地理国情（市情）普查外业信息采集     

白中洁 《东北测绘》2014,(6):159-161

地理国情监测不仅扩大了测绘行业的内涵,更重要的是,对我国总体布局和规划提供了可靠的依据。目前,在全国范围内逐步开展地理国情普查工作,我分院按照安排,以厦门市为试点,对其进行了外业的调查与核查工作。结合实地作业情况来看,可以在地理国情普查内容与指标基本不变的前提下,依据地域的不同增加分类或修改部分类别的内涵。为今后全面普查工作的顺利开展,对现有的作业方式和作业内容都应有一定的规范。  相似文献   

Lake Ladoga ice phenology: Mean condition and extremes during the last 65 years     

Sergey Karetnikov  Mikhail Naumenko 《水文研究》2011,25(18):2859-2867

Winter conditions play an important role for the largest lake in Europe—Lake Ladoga. The ice cover lasts for 171 ± 3 days on average from the early November until the mid‐May. We investigated the ice regime of Lake Ladoga using a constructed ice database of aircraft surveys and satellite images. More than 1250 surveys of the lake's ice cover from 1943 to 2010 were collected and analysed to determine mean and extreme ice conditions for winters of different types of severity. The time series of ice cover percentage over the lake was plotted. On average, 18 observational ice charts were made every winter. Individual ice phenology records show considerable year‐to‐year variation. For this reason, records typically have been combined and analysed as groups (categories). Extremely cold winters were determined as winters with complete ice cover that lasts more than three months which is approximately 90% quartiles from all winters with complete ice cover. The lake surface was completely covered with ice for more than three months during 5 seasons. Extremely warm winters when the maximum ice cover was less than 70% of the lake area occurred during 5 seasons as well. A basic relationship between the winter severity as winter maximum of accumulated freezing degree‐days (AFDD) and the earlier derived Relative Ice Cover Index (RICI) was established. We have used teleconnection indices such as North Atlantic Oscillations (NAO) and Arctic Oscillation (AO) for the period from October to May for estimation of different types of Lake Ladoga's ice conditions. The AO index in winter months and local winter maximum of AFDD explained much of the interannual variation in ice cover. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Energy balance and evaporation loss of an irrigation reservoir equipped with a suspended cover in a semiarid climate (south‐eastern Spain)     

B. Gallego‐Elvira  A. Baille  B. Martin‐Gorriz  J. F. Maestre‐Valero  V. Martínez‐Alvarez 《水文研究》2011,25(11):1694-1703

The main objective of this study was to assess the impact of a suspended cover on the evaporation loss of an agricultural water reservoir (AWR). To this aim, a detailed data collection was carried out in a typical AWR located in south‐eastern Spain during 2 consecutive years. During the first year, the reservoir remained uncovered, while during the second year it was covered with a double black polyethylene (PE) shade cloth. On an annual scale, it was observed that the cover can provide a reduction of evaporation loss of 85%. Two approaches, energy balance and mass transfer, were used to analyse the effect of the cover on the evaporation process. Important modifications were observed on the magnitude, sign, annual trend and relative weight of the components of the energy balance. The changes were ascribed to the strong reduction of net radiation and to the substantial weight of the heat storage and sensible heat flux in the energy balance. A relevant finding was the contrast between the patterns of the annual evaporation curve for open‐water and covered conditions. The mass transfer approach allowed discriminating between the wind‐ and radiation‐shelter effects on the evaporation term. The reduction in water‐to‐air vapour deficit was the main factor explaining the high efficiency of the cover, whereas the reduction of the mass transfer coefficient was a modulating factor that accounted for the wind‐shelter effect. Overall, both approaches provided a sound basis to describe and explain the physical mechanisms underlying the high performance of the tested cover. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Reef status in the Rasfari region (North Malé Atoll,Maldives) five years before the mass mortality event of 1998     

Carla Morri  Stefano Aliani  Carlo Nike Bianchi 《Estuarine, Coastal and Shelf Science》2010

The Maldives was severely hit by massive coral bleaching and subsequent mortality in 1998. The results of reef monitoring in the following years have supported contrasting views about their recovery potential, partly because of the scarcity of information on the situation before 1998. Quantitative data on coral assemblages collected in 1993 in the Rasfari region (North Malé Atoll) may provide a base-line for the evaluation of the present status of the Maldivian reefs. Five years before the 1998 mortality, most coral communities appeared to be similar, in terms of both coral cover and growth-form composition, to those described in 1958 and 1964, notwithstanding increased human pressure and local events such as minor bleaching episodes in 1987 and crown-of-thorns starfish (COTS) attacks in 1989. Three lessons can be learnt from these results to help to understand the present situation, some ten years after the 1998 mass mortality. First, Maldivian reefs proved in the past to be capable of maintaining flourishing coral life despite various disturbances. Second, four years had been sufficient for complete reef recovery after a (minor) bleaching event. Third, recovery after both COTS attack and bleaching follows a predictable path suggesting that the presence of a three-dimensional community structure, which should reduce post settlement mortality of coral recruits, is essential for rapid coral recovery. As coral recruitment remains high and large tabular Acropora colonies are now reappearing, it is expected that Maldivian reefs should return to their original condition within the next few years.  相似文献   

