Correction to: Atmospheric Turbulence Measurements at a Coastal Zone with and without Fog     

Grachev  Andrey A.  Krishnamurthy  Raghavendra  Fernando  Harindra J. S.  Fairall  Christopher W.  Bardoel  Stef L.  Wang  Sen 《Boundary-Layer Meteorology》2021,181(2-3):423-424

Boundary-Layer Meteorology -  相似文献   

Direct Numerical Simulation of a Turbulent Channel Flow with Forchheimer Drag     

Bhattacharjee  Soumak  Mortikov  Evgeny  Debolskiy  Andrey  Kadantsev  Evgeny  Pandit  Rahul  Vesala  Timo  Sahoo  Ganapati 《Boundary-Layer Meteorology》2022,185(2):259-276

Boundary-Layer Meteorology - We characterize the turbulent flow, using direct numerical simulations (DNS), within a closed channel between two parallel walls with a canopy of constant areal density...  相似文献   

Sensitivity of the last glacial inception to initial and surface conditions     

Claudia Kubatzki  Martin Claussen  Reinhard Calov  Andrey Ganopolski 《Climate Dynamics》2006,27(4):333-344

We investigate the sensitivity of simulations of the last glacial inception (LGI) with respect to initial (size of the Greenland ice sheet) and surface (state of ocean/vegetation) conditions and two different CO₂ reconstructions. Utilizing the CLIMBER-2 Earth system model, we obtain the following results: (a) ice-sheet expansion in North America at the end of the Eemian can be reduced or even completely suppressed when pre-industrial or Eemian ocean/vegetation is prescribed. (b) A warmer surrounding ocean and, in particular, a large Laurentide ice sheet reduce the size of the Greenland ice sheet before and during the LGI. (c) A changing ocean contributes much stronger to the expansion of the Laurentide ice sheet when we apply the CO₂ reconstruction according to Barnola et al. (Nature 329:408–414, 1987) instead of Petit et al. (Nature 399:429–436, 1999). (d) In the fully coupled model, the CO₂ reconstruction used has only a small impact on the simulated ice sheets but it does impact the course of the climatic variables. (e) For the Greenland ice sheet, two equilibrium states exist under the insolation and CO₂ forcing at 128,000 years before present (128 kyear BP); the one with an ice sheet reduced by about one quarter as compared to its simulated pre-industrial size and the other with nearly no inland ice in Greenland. (f) Even the extreme assumption of no ice sheet in Greenland at the beginning of our transient simulations does not alter the simulated expansion of northern hemispheric ice sheets at the LGI.  相似文献   

硅酸盐-盐（硫酸盐）流体不混溶：蒙古南部Mushugai-Khuduk含火成碳酸岩杂岩体矿物中的熔体包裹体研究   总被引：1，自引：0，他引：1  

IrinaA.Andreeva Vyacheslav I.Kovalenko Vladimir B.Naumov 《岩石学报》2007,23(1):73-82

Crystalline and melt inclusions were studied in garnet,diopside,potassium feldspar,and sphene from the garnet syenite porphyry of the carbonatite-bearing complex Mushugai-Khuduk,southern Mongolia.Phlogopite,clinopyroxene,albite,potassium feldspar,spheric,wollastonite,magnetite,Ca and Sr sulfates,fluorite,and apatite were identified among the crystalline inclusions. The melt inclusions were homogenized at 1010～1080℃and analyzed on an electron microprobe.Silicate,salt,and combined silicate- salt melt inclusions were found.Silicate melts show considerable variations in SiO_2 concentration(56 to 66wt% ),high Na_2O K_2O (up to 17wt% ),and elevated Zr,F,and C1 contents.In terms of bulk rock chemistry,the silicate melts are alkali syenites.During thermometric experiments,salt melt inclusions quenched into homogeneous glasses of predominantly sulfate compositions containing no more than 1.3wt% SiO_2.These melts are enriched in alkalis,Ba,Sr,P,F,and C1.The investigation of the silicate and salt melt inclusions in minerals of the garnet syenite porphyries indicate that these rocks were formed under influence of the processes of crystallization differentiation and magma separation into immiscible silicate and salt(sulfate)liquids.  相似文献   

Aqueous fluids and hydrous melts in high-pressure and ultra-high pressure rocks: Implications for element transfer in subduction zones   总被引：10，自引：0，他引：10  

Jrg Hermann  Carl Spandler  Alistair Hack  Andrey V. Korsakov 《Lithos》2006,92(3-4):399-417

