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61.
Maritime network dynamics before and after international events 总被引:1,自引:0,他引:1
Investigating the influence of international events on global maritime networks is a challenging task that must comprehensively incorporate geographical, political, and maritime sciences. Understanding global maritime network dynamics is an initial and critical step in this investigation. This study proposes an automatic identification system (AIS)-based approach to understanding maritime network dynamics before and after international events. In this approach, a spatiotemporal modeling method is introduced to measure the similarity in shipping trends before and after international events. Then, a spatiotemporal analytic framework is proposed to understand the maritime network dynamics by grouping similar situation, and assessing possible indirect effects within a network. Finally, three case studies of international events, military conflict, lifted economic sanctions, and government elections, were used to investigate the observed network dynamics possibly affected by international events. The results indicate that container, tanker, and bulk shipping between India and its connected countries all declined more than 69% after military conflicts between India and Pakistan in August 2015. Tanker shipping between Iran and the United Arab Emirates increased 51% after economic sanctions on Iran were lifted. Container shipping between Sri Lanka and Singapore, Malaysia, and India increased more than 74% after the general election in Sri Lanka. These investigations demonstrate the feasibility of the proposed approach in assessing the possible effects of international events on maritime network dynamics. 相似文献
62.
In this paper, a sudden heavy rainfall event is analyzed, which occurred over the Yellow River midstream during 5–6 August 2014. We used observational, NCEP/NCAR reanalysis, high-resolution satellite, and numerical simulation data. The main results are as follows. Under an unfavorable environmental circulation, inadequate water vapor and unfavorable dynamic conditions but sufficient energy, a local sudden heavy rainfall was caused by the release of strong unstable energy that was triggered by cold air transport into middle and lower layers and the propagation of gravity waves. The distributions of rain area, rain clusters, and 10-minute rainfall showed typical mesoscale and microscale fluctuation characteristics. In the mesoscale rain area or upstream, there was a quasi-stationary wave of mesoscale gravity waves with their propagation downstream. In the course of propagation from southwest to northeast, the wavelength became longer and the amplitude attenuated. In the various phases of gravity wave development, there were evident differences in the direction of the wave front. Wave energy was mainly in the lower layers. Unstable vertical wind shear at heights of 1–6 km provided fluctuation energy for the gravity waves. The mechanisms of heavy rainfall formation were different at Linyou and Hancheng stations. Diabatic heating was the main source of disturbed effective potential energy at Linyou. The explosive short-period strong precipitation was caused by the release of strong effective potential energy triggered by the gravity waves, and its development and propagation after that energy maximized. In contrast, the latent heat release of upstream precipitation was the main source of disturbed effective potential energy at Hancheng. This formed a positive feedback mechanism that produced continuous precipitation. In the studied event, the development of westerly belt systems had disturbed the wind field. The contribution of kinetic energy generated by this disturbance could not be ignored. The Froude number, mountain shape parameter, and ratio between mountain height and temperature inversion layer thickness had various effects of atmosphere and terrain on mesoscale and microscale mountain waves. In upper and lower layers, there were five airflows that were strengthened by the terrain. All these had important influences on local heavy rainfall at Linyou and Hancheng stations. 相似文献
63.
This study investigates the relationship between summer low-frequency rainfall over southern China and tropical intraseasonal oscillation (ISO) in the atmosphere by examining systematically the propagation features of the tropical ISO in terms of focusing on five large-scale low-frequency rainfall regimes in summer over southern China. It is demonstrated that there is a close linkage between the five rainfall regimes over southern China and the northward propagation of the tropical ISO. The moist ISO signals, which influence the low-frequency rainfall events in different regions of southern China, mainly propagate northwestward from the tropical ocean to the southeast of China. The southeast China rainfall regime is intimately associated with the moist ISO signals propagating northwestward from the equatorial mid-western Pacific Ocean. For both the Yangtze River regime and South of Yangtze River regime, the moist ISO signals over the northern South China Sea show an evident northward propagation towards the Yangtze River region, and then propagate westward. It is further found that the interaction between the northward propagation of low-latitude ISO signals and the southward propagation of high-latitude ISO signals can also make a clear influence on the low-frequency rainfall in southern China. For the Southern China regime, the moist ISO signals show a significant northward propagation from the Philippines. Moreover, for the rainless regime, southern China is under dry ISO signals’ control, and the latter shows no clear propagation to southern China. This study may provide insights for the extended-range forecasting of summer rainfall in southern China. 相似文献
64.
