Alexey ROZANOV  Tatyana MALUP  Taisiya ALESHINA  Elena LAZAREVA  Oxana TARAN  Tatyana GORYACHKOVSKAYA  Vladimir IVANISENKO  Sergey PELTEK 《《地质学报》英文版》2014,88(Z1):61-62

正Salt Lake is one of the lakes in the system,consisting of a huge amount of salt and bitter-salty lakes in Novosibirsk Oblast and Altai Krai.These lakes are unique and highly unstable systems where the parameters of geochemical  相似文献   

The restricted two-body problem in constant curvature spaces     

Alexey V. Borisov  Ivan S. Mamaev 《Celestial Mechanics and Dynamical Astronomy》2006,96(1):1-17

We perform the bifurcation analysis of the Kepler problem on and . An analog of the Delaunay variables is introduced. We investigate the motion of a point mass in the field of a Newtonian center moving along a geodesic on and (the restricted two-body problem). For the case of a small curvature, the pericenter shift is computed using the perturbation theory. We also present the results of numerical analysis based on an analogy with the motion of a rigid body.  相似文献   

Impact of stratospheric variability on tropospheric climate change     

Mauro Dall’Amico  Peter A. Stott  Adam A. Scaife  Lesley J. Gray  Karen H. Rosenlof  Alexey Yu. Karpechko 《Climate Dynamics》2010,34(2-3):399-417

An improved stratospheric representation has been included in simulations with the Hadley Centre HadGEM1 coupled ocean atmosphere model with natural and anthropogenic forcings for the period 1979–2003. An improved stratospheric ozone dataset is employed that includes natural variations in ozone as well as the usual anthropogenic trends. In addition, in a second set of simulations the quasi biennial oscillation (QBO) of stratospheric equatorial zonal wind is also imposed using a relaxation towards ERA-40 zonal wind values. The resulting impact on tropospheric variability and trends is described. We show that the modelled cooling rate at the tropopause is enhanced by the improved ozone dataset and this improvement is even more marked when the QBO is also included. The same applies to warming trends in the upper tropical troposphere which are slightly reduced. Our stratospheric improvements produce a significant increase of internal variability but no change in the positive trend of annual mean global mean near-surface temperature. Warming rates are increased significantly over a large portion of the Arctic Ocean. The improved stratospheric representation, especially the QBO relaxation, causes a substantial reduction in near-surface temperature and precipitation response to the El Chichón eruption, especially in the tropical region. The winter increase in the phase of the northern annular mode observed in the aftermath of the two major recent volcanic eruptions is partly captured, especially after the El Chichón eruption. The positive trend in the southern annular mode (SAM) is increased and becomes statistically significant which demonstrates that the observed increase in the SAM is largely subject to internal variability in the stratosphere. The possible inclusion in simulations for future assessments of full ozone chemistry and a gravity wave scheme to internally generate a QBO is discussed.  相似文献   

Model-based remote sensing algorithms for particulate organic carbon (POC) in the Northeastern Gulf of Mexico     

Young Baek Son  Wilford D. Gardner  Alexey V. Mishonov  Mary Jo Richardson 《Journal of Earth System Science》2009,118(1):1-10

Hydrographic data, including particulate organic carbon (POC) from the Northeastern Gulf of Mexico (NEGOM) study, were combined with remotely-sensed SeaWiFS data to estimate POC concentration using principal component analysis (PCA). The spectral radiance was extracted at each NEGOM station, digitized, and averaged. The mean value and spurious trends were removed from each spectrum. De-trended data included six wavelengths at 58 stations. The correlation between the weighting factors of the first six eigenvectors and POC concentration were applied using multiple linear regression. PCA algorithms based on the first three, four, and five modes accounted for 90, 95, and 98% of total variance and yielded significant correlations with POC with R ² = 0.89, 0.92, and 0.93. These full waveband approaches provided robust estimates of POC in various water types. Three different analyses (root mean square error, mean ratio and standard deviation) showed similar error estimates, and suggest that spectral variations in the modes defined by just the first four characteristic vectors are closely correlated with POC concentration, resulting in only negligible loss of spectral information from additional modes. The use of POC algorithms greatly increases the spatial and temporal resolution for interpreting POC cycling and can be extrapolated throughout and perhaps beyond the area of shipboard sampling.  相似文献   

Ubiquitous post-peak zircon in an eclogite from the Kumdy-Kol,Kokchetav UHP-HP Massif (Kazakhstan): Significance of exhumation-related zircon growth and modification in continental-subduction settings     

Sergei Yu. Skuzovatov  Vladislav S. Shatsky  Alexey L. Ragozin  Kuo-Lung Wang 《Island Arc》2021,30(1):e12385

