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11.
Seasonal and monthly variations of heat flux have been investigated in this study using the Modular Ocean Model of version 3 (MOM 3) simulations and 52 years Simple Ocean Data Assimilation (SODA) products. These variations of the heat flux in different boxes of the Bay of Bengal (BOB) in different depths show the different behavior of the boxes. It is seen that the model and SODA results are comparable. The basin shows north-south variation in the surface from winter to spring whereas there is east-west variation in the mixed layer throughout the year except winter. The remote effect caused by warm water penetration from Pacific Ocean through the Strait of Malacca and coastal Kelvin waves keeps the basin warm most of the year. This article addresses the mechanisms of the seasonal variation of the vertical structure of the temperature and heat flux components. 相似文献
12.
Eirin Kar Suman Sourav Baral Arun Kumar Saraf Josodhir Das Gaurav Singh Susanta Borgohain 《Journal of the Indian Society of Remote Sensing》2017,45(1):79-88
Kachchh basin is a Mesozoic rift basin under the influence of many active faults. This in turn gives rise to marked structural complexity and associated seismicity. Remote Sensing study of geomorphic evidences of these faults has been carried out using satellite images and is validated using morphometric analysis and digital elevation model data. Satellite images not only help in identifying expression of active faults and active tectonics on a macroscopic scale, but also provide the image characteristics of active faults directly. A few faults along with nature of lateral displacement could be identified from the Kachchh area. Morphometric analysis viz., sinuosity, asymmetry factor and hypsometry indicated affected streams and drainage basins due to fault activity. 相似文献
13.
Geomorphology,sedimentology and minimum exposure ages of streamlined subglacial landforms in the NW Himalaya,India 
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下载免费PDF全文 Sourav Saha Milap C. Sharma Madhav K. Murari Lewis A. Owen Marc W. Caffee 《Boreas: An International Journal of Quaternary Research》2016,45(2):284-303
Streamlined subglacial landforms that include drumlins in three study areas, the upper Chandra valley around Chandra Tal, the upper Spiti Valley and the middle Yunam Valley of the NW Himalaya of India were mapped and studied using geomorphic, sedimentological and geochronological methods. These streamlined subglacial landforms include a variety of morphological types, including: (i) half egg‐shaped forms; (ii) complex superimposed forms; (iii) dome‐shaped forms; (iv) inverse forms; and (v) flat‐topped symmetrical forms. Sedimentological data indicate that subglacial deformational processes are responsible for the formation of the streamlined subglacial landforms in the Chandra Tal and upper Spiti Valley study areas. In contrast, streamlined landforms in the middle Yunam Valley are the result of melt‐out and subglacial erosional processes. In the Yunam Valley study area, 11 new cosmogenic 10Be surface exposure ages were obtained for boulders inset into the crests of streamlined subglacial landforms and moraines, and also for a bedrock surface. The streamlined landforms date to 8–7 ka, providing evidence of an early Holocene valley glaciation, and older moraines date to ～17–15 and 79–52 ka, representing other significant valley glacial advances in the middle Yunam Valley. The subglacial landforms in the Chandra Valley provide evidence for a ≥300‐m‐thick Lateglacial glacier that advanced southeast, overtopping the Kunzum Range, and advancing into the upper Spiti Valley. The streamlined subglacial landforms in these study areas of the NW Himalaya highlight the usefulness of such landforms in developing glacial chronostratigraphy and for understanding the dynamics of Himalayan glaciation. 相似文献
14.
Using the method of two-dimensional spectroscopy, we have investigated the kinematics and distribution of the gas and stars
at the center of the early-type spiral galaxy NGC 7177 with a mediumscale bar as well as the change in the mean age of the
stellar population along the radius. A classical picture of radial gas inflow to the galactic center along the shock fronts
delineated by dust concentration at the leading edges of the bar has been revealed. The gas inflow is observed down to a radius
R = 1″.5−2″, where the gas flows at the inner Lindblad resonance concentrate in an azimuthally highly inhomogeneous nuclear
star formation ring. The bar in NGC 7177 is shown to be thick in z coordinate—basically, it has already turned into a pseudo-bulge as a result of secular dynamical evolution. The mean stellar
age inside the star formation ring, in the galactic nucleus, is old, ∼10 Gyr.Outside, at a distance R = 6″−8″ from the nucleus, the mean age of the stellar population is ∼2 Gyr. If we agree that the bar in NGC 7177 is old,
then, obviously, the star formation ring has migrated radially inward in the last 1–2 Gyr, in accordance with the predictions
of some dynamical models. 相似文献
15.
