中国东部中新生代构造格局和岩浆岩带的形成与演化   总被引：7，自引：0，他引：7  

汤加富  高天山  李怀坤 《华北地质》2004,27(2):65-74

在研究印支期秦岭-大别-苏鲁造山带的形成与地幔差速环流的基础上，系统综合了中国东部中新生代的基底构造对断裂构造的控制，深层构造对隆凹与断陷盆地的制约，伸展构造在陆内及陆缘外的表现，岩浆岩带的时空分布及展布特点等规律，依据中国东部中新生代构造格局与岩浆岩带在时空分布上的宽阔性、方向性、迁移性、分带性，特别是深层构造对浅层断裂构造、伸展构造的制约，以及岩浆岩带、隆起与盆地等自西向东迁移特点，提出其形成机制可能与强大地幔东向差速环流有关。  相似文献   

第二松花江流域水电厂综合中长期水文预报的分析研究     

范垂仁谢武贤  关志成冷雪 范思毅 《水文》2004,24(2):31-34,54

基于对第二松花江流域上游小山、松山、两江水电站中长期水文预报研究成果，论述了综合中长期水文预报的研究思路和定性预报、定量预报的分析研究方法。该研究通过2002年实践检验，具有较高的预报精度。  相似文献   

富宁两次大暴雨的对比研究     

张文  蒋盛闻 《云南地理环境研究》2004,(Z1)

对比云南富宁2001年“8·25”与2004年“5·15”两次大暴雨过程前后的雨量分布、灾情、大气环流背景,以及反映大气水汽、热力、动力条件的部分物理量场,分析它们在两次过程中的异同点,讨论各类条件对暴雨落区的指示性情况,并对“5·15”过程的雷达回波资料作简单的定量分析。  相似文献   

GFC-120型自走式反循环钻机的研制          下载免费PDF全文

张西坤  宋秋锋  杨杰  张军  李建民 《探矿工程》2005,32(12):35-37

GFC-120型钻机为自走式动力头回转反循环钻机，用于降水井和护坡桩基础孔以及小型水井的施工。介绍了其性能特点、主要技术参数、结构及工作原理。  相似文献   

金塔绿洲风场与温湿场特征的数值模拟   总被引：1，自引：4，他引：1  

吕世华  尚伦宇 《中国沙漠》2005,25(5):623-628

使用美国NCAR新版MM5V3.6非静力平衡模式,采用三重嵌套的降尺度方法,模拟研究了甘肃河西走廊金塔绿洲风场与温湿场特征。结果表明:由于绿洲的存在,绿洲沙漠系统产生的次级环流对局地环流有一定影响;平流作用将沙漠中的干热空气送向绿洲,绿洲近地层会出现逆温,感热向地表输送;沙漠上由于临近绿洲的水汽平流作用,上层大气湿度比低层更大,这就是逆湿现象。  相似文献   

Using stable isotopes to understand seasonal and interannual dynamics in moisture sources and atmospheric circulation in precipitation          下载免费PDF全文

Yu Tang  Xianfang Song  Yinghua Zhang  Dongmei Han  Likun Ai  Tianbao Zhao  Yajun Wang 《水文研究》2017,31(26):4682-4692

Stable isotopes in precipitation are useful tracers to strengthen understanding of climate change and hydrological processes. In this study, the moisture sources of 190 precipitation events in Beijing were analysed using the Hybrid Single‐particle Lagrangian Integrated Trajectory model, based on which we studied the relation between variations in precipitation δ¹⁸O and dynamics in moisture sources and atmospheric circulation in seasonal and interannual timescales. Categorization of 7 groups of moisture sources was performed, among which oceanic moisture sources presented lower δ¹⁸O in precipitation than continental moisture sources. The results show that seasonal variations of precipitation δ¹⁸O were caused by changes of moisture sources. In summer, moisture from proximal oceans dominated vapour transport to Beijing due to increasing monsoon strength and resulted in a relatively small variation of precipitation δ¹⁸O. At the interannual timescale, the variations of δ¹⁸O in summer precipitation were related to dynamics in oceanic moistures, showing depleted values when the contribution of oceanic moistures, especially the proportion of long‐distance oceanic moisture, was high. Further analysis indicated that changes of oceanic moisture sources were controlled by the strength of summer monsoons. These findings address the complexity of moisture sources in midlatitude monsoon areas and suggest that isotopic signals in precipitation have the potential to deduce changes in moisture sources and atmospheric circulation and can therefore serve for palaeoclimate reconstruction.  相似文献   

Flow processes and sedimentation in unidirectionally migrating deep‐water channels: From a three‐dimensional seismic perspective          下载免费PDF全文

Chenglin Gong  Yingmin Wang  Ronald J. Steel  Jeff Peakall  Xiaoming Zhao  Qiliang Sun 《Sedimentology》2016,63(3):645-661

