Consistent Two-Equation Closure Modelling for Atmospheric Research: Buoyancy and Vegetation Implementations     

Andrey Sogachev  Mark Kelly  Monique Y. Leclerc 《Boundary-Layer Meteorology》2012,145(2):307-327

A self-consistent two-equation closure treating buoyancy and plant drag effects has been developed, through consideration of the behaviour of the supplementary equation for the length-scale-determining variable in homogeneous turbulent flow. Being consistent with the canonical flow regimes of grid turbulence and wall-bounded flow, the closure is also valid for homogeneous shear flows commonly observed inside tall vegetative canopies and in non-neutral atmospheric conditions. Here we examine the most often used two-equation models, namely and E − ω (where is the dissipation rate of turbulent kinetic energy, E, and is the specific dissipation), comparing the suggested buoyancy-modified closure against Monin–Obukhov similarity theory. Assessment of the closure implementing both buoyancy and plant drag together has been done, comparing the results of the two models against each other. It has been found that the E − ω model gives a better reproduction of complex atmospheric boundary-layer flows, including less sensitivity to numerical artefacts, than does the model. Re-derivation of the equation from the ω equation, however, leads to the model implementation that produces results identical to the E − ω model. Overall, numerical results show that the closure performs well, opening new possibilities for application of such models to tasks related to the atmospheric boundary layer—where it is important to adequately account for the influences of both vegetation and atmospheric stability.  相似文献   

Will climate change exacerbate water stress in Central Asia?   总被引：3，自引：0，他引：3  

Tobias Siegfried  Thomas Bernauer  Renaud Guiennet  Scott Sellars  Andrew W. Robertson  Justin Mankin  Peter Bauer-Gottwein  Andrey Yakovlev 《Climatic change》2012,112(3-4):881-899

Millions of people in the geopolitically important region of Central Asia depend on water from snow- and glacier-melt driven international rivers, most of all the Syr Darya and Amu Darya. The riparian countries of these rivers have experienced recurring water allocation conflicts ever since the Soviet Union collapsed. Will climate change exacerbate water stress and thus conflicts? We have developed a coupled climate, land-ice and rainfall-runoff model for the Syr Darya to quantify impacts and show that climatic changes are likely to have consequences on runoff seasonality due to earlier snow-melt. This will increase water stress in unregulated catchments because less water will be available for irrigation in the summer months. Threats from geohazards, above all glacier lake outbursts, are likely to increase as well. The area at highest risk is the densely populated, agriculturally productive, and politically unstable Fergana Valley. Targeted infrastructural developments will be required in the region. If the current mismanagement of water and energy resources can be replaced with more effective resource allocation mechanisms through the strengthening of transboundary institutions, Central Asia will be able to successfully address these future climate-related challenges.  相似文献   

A multi-proxy approach for revealing recent climatic changes in the Russian Altai   总被引：2，自引：0，他引：2  

Olga V. Sidorova  Matthias Saurer  Vladimir S. Myglan  Anja Eichler  Margit Schwikowski  Aleksander V. Kirdyanov  Marina V. Bryukhanova  Oksana V. Gerasimova  Ivan A. Kalugin  Andrey V. Daryin  Rolf T. W. Siegwolf 《Climate Dynamics》2012,38(1-2):175-188

For the first time we present a multi-proxy data set for the Russian Altai, consisting of Siberian larch tree-ring width (TRW), latewood density (MXD), δ¹³C and δ¹⁸O in cellulose chronologies obtained for the period 1779–2007 and cell wall thickness (CWT) for 1900–2008. All of these parameters agree well between each other in the high-frequency variability, while the low-frequency climate information shows systematic differences. The correlation analysis with temperature and precipitation data from the closest weather station and gridded data revealed that annual TRW, MXD, CWT, and δ¹³C data contain a strong summer temperature signal, while δ¹⁸O in cellulose represents a mixed summer and winter temperature and precipitation signal. The temperature and precipitation reconstructions from the Belukha ice core and Teletskoe lake sediments were used to investigate the correspondence of different independent proxies. Low frequency patterns in TRW and δ¹³C chronologies are consistent with temperature reconstructions from nearby Belukha ice core and Teletskoe lake sediments showing a pronounced warming trend in the last century. Their combination could be used for the regional temperature reconstruction. The long-term δ¹⁸O trend agrees with the precipitation reconstruction from the Teletskoe lake sediment indicating more humid conditions during the twentieth century. Therefore, these two proxies could be combined for the precipitation reconstruction.  相似文献   

