LOCAL POTENTIAL AND PRINCIPLE OF VORTICITY CONSERVATION

In this paper,the local potential of nondivergent flow on beta plane is derived from the motion equa-tion.The conservation principle for vorticity is obtained when the local potential tends to be minimumwith the variational technique.Some other properties st,ch as Lagrangian of vorticity equation,energyetc.are also discussed briefly in the paper.     

POTENTIAL VORTICITY STRUCTURE OF SUMMER CYCLONES OVER THE CHANGJIANG-HUAIHE VALLEY

Based on the theory of Ertel potential vorticity,the isentropic potential vorticity maps and vertical pro-files of potential vorticity for two summer cyclones over the Changjiang-Huaihe Valley are analysed.Afterdiscussing a possible mechanism for the genesis and development of such systems and their differences fromtypical extratropical cyclones,a conceptual model for their activities is proposed:A weak disturbance in the mid-level of troposphere originated from around the Qinghai-Xizang Plateau may cause heavy precipitation underfavourable conditions and latent heat release in the mid-troposphere leads to downward extension of cycloniccirculation and a wave on the quasi-stationary front.This weak cyclone can develop substantially and becomea typical extratropical cyclone only when air from the lower stratosphere flows downslope along isentropic sur-faces into the region of interest.     

Hillslope erosion by rainstorms–a magnitude-frequency analysis

Daily rainfall data for four stations in Europe and east Africa are used to obtain, by means of magnitude-frequency analysis, a measure of the Cumulative Erosion Potential (CEP) that takes into account rainfall characteristics, soil water storage, and granulometric properties of soils. The CEP has the advantage of being calculated from generally available published rainfall data, so that wide regional coverage is possible. Together with additional data on the surface configuration and on seasonal variations of rainfall and plant cover, the CEP can provide a basis for estimating hillslope erosion by overland flow.     

磁层-电离层-热层耦合的模式计算和分析

对磁层-电离层电动耦合和电离层发电机两种效应进行了模式计算,并对所得的一些耦合现象作了综合讨论.结果表明,在中低纬和赤道区的电离层和地磁研究中必须考虑磁层-电离层耦合效应向中低纬区的穿透和屏蔽;潮汐发电机效应对极光区（电导率增高时）的作用也值得重视.这两效应的特征和相对重要性随磁暴的发展阶段而异,在高低纬区也各不相同,但都有明显的晨昏不对称性.此外,弱磁扰对中低纬电离层形态的影响也不容忽视.     

Zero-frequency tidal distrotion due to the orbital elements of tide-forming bodies

Summary It has been proved that orbital elements of perturbing bodies should be taken into account when 10^–10 accuracy is required for zero-frequency tidal distortion in the second zonal Stokes parameter of the geopotential. A solution at the 10^–15 level of magnitude has been presented. The zero-frequency tidal distortion in the fourth zonal Stokes parameter has been derived as 1·3×10^–10 if the secular Love number is unity. It should be reflected in the geopotential models respecting the 10^–10 level of magnitude.     

贺根山蛇绿岩带航磁异常特征及成矿潜力分析

铬铁矿贺根山蛇绿岩带地处西伯利亚板块和华北板块的汇聚部位,该带出露中国北方最大的超基性岩体群,大小有超过超过30个超基性岩块,其中自西向东分布的朝根山,贺根山,崇根山,乌兹尼黑为最大的蛇绿岩块。与超基性岩关系最密切的矿产莫过于铬铁矿,数年来很多学者针对贺根山蛇绿岩的含矿性做了大量工作(白文吉等1993,1995; Miao Laicheng et al.,2008;段明,2009,2015;黄竺,2015;王成,2016),该带分布的铬铁矿床（点）众多,有代表性矿床(点)为赫根敖拉、733和3756,然而能达到工业开采的矿床只有3756。近些年在该地区的找矿勘查工作未取得突破,笔者认为很多原因在于该区覆盖面积太大,找矿靶区定位不准以及对隐伏的矿体勘查力度不够。2013-2015年天津地质调查中心在2009~2011年度新飞的航磁资料基础之上对该区进行了航磁异常查证与评价研究工作,对该区的成矿潜力与找矿方向提出了心得认识。     

