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101.
The present study is carried out to examine the performance of a regional atmospheric model in forecasting tropical cyclones
over the Bay of Bengal and its sensitivity to horizontal resolution. Two cyclones, which formed over the Bay of Bengal during
the years 1995 and 1997, are simulated using a regional weather prediction model with two horizontal resolutions of 165 km
and 55 km. The model is found to perform reasonably well towards simulation of the storms. The structure, intensity and track
of the cyclones are found to be better simulated by finer resolution of the model as compared to the coarse resolution. Rainfall
amount and its distribution are also found to be sensitive to the model horizontal resolution. Other important fields, viz.,
vertical velocity, horizontal divergence and horizontal moisture flux are also found to be sensitive to model horizontal resolution
and are better simulated by the model with finer horizontal grids. 相似文献
102.
The characteristic features of the marine boundary layer (MBL) over the Bay of Bengal during the southwest monsoon and the
factors influencing it are investigated. The Bay of Bengal and Monsoon Experiment (BOBMEX) carried out during July–August
1999 is the first observational experiment under the Indian Climate Research Programme (ICRP). A very high-resolution data
in the vertical was obtained during this experiment, which was used to study the MBL characteristics off the east coast of
India in the north and south Bay of Bengal. Spells of active and suppressed convection over the Bay were observed, of which,
three representative convective episodes were considered for the study. For this purpose a one-dimensional multi-level PBL
model with a TKE-ε closure scheme was used. The soundings, viz., the vertical profiles of temperature, humidity, zonal and
meridional component of wind, obtained onboard ORV Sagar Kanya and from coastal stations along the east coast are used for
the study. The temporal evolution of turbulent kinetic energy, marine boundary layer height (MBLH), sensible and latent heat
fluxes and drag coefficient of momentum are simulated for different epochs of monsoon and monsoon depressions during BOBMEX-99.The
model also generates the vertical profiles of potential temperature, specific humidity, zonal and meridional wind. These simulated
values compared reasonably well with the observations available from BOBMEX. 相似文献
103.
Contrasting metamorphic evolution of metasedimentary rocks from the Çine and Selimiye nappes in the Anatolide belt, western Turkey 总被引:1,自引:0,他引:1
J. L. Régnier U. Ring C. W. Passchier K. Gessner T. Güngör 《Journal of Metamorphic Geology》2003,21(7):699-721
Abstract P–T conditions, mineral isograds, the relation of the latter to foliation planes and kinematic indicators are used to elucidate the tectonic nature and evolution of a shear zone in an orogen exhumed from mid‐crustal depths in western Turkey. Furthermore, we discuss whether simple monometamorphic fabrics of rock units from different nappes result from one single orogeny or are related to different orogenies. Metasedimentary rocks from the Çine and Selimiye nappes at the southern rim of the Anatolide belt of western Turkey record different metamorphic evolutions. The Eocene Selimiye shear zone separates both nappes. Metasedimentary rocks from the Çine nappe underneath the Selimiye shear zone record maximum P–T conditions of about 7 kbar and >550 °C. Metasedimentary rocks from the overlying Selimiye nappe have maximum P–T conditions of 4 kbar and c. 525 °C near the base of the nappe. Kinematic indicators in both nappes are related to movement on the Selimiye shear zone and consistently show a top‐S shear sense. Metamorphic grade in the Selimiye nappe decreases structurally upwards as indicated by mineral isograds defining the garnet‐chlorite zone at the base, the chloritoid‐biotite zone and the biotite‐chlorite zone at the top of the nappe. The mineral isograds in the Selimiye nappe run parallel to the regional SR foliation, parallel the Selimiye shear zone and indicate that the Selimiye shear zone formed during this prograde greenschist to lower amphibolite facies metamorphic event but remained active after the peak of metamorphism. 40Ar/39Ar mica ages and the tectonometamorphic relationship with the Eocene Cyclades–Menderes thrust, which occurs above the Selimiye nappe in the study area, suggests an Eocene age of metamorphism in the Selimiye nappe. Metasedimentary rocks of the Çine nappe 20–30 km north of the Selimiye shear zone record maximum P–T conditions of 8–11 kbar and 600–650 °C. An age of about 550 Ma is indicated for amphibolite facies metamorphism and associated top‐N shear in the orthogneiss of the Çine nappe. Our study shows that simple monophase tectonometamorphic fabrics do not always indicate a simple orogenic development of a nappe stack. Preservation in some areas and complete overprinting of those fabrics in other areas apparently occur very heterogeneously. 相似文献
104.
