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1.
加强煤矿水害防治工作的法规依据和对策建议 总被引：2，自引：3，他引：2
近年来,我国煤矿重特大水害事故多发,给国家和人民生命财产造成了巨大损失,党中央、国务院领导对此高度重视,并要求尽快加强煤矿水害防治工作,根据国家安全生产监督管理总局(国家煤矿安全监察局)下发了“关于加强煤矿水害防治工作的紧急通知,”及全国煤矿水害防治工作座谈会,论述了当前加强煤矿水害防治工作的几个重要问题。 相似文献
2.
A hierarchy of climate models have been developed and applied to the problem of doubling the CO2 concentration in the atmosphere. Currently available general circulation models include the most complete treatment of the
global wanning and are capable of providing changes in several of the meteorological parameters in time scales of half a century
or even more. Much skill is gradually being achieved now for future climate simulations. In this paper, we have attempted
to describe the response of the National Center for Atmospheric Research Climate Community Model (NCAR CCM), whose performance
for northern hemispheric climate simulations was reported to be very satisfactory to Indian region. The seasonal (winter and
summer) changes in surface temperature, rainfall and soil moisture expected over the Indian sub-continent due to doubling
of CO2 in the atmosphere as inferred from model output statistics are discussed. A probable scenario for sea level rise along the
Indian coastline by the year 2030 AD as a result of ocean water’s expansion due to global warming is outlined. These projections
should not be treated as predictions of what is going to happen over the Indian sub-continent. Rather, they merely illustrate
to what extent we might be affected by the future climate change. 相似文献
3.
Sedimentary strata on top of some laccolithic intrusions are nearly horizontal and little deformed, but are bent into steeply dipping monoclinal flexures over the peripheries of these intrusions. This form of bending is not explained by previous theories of laccolithic intrusion, which predict either horizontal undeformed strata over the center and faulted strata around the periphery, or strata bent continuously into a dome. However, a slight generalization of these theories accomodates the observed form and contains the previous forms as special cases. A critical assumption is that the strength of contacts within a multilayered overburden is overcome locally by layer-parallel shear. If this strength is less than the strength of the layers themselves, then layers over the center remain bonded together and display negligible bending, whereas layers over the periphery slip over one another and are readily bent into a monoclinal flexure. 相似文献
4.
为研究降雨过程雨强随历时的变化关系,利用中国14个气象站近40年逐分钟降雨资料,采用动态K均值聚类法并根据雨峰在降雨过程中出现的位置,将中国10256次降雨过程分为4种类型,即降雨前期集中型（Ⅰ型）、降雨中期集中型（Ⅱ型）、降雨后期集中型（Ⅲ型）和降雨均匀分布型（IV型）。结果表明:中国Ⅰ型降雨出现频次最高,占47.1%;Ⅱ型次之,占21.2%;Ⅲ型和IV型出现频次相当,分别占15.3%和16.4%。夏季Ⅰ型降雨发生频次占绝对优势,为夏季总降水过程的52.2%;冬季各类雨型发生频次相差不大。Ⅰ型多为短历时高强度降雨,而IV型多为长历时低强度降雨,Ⅱ型和Ⅲ型居中。历时越短时,Ⅰ型降雨的比重越大;随着降雨历时的增加,Ⅰ型降雨的比重明显下降,IV型降雨的比重增加。 相似文献
5.
基于1979-2015年中国大陆824个气象站点逐日降水观测资料,采用相对误差、相关系数以及探测率等指标,评估新发布的格网化降水产品Multi-Source Weighted-Ensemble Precipitation（MSWEP）在中国大陆区域的精度;采用改正的Mann-Kendall趋势法,对比分析MSWEP在降水量趋势分析中的可靠性。研究表明:① MSWEP对中国大陆区域降水整体上存在高估现象,而在华北区域存在低估现象;② MSWEP对微量降水和强降水事件分别存在高估和低估现象;③ MSWEP和降水资料在年和月尺度上具有较好的相关系数,在日尺度上相关系数较低;④ MSWEP和站点观测的年降水量变化趋势存在较大空间分布差异,但在春季、秋季和冬季,空间分布特征较为一致。 相似文献
6.
