Phase variability of Sq (H) on normal quiet days in the equatorial electrojet region

Summary. From a study of 'abnormal quiet days' (AQDs) at equatorial latitudes it was found earlier (Sastri) that the occurrence of an abnormal Sq ( H ) phase confined to the equatorial electrojet belt is closely associated with the incidence of complete or partial counter-electrojet (CEJ) conditions (marked daytime depressions in the H field in the electrojet region) for about 5 hr around the normal time interval of the diurnal maximum of the H field. In this paper, we investigate the causative mechanism of the Sq ( H ) phase variability on 'normal quiet days' (NQDs), defined as days on which the diurnal maximum of the H field occurs in the time interval 0930-1230 LT, in the equatorial electrojet belt using published geomagnetic data of stations in the Indian equatorial region. It is found that much of the phase variability of Sq ( H ) on NQDs may be caused by the influence of southward (negative) perturbation fields in the H component, similar in nature to those associated with AQDs but of a much smaller amplitude, close to the usual time of the diurnal maximum of the H field. The perturbation fields are noticed to be essentially of the ionospheric dynamo region origin. Possible mechanisms that might give rise to the observed perturbation fields are discussed.     

Muslim geographies and the politics of purification in Sri Lanka after the 2004 tsunami

In this paper, we argue that the politics of aid in Sri Lanka 'after' the 2004 Indian Ocean tsunami accentuated what we call the 'politics of purification'– the fragmented ethnic politics of territoriality – in Sri Lanka's east. The politics of purification entail geographical imaginations of a nation as 'the same people living in the same place'. We illustrate this with a case study on Muslim geographies in Kalmunai Divisional Secretariat division, on the coast of Ampara District, southeast Sri Lanka, where the politics of relocating Muslim families from the buffer zone created the conditions for the geographical imaginations of the politics of purification to play out. At the same time, our study indicates the antinomies of purification and the political fragmentation of Muslim geographies.     

Ecology and population structure of theArtemia parthenogenetica,population inhabiting a major saltern in Sri Lanka

The structure of the naturally occurringArtemia parthenogenetica population inhabiting the Mahalewaya Saltern in Sri Lanka was studied over an annual cycle, together with accompanying variations in the physico-chemical characteristics of its pond waters.Artemia was found only in the serially connected earthen ponds that serve as condenser pans in the saltern. Over the 12-month period of study, salinities in these ponds ranged from 81.5 to 199.6 ppt, temperatures from 28.2 to 33.6°C, pH from 7.9 to 9.1 and dissolved oxygen from, 1.1 to 9.0 mg L^–1. The physico-chemical characters varied along a gradient across the three ponds, with salinity and temperature increasing with proximity of the condenser pans to the crystallizers of the saltern and dissolved, oxygen values showing the opposite trend. The ponds containingArtemia were shallow and had a maximum depth of 37 cm. Gross primary productivity ranged from negative values to 686.4 mg C m^–2 day^–1. Rainfall was distributed non-uniformly almost throughout the year, most of it being experienced from August to October, with a 254 mm maximum in October and lesser rainfall from December to May. Population numbers ranged from zero to 125 individuals L^–1 and declined with increasing salinities and temperatures which related, spatilly, to increasing proximity of ponds to crystallizers and temporally, to the dry weather periods. Recruitment was best at low salinities and temperatures (104 to 114 ppt and 28.2 to 30.5°C) but also took place, although, at reduced intensities, up to 174 ppt salinity and 32.2°C temperature. Populations were mostly dominated by instar I stage nauplii with adult stages predominating only during periods of high salinity and temperature. Water management practices for salt production in the salterns included maintaining shallow depths that lead to high water temperatures and pond irrigation procedures that resulted in abrupt salinity changes. Such practices limited the size of theArtemia population as well as prevented its spread into the numerous ponds of the saltern.     