A New Method of Calibration of Photographic Plates from Three Historic Data Sets     

Andrey G. Tlatov  Alexei A. Pevtsov  Jagdev Singh 《Solar physics》2009,255(2):239-251

  相似文献   

A Century of Solar Ca <Emphasis Type="SmallCaps">ii</Emphasis> Measurements and Their Implication for Solar UV Driving of Climate     

Peter Foukal  Luca Bertello  William C. Livingston  Alexei A. Pevtsov  Jagdev Singh  Andrey G. Tlatov  Roger K. Ulrich 《Solar physics》2009,255(2):229-238

Spectroheliograms and disk-integrated flux monitoring in the strong resonance line of Ca ii (K line) provide the longest record of chromospheric magnetic plages. We compare recent reductions of the Ca ii K spectroheliograms obtained since 1907 at the Kodaikanal, Mt. Wilson, and US National Solar Observatories. Certain differences between the individual plage indices appear to be caused mainly by differences in the spectral passbands used. Our main finding is that the indices show remarkably consistent behavior on the multidecadal time scales of greatest interest to global warming studies. The reconstruction of solar ultraviolet flux variation from these indices differs significantly from the 20th-century global temperature record. This difference is consistent with other findings that, although solar UV irradiance variation may affect climate through influence on precipitation and storm tracks, its significance in global temperature remains elusive.  相似文献   

Robotic optical telescopes global network MASTER II. Equipment, structure, algorithms     

Victor G. Kornilov  Vladimir M. Lipunov  Evgeny S. Gorbovskoy  Aleksander A. Belinski  Dmitry A. Kuvshinov  Natalia V. Tyurina  Nikolai I. Shatsky  Anatoly V. Sankovich  Aleksander V. Krylov  Pavel V. Balanutsa  Vadim V. Chazov  Artem S. Kuznetsov  Dmitry S. Zimnuhov  Victor A. Senik  Andrey G. Tlatov  Aleksander V. Parkhomenko  Denis V. Dormidontov  Vadim V. Krushinsky  Ivan S. Zalozhnyh  Aleksander A. Popov  Sergey A. Yazev  Nikolai M. Budnev  Kirill I. Ivanov  Evgeny N. Konstantinov  Oleg A. Gress  Oleg V. Chvalaev  Vladimir V. Yurkov  Yury P. Sergienko  Irina P. Kudelina 《Experimental Astronomy》2012,33(1):173-196

Presented paper describes the basic principles and features of the implementation of a robotic network of optical telescopes MASTER, designed to study the prompt (simultaneous with gamma radiation) optical emission of gamma-ray bursts and to perform the sky survey to detect unknown objects and transient phenomena. With joint efforts of Sternberg astronomical institute, High altitude astronomical station of the Pulkovo observatory, Ural state university, Irkutsk state university, Blagoveshchensk pedagogical university, the robotic telescopes MASTER?II near Kislovodsk, Yekaterinburg, Irkutsk and Blagoveshchensk were installed and tested. The network spread over the longitudes is greater than 6?h. A further expansion of the network is considered.  相似文献   

Satellite-based analysis of the spatial patterns of fire- and storm-related forest disturbances in the Ural region,Russia     

Shikhov  Andrey N.  Perminova  Ekaterina S.  Perminov  Sergey I. 《Natural Hazards》2019,97(1):283-308

Natural Hazards - Large-scale wildfires and windstorms are the most important disturbance agents for the Russian boreal forests. The paper presents an assessment of fire-related and wind-induced...  相似文献   

Prestack data enhancement with phase corrections in time-frequency domain guided by local multidimensional stacking     

