梅雨期3类不同形成机制的暴雨

通过对1998—2007年观测资料的分析,根据影响梅雨期暴雨发生、发展机制的不同,将梅雨期暴雨分为外强迫型、自组织型和非组织化局地型3种类型。外强迫型主要包括冷槽推进型、西南涡移出型和北槽南涡型,该类型暴雨主要是由大尺度环流的动力强迫抬升和冷空气侵入形成的不稳定层结共同作用而产生;在3类外强迫型中,高低空急流相互作用和冷槽的影响形式有很大不同。在自组织型中,暴雨对流系统具有较长生命周期,并以合并增长、上下游发展和新生中尺度涡旋等形式而传播、发展,是在切变线、水汽辐合带和低空急流等弱环境强迫下形成的一类暴雨。在非组织化局地型中,主要有山区午后强对流和副热带高压边缘对流不稳定两种形式,局地对流不稳定是暴雨产生的主要原因。不同的形成机制,导致出现了不同类型的梅雨期暴雨,相应地这些不同类型的梅雨期暴雨具有不同的预报难度。     

Optimal interventions for flood control,drainage and irrigation project improvements

ABSTRACT

A Mixed-Integer Nonlinear Programming (MINLP) model is formulated and solved in this study to optimize environmental sustainability of flood control, drainage, and irrigation (FCDI) projects in the deltaic regions of Bangladesh. The model optimizes the value of integrated resource benefit, a dimensionless variable defined to measure the environmental sustainability based on the water, agricultural and ecological resources, with a set of project interventions being the major drivers. The resource benefits were evaluated with the help of several indicators, such as flood, navigability, salinity, waterlogging, cropping intensity, land loss and vegetation. The solution of MINLP model provided optimal values of the decision variables, which are the quantities of project interventions (e.g. length and height of dike, number of sluices and drainage inlets, lengths of drainage canals, erosion protection and afforestation works). The approach and the MINLP formulation presented in this study can be used for any real-life FCDI project improvements.     

Effects of two-temperature electrons, external oblique magnetic field, concentration of charged dust grains and higher-order nonlinearity on dust ion-acoustic solitary waves in Saturn's E-ring

The purpose of the present work is to investigate some nonlinear properties of the dust ion-acoustic (DIA) solitary waves in a four-component hot-magnetized dusty plasma consisting of charged dust grains, positively charged ions and two-temperature isothermal electrons. Applying a reductive perturbation theory, a nonlinear Korteweg-de Vries (KdV) equation for the first-order perturbed potential and a linear inhomogeneous KdV-type equation for the second-order perturbed potentials are derived. Stationary solutions of these coupled equations are obtained using a renormalization method. A method based on energy consideration is used to obtain a condition for stable solitons. The effects of two different types of isothermal electrons, external oblique magnetic field, concentration of negatively (positively) charged dust grains and higher-order nonlinearity on the nature of the DIA solitary waves are discussed. The numerical results are applied to Saturn's E-ring.     

Producing interventions for AIDS-affected young people in Lesotho’s schools: Scalar relations and power differentials

Children and youth are a key target group for interventions to address southern Africa’s AIDS pandemic. Such interventions are frequently implemented through schools, and are often complex products of negotiation between a range of institutional actors including international agencies, NGOs, government departments and individual schools. These institutions not only stand in different (horizontally scaled) spatial relationships to students in schools; they also appear to operate at different hierarchical levels. Empirical research with policy makers and practitioners in Lesotho, however, reveals how interventions are produced through flows of knowledge, funding and personnel within and between institutions that make it difficult to assert that any intervention is manifestly more international or more local than any other. Scale theory offers the metaphor of a network or web which usefully serves to move attention away from discrete organisations, sectors and scalar positionings and onto the relationships and flows between them. Nevertheless, organisations and development interventions are often partly structured in scalar hierarchical ways that express substantive power differentials and shape the forms of interaction that take place, albeit not binding them to strict binaries or nested hierarchies. A modified network metaphor is useful in aiding understanding of how particular interventions are produced through intermeshing scales and diverse fluid interactions, and why they take the form they do.     

National ownership in the implementation of global climate policy in Uganda

Abstract

This article explores the history, from a developing country perspective, of how external interventions to implement global policies on the Climate Convention and the Clean Development Mechanism (CDM) have been integrated into national development policy frameworks in the period 1990–2005. The main question asked is to what extent external interventions have formed part of a country-driven approach in Uganda. The conflicting national and global priorities concerning the need for adaptation to the impacts of climate change versus the need for global mitigation of greenhouse gases (GHGs) are explored first. Against this background, Uganda's policy response to climate change is reviewed. National climate policies are found not to exist, and the implementation of global policies is not integrated into national policy frameworks, partly due to conflicting national and global priorities. Given limited national awareness and the fact that climate policy is marginal compared to other national interests in Uganda, the experiences with donor support for the implementation of global climate policy nationally are analysed. This article demonstrates that neither national policies nor national management of donor support have secured a country-driven approach to external interventions in Uganda.     