Geographies of eviction,expulsion and marginalization: stories and coping capacities of the Veddhas,Sri Lanka

This paper identifies why the Veddhas, the indigenous population of Sri Lanka, have been exposed to forced relocation and marginalization at various historical junctures. Their history is a dramatic story of eviction, expulsion and marginalization, and a sad story of deprivation, ethnic discrimination and lack of human rights. The disempowerment of the Veddhas primarily relates to the dominating powers of authority of the Sri Lankan State and its effectuation of detrimental development policies and practices. The key concepts of marginalization, eviction and expulsion are discussed in relation to an analytical model illustrating how external and internal factors, collective capabilities and individual characteristics interact on and influence people's coping capacity. Veddhas in two villages have given accounts of their understanding of the situation. It is concluded that the disempowerment and disappearance of the Veddha culture are due to ignorance and the unwillingness of the State to procure an enabling environment that would improve the coping capacity of its indigenous population.     

Tsunamigenic incisions produced by the December 2004 earthquake along the coasts of Thailand, Indonesia and Sri Lanka

Field observations and satellite images indicate that tsunami waves exhibit specific patterns during flooding and recession forming characteristic incisions in the coastal landscape. To study these incisions we analyze high resolution remote sensing images of the coastline of Indonesia, Thailand and Sri Lanka impacted by the tsunami of December 26th, 2004. The analysis sheds light on the different mechanisms by which currents scour incisions during the flooding and receding phases of a tsunami. During flooding the high velocity flow indents the levees of existing tidal channels and bays, leaving short flood scours. The receding water then dissects the coastline with equally spaced return channels widening toward the coast.     

关于“界点”型海岛的地缘定位研究 ——以海南岛和济州岛的比较研究为中心

从现代地缘政治学的角度来讲,海洋主权直接维系着国家的兴衰更替,作为海疆基本划界标准之一,海岛是海洋上极为重要的领土标志和主权归属象征,因而地处海疆边界的海岛自然容易成为海权争端的导火索,多方交界的海岛或附近海域更是如此。目前我国周边海域争端不断,海洋权益面临严峻考验,如何审视这种边界海岛的战略定位也将成为我国维护海权的一大课题。为此,以下将尝试借用相应的陆疆概念---“界点”,以海南岛和韩国济州岛为例,分析处于多方势力海疆交界处的海岛地缘形势,以期探索一种新的海疆主权范式,进而对我国维护海洋权益、保护海洋疆土起到一定的启发作用。     

Livelihoods in a Conflict Setting: A Case Study of the Ethnically Bordered Agricultural Villages in Ampara District,Sri Lanka

En følge av Verdenskrigen var bl. a. at Finnland den 6. december 1917 proklamerte sin selvstendighet, og i juli 1919 antok Finnland den republikanske regjeringsform. Med Russland stod den nye republikk på krigsfot til freden i Dorpat undertegnedes den 14. oktober 1920. Denne fred godkjentes av den finske riksdag den 1. desember samme år. Ved denne fred avstod Russland til Finnland Petsamo-området. Dette område, som på norsk har vært benevnt Petchenga eller Pasvik-Peisen området, er nu Finnlands nordligste landsdel, og gjennem denne erhvervelse har Finnland fått kyst til Nord-Ishavet.     

Luminescence chronology of incision and channel pattern changes in the River Ganga, India

The River Ganga in the central Gangetic plain shows the incision of 20 m of Late Quaternary sediments that form a vast upland terrace (T₂). The incised Ganga River Valley shows two terraces, namely the river valley (terrace-T₁) and the present-day flood plain (terrace-T₀). Terrace-T₁ shows the presence of meander scars, oxbow lakes, scroll plains, which suggests that a meandering river system prevailed in the past. The present-day river channel flows on terrace-T₀ and is braided, sensu stricto. It is thus inferred that the River Ganga experienced at least two phases of tectonic adjustments: (1) incision and (2) channel metamorphosis from meandering to braided.Optical dating of samples from three different terraces has bracketed the phase of incision to be <6 and 4 ka. Different ages of the top of terrace-T₂ show that this surface experienced differential erosion due to tectonic upwarping in the region, which also caused the river incision. River metamorphosis occurred some time during 4 and 0.5 ka.     

