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71.
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Huaibei area is an important iron-copper metallogenic area in northern Anhui Province. In order to summarize the metallogenic series and regularity of skarn-type deposits systematically in this area, based on recent prospecting results and the diagenesis and metallogenic chronology, the authors systematically investigated the geological characteristics and metallogenic conditions of the known deposits and divided thern into three metallogenic series. They are skarn-type iron-copper-gold metallogenic series related to high-K calc-alkali intrusive rocks, skarn-type iron-gypsum metallogenic series related to high-K calc-alkaline intrusive rocks and skarn-type iron-light rare earth metallogenic series related to monzogranite. Then the geological characteristics and metallogenic regularity of four typical deposits were discussed respectively. The results show that the deposit formation can be divided into two stages in this area, and the metallogenic space is controlled by deep faults, arc structures and magmatic belts. Finally, the regional metallogenic models of Qianchang type, Yangqiaozi type and Wangchang type iron polymetallic deposits in the early stage of Early Cretaceous and Qiganlou type iron-light rare earth deposits in the late stage of Early Cretaceous were established. 相似文献
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This study investigated the effects of landfall on the structure of a
tropical cyclone (TC). Numerical simulations were performed using the
Weather Research and Forecasting Model on a β-plane. Two landfall
experiments, one with an east--west and another with a north--south oriented
coastline, were performed.
Similar to previous studies on an f-plane, large-scale flows in the
low-to-middle troposphere were modified due to friction. A pair of counter
rotating gyres was found, which was shown to be consistent with the slight
deflection of the TC relative to the control experiment without land.
Compared to previous f-plane simulations, because of the inherent asymmetries
due to the β-gyres, the large-scale pattern of flows and
convergences/divergences related to friction were found to depend on
coastline orientations. On the other hand, regardless of the coastline
orientation, convergences were found to be stronger to the left for both
cases near landfall, as in previous f-plane simulations. Such a convergence
pattern subsequently induced a change in convection and rainfall at the
eyewall. 相似文献
77.
Over the years, the Hong Kong Observatory has carried out scientific studies to evaluate the observed climate trends and project the future climate in Hong Kong. Analysis of the meteorological observations at the observatory's headquarters in Tsim Sha Tsui since 1885 reveals that the temperature rise in Hong Kong during the past 124 years is in accord with the global rising trend. The accelerated rising trend in the mean temperature in last few decades may be attributed to the anthropogenic influences, especially urbanization. A similar increasing trend is also observed for rainfall. Other observations such as increasing cloud amount and decreasing total global solar radiation are all consistent with the global trend. Studies of past occurrences of extreme temperature and rainfall have also been carried out. The results indicate that cold episodes have become rarer while very hot days and heavy rain events are becoming more frequent. The observatory also makes use of the data from the Fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change (IPCC) and employs statistical downscaling techniques to carry out projections of temperature and precipitation in the 21st century. It is found that the rise in temperature in Hong Kong will be slightly higher than the global mean in the 21st century. The annual rainfall in Hong Kong is also expected to rise by the end of the 21st century, so is its year-to-year variability. 相似文献
78.
A limited-area primitive equation model is used to study the role of the β-effect and a uniform current on tropical cyclone (TC) intensity.It is found that TC intensity is reduced in a non-quiescent environment compared with the case of no uniform current.On an f-plane,the rate of intensification of a tropical cyclone is larger than that of the uniform flow.A TC on a β-plane intensifies slower than one on an f-plane.The main physical characteristic that distinguishes the experiments is the asymmetric thermodynamic (including convective) and dynamic structures present when either a uniform flow or β-effect is introduced.But a fairly symmetric TC structure is simulated on an f-plane.The magnitude of the warm core and the associated subsidence are found to be responsible for such simulated intensity changes.On an f-plane,the convection tends to be symmetric,which results in strong upper-level convergence near the center and hence strong forced subsidence and a very warm core.On the other hand,horizontal advection of temperature cancels part of the adiabatic heating and results in less warming of the core,and hence the TC is not as intense.This advective process is due to the tilt of the vortex as a result of the β-effect.A similar situation occurs in the presence of a uniform flow.Thus,the asymmetric horizontal advection of temperature plays an important role in the temperature distribution.Dynamically,the asymmetric angular momentum (AM) flux is very small on an f-plane throughout the troposphere.However,the total AM exports at the upper levels for a TC either on aβ-plane or with a uniform flow environment are larger because of an increase of the asymmetric as well as symmetric AM export on the plane at radii >450 km,and hence there is a lesser intensification. 相似文献
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SIEW HUNG CHAN 《Geophysical Prospecting》1971,19(4):791-797
Nomograms are presented for the purpose of rapid computation of the apparent resistivity functions from the field data for symmetrical and unsymmetrical linear electrode arrays. 相似文献