Recent studies in northwest New Guinea have shown the presence of at least two marginal basins of different age, both of which formed in back-arc settings. The older basin opened between the Middle Jurassic and Early Cretaceous, a remnant of which is now preserved as the New Guinea Ophiolite. Its obduction started at 40 Ma and it was finally emplaced on the Australian margin at 30 Ma. The younger basin was active during the Oligocene to Middle Miocene and was obducted in the Early Pliocene. Studies of the western edge of the Philippine Sea also reveal an important deformation of the Philippine arc in the Oligocene, which hitherto has remained unexplained. Using information from these systems, paleomagnetic results, kinematic reconstructions and geochemistry of the supra-subduction ophiolite, we present a plate model to explain the region's Eo–Oligocene development. We suggest that an extensive portion of oceanic crust extended the Australian Plate a considerable distance north of the Australian Craton. As Australia began its steady 7–8 cm/year northward drift in the Early Eocene, this lithosphere was subducted. Thus, the portion of the Philippine Sea Plate carrying the Taiwan–Philippine Arc to its present site may have actually been in contact with the ophiolite now in New Guinea and obduction led to deformation of the Philippine Sea Plate itself. Neogene Plate kinematics transported the deformed belt in contact with the Sunda block in the Late Miocene and Pliocene. This interpretation has implications for the origin for the Philippine Sea Plate and the potential incorporation of continental fragments against its boundaries. 相似文献
105.
106.
Meso-gamma scale forecasts using the nonhydrostatic model LM 总被引:10,自引:0,他引:10
J. Steppeler G. Doms U. Schättler H. W. Bitzer A. Gassmann U. Damrath G. Gregoric 《Meteorology and Atmospheric Physics》2003,82(1-4):75-96
Summary ?The nonhydrostatic model LM was developed for small scale operational predictions. Advances in computer development will
give the possibility of operational models of a rather fine scale, which will cover the meso-gamma scale. The LM is currently
applied at a scale of 7 km and an increase of the operational resolution to 2.5 km is planned for the next few years. Predictions
of such high resolution require to abandon the hydrostatic assumption, which is used with most current operational weather
prediction models. The LM was designed to cover all resolutions from 50 m to 50 km with an efficiency making it suitable for
operational use. It is a fully elastic model, using second order centred finite differences. The time integration is done
using the Klemp–Wilhelmson method, treating the slow modes by a larger time step than the fast modes. The vertical propagation
of the fast waves is done implicitly.
After describing the design of the LM, this paper gives examples of model predictions at the meso-γ scale. Some results of
the current operational application at the resolution 7 km are presented. Deficiencies in the localisation of model generated
precipitation are investigated using an idealised bell shaped mountain and applying different resolutions. In this way the
convergence to the correct solution can be investigated. From these results it is concluded, that orographic filtering is
necessary and the effect of such filtering on precipitation forecasts is investigated. Finally, the prediction of a squall
line over northern Germany is shown in order to demonstrate the potential of the model in forecasting the meso-γ scale.
Received May 15, 2001; revised September 21, 2001 相似文献
107.
