中国西南地区5月降水与阿拉伯海季风关系的年代际变化     

经皓童  孙建奇  于水  华维 《大气科学》2021,45(5):1087-1098

本文利用1960～2017年中国西南地区115个台站观测降水资料和日本气象厅发布的55年再分析资料集,研究了中国西南地区5月降水变异的主导模态及其与阿拉伯海季风的关系。结果显示,中国西南地区5月降水的第一主导模态主要表现为全区一致的变异特征;该模态与同期5月阿拉伯海季风强度异常关系密切,但两者的关系在20世纪70年代后期发生了显著的年代际变化。在1960～1976年,阿拉伯海季风异常所引起的低层大气环流和水汽输送异常主要集中在阿拉伯海到孟加拉湾一带;阿拉伯海季风异常所引起的大气环流不能到达中国西南地区,因此它对中国西南地区5月降水的影响偏弱。但在1981～2017年,阿拉伯海季风异常可以导致整个北印度洋到南海地区的大气环流异常,进而引起中国西南地区水汽和垂直运动的变化,最终对该地区5月降水产生显著的影响。进一步的研究显示,阿拉伯海季风与中国西南地区5月降水关系的变化可能与季风自身的年代际变率有关。阿拉伯海季风在20世纪70年代末之前变率偏弱,其引起的环流异常也偏弱;相反在20世纪70年代末之后,其变率增强,它引起的大气环流异常也偏强,可以延伸到中国西南地区,进而影响到西南地区的5月降水。因此,季风变率的强弱可能在季风对西南地区5月降水的影响中起着非常重要的作用。  相似文献   

Temporal precipitation trend analysis at the Langat River Basin,Selangor, Malaysia     

Narges Palizdan  Yashar Falamarzi  Yuk Feng Huang  Teang Shui Lee  Abdul Halim Ghazali 《Journal of Earth System Science》2015,124(8):1623-1638

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Exact solution of phantom dark energy model     

王文福  税正伟  唐斌 《海洋学报(英文版)》2010,29(11)

We investigate the phantom dark energy model derived from the scalar field with a negative kinetic term. By assuming a particular relation between the time derivative of the phantom field and the Hubble function, an exact solution of the model is constructed. Absence of the `big rip' singularity is shown explicitly. We then derive special features of phantom dark energy model and show that its predictions are consistent with all astrophysical observations.  相似文献   

Dynamics of charged particles and perpendicular diffusion in turbulent magnetic field   总被引：1，自引：0，他引：1  

Xinliang?Gao  Quanming?LuEmail author  Shui?Wang 《Astrophysics and Space Science》2011,335(2):399-403

A test particle code is employed to explore the dynamics of charged particles and perpendicular diffusion in turbulent magnetic field, where a three-dimensional (3D) isotropic turbulence model is used in this paper. The obtained perpendicular diffusion at different particle energies is compared with that of the nonlinear guiding center (NLGC) theory. It is found that the NLGC theory is consistent with test particle simulations when the particle energies are small. However, the difference between the NLGC theory and test particle simulations tends to increase when the particle energy is sufficiently large, and the threshold is related to the turbulence bend-over length. In the NLGC theory, the gyrocenter of a charged particle is assumed to follow the magnetic field line. Therefore, when the particle has sufficiently large energy, its gyroradius will be larger than the turbulence bend-over length. Then the particle can cross the magnetic field lines, and the difference between the test particle simulations and NLGC theory occurs.  相似文献   

Quantitative Analysis of CME Deflections in the Corona     

Bin Gui  Chenglong Shen  Yuming Wang  Pinzhong Ye  Jiajia Liu  Shui Wang  Xuepu Zhao 《Solar physics》2011,271(1-2):111-139

In this paper, ten CME events viewed by the STEREO twin spacecraft are analyzed to study the deflections of CMEs during their propagation in the corona. Based on the three-dimensional information of the CMEs derived by the graduated cylindrical shell (GCS) model (Thernisien, Howard, and Vourlidas in Astrophys. J. 652, 1305, 2006), it is found that the propagation directions of eight CMEs had changed. By applying the theoretical method proposed by Shen et?al. (Solar Phys. 269, 389, 2011) to all the CMEs, we found that the deflections are consistent, in strength and direction, with the gradient of the magnetic energy density. There is a positive correlation between the deflection rate and the strength of the magnetic energy density gradient and a weak anti-correlation between the deflection rate and the CME speed. Our results suggest that the deflections of CMEs are mainly controlled by the background magnetic field and can be quantitatively described by the magnetic energy density gradient (MEDG) model.  相似文献   

化学融雪剂对小球藻生长和生理特性的影响          下载免费PDF全文

胡水  李法云  范志平  程志辉  高群  张营 《气象与环境学报》2013,29(3):102-106

寒冷地区道路表面除雪化冰使用的化学融雪剂随着地表径流进入水体,将影响水生态系统中的水生生物正常生长,并破坏水生态系统平衡。为研究化学融雪剂对水生生物的毒性效应,分析了不同浓度有机融雪剂对小球藻生长特征、藻细胞光和色素、蛋白质及多糖含量的影响。结果表明：浓度为2 g·L^-1时有机融雪剂对小球藻生长无明显影响,当融雪剂浓度为4 g·L^-1时,小球藻细胞生长表现出明显抑制效应,且抑制效应随融雪剂浓度增加呈显著上升趋势(P<0.01);当融雪剂浓度小于4 g·L^-1时,有机融雪剂对小球藻细胞内叶绿素a合成有明显促进作用,但随着有机融雪剂处理浓度升高,藻细胞内叶绿素a含量逐渐下降。当融雪剂的处理浓度大于4 g·L^-1的时候,藻细胞内蛋白质和多糖含量与对照组相比呈显著下降趋势(P<0.01)。这说明融雪剂浓度高于4 g·L^-1时会抑制水体中小球藻正常生长繁殖,破坏藻体细胞,最终导致水生态系统平衡被破坏。  相似文献   