O. K. Sil’chenko 《Astronomy Letters》2005,31(4):227-238
We analyze data from the SAURON integral-field spectrograph of the William Herschel 4-m telescope for five lenticular galaxies in which we previously found chemically decoupled nuclei from observations with the Multipupil Fiber Spectrograph of the 6-m Special Astrophysical Observatory telescope. In a larger field of view, we confirmed the presence of peaks of the equivalent width of the Mg Ib λ5175 absorption line in the nuclei of all five galaxies. However, the structure of the chemically decoupled regions turned out to be highly varied even in such a small sample: from compact unresolved knots to disks with an extent of several hundred parsecs and, in one case, a triaxial compact minibar-type structure. We confirmed the presence of an inner gaseous polar ring in NGC 7280 and found it in NGC 7332. In their outer parts, the planes of these polar rings are warped toward the plane of stellar rotation in such a way that the gas counterrotates with respect to the stars. This behavior of the gas in a triaxial potential was predicted by several theoretical models. 相似文献
16.
Astronomy Reports - The origin of several rings in lenticular galaxies with no signs of ongoing or recent star formation (without emission lines and a signal in the ultraviolet spectral range) is... 相似文献
17.
Dark energy models inspired by the cosmological holographic principle are studied in homogeneous isotropic spacetime with a general choice for the dark energy density \(\rho_{d}=3(\alpha H^{2}+\beta\dot{H})\) . Special choices of the parameters enable us to obtain three different holographic models, including the holographic Ricci dark energy (RDE) model. Effect of interaction between dark matter and dark energy on the dynamics of those models are investigated for different popular forms of interaction. It is found that crossing of phantom divide can be avoided in RDE models for β>0.5 irrespective of the presence of interaction. A choice of α=1 and β=2/3 leads to a varying Λ-like model introducing an IR cutoff length Λ ?1/2. It is concluded that among the popular choices an interaction of the form Q∝Hρ m suits the best in avoiding the coincidence problem in this model. 相似文献
18.
With the means of panoramic spectroscopy at the SAO RAS BTA telescope, we investigated the properties of stellar populations
in the central regions of five early-type galaxies—the NGC524 group members. The evolution of the central regions of galaxies
looks synchronized: the average age of stars in the bulges of all the five galaxies lies in the range of 3–6Gyr.Four of the
five galaxies revealed synchronized bursts of star formation in the nuclei 1–2 Gyr ago. The only galaxy, in which the ages
of stellar population in the nucleus and in the bulge coincide (i.e. the nuclear burst of star formation did not take place)
isNGC502, the farthest from the center of the group of all the galaxies studied. 相似文献
19.
Gully cut‐and‐fill cycles as related to agro‐management: a historical curve number simulation in the Tigray Highlands 下载免费PDF全文
下载免费PDF全文 Sil Lanckriet Amaury Frankl Gebrekidan Mesfin Katrien Descheemaeker Jan Nyssen 《地球表面变化过程与地形》2015,40(6):796-808
Gully cut‐and‐fill dynamics are often thought to be driven by climate and/or deforestation related to population pressure. However, in this case‐study of nine representative catchments in the Northern Ethiopian Highlands, we find that neither climate changes nor deforestation can explain gully morphology changes over the twentieth century. Firstly, by using a Monte Carlo simulation to estimate historical catchment‐wide curve numbers, we show that the landscape was already heavily degraded in the nineteenth and early twentieth century – a period with low population density. The mean catchment‐wide curve number (> 80) one century ago was, under the regional climatic conditions, already resulting in considerable simulated historical runoff responses. Secondly, twentieth century land‐cover and runoff coefficient changes were confronted with twentieth century changing gully morphologies. As the results show, large‐scale land‐cover changes and deforestation cannot explain the observed processes. The study therefore invokes interactions between authigenic factors, small‐scale plot boundary changes, cropland management and sociopolitical forces to explain the gully cut processes. Finally, semi‐structured interviews and sedistratigraphic analysis of three filled gullies confirm the dominant impact of (crop)land management (tillage, check dams in gullies and channel diversions) on gully cut‐and‐fill processes. Since agricultural land management – including land tenure and land distribution – has been commonly neglected in earlier related research, we argue therefore that it can be a very strong driver of twentieth century gully morphodynamics. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
20.
Two-color photometric data obtained on the 6-m telescope of the Special Astrophysical Observatory are used to analyze the
structure of 13 large disk galaxies in the NGC 80 group. Nine of the 13 studied galaxies are classified as lenticular galaxies.
The stellar populations in the galaxies are very diverse, from old stars with ages of T > 10 billion years (IC 1541) to relatively young stars with ages of T ∼ 1–3 billion years (IC 1548, NGC 85); in one case, star formation is ongoing (UCM 0018+2216). In most of the studied galaxies,
more precisely in all of them brighter than M
B ∼ −18, two-tiered stellar disks are detected, whose radial surface-brightness profiles can be described by two exponential
segments with different characteristic scales—shorter near the center and longer at the periphery. All of the dwarf S0 galaxies
with single-tiered disks are close companions to larger galaxies. Except for this fact, no dependence of the properties of
S0 galaxies on distance from the center of the group is found. Morphological signs of a “minor merger” are found in the lenticular
galaxy NGC 85. Based on these last two results, it is concluded that the most probable mechanism for their transformation
of spiral into lenticular galaxies in groups is gravitational (minor mergers and tidal interactions). 相似文献