东亚夏季大气环流和气候对冬季海温异常的邻响应和遥响应 总被引:1,自引:1,他引:0
本文通过IAP-GCM的数值模拟,研究了全球大气环流对黑潮海域和赤道东太平洋冬季SST异常的响应,并着重比较东亚大气环流和气候对黑潮区SSTA的响应(邻响应)和对赤道东太平洋SSTA的响应(遥响应)。首先,无论是黑潮区SSTA引起的邻响应还是赤道东太平洋SSTA所引起的遥响应对东亚大气环流和气候变化的影响都是明显而重要的。由于在大气中低频振荡被激发出来,其响应将持续较长时间。进一步分析表明,东亚大气环流对黑潮区或赤道东太平洋冬季正SSTA的响应都将造成华北地区夏季的多雨,其数值模拟结果与观测相一致。另外,赤道西太平洋地区大气的异常(尤其是对流活动)对于东亚地区大气环流和气候变化有重要作用 相似文献
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66.
青藏高原冰川对气候变化的响应及趋势预测 总被引:49,自引:3,他引:46
青藏高原是世界上中低纬度地区最大的现代冰川分布区,这里冰川末端在近百年来总的进退变化趋势是退缩,但在本世纪初至20~30年代和70~80年代间多数冰川曾出现过稳定甚至前进。对比近百年来气候变化,冰川变化虽然滞后于温度变化,但它们之间存在着很好的对应关系,多数冰川对温度变化滞后时间在10~20年间。根据80年代以来平均物质净平衡值,大致将青藏高原划分为:内部为平衡或正平衡区;向外为负平衡区;边缘为强负平衡区。以冰川对气候响应滞后关系预测,在今后10~20年间,青藏高原边缘冰川末端仍继续处于后退,而高原内部冰川末端位置变化不大。 相似文献
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69.
高频旋回分析有利于揭示浅水碳酸盐岩台地海平面升降、沉积物响应、古地理单元演化及对盆地内沉积分异影响等诸多沉积学信息。依据鄂尔多斯盆地横山地区丰富的钻井取心资料,通过岩石类型、典型五级旋回结构等分析,对中奥陶统马家沟组马五6亚段开展了高频旋回研究。研究表明: (1)基于研究区内马五6亚段碳酸盐岩与蒸发岩共生组合的9种岩石类型,识别出5种典型T-R单旋回,其中旋回Ⅰ、Ⅱ、Ⅲ为云质潟湖—颗粒滩—灰泥丘沉积,Ⅳ、Ⅴ为膏盐质潟湖沉积,并以5种单旋回为基本单元搭建骨架井五级高频旋回结构剖面;(2)依据五级高频旋回结构剖面建立的Fischer图解,认为马五6亚段处于三级旋回晚期,内部发育“2个”四级旋回,具有初次海退—快速海侵—再次海退的相对海平面变化趋势;(3)结合五级旋回厚度统计,认为第1套四级旋回沉积期处于隆拗格局发育阶段,该时期横山凸起作为水下高地,对东西两侧海水封隔明显;至第2套四级旋回沉积阶段,填平补齐作用导致横山凸起影响减弱,海水循环得到改善,凸起东西两侧盐度明显下降。以马五6亚段为例的高频旋回研究,在横山地区马五6亚段地层学、沉积学研究中取得了较好的效果,以期在鄂尔多斯盆地马家沟组未来研究中得到进一步推广和实践。 相似文献
70.
A study on seismic source process in short- term and imminent stage before destructive mining shock 总被引:2,自引:0,他引:2
ntroductionStudyonseismicsourceprocesinshorttermandimminentstagebeforeearthquakeisaconcernedprobleminrecentseismologicalfiel... 相似文献