Tropical westerlies over Pangaean sand seas 总被引：1，自引：0，他引：1
David B. Loope Maureen B. Steiner† Clinton M. Rowe Nicholas Lancaster‡ 《Sedimentology》2004,51(2):315-322
Cross‐equatorial, westerly winds are key features of tropical circulation in monsoonal regions. Although prominent in numerical climate models of Pangaea (the supercontinent straddling earth's equator, Late Palaeozoic to Early Mesozoic), such flow has not been confirmed previously by migration directions of ancient dunes. Wind‐blown sandstones that span 100 million years of earth history are widely exposed in south‐western USA. If recent palaeomagnetic data from the Colorado Plateau are used to correct Mesozoic palaeogeographic maps, the Plateau is placed about 10° further south than previously assumed, and the prevailing north‐westerly surface winds recorded by dune‐deposited sandstones are explicable as cross‐equatorial westerlies – the hallmark of modern monsoon circulation. Permian to Early Jurassic dunes were driven by north‐westerlies produced by a steep pressure gradient spanning the supercontinent during December–January–February. Although winds are light in most modern, near‐equatorial settings, the East African Jet accounts for more than half the cross‐equatorial flow in June–July–August. The thicknesses of annual depositional cycles within the Navajo Sandstone indicate that the near‐equatorial, north‐westerly winds that drove these particular dunes were stronger than the modern East African Jet. The Early Jurassic dunes that deposited the thick cycles were positioned west of the dominant (southern hemisphere) thermal low and against highlands to the west – a setting very similar to the East African Jet. The mountains along the western coast of Pangaea not only enhanced wind strength, but also cast a rain shadow that allowed active dunes to extend very close to the palaeoequator. 相似文献
7.
The Mozambique Ridge is an aseismic oceanic plateau in the southwestern Indian Ocean. During the separation of Antarctica and South Africa in the Early Cretaceous, the Mozambique Ridge was segmented by fracture zones which were assumed to become inactive during the Cenomanian, when Africa and Antarctica were finally separated. However, the existence of active normal faulting in the central part of the Mozambique Ridge was demonstrated by single and multichannel seismic surveys. Numerical modelling of the stress distribution caused by the crustal structure of the Mozambique Ridge and the adjacent oceanic basins suggests the possible existence of a zone with average horizontal tension up to 70 MPa along the central part of this passive ridge, which may cause the modern fault activity. These stresses also cause an additional dynamic anomaly which can explain small variations of the geoid anomaly over the ridge. 相似文献
8.
Data collected by Magsat have been extensively used by Indian scientists in studies of the crust beneath India. Results obtained
by various workers have been summarized and the reasons for differences in findings have been discussed. It is concluded that
methods that work well for higher latitudes do not give the best estimates of crustal field and magnetization in equatorial
regions. A better estimate of the crustal component is obtained when the external current contribution is estimated using
the symmetry properties of associatedX and Z-fields. Inversion technique that provides stable crustal magnetization in midlatitudes, becomes unstable near the equator.
Why such an instability arises and how it can be circumvented are discussed. That the Peninsular shield, the Ganga basin and
the Himalayas are three different geotectonic blocks is clearly reflected in the magnetization distribution. A thick magnetic
crust under Aravalli, Singhbum and Dharwar suggest these areas to be comparatively stable. In general, seismic, gravity and
heat flow data agree characteristically well with the magnetization estimates. 相似文献
9.
Quantitative precipitation forecasting (QPF) has been attempted over the Narmada Catchment following a statistical approach.
The catchment has been divided into five sub-regions for the development of QPF models with a maximum lead-time of 24 hours.
For this purpose the data of daily rainfall from 56 raingauge stations, twice daily observations on different surface meteorological
parameters from 28 meteorological observatories and upper air data from 11 aerological stations for the nine monsoon seasons
of 1972–1980 have been utilized. The horizontal divergence, relative vorticity, vertical velocity and moisture divergence
are computed using the kinematic method at different pressure levels and used as independent variables along with the rainfall
and surface meteorological parameters. Multiple linear regression equations have been developed using the stepwise procedure
separately with actual and square root and log-transformed rainfall using 8-year data (1972–1979). When these equations were
verified with an independent data for the monsoon season of 1980, it was found that the transformed rainfall equations fared
much better compared to the actual rainfall equations. The performance of the forecasts of QPF model compared to the climatological
and persistence forecasts has been assessed by computing the verification scores using the forecasts for the monsoon season
of 1980. 相似文献
10.