Effectiveness of monsoon floods on the Tapi River, India: role of channel geometry and hydrologic regime

Geomorphic effects of floods are a function of several controlling factors, such as magnitude, frequency, rate of sediment movement, flood power, duration of effective flows, sequence of events and the channel geometry. In this paper, these measures of effectiveness have been evaluated for the monsoon-dominated, flood-controlled and incised Tapi River, India by defining four flow categories: low flows, moderate flows, floods and large floods. Ratios between effectiveness parameters of moderate flows on one hand and the floods, large floods and maximum floods on the other, were computed to understand the relative importance of moderate and large flows. In addition to this, stream-power graphs for large floods were constructed, and the changes in channel form were analyzed by using multi-date cross-sections. The results of the study indicate that the morphological characteristics of the bedrock as well as the alluvial channels of the monsoonal and incised Tapi River are maintained by large-magnitude, but low frequency floods that occur at long intervals. Because the channel is incised the effectiveness of large flows is accentuated. The incised channel form enhances the role of large floods by reducing the width–depth ratio, and by increasing the velocity as well as the energy per unit area. The low and moderate flows are superior to high-magnitude flows, only in terms of suspended sediment transport and frequency of occurrence. Another conclusion is that the suspended sediment carried by flows may not be the most appropriate criterion for measuring the geomorphic effectiveness of flows, particularly for monsoonal rivers.     

哈尔滨市道路系统与城市热岛关系研究

采用哈尔滨市1989,2001,2007年Landsat TM遥感影像资料,利用单窗算法对地面温度进行反演,分析哈尔滨市热场的分布情况,并与20世纪90年代地形图结合来分析道路系统间的温度情况及其与城市热岛的关系.结果表明:铁路和公路温度差异显著且处于不同温度区的铁路温度也有显著的差异;铁路沿线地区热岛效应比较显著,铁路能使周围一定区域温度升高;公路系统作为一种特殊的廊道系统,对城市热岛有一定的阻隔、减缓作用;哈尔滨市铁路对热岛的影响范围不超过300 m,公路对城市热岛的降温作用最大值不超过0.4℃,在120 m以外降低作用很小或没有;绿化率的不同也影响道路对城市热岛的作用效果.     

Relationship between energy dissipation rate and channel morphology in the development of the model braided channel

1 IntroductionA certain pattern of channel is the product of its self-adjustment under given boundary, discharge and sediment conditions[1]. A lot of experiments have been performed in flumes, usually with an initially-regulated straight channel being constructed in the flume, to determine the impact of these conditions on channel morphologies and patterns[2-6]. Schumm's experiments[3] demonstrated that when the bed-load channels transport only sand at constant discharge, channels develop from…     

Relationship between energy dissipation rate and channel morphology in the development of the model braided channel

A certain pattern of channel is the product of its self-adjustment under given boundary, discharge and sediment conditions. Based upon the principle of process-response model, an experimental study with 18 runs is carried out in LESRC. This paper is focused on the variation of the energy dissipation versus the channel morphology during and after the bedmaking process of braided channel. The results show that there exists a good empirical relationship between the energy dissipation rate and channel morphology. According to this relationship and the theory of minimum rate of energy dissipation, the authors explain the metamorphosis of the model channel with the development of the braided river.     

Grain-size features of aeolian sand on the east coast of Hainan Island and the revealed evolutionary processes of the sedimentary environment

The Mudui stratigraphic section represents the typical records of sedimentation processes of sand dunes and interdune depressions on the east coast of Hainan Island.Based on high-density sampling and optically stimulated luminescence(OSL) dating of the strata of the section,the grain-size composition,grain-size parameters,cumulative distribution probability curve,and grain-size-sensitivity indexes(SC/D) were analyzed.The analyzed results show that the grain-size features of aeolian sand,weakly developed sandy paleosol,two-facies(aeolian and aqueous) deposits,and lagoon deposits are all different.This indicates four evolutionary phases of the sedimentary environment of the east coast of Hainan Island since 38 ka B.P.Phase I:38-22 ka B.P.;phase II:22-17 ka B.P.;phase III:17-10 ka B.P.;phase IV:10 ka B.P.-present.The climate experienced the hot-wet/hot-dry,hot-wet/hot-dry,and warm-wet/hot-wet fluctuations,and the sedimentary environment also underwent lagoon deposition,dune and interdune depression deposition,dune stabilization and soil development,shifting sand deposition,and evolutionary processes.     