U–Pb geochronological, trace-element and Lu–Hf isotopic studies have been made on zircons from ultrahigh-pressure (UHP) mafic eclogite from the Kumdy-Kol area, one of the diamond-facies domains of the Kokchetav Massif (northern Kazakhstan). The peak eclogitic assemblage equilibrated at > 900 °C, whereas the bulk sample composition displays light rare-earth element (LREE) and Th depletion evident of partial melting. Zircons from the eclogite are represented by exclusively newly formed metamorphic grains and have U–Pb age spread over 533–459 Ma, thus ranging from the time of peak subduction burial to that of the late post-orogenic collapse. The major zircon group with concordant age estimates have a concordia age of 508.1 ±4.4 Ma, which corresponds to exhumation of the eclogite-bearing UHP crustal slice to granulite- or amphibolite-facies depths. This may indicate potentially incoherent exhumation of different crustal blocks within a single Kumdy-Kol UHP domain. Model Hf isotopic characteristics of zircons (ε_Hf(t) +1.5 to +7.8, Neoproterozoic model Hf ages of 1.02–0.79 Ga) closely resemble the whole-rock values of the Kumdy-Kol eclogites and likely reflect in situ derivation of HFSE source for newly formed grains. The ages coupled with geochemical systematics of zircons confirm that predominantly late zircon growth occurred in Th–LREE-depleted eclogitic assemblage, that experienced incipient melting and monazite dissolution in melt at granulite-facies depths, followed by amphibolite-facies rehydration during late-stage exhumation-related retrogression.  相似文献   

Holocene hydrological variability of Lake Ladoga,northwest Russia,as inferred from diatom oxygen isotopes     

Svetlana S. Kostrova  Hanno Meyer  Hannah L. Bailey  Anna V. Ludikova  Raphael Gromig  Gerhard Kuhn  Yuri A. Shibaev  Anna V. Kozachek  Alexey A. Ekaykin  Bernhard Chapligin 《Boreas: An International Journal of Quaternary Research》2019,48(2):361-376

This article presents a new comprehensive assessment of the Holocene hydrological variability of Lake Ladoga, northwest Russia. The reconstruction is based on oxygen isotopes of lacustrine diatom silica (δ¹⁸O_diatom) preserved in sediment core Co 1309, and is complemented by a diatom assemblage analysis and a survey of modern isotope hydrology. The data indicate that Lake Ladoga has existed as a freshwater reservoir since at least 10.8 cal. ka BP. The δ¹⁸O_diatom values range from +29.8 to +35.0‰, and relatively higher δ¹⁸O_diatom values around +34.7‰ between c. 7.1 and 5.7 cal. ka BP are considered to reflect the Holocene Thermal Maximum. A continuous depletion in δ¹⁸O_diatom since c. 6.1 cal. ka BP accelerates after c. 4 cal. ka BP, indicating Middle to Late Holocene cooling that culminates during the interval 0.8–0.2 cal. ka BP, corresponding to the Little Ice Age. Lake‐level rises result in lower δ¹⁸O_diatom values, whereas lower lake levels cause higher δ¹⁸O_diatom values. The diatom isotope record gives an indication for a rather early opening of the Neva River outflow at c. 4.4–4.0 cal. ka BP. Generally, overall high δ¹⁸O_diatom values around +33.5‰ characterize a persistent evaporative lake system throughout the Holocene. As the Lake Ladoga δ¹⁸O_diatom record is roughly in line with the 60°N summer insolation, a linkage to broader‐scale climate change is likely.  相似文献   

Another Year of Record Heat for the Oceans     

Lijing CHENG  John ABRAHAM  Kevin E.TRENBERTH  John FASULLO  Tim BOYER  Michael E.MANN  Jiang ZHU  Fan WANG  Ricardo LOCARNINI  Yuanlong LI  Bin ZHANG  Fujiang YU  Liying WAN  Xingrong CHEN  Licheng Feng  Xiangzhou SONG  Yulong LIU  Franco RESEGHETTI  Simona SIMONCELLI  Viktor GOURETSKI  Gengxin CHEN  Alexey MISHONOV  Jim REAGAN  Guancheng LI 《大气科学进展》2023,40(6):963-974

Changes in ocean heat content(OHC), salinity, and stratification provide critical indicators for changes in Earth’s energy and water cycles. These cycles have been profoundly altered due to the emission of greenhouse gasses and other anthropogenic substances by human activities, driving pervasive changes in Earth’s climate system. In 2022, the world’s oceans, as given by OHC, were again the hottest in the historical record and exceeded the previous 2021 record maximum.According to IAP/CAS data, ...  相似文献