The effect of a surface data assimilation technique and the traditional four-dimensional data assimilation on the simulation of a monsoon depression over India using a mesoscale model

The objective of this study is to investigate the impact of a surface data assimilation (SDA) technique, together with the traditional four-dimensional data assimilation (FDDA), on the simulation of a monsoon depression that formed over India during the field phase of the 1999 Bay of Bengal Monsoon Experiment (BOBMEX). The SDA uses the analyzed surface data to continuously assimilate the surface layer temperature as well as the water vapor mixing ratio in the mesoscale model. The depression for the greater part of this study was offshore and since successful application of the SDA would require surface information, a method of estimating surface temperature and surface humidity using NOAA-TOVS satellites was used. Three sets of numerical experiments were performed using a coupled mesoscale model. The first set, called CONTROL, uses the NCEP (National Center for Environmental Prediction) reanalysis for the initial and lateral boundary conditions in the MM5 simulation. The second and the third sets implemented the SDA of temperature and moisture together with the traditional FDDA scheme available in the MM5 model. The second set of MM5 simulation implemented the SDA scheme only over the land areas, and the third set extended the SDA technique over land as well as sea. Both the second and third sets of the MM5 simulation used the NOAA-TOVS and QuikSCAT satellite and conventional upper air and surface meteorological data to provide an improved analysis. The results of the three sets of MM5 simulations are compared with one another and with the analysis and the BOBMEX 1999 buoy, ship, and radiosonde observations. The predicted sea level pressure of both the model runs with assimilation resembles the analysis closely and also captures the large-scale structure of the monsoon depression well. The central sea level pressures of the depression for both the model runs with assimilation were 2–4 hPa lower than the CONTROL. The results of both the model runs with assimilation indicate a larger spatial area as well as increased rainfall amounts over the coastal regions after landfall compared with the CONTROL. The impact of FDDA and SDA, the latter over land, resulted in reduced errors of the following: 1.45 K in temperature, 0.39 m s⁻¹ in wind speed, and 14° in wind direction compared with the BOBMEX buoy observation, and 1.43 m s⁻¹ in wind speed, 43° in wind direction, and 0.75% in relative humidity compared with the CONTROL. The impact of SDA over land and sea compared with SDA over land only showed a further marginal reduction of errors: 0.23 K in air temperature (BOBMEX buoy) and 1.33 m s⁻¹ in wind speed simulations.     

An application of micropaleontology-sequence stratigraphy method in stratigraphic division

The formation of the Paleogene in the Chengbei fault-step zone of the Dagang off-shore area is very complex and the stratigraphic division and correlation are relatively difficult. A method of micropaleontology-sequence stratigraphy is proposed herein. The study considers Well Zhangcan 1 as an example to prove that the scheme of stratigraphic division is feasible by conducting micropaleontology-sequence stratigraphy in the Guanjiapu area of the Chengbei faultstep zone. The application of micropaleontology-sequence stratigraphy method indicates that Member 1 of the Shahejie Formation in Well Zhuanghai 808×1 and Member 3 of the Dongying Formation of the Paleogene exist. Translated from Acta Micropalaeontologica Sinica, 2005, 22(4): 417–424 [译自: 微体古生物学报]     

济阳坳陷车西地区隐蔽油气藏发育特征及勘探潜力

车西地区因自身地质结构特点在勘探初期以来一直以隐蔽油气藏为主。其中,北部陡坡带二台阶滑脱潜山油气藏、中部洼陷带浊积岩性油气藏、南部缓坡断阶带低位扇岩性油气藏是该区最为典型的隐蔽油气藏。本文从形成机制、成藏主控因素等多方面阐述了上述隐蔽油气藏的发育特征。在此基础上,结合目前油气分布特征,进一步分析了不同区带隐蔽油气藏的勘探潜力。认为在不同区带、层系和油藏类型上有明显的不均衡性,勘探潜力较大。     

南堡凹陷老爷庙油田新近系储层特征与油气成藏

南堡凹陷老爷庙油田新近系馆陶组和明化镇组仍是目前勘探和开发的重点层段。新近系以河流相沉积为主,储层岩石类型以长石砂岩和岩屑长石砂岩为主;孔隙结构以中孔和大孔为主,分选较好;储层成岩作用相对较弱,碳酸盐析出是降低原生孔隙的重要因素,孔隙类型以粒间孔为主,馆陶组见少量粒间溶孔和粒内溶孔。储层成岩作用对油气聚集有利,储层沉积微相控制了油气的聚集和分布,河道和废弃河道砂体具有良好的储盖配置关系,是最有利的油气聚集相带;心滩砂体由于其封盖条件不如河道砂体优越,而含油气性相对较差。     

Lacustrine transgressions in the late Cenozoic Ussuri-Khanka depression (Primor’e)

In the Ussuri-Khanka depression of Primorye, the Quaternary alluvial-lacustrine and lacustrine sedimentogenesis progressed under conditions of transgressive accumulation in response to the depression tectonic subsidence and recurrent climatic fluctuations. The alluvial dams and irregular accumulation are proved to have been the leading factors of lakes’ formation within the depression. As is shown, fluctuations of the water level in limnic reservoirs depended on the climatic changes. New data considered in this work confirm the lacustrine genesis of a greater part of the Middle Pleistocene-Holocene sedimentary succession in the Khanka depression. Two transgressive phases, when the water level in the lakes rose by 1.5–2.0 m above the present one, are established for the Subboreal. The general conclusion is that the mesorhythmic structure of the sedimentary succession in the Ussuri-Khanka depression reflects the influence of climatic fluctuations in the Late Cenozoic.     