2013年浙江两次汛期暴雨过程对比分析

利用NCEP/NCAR再分析资料,对2013年4月29日(4.29)和6月6日(6.6)浙江两次汛期暴雨的天气形势场、热力动力和水汽条件进行对比分析,研究浙江暴雨的机理,为暴雨预报提供依据。结果表明:1)4.29暴雨影响系统高层为西风槽、低层为低涡;6.6暴雨高低层影响系统均为低涡。2)4.29暴雨高空西风急流强,垂直方向上存在正向环流圈,低层辐合对应高层辐散;6.6暴雨高空西风弱,垂直方向上无明显环流圈,散度场分布较复杂。3)4.29暴雨主要水汽来源为孟加拉湾、南海-西太平洋;6.6暴雨主要水汽来源为孟加拉湾、南海-西太平洋和东海。4)4.29暴雨过程中锋区呈东西走向,有较强冷空气侵入,而6.6暴雨过程中锋区呈东南-西北走向,只有较弱冷空气侵入。     

琼-粤西-桂东南成矿带资源特征与潜力分析

琼-粤西-桂东南成矿带含广西壮族自治区东南部分地区、广东省西南部分地区以及海南省全部。该区位于欧亚板块、印度板块和太平洋板块接合区。大地构造属于武夷云开岛弧系。本文以新的研究成果和找矿突破为基础,通过综合分析,在该地区划分新的重要成矿部署区带,并命名为琼-粤西-桂东南成矿带。本区成矿地质条件优越,矿产丰富多彩。目前已涌现像抱伦金矿、富湾铅锌银矿、大降坪硫铁矿为代表的一大批大型、超大型矿床。对本成矿带的矿床成矿特征进行了研究,划分了14个成矿系列,建立了成矿谱系,并对资源潜力进行了评价。研究区主要矿床类型为沉积变质型、热水沉积型、热液脉型、接触交代型、斑岩型和表生型。成矿受构造作用影响明显。在此基础上,部署了广东云浮地区金、银、铁矿重点远景区、广西陆川地区金银一般远景区、海南石碌铁、金矿一般远景区。为指导本区勘查工作提供了依据。     

Complex coastal change in response to autogenic basin infilling: An example from a sub‐tropical Holocene strandplain

Thick bay‐fill sequences that often culminate in strandplain development serve as important sedimentary archives of land–ocean interaction, although distinguishing between internal and external forcings is an ongoing challenge. This study employs sediment cores, ground‐penetrating radar surveys, radiocarbon dates, palaeogeographic reconstructions and hydrodynamic modelling to explore the role of autogenic processes – notably a reduction in wave energy in response to coastal embayment infilling – in coastal evolution and shoreline morphodynamics. Following a regional 2 to 4 m highstand at ca 5·8 ka, the 75 km² Tijucas Strandplain in southern Brazil built from fluvial sediments deposited into a semi‐enclosed bay. Holocene regressive deposits are underlain by fluvial sands and a Pleistocene transgressive–regressive sequence, and backed by a highstand barrier‐island. The strandplain is immediately underlain by 5 to 16 m of seaward‐thickening, fluvially derived, Holocene‐age, basin‐fill mud. Several trends are observed from the landward (oldest) to the seaward (youngest) sections of the strandplain: (i) the upper shoreface and foreshore become finer and thinner and shift from sand‐dominated to mud‐dominated; (ii) beachface slopes decrease from >11° to ca 7°; and (iii) progradation rates increase from 0·4 to 1·8 m yr^?1. Hydrodynamic modelling demonstrates a correlation between progressive shoaling of Tijucas Bay driven by sea‐level fall and sediment infilling and a decrease in onshore wave‐energy transport from 18 to 4 kW m^?1. The combination of allogenic (sediment supply, falling relative sea‐level and geology) and autogenic (decrease in wave energy due to bay shoaling) processes drove the development of a regressive system with characteristics that are rare, if not unique, in the Holocene and rock records. These findings demonstrate the complexities in architecture styles of highstand and regressive systems tracts. Furthermore, this article highlights the diverse internal and external processes and feedbacks responsible for the development of these intricate marginal marine sedimentary systems.