N. Mölders U. Haferkorn J. Döring G. Kramm 《Meteorology and Atmospheric Physics》2003,84(1-2):137-156
Summary ¶Various water budget elements (water supply to the atmosphere, ground water recharge, change in storage) are predicted by HTSVS for a period of 2050 days. The predicted water budget elements are evaluated by routine lysimeter data. The results show that land surface models need parameterizations for soil frost, snow effects and water uptake to catch the broad cycle of soil water budget elements. In principle, HTSVS is able to simulate the general characteristics of the seasonal changes in these water budget elements and their long-term accumulated sums. Compared to lysimeter data, there is a discrepancy in the predicted water supply to the atmosphere for summer and winter which may be attributed to the hardly observed plant physiological parameters like root depth, LAI, shielding factor, etc., the lack of measured downward long-wave radiation, and some simplifications made in the parameterizations of soil frost and snow effects. The fact that high resolution data for the evaluation of model results are missing and evaluation is made on the basis of the data from routine stations of a network is typical for the results of long-term studies on climate. Taking into account the coarse resolution of climate models, the coarse vertical resolution that is used in their LSMs, and the lack of suitable parameters needed, it seems that discrepancies in the order of magnitude found in this study are a general uncertainty in the results of land surface modeling on typical spatial and temporal scales of the climate system.Received October 8, 2001; revised February 15, 2002; accepted September 20, 2002
Published online: April 10, 2003 相似文献
108.
The analysis of various factors influencing mineral availability documents future short-and long-term mineral-commodity supply trends. The lifetime of reserves, the development of the relative importance of production centres and the forecasting of the depletion of a resource base are mainly geological factors, although the category “reserves”, in contrast to “resources”, is determined by technical and economical aspects. These three factors govern the short-and long-term supply of mineral commodities. The intensity-of-use factors and the growth rate of consumption are variables related to the demand of mineral commodities. They influence the decision of companies for certain commodities as targets for exploration and investment in production centres. Both factors control the short-to medium-term mineral supply. Finally, the lead time to production is a technical variable, although influenced by ore deposit type, and controls short-term mineral availability. 相似文献
109.
This paper presents an updated interpretation of seismic anisotropy within the uppermost mantle of southern Germany. The dense network of reversed and crossing refraction profiles in this area made it possible to observe almost 900 traveltimes of the Pn phase that could be effectively used in a time-term analysis to determine horizontal velocity distribution immediately below the Moho. For 12 crossing profiles, amplitude ratios of the Pn phase compared to the dominant crustal phase were utilized to resolve azimuthally dependent velocity gradients with depth. A P -wave anisotropy of 3–4 per cent in a horizontal plane immediately below the Moho at a depth of 30 km, increasing to 11 per cent at a depth of 40 km, was determined. For the axis of the highest velocity of about 8.03 km s−1 at a depth of 30 km a direction of N31°F was obtained. The azimuthal dependence of the observed Pn amplitude is explained by an azimuth-dependent sub-Moho velocity gradient decreasing from 0.06 s−1 in the fast direction to 0 s−1 in the slow direction of horizontal P -wave velocity. From the seismic results in this study a petrological model suggesting a change of modal composition and percentage of oriented olivine with depth was derived. 相似文献
110.
The Uplift of the Longmenshan Thrust Belt and Subsidence of the West Sichuan Foreland Basin 总被引:8,自引:0,他引:8
Liu Shugen Luo Zhili Dai Sulan Changlu Institute of Technology Chengdu Sichuan ChinaDennis Arne Dalhousie U niversity Canadaand C.J.L. Wilson Melbourne U niversity Australia Jiang M inxi 《《地质学报》英文版》1996,70(1):16-26
Based on fission track dating of apatite, and measurement of vitrinite reflectance of rock samples from the Longmenshan (Longmen Mountain)area and the West Sichuan foreland basin and computer modelling it is concluded that (l)the Songpan-Garze fold belt has uplifted at least by 3-4 km with an uplift rate of no less than 0.3-0.4 mm/a since 10 Ma B.P.; (2) the Longmenshan thrust nappe belt has uplifted at least by 5-6 km with an uplift rate of more than 0.5- 0.6 mm /a since 10 Ma B.P.; (3) the Longmenshan detachment belt has uplifted by 1 - 2 km at a rate of 0.016-0.032 mm/a since 60 Ma B.P.; (4) the West Sichuan foreland basin has uplifted by 1.7-3 km at a rate of 0.028-0.05 mm/a since 60 Ma B.P.; (5) the uplift rate of the area on the west side of the Beichuan-Yingxiu-Xiaoguanzi fault for the last 10 Ma is 40 times as much as that on its east side; (6) the uplifting of the the Songpan - Garze fold belt and the subsidence of the West Sichuan foreland basin 60 Ma ago exhibit a mirro-image correlation, i.e 相似文献