天山北麓两次暴雪天气对比分析          下载免费PDF全文

牟欢  赵丽  孙硕阳  汤浩  贾健 《干旱区地理》2019,42(6):1262-1272

利用常规气象观测资料、NCEP/NCAR 1°×1°（美国气象环境预报中心—NCEP和美国国家大气研究中心—NCAR）再分析资料、全球同化系统(GDAS)数据、引入基于拉格朗日方法的气流轨迹模式（HYSPLIT_v4.9）、FY-2E卫星资料、多普勒雷达产品,对2014年2月和2016年3月天山北麓的两次暴雪天气过程进行了诊断分析。结果表明：两次暴雪过程的降雪落区均是出现在500 hPa槽前、低层切变或辐合区、高层辐散区、温度平流梯度在垂直方向大值区、相当黑体亮度温度(TBB)中心边缘的梯度较大处重叠区域。通过诊断发现,2016年暴雪天气的暴雪区上空有类似于暴雨过程的湿对称不稳定存在,使得大气潜在不稳定能量较大,为暴雪提供了不稳定机制。而在2014年暴雪天气中没有发现湿对称不稳定,说明条件对称不稳定并不是造成暴雪的唯一原因,还可能受别的不稳定机制或动力因子、热力因子影响,但其对单位时间内降雪强度有明显的增幅作用。分析雷达回波特征的演变发现,雷达回波中心的强度、持续时间、范围与强降雪中心的变化一致。  相似文献   

The nature and origin of light hydrocarbon gases associated with mineralization in the Northern Pennines     

J. Ferguson 《Marine and Petroleum Geology》1988,5(4)

Earlier studies have shown the occurrence of anomalous amounts of methane in rocks associated with lead/zinc mineralization in a number of deposits in the British Isles and Europe. This has led to speculation that the gas may have originated either as a consequence of reactions involved in the mineralization process or as a result of maturation of the organic matter in the sediment or from a deep source. New data are presented showing the distribution of light hydrocarbon gases from fluid inclusions in minerals from the North and South Pennine Orefields which differ from those observed in the host rocks. Possible sources for the gases in the host rocks and the minerals are examined. Based on the close correlation between the distribution of the gases in the carbonate rocks of Northern England and the conodont colour alteration index map for the area, it is suggested that the anomalous amounts of methane gas in the Northern Pennine host rocks are the result of maturation prior to mineralization. The distribution of gases in the fluid inclusions in the minerals serves as a distinguishing feature, and two assemblages are recognized from the South Pennine Orefield, both of which are distinct from that of the Northern Pennines. It is concluded that these gases, trapped at the time of mineralization, originate as a consequence of reactions which occurred during mineral deposition.  相似文献   

网形结构对重力数据分析结果的影响     

隗寿春  祝意青  梁伟锋  赵云峰  李杰  艾力夏提·玉山 《大地测量与地球动力学》2018,38(10):1063-1067

为分析网形结构对重力网平差结果的影响,利用北天山测网改造后的最新4期流动重力观测数据,分析测网中存在长支线对整网数据处理结果的影响。结果显示,长支线的存在使北天山最大异常变化达到260 μGal。将支线连成闭合环再进行平差计算,得到的最大重力变化量减小到60 μGal,表明测线上的误差积累导致支线末端测点重力值可靠性差,严重影响异常重力变化的识别。由于观测原因形成长支线时,为正确识别异常信息,采取适当的数据处理方法,将支线连接成闭合环,可以有效提高测网整体平差结果的可靠性。  相似文献   

Processes of magma/wet sediment interaction in a large-scale Jurassic andesitic peperite complex, northern Sierra Nevada, California   总被引：3，自引：0，他引：3  

Richard E. Hanson  Ulysses S. Hargrove 《Bulletin of Volcanology》1999,60(8):610-626