Controls on surface water chemistry in two lake‐watersheds in the Adirondack region of New York: differences in nitrogen solute sources and sinks     

Mari Ito  Myron J. Mitchell  Charles T. Driscoll  Robert M. Newton  Chris E. Johnson  Karen M. Roy 《水文研究》2007,21(10):1249-1264

The southwestern Adirondack region of New York receives among the highest rates of atmospheric nitrogen (N) deposition in the USA. Atmospheric N deposition to sensitive ecosystems, like the Adirondacks, may increase the acidification of soils through losses of exchangeable nutrient cations, and the acidification of surface waters associated with enhanced mobility of nitrate (NO₃^?). However, watershed attributes, including surficial terrestrial characteristics, in‐lake processing, and geological settings, have been found to complicate the relationships between atmospheric N deposition and N drainage losses. We studied two lake‐watersheds in the southwestern Adirondacks, Grass Pond and Constable Pond, which are located in close proximity (～26 km) and receive similarly high N deposition, but have contrasting watershed attributes (e.g. wetland area, geological settings). Since the difference in the influence of N deposition was minimal, we were able to examine both within‐ and between‐watershed influences of land cover, the contribution of glacial till groundwater inputs, and in‐lake processes on surface water chemistry with particular emphasis on N solutes and dissolved organic carbon (DOC). Monthly samples at seven inlets and one outlet of each lake were collected from May to October in 1999 and 2000. The concentrations of NO₃^? were high at the Grass Pond inlets, especially at two inlets, and NO₃^? was the major N solute at the Grass Pond inlets. The concentrations of likely weathering products (i.e. dissolved Si, Ca²⁺, Mg²⁺, Na⁺) as well as acid neutralizing capacity and pH values, were also particularly high at those two Grass Pond inlets, suggesting a large contribution of groundwater inputs. Dissolved organic N (DON) was the major N solute at the Constable Pond inlets. The higher concentrations of DON and DOC at the Constable Pond inlets were attributed to a large wetland area in the watershed. The DOC/DON ratios were also higher at the Constable Pond inlets, possibly due to a larger proportion of coniferous forest area. Although DON and DOC were strongly related, the stronger relationship of the proportion of wetland area with DOC suggests that additional factors regulate DON. The aggregated representation of watershed physical features (i.e. elevation, watershed area, mean topographic index, hypsometric‐analysis index) was not clearly related to the lake N and DOC chemistry. Despite distinctive differences in inlet N chemistry, NO₃^? and DON concentrations at the outlets of the two lakes were similar. The lower DOC/DON ratios at the lake outlets and at the inlets having upstream ponds suggest the importance of N processing and organic N sources within the lakes. Although an inverse relationship between NO₃^? and DOC/DON has been suggested to be indicative of a N deposition gradient, the existence of this relationship for sites that receive similar atmospheric N deposition suggest that the relationship between NO₃^? and the DOC/DON ratio is derived from environmental and physical factors. Our results suggest that, despite similar wet N deposition at the two watershed sites, N solutes entering lakes were strongly affected by hydrology associated with groundwater contribution and the presence of wetlands, whereas N solutes leaving lakes were strongly influenced by in‐lake processing. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Permafrost‐thaw‐induced land‐cover change in the Canadian subarctic: implications for water resources     

W.L. Quinton  M. Hayashi  L.E. Chasmer 《水文研究》2011,25(1):152-158

Climate warming and human disturbance in north‐western Canada have been accompanied by degradation of permafrost, which introduces considerable uncertainty to the future availability of northern freshwater resources. This study demonstrates the rate and spatial pattern of permafrost loss in a region that typifies the southern boundary of permafrost. Remote‐sensing analysis of a 1·0 km² area indicates that permafrost occupied 0·70 km² in 1947 and decreased with time to 0·43 km² by 2008. Ground‐based measurements demonstrate the importance of horizontal heat flows in thawing discontinuous permafrost, and show that such thaw produces dramatic land‐cover changes that can alter basin runoff production in this region. A major challenge to northern water resources management in the twenty‐first century therefore lies in predicting stream flows dynamically in the context of widely occurring permafrost thaw. The need for appropriate water resource planning, mitigation, and adaptation strategies is explained. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Rehabilitation and Sustainable Use Pattern of Rocky-desertified Land in Southwest China''s Poverty-stricken Karst Mountainous Areas——A Case Study in Benggu Township, Xichou County, Yunnan, China     