中国大陆上空水汽资源 总被引：6，自引：0，他引：6
根据１９８１～１９８６年计算结果，指出我国大陆上空拥有水汽资源年总量＋３３１８４．４亿ｍ＾３暖季（４～１０月）＋３０４９４．１２亿ｍ＾３寒季（１１～次年３月）＋２６９０．２８亿ｍ＾３，全年唯有气温最低的隆冬（１２～次年２月），是水汽资源亏耗（－７７３．６３亿ｍ＾３）季节，而夏季（６～８月）则是我国大陆上空水汽资源最关键的汇聚时期，资源量＋１８１９７．５６亿ｍ＾３，１６号，１４份边界分别为１１～５月 相似文献
11.
Natural Hazards - Using a high-resolution daily gridded rainfall data set for the period 1951–2015, new objective criteria were developed to determine rainstorms over the Indian region during... 相似文献
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14.
煤田构造研究——思路与方法 总被引：2，自引：1，他引：2
中国含煤岩系赋存状况的显著特点,是后期构造变形及其变形的时空差异性,造成这种特殊煤田地质条件的控制因素主要包括地球动力学环境、构造演化进程、深部构造与基底属性、构造应力场作用、煤系和上覆下伏岩性组合等五个方面。针对我国煤田构造的发育特点,提出了煤田构造研究的思路,总结了适用于煤田构造研究的技术手段及其主要用途。 相似文献
15.
Modern coastal areas have natural and transported rocks (armourstone) on which various types of organisms live. Burrowing,
boring and feeding by these organisms can destroy or modify the coastal rocks and hence change the coastal morphology. Two
rock types and three dominant types of organisms have been studied in Mersin Bay, Eastern Mediterranean of southern Turkey.
In this study area, Plio-Quaternary conglomerates and variously aged limestone armourplates have been affected by Phoronida
worms, bivalve Brachidontes pharaonis (Fischer P. 1870) and the limpet Patella sp. Phoronida colonies were found covering the hard substratum as a mat and form tubular endolithes of 35.0 mm depth and
1.5 mm diameter, whilst Brachidontes pharaonis (Fischer P. 1870) form 44 mm deep vase-shaped gastrochaenolites. The bioerosive activity of Limpet Patella sp., found intertidal and within the spray zone, cannot be significantly observed on the rocks over short time periods. The
soft sandy matrix of the conglomerates present were found to disintegrate by bioerosional processes, with the released gravels
being transported and deposited onto the beach. Within the armourstone limestone blocks, a maximum of 44.0 mm deep holes developed
after 50–60 years. However, these biological activities do not threaten the stability of the blocks due to their hard and
homogeneous internal structure. Furthermore, the organism colonies that cover these rocks as a strong mat (maximum 29.0 mm)
act to protect their surfaces from further biological attack and wave action. 相似文献
16.
全球横波低速异常体成像发现: Jason超级地幔柱与Tuzo超级地幔柱彷佛植根于地球外核顶部、生长在核幔边界(core mantle boundary, CMB)上的两株榕树,我们将其命名为超级地幔树(super mantle tree),以突出Jason超级地幔柱与Tuzo超级地幔柱连接地核与地壳的纽带特征,强调它们在地球演化过程中对全球构造的作用。地幔柱仅是超级地幔树的局部分支。我们定义超级地幔树为4层结构：① 植根于地球外核顶部;② 1600~2890 km为“树干”; ③ 110~1600 km为“树冠”;④ 110 km以上为“树枝”。“树枝”平面分布形态与全球板块轮廓大致相似,意味着板块构造可能起始于地球110 km处。推测地球深度1550~1600 km之间可能存在一个地球化学过渡层;Jason超级地幔树与Tuzo超级地幔树之间可能存在地球化学分隔面(简称地幔分隔面),地幔分隔面将地球划分为太平洋半球与大西洋半球;它的地面投影北端大致指向地磁北极,南端基本指向地磁南极。外核顶部脉动作用可能是地幔运动的动因,地核运动控制地幔运动。Tuzo超级地幔树逆时针旋转控制大西洋半球旋转形态,Tuzo超级地幔树的“细树干”伸向南大西洋,
Tuzo超级地幔树“粗树干”伸向北大西洋,使得中大西洋脊减薄。Jason超级地幔树顺时针旋转控制太平洋半球旋转形态以及环太平洋地区地貌构造形态。青藏高原及邻区地质地球物理三维构造模型说明：向北运动的Tuzo超级地幔树“树枝”与向西运动的Jason超级地幔树“树枝”共同作用,形成青藏高原东构造结。 相似文献
17.