 The Middle Jurassic Tuttle Lake Formation in the northern Sierra Nevada, California, comprises a thick volcaniclastic sequence deposited in a submarine island-arc setting and penetrated by numerous related hypabyssal intrusions. A composite andesite-diorite intrusive complex ≥4.5 km long and ≥1.5 km thick was emplaced while the host Tuttle Lake sediments were still wet and unconsolidated. Large parts of the intrusive complex consist of peperite formed where andesitic magma intruded and intermixed with tuff, lapilli-tuff and tuff-breccia. The southern half of the complex consists of augite-phyric andesite containing peperite in numerous small, isolated pockets and in more extensive, laterally continuous zones. The peperites comprise three main types recognized previously in other peperite studies. Fluidal peperite consists of small (≤30 cm), closely spaced, at least partly interconnected, globular to amoeboid andesite bodies enclosed by tuff. This peperite type developed during intrusion of magma into fine-grained wet sediment along unstable interfaces, and fluidization of the sediment facilitated development of complex intrusive geometries. Blocky peperite and mixed blocky and fluidal peperite formed where magma intruded coarser sediment and underwent variable degrees of brittle fragmentation by quenching and dynamic stressing of rigid margins, possibly aided by small steam explosions. The northern half of the intrusive complex consists predominantly of a different type of peperite, in which decimetre-scale plagioclase-phyric andesite clasts with ellipsoidal, elongate, or angular, polyhedral shapes are closely packed to widely dispersed within disrupted host sediment. Textural features suggest the andesite clasts were derived from conduits through which magma was flowing, and preserved remnants of the conduits are represented by elongate, sinuous bodies up to 30 m or more in length. Disruption and dispersal of the andesite clasts are inferred to have occurred at least partly by steam explosions that ripped apart a network of interconnected feeder conduits penetrating the host sediments. Closely packed peperite is present adjacent to mappable intrusions of coherent andesite, and along the margin of a large mass of coarse-grained diorite. These coherent intrusions are considered to be major feeders for this part of the complex. Examples of magma/wet sediment interaction similar in scale to the extensive peperites described here occur elsewhere in ancient island-arc strata in the northern Sierra Nevada. Based on these and other published examples, large-scale peperites probably are more common than generally realized and are likely to be important in settings where thick sediment sequences accumulate during active volcanism. Careful mapping in well-exposed terrains may be required to recognize large-scale peperite complexes of this type. Received: 8 June 1998 / Accepted: 4 December 1998  相似文献   

西秦岭北带丹凤群发育特征及金找矿方向   总被引：2，自引：0，他引：2  

杜玉良  李林科 《甘肃地质》1999,8(1):1-5

位于西秦岭北带的丹凤群是一套浅—中等变质的绿片岩系,原岩为一套以基性—中酸性火山岩为主夹正常陆源碎屑岩、碳酸盐岩的岩石组合。该变质岩系分布区金的地球化学丰度高,断裂作用和岩浆活动十分强烈。丹凤群兼具基性—中酸性火山岩、印支—燕山期断裂构造及中酸性岩体“三位一体”成矿条件的地段是成金的有利部位  相似文献   

新疆塔里木盆地北部石炭纪孢子带及其地质意义   总被引：2，自引：0，他引：2  

高联达  何卓生 《甘肃地质》1999,8(1):14-27,T002

塔里木盆地北部石炭纪孢子花粉非常丰富,属种众多,保存完美,经研究共计有７４属,２３１种。根据孢子花粉演化及其在地层中的分布规律,自上而下划分出９个孢子带：９Ｐｒｏｐｒｉｓｐｏｒｉｔｅｓｌａｅｖｉｇａｔｕｓ－Ｇｒｕｍｏｓｉｓｐｏｒｉｔｅｓｖａｒｉｏｒｅｔｉｃｕｌａｔｕｓ（ＬＶ）带８Ｂｅｌｉｓｐｏｒｉｔｅｓｎｉｔｉｄｕｓ－Ｍｕｒｏｓｐｏｒａｃａｎｄｉｐｌｉｃａｔａ（ＮＣ）带７Ｒａｉｓｔｒｉｃｋｉａｎｉｇｒａ－Ｓｃｈｕｌｚｏｓｐｏｒａｃａｍｐｙｌｏｐｔｅｒａ（ＮＣ）带６Ｌｙｃｏｓｐｏｒａｐｕｓｉｌａ（ＰＵ）带５Ｓｃｈｏｐｆｉｔｅｓｃｌａｖｉｇｅｒ－Ａｕｒｏｒａｓｐｏｒａｍａｃｒａ（ＣＭ）带４Ｓｐｅｌａｅｏｔｒｉｌｅｔｅｓｐｒｅｔｉｏｓｕｓ－Ｒａｉｓｔｒｉｃｋｉａｃｌａｖａｔａ（ＰＣ）带３Ｓｐｅｌａｅｏｔｒｉｌｅｔｅｓｂａｌｔｅａｔｕｓ－Ｒｕｇｏｓｐｏｒａｐｏｌｙｐｔｙｃｈａ（ＢＰ）带２Ｋｒａｅｕｓｅｌｉｓｐｏｒｉｔｅｓｈｉｂｅｒｎｉｃｕｓ－Ｕｍｂｏｎａｔｉｓｐｏｒｉｔｅｓｄｉｓｔｉｎｃｔｕｓ（ＨＤ）带１Ｖａｌａｔｉｓｐｏｒｉｔｅｓｖｅｒｕｃｏｓｕｓ－Ｒｅｔｕｓｏｔｒｉｌｅｔｅｓｉｎｃｏｈａｔｕｓ?  相似文献   

不同构造环境下的壳─幔过渡带结构   总被引：7，自引：1，他引：6  

赵俊猛  张先康  赵国泽  刘国栋  卢造勋 《地学前缘》1999,(3)

