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81.
82.
<正>A mesoscale convective system (MCS) is an organized cluster of thunderstorms known to be the most important convective mode in causing disastrous high-impact weather, such as heavy rainfall, hail, damaging winds, and tornadoes. The small spatial scale and fast temporal evolution of MCSs make their observation and prediction very challenging. East Asia is home to the world’s most prominent monsoon, setting the stage for various severe convective weather events. MCSs and their associated ... 相似文献
83.
Frontal upwelling is an important phenomenon in summer in the Yellow Sea (YS) and plays an essential role in the distribution of nutrients and biological species. In this paper, a three-dimensional hydrodynamic model is applied to investigate the characteristics and influencing factors of frontal upwelling in the YS. The results show that the strength and distribution of frontal upwelling are largely dependent on the topography and bottom temperature fronts. The frontal upwelling in the YS is stronger and narrower near the eastern coast than near the western coast due to the steeper shelf slope. Moreover, external forcings, such as the meridional wind speed and air temperature in summer and the air temperature in the preceding winter and spring, have certain influences on the strength of frontal upwelling. An increase in air temperature in the previous winter and spring weakens the frontal upwelling in summer; in contrast, an increase in air temperature in summer strengthens the frontal upwelling. When the southerly wind in summer increases, the upwelling intensifies in the western YS and weakens in the eastern YS. The air temperature influences the strength of upwelling by changing the baroclinicity in the frontal region. Furthermore, the meridional wind speed in summer affects frontal upwelling via Ekman pumping. 相似文献
84.
等离子体波动与带电粒子的共振相互作用一直是磁层物理学的研究热点.作为一种常见的宽频、右旋极化等离子体波动, 等离子体层嘶声在地球磁层电子的损失过程中起到了重要作用.其中, 嘶声波对电子的回旋共振散射被认为是辐射带槽区形成的主要机制, 而人们对嘶声波与电子的弹跳共振机制的理解却相对匮乏.本文旨在细致研究嘶声波与槽区电子的弹跳共振相互作用, 明确其对槽区电子动态演化过程的影响.研究发现, 嘶声波与电子的弹跳共振可以造成槽区电子在高投掷角(80°~90°)处明显的投掷角扩散.相比于低能(<~100 keV)电子, 嘶声波引起的高能(>~100 keV)电子的弹跳共振效应明显更强.槽区电子的弹跳共振投掷角扩散系数对于L-shell、地磁活动条件和共振阶数都有着很强的依赖性.随着L-shell的增大和地磁活动的增强, 嘶声波对电子的弹跳共振散射效应显著增强.对于低能电子, 共振阶数对总散射系数的贡献随阶数的升高而增大; 而对于低L-shell处的高能电子, 共振阶数对总散射系数的贡献随阶数的升高而呈现先增大后减小的趋势.嘶声波与槽区电子的弹跳共振相互作用可以有效地将高投掷角电子散射到较低的投掷角上, 进而在回旋共振机制的协助下将它们散射到损失锥中.因此, 未来在地球槽区电子动力学建模过程中有必要考虑等离子体层嘶声对电子的弹跳共振散射效应.
相似文献85.
碱性岩型铌-稀土矿床是重要的铌-稀土矿资源类型。河南省方城县大庄铌-稀土矿位于华北克拉通南缘,是近年来新发现的一例赋存于霞石正长岩中的,具有中型规模的碱性岩型矿床。大庄矿区内共圈定17个NW—SE向带状展布的,呈囊状、不规则状、透镜状产出的铌-稀土矿体。铌-稀土矿石主要赋存于角闪霞石正长岩和黑云母正长岩中。矿石矿物主要为烧绿石、氟碳铈镧矿、褐钇铌矿和富铌榍石等。矿石的结构主要有斑状结构、他形粒状结构、半自形粒状结构、包含结构、交代结构、共生结构、伟晶结构等。矿石构造分为块状、脉状和片麻状构造等。热液蚀变包括萤石化、绢云母化、绿帘石化和绿泥石化等。碱性岩样品具有低SiO2、富碱、高铝的特征,稀土元素总量较高,轻重稀土分异明显,具有明显的负Eu异常,富集Nb、Ta、Th、U、Zr、Hf等高场强元素,明显亏损Ba、Sr、P、Ti等元素。碱性岩全岩(87Sr/86Sr)i=0.68158~0.71090,εNd(t)=―1.11~―0.37,两阶段模式年龄(tDM2 相似文献
86.
河南3次重污染天气过程的气象条件诊断及传输影响分析 总被引:1,自引:0,他引:1
利用空气质量监测数据、气象常规观测资料、L波段雷达探空资料、EC-Intrim再分析资料和NCEP全球资料同化系统提供的再分析资料,以及HYSPLIT模式模拟结果,分析了2016年12月至2017年1月间发生在河南的3次重污染天气过程的影响范围、气象条件和传输影响等。结果表明,3次过程河南地区均呈现出500 hPa等高线平直、9251000 hPa风垂直切变小和海平面气压场均压等特征。在近地面,3次过程在污染开始和加强时段均有小风和低湿特征,过程临近结束时有大风或增湿出现。前两次污染过程为干霾过程,均因加强的偏西风而结束,但是在结束阶段,相较于第1次过程的西南风,第2次过程的西北风能更快速有效地清除污染物;第3次过程为湿霾(雾、霾混合)过程,因偏东风而结束,但由于偏东风风力较小,对污染物彻底清除能力有限,过程结束后很快出现反复。郑州近地面存在明显逆温和“上干下湿”的层结特征,这种“干暖盖”严重阻碍着空气的对流运动,使近地层的污染物垂直扩散能力变弱,从而导致污染加重。HYSPLIT后向轨迹传输影响显示,第1次过程主要以省外西北路输送为主,后两次过程主要以本省和本地累积为主。 相似文献
87.