O. S. R. U. Bhanu Kumar C. V. Naidu S. R. L. Rao 《Journal of Earth System Science》2004,113(3):313-319
An analysis of the mean monthly data of 124 years reveals that the relationship between the Southern Oscillation Index in
September and the winter monsoon rainfall (WMR) over Coastal Andhra Pradesh (CAP) is variable and non-stationary. In the recent
four decades, however, SOI (Sept) is negatively and significantly correlated with CAP WMR. A similar analysis is performed
using 50 years of mean monthly SSTs over Nino-3.4 region in August and September and CAP WMR to detect a possible relationship
and there is a striking positive relation between them. In both of the above cases, the September signal is more significant
in the recent four decades than for the other months and seasons for probable prediction of CAP WMR. Finally, to examine the
influence of SO on the winter monsoon rainfall, a non-parametric test “Mann-Whitney Rank Statistics” test has been applied
to the rainfall associated with extreme positive and negative SOI events 相似文献
18.
利用1983年国内外149个探空站全年资料,系统地研究了中国大陆上空的涡动水汽输送,包括涡动水汽输送的路径、收支量及其时空分布特点。研究表明,我国夏半年是涡动水汽源地,冬半年是汇地;涡动水汽以春、秋的4、10月最强,30°～40°N间最为活跃;涡动水汽净输送量在华北、西北、东北均超过总输送净量的50%;涡动水汽的经向性十分明显,经由长江流域北界输入北方的涡动水汽量占总输送量的91%强,表明它是把湿润地区暖湿水汽输向干旱、半干旱地区的主要机制,这不仅对北方大气湿度的维持,而且对其降水都有着特殊的贡献。 相似文献
19.
An experimental study was undertaken in a large-scale wind tunnel to investigate sand particle dislodgement by wind over time in the absence of grain-bed collisions. Aerodynamic dislodgement was measured for six groups of sand particles under two known wind velocity profiles. The results show that the dislodgement rate for both fine and coarse particles decreases rapidly during the transition of the particle surface from a non-wind-worked condition to a wind-worked condition, and that the dislodgement rate continues to decay under a wind-worked condition even though the mean grain size of surface particles remains nearly the same. A previously developed theoretical method for calculating the number of particles left on the bed by wind was developed further. The derived method was used to calculate the time-decay of the dislodgement rate and the length of time required for the dislodgement rate to reach an equilibrium. The length of time for dislodgement rate to reach an equilibrium in this study is of the order of 10–15 min. This not only provides further observation of the second, long stage of aeolian sediment transport system development reported previously but also indicates a potentially large variation in the time-decay of transport rate under different conditions. The results indicate that the time-decay of the particle dislodgement rate is related to sorting processes. Because of the artificial method of preparation of the grain surface and the wind velocity profiles, the results of this study should be applied with caution to natural conditions. 相似文献
20.
Geochemistry of dust aerosol over the Eastern Pamirs 总被引：1，自引：0，他引：1
The Pamirs are situated in the inner part of the Asian continent, a region which plays a critical role in Asian dust emission and transport. This study measured the elemental composition of atmospheric dust aerosol samples collected during the period between July 2004 and April 2006 at Mt. Muztagata, Eastern Pamirs, at a high-altitude (38°17′N, 75°01′E, 4430 m). The Muztagata aerosol samples show Ca/Al (∼0.7) and Fe/Al (∼0.7) ratios that are distinguishable from those from other sites. The La/Th ratios (averaging 2.30-2.36) and Th/U ratios (averaging 2.75-3.11) indicate typical eolian deposition. The dust aerosol samples have very similar rare earth element (REE) patterns, with relative enrichment of light REE, a slight depletion of heavy REE, and a strongly negative europium anomaly (δEu values averaging 0.65). The Muztagata dust shows homogeneity of composition during the sampling period, with minor variations due to seasonal effects and possible different air mass, suggesting the possibility of a well-mixed atmospheric background dust on a regional scale. The zonal Westerlies dominate and the longitude circulations are relatively very weak for dust transport dynamics in the Pamirs and Tien Shan regions. Our results demonstrate a distinct difference in elemental composition between dust over the Eastern Pamirs and that over Inilchek, Central Tien Shan, indicating that the Asian dust emission regions have great variations in their chemical properties, and provide a better constraint on the climatic impact of Asian dust. 相似文献