YANG Zisheng  LIU Yansui  BAO Guangjing  LI Zhiguo  HE Yimei 《山地科学学报》2006,(3)

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Norwegian sea‐surface palaeoenvironments of marine oxygen‐isotope stage 3: the paradoxical response of dinoflagellate cysts     

F. Eynaud  J. L. Turon  J. Matthiessen  C. Kissel  J. P. Peypouquet  A. de Vernal  M. Henry 《第四纪科学杂志》2002,17(4):349-359

High‐resolution marine palynological data have been obtained from two very long sediment cores (MD952009 and MD952010) retrieved from the southern Norwegian Sea. The dinoflagellate cyst assemblages show pronounced fluctuations in composition, which correlate strongly with magnetic susceptibility records and also mimic the δ¹⁸O signal of the GISP2 Greenland ice‐core. If focusing on the period from 48 to 30 cal. kyr BP, this correlation suggests a paradoxical response of the sea‐surface environments to the atmospheric conditions over Greenland: when the Greenland δ¹⁸O signal reflects warm interstadial conditions, the Norwegian Sea depicts cold sea‐surface temperatures with quasi‐perennial sea‐ice cover (based on dinoflagellate cysts). In contrast, when the Greenland δ¹⁸O records cold stadial periods, the Norwegian Sea‐surface temperatures are warm (based on dinoflagellate cysts), probably linked to inflow of the North Atlantic Drift. These results, similar in both cores, are contrary to those of previous studies and shed light on a possible decoupling of Norwegian sea surface‐water conditions and atmospheric conditions over Greenland. This decoupling could be linked to an atmosphere–ocean system behaving similar to that which the Northern Hemisphere is experiencing at present, i.e. strongly variable owing to the North Atlantic Oscillation. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

北极河流径流量变化及影响因子分析   总被引：5，自引：0，他引：5       下载免费PDF全文

隋翠娟  张占海  刘骥平  单琰焱 《海洋学报》2008,30(4):39-47

利用最新的北极径流资料(R-arcticNET V3.0和Arctic RIMS),对进入北冰洋的4条主要河流的季节及年代际变化进行诊断分析。结果表明:入海径流在4-6月的大幅增加主要是由气温达到融点后积雪融化造成的,降水的作用次之。总的来说,欧亚区域在过去的70年里入海径流量是增加的,而北美区域在近30年里入海径流量是减小的,但注入北冰洋的径流总量是增大的。值得注意的是入海径流的年代际变化在不同季节增减趋势显著不同,夏季和秋季径流量减小,而其他两个季节径流量增大。进一步分析了影响入海径流变化的一些气候因子,结果表明:北大西洋涛动(北太平洋指数)与欧亚(北美)区域的冬、春季径流量存在正相关。春季气温与春季径流量呈正相关,而与夏季径流量呈负相关。降水与径流量基本上为同步正相关。春季积雪覆盖面积与春季径流量为负相关,而与夏季径流量为正相关,夏季积雪覆盖面积与夏季的径流量为正相关。  相似文献   

我国土地利用/覆被研究的热点与应用发展问题   总被引：2，自引：0，他引：2  

宋乃平  张凤荣  王磊  杨洋 《地球信息科学学报》2008,10(1):60-66

本文回顾了国内土地利用调查和土地利用/覆被变化(以下简称LUCC)的研究历程,认为20世纪80年代前的半个世纪,我国以土地调查为主的土地利用研究发展缓慢。到了80年代后,由于遥感技术由实验走向实用、地理信息系统技术的普及,加之IGBP和HDP两大组织发起的土地利用/覆被变化研究,这一领域的研究得到了极大地推动。目前,该领域存在着技术潮流、驱动力研究潮流、环境效应研究潮流、景观生态学潮流等热点,这对于推动LUCC的多学科深入研究具有积极作用;指出了土地利用/覆被变化研究中存在的"重技术轻学理"现象、微观机理研究不足、忽视土地利用替代性研究、土地可持续利用评价针对性不够、研究的服务对象单一等问题,LUCC研究要在克服这些问题中发展;由此提出,在经过一定的领域拓展、案例积累、技术准备等基础工作之后,我国土地利用/覆被变化研究应针对前述问题,加强理论建设,探索模型建立,拓展区域应用,发挥多学科核心作用,在理论建设、数学模型表达、机理探讨等方面,为现代地理学做出贡献,为地理学的社会作用和应用拓展更加广阔的空间。  相似文献