邹家山4号带产状多变矿体生产探矿验证及分析     

胡荣泉  余水  刘虎  汪拥军  贾志远 《华东地质学院学报》2013,(Z2):9-12

对4号矿带进行矿山生产地质探矿和回采工作,是从1997年721-14矿井技术改造工程开始的,随着721-15采铀工程井下巷道的开拓、探矿等工程的实施,目前从平面看,已经从13线工作至61线,从标高看,已经从-50 m工作至-250 m。作为矿山的开采者,如何合理运用探矿方法,提高生产探矿效率,最大限度的回收资源,是目前需要解决的问题。从实践中不断摸索,验证,得出了一套自己的工作经验和工作方法。4号带矿体生产探矿,总结起来就是"平面要完全揭露、竖向要找准重点、多种勘探方式相结合、找准赋存规律";其产状变化依然有规律可循,从局部看看,4号带矿体走向变化主要有北东、北西、南北三组,看似杂乱无章,但从总体上看,它的变化有着密集性。  相似文献   

An evaluation of heavy metal pollution within historic cultural strata at a specialized salt production site at Zhongba in the Three Gorges Reservoir region of the Yangtze River, China   总被引：3，自引：0，他引：3  

XiaoSi Tian  Cheng Zhu  ZhiBin Sun  Tao Shui 《Environmental Earth Sciences》2013,69(7):2129-2138

The concentrations of Hg, Cu, Pb, Cr, and Ni in soil samples collected from a specialized salt production site at Zhongba in the Three Gorges Reservoir region of the Yangtze River in China were analyzed to reconstruct the heavy metal contamination contexts of different historic periods over the last 4,500 years. The results show that the observed sequence for individual levels of heavy metal pollution was as follows: Hg > Cu > Ni > Pb ≈ Cr. Hg pollution was high during every time period except the Ming Dynasty, with peaks being observed from the Spring and Autumn period. The pollution of Cu and Ni peaked during the Xi Zhou and Xia Dynasties, respectively. The pollution level of Pb has gradually increased since the Qin Dynasty and has coincided with the use of leaded gasoline. Cr contamination was moderate in all soil strata with little indication of change. Comprehensive heavy metal contamination was high during all of these periods, except during the Ming Dynasty, with peaks being observed between the Spring and Autumn Period and throughout the Warring States Period. Enrichment factors (EFs) were used to obtain information on heavy metal sources. The EFs indicate that most of the Hg and Cu originated from human activities, whereas Pb, Cr, and Ni predominantly came from crust weathering. Several preliminary inferences regarding the development of heavy metal utilization in the area were generated. Cu usage had developed well during the Xi Zhou Dynasty and the Autumn Period. Hg usage emerged during the Xia Dynasty and matured between the Spring and Autumn Period and the Warring States Period. Ni usage conceivably started during the Xia Dynasty. Other factors, such as religious activities, technology, environmental awareness and the intensity of salt production, have also affected heavy metal pollution concentrations.  相似文献   

Regional precipitation trend analysis at the Langat River Basin,Selangor, Malaysia   总被引：1，自引：0，他引：1  

Narges Palizdan  Yashar Falamarzi  Yuk Feng Huang  Teang Shui Lee  Abdul Halim Ghazali 《Theoretical and Applied Climatology》2014,117(3-4):589-606

Various hydrological and meteorological variables such as rainfall and temperature have been affected by global climate change. Any change in the pattern of precipitation can have a significant impact on the availability of water resources, agriculture, and the ecosystem. Therefore, knowledge on rainfall trend is an important aspect of water resources management. In this study, the regional annual and seasonal precipitation trends at the Langat River Basin, Malaysia, for the period of 1982–2011 were examined at the 95 % level of significance using the regional average Mann–Kendall (RAMK) test and the regional average Mann–Kendall coupled with bootstrap (RAMK–bootstrap) method. In order to identify the homogeneous regions respectively for the annual and seasonal scales, firstly, at-site mean total annual and separately at-site mean total seasonal precipitation were spatialized into 5 km?×?5 km grids using the inverse distance weighting (IDW) algorithm. Next, the optimum number of homogeneous regions (clusters) is computed using the silhouette coefficient approach. Next, the homogeneous regions were formed using the K-mean clustering method. From the annual scale perspective, all three regions showed positive trends. However, the application of two methods at this scale showed a significant trend only in the region AC1. The region AC2 experienced a significant positive trend using only the RAMK test. On a seasonal scale, all regions showed insignificant trends, except the regions I1C1 and I1C2 in the Inter-Monsoon 1 (INT1) season which experienced significant upward trends. In addition, it was proven that the significance of trends has been affected by the existence of serial and spatial correlations.  相似文献   

等离子体湍动对准垂直激波中粒子加速的影响          下载免费PDF全文

郝宇飞  陆全明  高新亮  单立灿  王水 《地球物理学报》2013,56(7):2171-2176

本文利用试验粒子方法研究了在考虑等离子体湍动的情况下带电粒子在准垂直激波中的加速, 在计算中, 我们采用组合模型来拟合等离子体湍动. 计算结果表明, 在存在等离子体湍动的情况下, 粒子可横越背景磁场运动, 从而被激波反射的上游粒子在到达下游后可被等离子体湍动散射回到上游, 并再次被激波反射并加速, 这样的过程可重复很多次, 因而粒子可被加速到很高的能量. 我们还研究了激波角, 粒子的初始能量和等离子体湍动的强度, 以及相干长度和两种湍动组分强度比与加速粒子的能谱之间的关系.  相似文献