High-pressure (HP) and ultra-high pressure (UHP) terranes are excellent natural laboratories to study subduction-zone processes. In this paper we give a brief theoretical background and we review experimental data and observations in natural rocks that constrain the nature and composition of the fluid phase present in HP and UHP rocks. We argue that a fluid buffered by a solid residue is compositionally well defined and is either an aqueous fluid (total amount of dissolved solids < 30 wt.%) or a hydrous melt (H₂O < 35 wt.%). There is only a small temperature range of approximately 50–100 °C, where transitional solute-rich fluids exist. A review of available experimental data suggest that in felsic rocks the second critical endpoint is situated at 25–35 kbar and  700 °C and hence must be considered in the study of UHP rocks. Despite this, the nature of the fluid phase can be constrained by relating the peak metamorphic conditions of rocks to the position of the wet solidus even if the peak pressure exceeds the pressure where the wet solidus terminates at the second critical endpoint. Transitional solute-rich fluids are expected in UHP terrains (P > 30 kbar) with peak temperatures of about 700 ± 50 °C. At higher temperatures, hydrous granitic melts occur whereas at lower temperatures aqueous fluids coexists with eclogite-facies minerals. This argument is complemented by evidence on the nature of the fluid phase from high-pressure terrains. We show that in the diamond-bearing, high-temperature UHP rocks from the Kokchetav Massif there are not only hydrous felsic melts, but probably also carbonate and sulfide melts present.

Hydrous quartzo-feldspathic melts are mainly produced in high temperature UHP rocks and their composition is relatively well constrained from experiments and natural rocks. In contrast, constraining the composition of aqueous fluids is more problematic. The combined evidence from experiments and natural rocks indicates that aqueous fluids liberated at the blueschist to eclogite facies transition are dilute. They contain only moderate amounts of LILE, Sr and Pb and do not transport significant amounts of key trace elements such as LREE, U and Th. This indicates that there is a decoupling of water and trace element release in subducted oceanic crust and that aqueous fluids are unable to enrich the mantle wedge significantly. Instead we propose that fluid-present melting in the sediments on top of the slab is required to transfer significant amounts of trace elements from the slab to the mantle wedge. For such a process to be efficient, top slab temperature must be at least 700–750 °C at sub-arc depth. Slab melting is likely to be triggered by fluids that derive from dehydration of mafic and ultramafic rocks in colder (deeper) portions of the slab.  相似文献   

Molecular modeling of water structure in nano-pores between brucite (001) surfaces     

Jianwei Wang  Andrey G Kalinichev 《Geochimica et cosmochimica acta》2004,68(16):3351-3365

Molecular dynamics (MD) computer simulations of liquid water held in one-dimensional nano-confinement by two parallel, electrostatically neutral but hydrophilic surfaces of brucite, Mg(OH)₂, provide greatly increased, atomistically detailed understanding of surface-related effects on the spatial variation in the structural ordering, hydrogen bond (H-bond) organization, and local density of H₂O molecules at this important model hydroxide surface. NVT-ensemble MD simulations (i.e., at constant number of atoms, volume and temperature) were performed for a series of model systems consisting of 3 to 30 Å-thick water layers (containing 35 to 360 H₂O molecules) confined between two 19 Å-thick brucite substrate layers. The results show that the hydrophilic substrate significantly influences the near-surface water structure, with both H-bond donation to the surface oxygen atoms and H-bond acceptance from the surface hydrogen atoms in the first surface layer of H₂O molecules playing key roles. Profiles of oxygen and hydrogen atomic density and H₂O dipole orientation show significant deviation from the corresponding structural properties of bulk water to distances as large as 15 Å (∼5 molecular water layers) from the surface, with the local structural environment varying significantly with the distance from the surface. The water molecules in the first layer at about 2.45 Å from the surface have a two-dimensional hexagonal arrangement parallel to brucite layers, reflecting the brucite surface structure, have total nearest neighbor coordinations of 5 or 6, and are significantly limited in their position and orientation. The greatest degree of the tetrahedral (ice-like) ordering occurs at about 4 Å from the surface. The translational and orientational ordering of H₂O molecules in layers further from the surface become progressively more similar to those of bulk liquid water. A quantitative statistical analysis of the MD-generated instantaneous molecular configurations in terms of local density, molecular orientation, nearest neighbor coordination, and the structural details of the H-bonding network shows that the local structure of interfacial water at the brucite surface results from a combination of “hard wall” (geometric and confinement) effects, highly directional H-bonding, and thermal motion. This structure does not resemble that of bulk water at ambient conditions or at elevated or reduced temperature, but shares some similarities with that of water under higher pressure.  相似文献   

The Use of Photometric Structural Analysis and Digitized Positional Observation Data to Study Small Celestial Bodies     

Nefedyev  Yu. A.  Bagrov  A. V.  Usanin  V. S.  Andreev  A. O.  Demina  N. Yu. 《Astronomy Reports》2021,65(5):427-434

Astronomy Reports - The problems of the study of small celestial bodies are an important component of modern space research. This applies both to the study of physicochemical and evolutionary...  相似文献   

A 450-ka long record of glaciation in Northern Mongolia based on studies at Lake Khubsugul: high-resolution reflection seismic data and grain-size variations in cored sediments     

Andrey Petrovich Fedotov  Michael A. Phedorin  Mark De Batist  Galina A. Ziborova  Alexsey Yu Kazansky  Michael Yu Semenov  Galina G. Matasova  Andrey V. Khabuev  Sergey A. Kugakolov  Sergey V. Rodyakin  Svetlana M. Krapivina  Tom Pouls 《Journal of Paleolimnology》2008,39(3):335-348