Sedimentary architecture and depositional controls of a Holocene wave‐dominated barrier‐island system

Barrier‐island system evolution is controlled by internal and external forcing mechanisms, and temporal changes in these mechanisms may be recorded in the sedimentary architecture. However, the precise role of individual forcing mechanisms is rarely well understood due to limited chronological control. This study investigates the relative role of forcing conditions, such as antecedent topography, sea‐level rise, sediment supply, storms and climate changes, on the evolution of a Holocene wave‐dominated barrier‐island system. This article presents temporal reconstruction of the depositional history of the barrier‐island system of Rømø in the Wadden Sea in unprecedented detail, based on ground‐penetrating radar profiles, sediment cores, high‐resolution dating and palynological investigations, and shows that ca 8000 years ago the barrier island formed on a Pleistocene topographic high. During the initial phase of barrier evolution, the long‐term sea‐level rise was relatively rapid (ca 9 mm year⁻¹) and the barrier was narrow and frequently overwashed. Sediment supply kept pace with sea‐level rise, and the barrier‐island system mainly aggraded through the deposition of a ca 7 m thick stack of overwash fans. Aggradation continued for ca 1700 years until sea‐level rise had decreased to <2 mm year⁻¹. In the last ca 6000 years, the barrier prograded 4 to 5 km through deposition of a 10 to 15 m thick beach and shoreface unit, despite a long‐term sea‐level rise of 1 to 2 mm year⁻¹. The long‐term progradation was, however, interrupted by a transgression between 4000 years and 1700 years ago. These results demonstrate that the large‐scale morphology of the Danish Wadden Sea shoreline influences the longshore sediment transport flux and the millennial‐scale dispersal of sediment along the shoreline. On decadal to centennial timescales, major storms induced intense beach and shoreface erosion followed by rapid recovery and progradation which resulted in a highly punctuated beach and shoreface record. Major storms contributed towards a positive sediment budget, and the sustained surplus of sediment was, and still is, instrumental in maintaining the aggradational–progradational state of the barrier island.     

外部性脑积水的CT与临床分析

探讨外部性脑积水（ＥＨ）的ＣＴ与临床表现特点及关系。材料与方法：搜集２４例ＥＨ的ＣＴ资料进行分析,并对其中１０例进行了临床与ＣＴ复查．结果：２４例ＣＴ上均有不同程度额顶部蛛网膜下腔增宽,大脑前纵裂增宽,并多伴有基底池扩大．复查显示,３个月全部为典型表现,６～１２个月ＣＴ征象逐渐减轻,２４个月大部分病例逐渐或完全恢复正常．临床症状随之减轻或消失．结论：ＥＨ是发生在婴儿早期的良性自愈性疾病,预后良好．     

Tectono-sedimentary evolution of the External Liguride units (Northern Apennines,Italy): insights in the pre-collisional history of a fossil ocean-continent transition zone

Abstract

In the Northern Apennines, the External Liguride (EL) units are interpreted as derived from the domain that joined the Ligure–Piemontese oceanic basin to the Adriatic plate continental margin. The EL units can be divided into two different groups according to the lithostratigraphic features of the basal complexes underlying the Upper Cretaceous–Lower Tertiary carbonate flysch (e.g. Helminthoid flysch). The first group includes the western successions characterized by Santonian–Campanian sedimentary melanges where slide blocks of lherzolitic mantle, gabbros, basalts, granulites, continental granitoids are represented. The second group is represented by the eastern successions where the Cenomanian–Campanian basal complexes mainly consist of sandstones and conglomerates where the mafic and ultramafic rocks are scarce or completely lacking. Their original substrate is represented by the Middle Triassic to Lower Cretaceous, mainly platform carbonate deposits, found as slices at the base of the eastern successions.

The stratigraphic features shown by the basal complexes allow the reconstruction of their source area that is assumed to be also representative for the pre-Upper Cretaceous setting. The proposed reconstruction suggests the occurrence in the EL domain of two distinct domains. The eastern domain was characterized by a thinned and faulted continental crust belonging to the Adriatic continental margin. The western domain was instead floored by subcontinental mantle associated with lower and upper continental crust, representing the ocean–continent transition. This setting is interpreted as the result of the opening of the Ligure–Piemontese oceanic basin by passive rifting, mainly developed by simple shear, asymmetric extension of the continental crust. © 2001 Éditions scientifiques et médicales Elsevier SAS     

大连地区酸雨外来源分析

应用Hysplit传输扩散模式计算2008-2009年大连地区酸雨和非酸雨期间的后向气流轨迹,利用条件概率和轨迹聚类法对气流轨迹进行分析,研究大连地区酸雨外来源。结果表明：外来源通过大气输送对大连地区酸沉降的贡献较大。大连地区酸雨主要受中国华东沿海至山东半岛经黄海中北部或经渤海及其西岸的近地面大气污染输送影响,中国华东、华南等南方内陆地区和日本海周边东亚国家对大连地区酸雨均有贡献。海洋性气团或北方大陆气团一般为大连地区非酸雨来源。     

Combined wavelet and principal component analysis (WEof) of a scale-oriented model of coastal ocean gravity waves

Coastal ocean numerical modeling is basically the representation of the dynamics of the coastal ocean in a chosen range of length scales and over an associated frequency band, including the modeling of both coherent processes and associated transient processes. The ocean dynamical features can be individually identified by combining wavelet analysis for time and frequency localization and principal component analysis to “decorrelate” physically consistent structures. In the present paper, the so-called WEof analysis is applied for the extraction of external gravity waves and internal gravity wave lower modes in a simple case of a flat bottom, constant Brunt-Väisälä ocean. It is shown that, with some well known restrictive assumptions, WEof analysis is an efficient candidate for the recognition of frequency localized dynamical processes.