Three‐dimensional seismic data were used to infer how bottom currents control unidirectional channel migration. Bottom currents flowing towards the steep bank would deflect the upper part of sediment gravity flows at an orientation of 1° to 11° to the steep bank, yielding a helical flow circulation consisting of a faster near‐surface flow towards the steep bank and a slower basal return flow towards the gentle bank. This helical flow model is evidenced by the occurrence of bigger, muddier (suggested by low‐amplitude seismic reflections) lateral accretion deposits and gentle channel wall with downlap terminations on the gentle bank and by smaller, sandier (indicated by high‐amplitude seismic reflectors) channel fills and steep channel walls with truncation terminations on the steep bank. This helical flow circulation promotes asymmetrical depositional patterns with dipping accretion sets restricted to the gentle bank, which restricts the development of sinuosity and yields unidirectional channel migration. These results aid in obtaining a complete picture of flow processes and sedimentation in submarine channels.  相似文献   

The impact of boreal autumn SST anomalies over the South Pacific on boreal winter precipitation over East Asia   总被引：1，自引：0，他引：1  

Juan AO  Jianqi SUN 《大气科学进展》2016,33(5):644-655

The possible mechanism behind the variability in the dipole pattern of boreal winter precipitation over East Asia is analyzed in this study. The results show that the SST anomalies(SSTAs) over the South Pacific Ocean(SPO) in boreal autumn are closely related to the variability in the dipole pattern of boreal winter precipitation over East Asia. The physical link between the boreal autumn SPO SSTAs and the boreal winter East Asian precipitation dipole pattern is shown to mainly be the seasonal persistence of the SPO SSTAs themselves. The seasonal persistence of the SPO SSTAs can memorize and transport the signal of the boreal autumn SSTAs to the following winter, and then stimulates a meridional teleconnection pattern from the SH to the NH, resulting in a meridional dipole pattern of atmospheric circulation over East Asia in boreal winter. As a major influencing factor, this dipole pattern of the atmospheric circulation can finally lead to the anomalous precipitation dipole pattern over East Asia in boreal winter. These observed physical processes are further confirmed in this study through numerical simulation. The evidence from this study, showing the impact of the SPO SSTAs in boreal autumn,not only deepens our understanding of the variability in East Asian boreal winter precipitation, but also provides a potentially useful predictor for precipitation in the region.  相似文献   

Anomalous Western Pacific Subtropical High during Late Summer in Weak La Nia Years: Contrast between 1981 and 2013     

Feng Xue  Fangxing Fan 《大气科学进展》2016,33(12):1351-1360

Both 1981 and 2013 were weak La Niña years with a similar sea surface temperature (SST) anomaly in the tropical Pacific, yet the western Pacific subtropical high (WPSH) during August exhibited an opposite anomaly in the two years. A comparison indicates that, in the absence of a strong SST anomaly in the tropics, the cold advection from Eurasian high latitudes and the convection of the western Pacific warm pool play important roles in influencing the strength and position of the WPSH in August. In August 1981, the spatial pattern of 500 hPa geopotential height was characterized by a meridional circulation with a strong ridge in the Ural Mountains and a deep trough in Siberia, which provided favorable conditions for cold air invading into the lower latitudes. Accordingly, the geopotential height to the north of the WPSH was reduced by the cold advection anomaly from high latitudes, resulting in an eastward retreat of the WPSH. Moreover, an anomalous cyclonic circulation in the subtropical western Pacific, excited by enhanced warm pool convection, also contributed to the eastward retreat of the WPSH. By contrast, the influence from high latitudes was relatively weak in August 2013 due to a zonal circulation pattern over Eurasia, and the anomalous anticyclonic circulation induced by suppressed warm pool convection also facilitated the westward extension of the WPSH. Therefore, the combined effects of the high latitude and tropical circulations may contribute a persistent anomaly of the WPSH in late summer, despite the tropical SST anomaly being weak.  相似文献   

5—6月东北冷涡持续活动及强度特征          下载免费PDF全文

刘刚  王宁  秦玉琳  曹玲  褚曲成  姚瑶 《应用气象学报》2016,27(1):47-55

利用1960—2012年5—6月NCEP/NCAR逐日再分析资料,基于冷涡经典定义,采取客观识别方法检索东北冷涡活动过程,根据东北冷涡活动时空变化特征给出东北冷涡持续活动过程标准, 通过冷涡强度指数进行定量化分析,该指数对冷涡持续活动过程具有较好表征意义。冷涡活动强对应5月乌拉尔山阻塞高压、贝加尔湖阻塞高压和6月鄂霍次克海阻塞高压活动频繁。通过强弱指数年合成,得到6月强指数年冷涡系统较深厚,集中于对流层中高层,冷心结构明显,具有一定大气斜压特征; 高层存在冷中心,低层有冷空气活动,中高层西风带呈明显的上游分流和下游汇合特征,分汇流之间呈东北高、西南低的偶极子阻塞形势;弱指数年冷涡系统较浅薄,主要集中在对流层中低层,冷心结构不明显,不存在阻塞形势。  相似文献