Andrey Bakulin  Dmitri Neklyudov  Ilya Silvestrov 《Geophysical Prospecting》2020,68(6):1811-1818

We present a new approach to enhancing weak prestack reflection signals without sacrificing higher frequencies. As a first step, we employ known multidimensional local stacking to obtain an approximate ‘model of the signal’. Guided by phase spectra from this model, we can detect very weak signals and make them visible and coherent by ‘repairing’ corrupted phase of original data. Both presented approaches – phase substitution and phase sign corrections – show good performance on complex synthetic and field data suffering from severe near-surface scattering where conventional processing methods are rendered ineffective. The methods are mathematically formulated as a special case of time-frequency masking (common in speech processing) combined with the signal model from local stacking. This powerful combination opens the avenue for a completely new family of approaches for multi-channel seismic processing that can address seismic processing of land data with nodes and single sensors in the desert environment.  相似文献   

Post‐Great Oxidation Event Orosirian–Statherian iron formations on the São Francisco craton: Geotectonic implications     

Carlos A. Rosire  Andrey Bekker  Vassily K. Rolim  Joo Orestes S. Santos 《Island Arc》2019,28(4)

The protocratonic core of the São Francisco craton assembled during the 2.1–2.0 Ga Transamazonian orogeny. Orosirian Fe‐rich sequences that extend from the northwestern border of the São Francisco protocraton (Colomi Group) to the southeast under the Espinhaço Belt (the < 1.99 Ga Serra da Serpentina Group) record the opening of an intracratonic basin with the episodically developed ferruginous waters prior to the initiation of the Espinhaço rift at 1.8 Ga. Ferruginous conditions developed again during deposition of the Canjica Iron Formation of the < 1.7 Ga Serra de São José Group in the Espinhaço rift (contemporaneously with felsic magmatism; Conceição do Mato Dentro Rhyolite and Borrachudos Granitic Suite) and extensive sandstones of the < (1666 ±32) Ma Itapanhoacanga and < (1683 ±11) Ma São João da Chapada Formations. In the upper São João da Chapada Formation, banded hematitic phyllite also records input of Fe‐rich fluids. The young age of these iron formations with respect to the conventionally accepted 1.88 Ga age for the youngest shallow‐marine Paleoproterozoic iron formations, the apparent absence of granular facies (granular iron formations), and yet shallow‐water (above fair‐weather base) depositional environment indicate that an unusual setting developed in a large basin after the Great Oxidation Event, in the aftermath of the Transamazonian orogeny. We propose that mantle plumes led to the opening of a previously unrecognized rift system, that could have caused the magmatism, supplied hydrothermal Fe and led to the opening of the Espinhaço, Pirapora, and Paramirim rifts, later obliterated by the Araçuaí orogenic belt during the Neoproterozoic to Early Paleozoic Brasiliano orogeny. The rift system did not develop into an open continental margin but probably evolved into a broad sag basin, stretching across the São Francisco and Congo cratons.  相似文献   

Lagrangian study of temporal changes of a surface flow through the Kamchatka Strait     

Sergey V. Prants  Andrey G. Andreev  Michael Yu. Uleysky  Maxim V. Budyansky 《Ocean Dynamics》2014,64(6):771-780

Using Lagrangian methods, we analyze a 20-year-long estimate of water flux through the Kamchatka Strait in the northern North Pacific based on AVISO velocity field. It sheds new light on the flux pattern and its variability on annual and monthly time scales. Strong seasonality in surface outflow through the strait could be explained by temporal changes in the wind stress over the northern and western Bering Sea slopes. Interannual changes in a surface outflow through the Kamchatka Strait correlate significantly with the Near Strait inflow and Bering Strait outflow. Enhanced westward surface flow of the Alaskan Stream across the 174°E section in the northern North Pacific is accompanied by an increased inflow into the Bering Sea through the Near Strait. In summer, the surface flow pattern in the Kamchatka Strait is determined by the passage of anticyclonic and cyclonic mesoscale eddies. The wind stress over the Bering basin in winter–spring is responsible for eddy generation in the region.  相似文献