中国土壤动物生态地理研究进展(英文) 总被引:7,自引:0,他引:7
This review summarizes main research findings in soil fauna eco-geography in China in the past 30 years.The subject areas and main results were overviewed including biodiversity and eco-geological distribution of soil fauna communities.Studies of ecological distributions of soil fauna and dynamic ranges in space from tropical,subtropical to temperate regions,and in categories from forest,grassland,desert,wetland,farmland to urban ecosystems,the responses and indications of soil fauna to soil environments.Ef... 相似文献
88.
滑坡是发生在我国山区的主要地质灾害类型,金沙江地区由于地势较高、地形复杂、多云多雨的特点,给传统的滑坡监测增加了难度。合成孔径雷达差分干涉测量技术(Differential interferometry synthetic aperture radar,D-InSAR)已在滑坡地面沉降监测中得到了广泛应用。本文选取金沙江上游沿岸作为研究区域,基于2018年8月11日与9月28日的Sentinel-1A影像及SRTM1数据,利用GAMMA软件及D-InSAR技术监测到金沙江地区的地表形变,成功识别出金沙江右岸的一处滑坡灾害。研究结果显示,在此滑坡的坡顶部分出现了约2.5 cm的沉降,而在坡底部分由于崩塌物的累积,地面出现了约3 cm的抬升。从实验结果可以得出,InSAR技术是一种有效的滑坡变形监测手段,利用Sentinel-1A卫星的SAR数据对滑坡区域进行形变监测,可以得到较好的干涉结果。 相似文献
89.
This paper comprehensively analyzes the characteristics and cause of the inshore intensification of super typhoon "Hato", the 13 th super typhoon in 2017. The aspects of typhoon structure, evolution of large-scale circulation and physical quantity field are analyzed using observation data from the Guangdong Automatic Station, Shenzhen Doppler Radar data, NCEP 1°×1° reanalysis data, NCEP 0.25°×0.25° sea surface temperature(SST) data, etc.Additionally, in order to investigate the influence of SST change on the intensity of "Hato", the WRF model and ECMWF 0.125°×0.125° reanalysis data are combined to conduct 3 sensitivity tests on"Hato". The results show that the favorable conditions for inshore intensification of "Hato"included the strengthening and westward extension of the subtropical high, continuous increase of low level moisture transport, an anomalous warm SST area north of 20°N in the South China Sea, an extreme divergence value in the northern South China Sea exceeding 6 ×10-5 s-1, and vertical environmental wind shear between 1.1 m/s-4.8 m/s. The intensity of"Hato"was very sensitive to changes in SST. When the SST rose or dropped by 2℃, the minimum central pressure of the typhoon changed by about 13 hPa or 11 hPa,respectively. SST indirectly influenced the intensity of the typhoon through affecting latent heat transport and sensible heat transport. 相似文献
90.
TRANSVERSE STRUCTURES FEATURES OF DIFFERENT DEPTHS DERIVED FROM BOUGUER GRAVITY ANOMALIES IN THE SOUTHERN SEGMENT OF TAN-LU FAULT ZONE 下载免费PDF全文
WANG Xin ZHANG Jing-fa JIANG Wen-liang JIANG Hong-bo TIAN Tian GAO Min FU Ping-jie 《地震地质》2016,38(2):370-385
To research the faults distribution and deep structures in the southern segment of Tan-Lu fault zone(TLFZ) and its adjacent area, this paper collects the Bouguer gravity data and makes separation by the multi-scale wavelet analysis method to analyze the crustal transverse structure of different depths. Meanwhile Moho interface is inversed by Parker variable density model. Research indicates that the southern segment of TLFZ behaves as a NNE-directed large-scale regional field gravity gradient zone, which separates the west North China-Dabie orogen block and the east Yangtze block, cutting the whole crust and lithosphere mantle. There are quite differences of density structures and tectonic features between both sides of this gradient belt. The sedimentary and upper crustal density structure is complex. The two east branches of TLFZ behave as linear gravity anomalous belt throughout the region, whereas the two west branches of TLFZ continue to extend after truncating the EW-trending gravity anomaly body. The lower crustal density structure is relatively simple. TLFZ behaves as a broad and gentle low abnormal belt, which reflects the Cretaceous-Paleogene extension environment caused graben structure. The two west branches of TLFZ, running through Hefei city, extend southward along the west margin of Feidong depression and pinch out in Shucheng area due to the high density trap occlusions in the south of Shucheng. The Feizhong Fault, Liu'an-Hefei Fault, and Feixi-Hanbaidu Fault intersect the two west branch faults of TLFZ without extending to the east. Recent epicenters are mainly located in conversion zones between the high-density and the low-density anomaly, especially in TLFZ and the junction of the faults, where earthquakes frequently occurred in the upper and middle crust. As strong earthquakes rarely occur in the southern segment of TLFZ, considering its deep feature of abrupt change of the Moho and intersections with many EW-trending faults, the hazard of strong earthquake cannot be ignored. 相似文献