On the spatial relationship between landslides and causative factors on Lantau Island, Hong Kong

This paper presents a statistical approach to study the spatial relationship between landslides and their causative factors at the regional level. The approach is based on digital databases, and incorporates such methods as statistics, spatial pattern analysis, and interactive mapping. Firstly, the authors propose an object-oriented conceptual model for describing a landslide event, and a combined database of landslides and environmental factors is constructed by integrating the various databases within such a conceptual framework. The statistical histogram, spatial overlay, and dynamic mapping methods are linked together to interactively evaluate the spatial pattern of the relationship between landslides and their causative factors. A case study of an extreme event in 1993 on Lantau Island indicates that rainfall intensity and the migration of the center of the rainstorm greatly influence the occurrence of landslides on Lantau Island. A regional difference in the relationship between landslides and topography is identified. Most of the landslides in the middle and western parts of the island occurred on slopes with slope angles of 25–35°, while in the eastern part, the corresponding range is 30–35°. Overlaying landslide data with land cover reveals that a large number of landslides occurred in the bareland and shrub-covered area, and in the transition zones between different vegetation types. The proposed approach can be used not only to analyze the general characteristics of such a relationship, but also to depict its spatial distribution and variation, thereby providing a sound basis for regional landslide prediction.     

Assessing the oscillation of channel geometry and meander migration cardinality of Bhagirathi River,West Bengal,India

Journal of Geographical Sciences - Lateral migration of the Bhagirathi River temporally creates unavoidable geomorphic hazards in West Bengal, India. The Bhagirathi River flows SW for ~67.30 km...     

兰州市城市热岛效应评价与灰色预测

利用兰州市及其郊区（永登、榆中、皋兰3县）1958—2004年气象观测资料分析了兰州市热岛强度的年变化规律,结果表明,1975年以后,兰州市城市热岛效应呈上升趋势,但热岛强度整体保持在3.0 ℃以下;1981—1998年平均热岛强度为3.30 ℃,1990年以后城郊热岛强度增加到3.6 ℃以上;1996年达到最高为4.25 ℃;根据兰州市社会发展状况及前人的研究结果,分别分析了兰州市城市热岛强度在1971—1980年、1990—1995年和1997—2003年3个时段的季节变化规律,未来兰州夏季热岛效应将会排在第一位。运用灰色关联度分析法对影响兰州市城市热岛效应的因子群进行了贡献测度分析,结果表明,人为热释放是造成兰州市城市热岛效应的关键因素;风速、总云量是影响兰州市城市热岛效应的主要气象因子。最后通过改进GM(1,1)模型的拟合与预测,结果与实际情况具有良好一致性,表明兰州市城市热岛效应有进一步加重的趋势。     

Interactions between a cushion plant (Azorella selago) and surface sediment transport on sub-Antarctic Marion Island

On sub-Antarctic Marion Island cushions of the dominant vascular plant species, Azorella selago, interact with the geomorphology of fellfield landscapes by affecting sediment distribution and ultimately terrace formation. Here, to understand the consequences of Azorella cushions for substrate movement and sorting, we quantified the size and shape of Azorella cushions and the grain size distribution of sediment surrounding these cushions, using a combination of image analysis approaches. Results show that as cushions become larger, they tend to become more elongated and grow more perpendicular to the slope. Mean and variance of grain size were greater upslope of Azorella cushions, while the number of particles was higher downslope of cushions, although these differences were not significant at all sites studied. Differences between upslope and downslope particle sizes were, however, not related to cushion elongation or growth angle as had been expected. The observed sediment partitioning is likely caused by a combination of frost-related sediment transport and Azorella cushions acting as sediment obstructions. Understanding these interactions between Azorella cushions and the landscape is especially important in the light of recent warming and drying on the island, as particle size affects soil properties such as water-holding capacity and frost susceptibility.