位于中国西北部的天山造山带与准噶尔盆地是典型的盆岭构造。通过对横跨天山造山带与准噶尔盆地的沙雅-布尔津地学断面地震宽角反射、折射资料进行小波分析,获得了天山造山带与准噶尔盆地壳-幔过渡带的详细结构。结果表明,天山造山带的壳-幔间是以多个薄层过渡的。这些薄层的层厚度2～3km不等,层速度高低相间,总厚度约20km,平均速度较低,接近塔里木盆地下地壳的速度。塔里木盆地北缘与准噶尔盆地的壳-幔间不具有这种特点,其壳-幔间主要表现为一级间断面。而位于中国东北部的间阳-海城-东沟深地震测深剖面所揭示的辽东台隆-辽河盆地-燕山台褶带壳-幔过渡带的结构似乎具有完全相反的特征：辽河盆地的壳-幔过渡带比较复杂,它由数个薄层叠合而成,总厚度达15km;辽东台隆与燕山台褶带壳-幔过渡带结构十分简单,皆以一级间断面过渡为主。研究认为,造成二者差异的主要原因是它们所处的构造环境不同：前者为挤压环境,而后者为伸展环境。在挤压环境下,复杂的壳-幔过渡带形成于造山带的下面;而在伸展环境下,复杂的壳-幔过渡带形成于盆地的下面。壳-幔过渡的复杂程度与构造活动性相联系,在一定程度上反映了岩石圈目前的构造活动水平。  相似文献   

对哈萨克斯坦,吉尔吉斯斯坦两国地下流体资料的初步分析   总被引：11，自引：4，他引：7  

高小其  王道 《内陆地震》1999,13(3):243-252

依据来自哈萨克斯坦,吉尔吉斯斯坦两国地下流体的交换资料,分析了它们对天山及其邻区强震的映震特征,认为：（１）水化学异常时间与水动态异常的时间不同;（２）气体,离子,水动态异常形态多样;（３）水化学正负正常不确定;（４）异常幅度变化复杂;（５）强震远场效应明显;（６）震后效应显著并具有不可逆性。  相似文献   

华北地区钻孔应力应变中短期预报指标和区域特征研究     

赵淑萍  冯志军 《高原地震》1999,(1)

经过长时间段（1969～1997年）,大区域（34°～42°N,110°～114°E）钻孔应力、应变台网异常时空扫描,得出的结论是：可把异常形态特征和异常区域特征作为中期或短期地震预报指标。  相似文献   

Eolian evidence from the Chinese Loess Plateau: the onset of the Late Cenozoic Great Glaciation in the Northern Hemisphere and Qinghai-Xizang Plateau uplift forcing   总被引：11，自引：0，他引：11  

Zhisheng An  Sumin Wang  Xihao Wu  Mingyang Chen  Donghuai Sun  Xiuming Liu  Fubao Wang  Li Li  Youbin Sun  Weijian Zhou  Jie Zhou  Xiaodong Liu  Huayu Lu  Yunxiang Zhang  Guangrong Dong  Xiaoke Qiang 《中国科学D辑(英文版)》1999,42(3):258-271

On the basis of a newly-constructed record of magnetic susceptibility (SUS) and the depositional rate change of eolian loess-red clay sequences in the last 7.2 Ma BP from the hea Plateau, together with a cornperison of a record of °¹⁸O values from the equatorial East Pacific Ocean and eolian Quartz flux variations fmm the North Pacific Ocean, the evolutiomuy process of the Late Cenozoic Great Glaciation in the Northern Hemisphere can be divided into three stages: the arrival stage around 7.2–3.4 Ma BP, the initial stage at about 3.4—2.6 Ma BP, and the Great Ice Age since 2.6 Ma BP. The evolution of the East Asian monsoon is characterized by paid winter and summer monsoons, and it is basically composed of the initial stage of weak winter and summer monsoons, the transitional stage of simultaneous increase in intensity of winter and summer monsoons, and the prevailing stage of strong winter and week summer monsoons, or weak winter and strong summer monsoons. The Late Cenowic global tectonic uplift, paaicdarly the Qinghai-Xizang Plateau uplift and the associated CO₂ concentration variation, controls the dng processes of the onset of Great Glaciation and the long-term changes of East Asian monsoom climate in the Northern Hemisphere to a large extent. The accelerating uplift of the Qinghai-Xizang Plateau between 3.4 and 2.6 Ma BP provided an important driving force to global climiatic change. Project supported by the foundation of Chinese Academy of Sciences (Grant No. KZ951-A1-402), the State Science and Technology Committee (Grant No. 95-pre-40)and the Chinese Nature Science Foundation (Grant No. 49672140)  相似文献