Origin and evolution of closed depressions in central Belgium,European loess belt

Closed depressions (CDs) are lower lying areas where the sediment eroded from the surrounding soil surfaces draining towards the CD is trapped in the system. CDs have been reported in several regions of the European loess belt and are attributed either to natural processes (e.g. dissolution of subsurface horizons) or to human intervention (e.g. quarrying). Previous studies focussed mainly on cropland areas where, however, only few and largely filled in CDs remain. The objectives of this study were to i) assess the spatial distribution of CDs under forest and cropland, ii) to determine and compare the morphology of CDs under forest and under cropland, and iii) to determine the origin and age of these CDs under forest. In a study area located partly in ancient forest (13 km²) and partly in cropland (29 km²), a systematic survey revealed the presence of 71 CDs under forest (5·3 CD.km^?2) and 30 CDs under cropland (1 CD.km^?2). Comparison of their morphology showed that CDs under forest were significantly deeper, with steeper sidewalls and a smaller surface area because of the erosion and deposition processes acting on the CDs under cropland. By comparing CDs that had been under cropland for different time intervals, the rate of this morphological evolution could be reconstructed. Analysis of the soil stratigraphy of two representative CDs in the ancient forest area confirmed their origin as quarries. Most probably, calcareous loess was excavated since this soil horizon, about two to five meters thick, was completely absent within the CDs. Dating of the infilling of one CD by optically stimulated luminescence (OSL) shows that the CD filled in between the first century BC and the fourth century AD. This dating corresponds to the dating of sediment deposits in nearby, human‐induced gullies that were attributed to an agricultural land use phase between the 18th century BC and the third century AD.     

一种基于数字伴潮海岸线的潮滩淹没区仿真算法

提出了一种基于数字伴潮海岸线（digital tide-coordinated shoreline，DTS）的潮滩淹没区仿真算法。此算法在建立数字潮滩模型和瞬时水位模型的基础上实时提取DTS。根据DTS的类型确定不连通的洼地，并快速计算其影响域，同时合理地确定潮滩与水面模型的表达方式，正确构建和显示淹没区。实验结果证明，本文算法在表达的准确性和计算的速度上明显优于传统算法。     

天山南北两侧山前坳陷带中新生代构造特征与地震

形成于中新生代的南天山库车山前坳陷带和北天山乌鲁木齐山前坳陷带表现出类似的几何学、运动学和动力学特征 ,即坳陷内都发育 4排近东西向展布的逆断裂 -背斜带 ;新生代 (特别是第四纪以来 )表现出强烈的由山体向盆地的逆冲活动 ;逆断裂 -背斜带的形成、演化和发展都受控于统一的近南北向构造应力场。然而 ,南北两个山前坳陷在变形强度、地球物理细结构、地球动力学环境等方面存在着明显的不同。对这些不同点进行了讨论 ,认为正是这些不同点的存在 ,使得天山南北两侧山前坳陷内的现今地震活动性显示出不对称性 ,即南天山库车山前坳陷 5级以上地震基本都分布在第 3排 (秋里塔格 )逆断裂 -背斜带上 ,而北天山乌鲁木齐山前坳陷 5级以上地震基本都分布在坳陷南部准噶尔南缘断裂附近及其以南的天山内部     

济阳坳陷南部古近系洪水—漫湖沉积

利用钻井取心、薄片鉴定、粒度分析、古生物鉴定及测井解释等资料和手段,对济阳坳陷南部古近系孔一段到沙四段底部沉积特征进行研究.结果表明,济阳坳陷在孔一段至沙四段沉积早期处于湖盆裂陷初期,沉积作用明显受季节性洪水注入影响,在东营、惠民两凹陷形成洪水-漫湖沉积体系.其主要岩性特征为：岩石类型以反映氧化环境的浅色碎屑岩类为主,成熟度较低,粒度分布和沉积构造反映其兼有重力流和牵引流的沉积特点,植物碎屑贫乏而生物扰动构造丰富且具周期性,砂体呈环带状分布.该沉积体系分为洪水水道末端、泥坪、砂坪、砂泥混合坪和漫湖风暴等5个微相和侧缘远源、近岸远源两类相层序.     

利用有机包裹体探讨塔里木盆地依奇克里克构造带下侏罗统油气运移与油气藏的存储条件

本文主要是对塔里木盆地库车坳陷东部的依奇克里克构造、克拉苏及吐格尔明三个构造带砂岩储层中包裹体进行了研究。利用包裹体的均一温度、有机包裹体的显微镜荧光特征、气相色谱、激光拉曼的成分分析,重点讨论了依奇克里克构造带成藏条件。通过对研究区储层中包裹体研究结合油气藏的分布特征认为在库车坳陷东部储层物性不是油气成藏的关键因素,封存条件才是控制该区油气能否成藏的决定因素。断层断在地层内部,对成藏有利,而地层产状较直立,断层直通到近地表,油气沿断层向上运移逃逸,包裹体是最好的证据。由储层包裹体温度、荧光特征和成分上的差异显示出在依奇克里克构造带至少有二次油气运移,第一期有机质低成熟时有过少量的油气运移,大量的油气运移是第二期。爆裂法进行群体包裹体气相色谱分析结果,显示出两个高峰区域,两个高峰区分别反应了轻烃与重烃“C”数上的差异,利用了514nm 和785nm两个激光波长,进行了激光拉曼分析,其测试结果显示出,断层开启的样品包裹体中 H_2O 都很高,CO_2含量很低,断层封闭的样品 H_2O 部很低,CO_2含量高,以次来判别储层的封闭条件。