We use high-resolution reflection seismic data and detailed grain-size analysis of a drill core (KDP-01) from Lake Khubsugul (northern Mongolia) to provide an improved reconstruction of the glacial history of the area for the last 450 ka. Grain-size analysis of suspended sediment load in modern rivers draining into the lake and of moraine material from the northern part of the catchment shows that the silt fraction is transported to the central part of the lake mainly by river suspension, whereas the clay fraction is mainly transported by glacial meltwater during deglaciation. The changes in of the clay/silt ratio in Lake Khubsugul sediments correlates well with the standard global paleoclimate records: low clay/silt ratios indicate warm climates, while a high clay/silt ratio reflects glacial erosion and cold climates. Pulses of clay input into the lake occur at the final stages of glacial periods (i.e., glacial maxima and subsequent onsets of deglaciation). The periodicity in glacial clay input in Lake Khubsugul is in tune with global periods of deglaciation, but there are differences in the intensity of the deglacial events for MIS-12 and MIS-2. These differences are attributed to specific conditions in regional distribution of moisture during glaciation, glacial ice volumes, and solar insolation intensity at the onset of deglaciation. Deglaciation of the Khubsugul glaciers occurred in response to an increase in summer solar insolation above a threshold value of 490 W/m². Two types of deglaciation can be distinguished: (1) slow melting during several tens of 1,000 years during weak increases in summer insolation, and (2) short and fast melting during several thousands of years in response to strong increases in summer insolation. The maximum ice volume in the area of Lake Khubsugul during the past 450 ka occurred during the period of 373–350 ka BP (MIS 11a-10) and was caused by high levels of moisture in the region, whereas the MIS-2 and MIS-12 glacial periods were characterized by minima in ice volume, due to the strong aridity in the region.  相似文献   

Climate extremes in South Western Siberia: past and future   总被引：1，自引：1，他引：0  

Degefie T. Degefie  Elisa Fleischer  Otto Klemm  Andrey V. Soromotin  Olga V. Soromotina  Andrey V. Tolstikov  Nikolay V. Abramov 《Stochastic Environmental Research and Risk Assessment (SERRA)》2014,28(8):2161-2173

In this study, the temporal and spatial trends of ten climate extreme indices were computed based on observed daily precipitation and on daily maximum and minimum temperatures at 26 weather stations in South Western Siberia during the period 1969–2011 and, based on projected daily maximum and minimum temperatures, during 2021–2050. The Mann–Kendall test was employed to analyze the temporal trend and a combination of multiple linear regressions and semivariogram functions were used to evaluate the regional spatial trends and the local spatial variability of climate extremes, respectively. The results show that the temperature-based climate extremes increase at a 0.05 significance level while none of the precipitation-based climate extremes did. Spatially, dominant gradients are observed along latitude: The northern taiga vegetation zone experiences a colder and wetter climate while the southern forest steppe zone is drier and hotter. Over time, a tendency towards homogenization of the regional climate is observed through a decrease of the spatial variability for most climate extreme indices. In the future, the most intense changes are anticipated for the bio-climate indicators “growing season length” and “growing degree days” in the north, while the warming indicators, “warm day” and “warm night” are expected to be high to the south.  相似文献   

Compact non-singular expansions in the exterior space of a reference ellipsoid for the gravitational gradients in the local north-oriented ellipsoidal and spherical reference frames     

Margarita S. Petrovskaya  Andrey N. Vershkov 《Studia Geophysica et Geodaetica》2016,60(1):1-16

Due to the complicated structure of their expressions, the ellipsoidal harmonic series for the derivatives of the Earth’s gravitational potential are commonly applied only on a reference ellipsoid. They depend on the first- and second-order derivatives of the associated Legendre functions of both kinds and contain a few singular terms. We construct ellipsoidal harmonic expansions in the exterior space for the first and second potential derivatives, which are similar to the series on the reference ellipsoid enveloping the Earth. We take a point P at an arbitrary altitude above the reference ellipsoid and construct the ellipsoid of revolution confocal to it, which passes through this point. The conventional complicated singular expressions for the first and second potential derivatives in the local north-oriented ellipsoidal reference frame, with the origin at the point P, are transformed into non-singular ellipsoidal harmonic series, which do not contain the first- and second-order derivatives of the associated Legendre functions. The resulting series have an accuracy of the squared eccentricity. These series can be applied for constructing a geopotential model, which is based, simultaneously, on the surface gravity data and the data of satellite missions, which provide measurements of the accelerations and/or the gravitational gradients. When the eccentricity of the considered external ellipsoid is equated to zero, the ellipsoid becomes an external sphere passing through the point P and the constructed ellipsoidal harmonic expansions are converted into non-singular spherical harmonic series for the first and second potential derivatives in the local north-oriented spherical reference frame.  相似文献