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1.
The effect of change in surface roughness on the precipitation regime in the coastal area of NE-Brazil 总被引：1，自引：0，他引：1
R. Roth 《GeoJournal》1984,8(3):205-209
The NE of Brazil is one of the earth's problematic semiarid areas. However, in the coastal area along the coast from Natal to Salvador precipitation is high enough to allow for a fully developed tropical vegetation. It is shown that this enhancement of annual precipitation is due to the dynamic convergence within the planetary boundary layer and that this effect can quantitatively be evaluated by simple model considerations. To do this the mass flux perpendicular to the coastline is calculated within the lower troposphere for an undisturbed PBL over land and over sea, by using the resistance law of the PBL and by integrating the equation of monion between the bottom and some height above the PBL. By using the equation of continuity the mean vertical motion due to the coastal convergence can be calculated. The relation of the calculated total amount of lifting near the coast on the rate of precipitation is calculated. Compared with the increase of precipitation due to orography it gives the same increase in precipitation per meter of lifting in the coastal area quantitatively and since this is strongly related to the roughness due to the vegetation along the coast it can be shown that deforestation — for instance to grow sugar-cane — in this area the annual amount of precipitation will decrease considerably. Once the coastal area will have been transformed to a desertlike structure, the coastal maximum of precipitation will diminish at all.
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2.
为了了解气温、降水量和人类活动对流域植被NDVI(normalized difference vegetation index)的影响,以长江流域为研究区,运用一元线性回归分析法和Theil-Sen Median趋势分析法研究了长江流域气温、降水量和植被NDVI变化特征,同时利用相关分析法和残差分析法探讨气温、降水量和人类活动对植被NDVI变化的影响.结果表明:1960—2015年长江流域年平均温度显著上升,而降水量的变化趋势并不显著;1982—2015年流域NDVI呈显著增加趋势;1982—2015年流域NDVI与气温的相关性较高,然而与降水量的相关性并不显著;人类活动使流域NDVI增加的区域主要分布于流域北部、东南和西南部分地区,而使NDVI下降的区域位于流域中西部区域和长三角地区.气温对长江流域植被NDVI变化的影响大于降水,气候变暖和人类活动对流域生态环境具有一定程度的影响. 相似文献
3.
Coastal hazard mapping in the Cuddalore region, South India 总被引：1，自引：0，他引：1
It is estimated that nearly one-third of India’s population lives on the coast and is dependent on its resources. Shoreline erosion, storm surges and extreme events have resulted in severe loss of human life, damage to ecosystems and to property along the coast of India. Studies carried out in the Cuddalore region of South India reveal that this low-lying coastal zone, which suffered significant erosion during the last century, has been severely affected by the tsunami of 2004, storm floods and cyclones. In response to these impacts, a variety of coastal defense measures and adaptation strategies have been implemented in the region, although with only limited success. In order to inform future coastal planning in this region, the work reported here identifies a composite hazard line, seaward of which coastal flooding events will have a return interval of less than 1 in 100 years. The area landward of the coastal hazard line will be unaffected by 100 years of coastal erosion at present day rates. The study directly supports the Integrated Coastal Zone Management (ICZM) Plan of the Tamil Nadu State through the identification and assessment of coastal hazards and the overall vulnerability to coastal flooding and erosion. The key results from this pilot study will be used directly by the State of Tamil Nadu in the protection of the coastal livelihoods, better conservation measures and sustainable development along the coast. This study is a step toward mapping the hazard line for the entire coast of India that helps protect human lives and property. 相似文献
4.
There are divergent views about the dominant factors controlling vegetation distribution in coastal deltas. To determine the
dominant factors controlling vegetation distribution, we explored the relationships between six abiotic factors (annual temperature,
annual precipitation, soil organic matter, soil moisture, soil salinity, soil pH) and vegetation patterns along a belt transect
throughout seven vegetation zones (bare beach, seepweed, common reed, meadow, rice, maize, woods) in the Liaohe Delta. The
methods of data analysis included the Kriging interpolation method, grade-ranks method, correlation analysis, Euclidean distance
analysis, and canonical correspondence analysis. Contrary to the view that climate controls vegetation pattern, our results
suggested that climate had a limited influence on vegetation pattern. Edaphic factors were shown to exert the strongest influence
on vegetation pattern, with soil salinity being identified as the dominant factor, followed by soil moisture, soil pH, and
soil organic matter. 相似文献
5.
广东省近50年极端降水事件的时空特征及成因分析 总被引：3，自引：1，他引：2
利用广东省境内25个测站1961~2010年逐日降水资料,综合运用Mann-Kendall检验、正交分解函数和Morlet小波分析等方法,剖析了广东省极端降水的空间结构分布与时间变化特征,并从水汽辐合的角度解释了极端降水的时空特征。结果表明:全省极端降水事件的总量、频次、强度空间分布差异较大,从北到南,极端降水总量和强度增加,频次减少;全省大部分区域极端降水总量和频次都有增加的趋势;广东省极端降水受大尺度天气系统的影响,存在全区一致的多雨或少雨,但也存在东西、四周、中心以及南北的差异;极端降水空间异常可分为4个气候区(异常型),即粤东北区,粤西区,粤中部区以及粤东沿海区,各降水异常区存在20a左右的长周期、10a左右较长周期的和3~4a的短周期振荡;广东省极端降水与极端水汽辐合对应关系较好,区域内水汽辐合的改变可能是影响广东省极端降水变化的重要气候因子。 相似文献
6.
利用动态泰森多边形模型,计算评价了中国1951-2006年全国尺度及各区域尺度的月、季、汛期、年等时段的降水量,并分析了年、季、汛期等降水量的时空分布、区域特征及其年际年内(月、季)变化等基本规律;分析诊断了年、季、汛期降水量的演变趋势、突变趋势、震荡周期等特性;对比分析了长期(1961-2006年)、近期(1980-2006年)以及近期与前期(1961-1979年)降水量的变化特征及其空间变化分布。结果表明,中国近期年降水量在环渤海湾600 mm等值线有所南移,100°E以西地区年降水量普遍增多;内蒙古中西部、海河沿海、黄河中部、淮河北部近期降水量比前期偏少10%以上,嫩江中部、长江下游、闽南沿海、西藏中北部、新疆中西部则偏多10%以上,而塔里木河、伊犁河上游偏多达30%以上。 相似文献
7.
8.
祁连山石羊河上游山区土壤侵蚀的环境因子特征分析 总被引：3，自引：1，他引：2
在GIS技术支持下, 运用通用水土流失方程USLE, 对祁连山北坡东段的哈溪林区的土壤侵蚀量及空间分布进行了模拟运算, 并定量分析了各种环境因子与土壤侵蚀之间的关系. 结果显示: 研究区平均土壤侵蚀模数为25.1 t·hm-2·a-1, 微度和轻度侵蚀面积占总面积的80%, 而强度到剧烈侵蚀产生的侵蚀量占78.3%; 各土地类型土壤侵蚀模数由高到低依次是裸地>草地>农田>灌丛>乔木林, 裸地侵蚀量占到总侵蚀量的54.9%; 乔木林和灌木林95%以上侵蚀面积属微度侵蚀区, 农田中度到剧烈侵蚀的面积比例达到35.9%, 高于草地和其他植被类型, 而草地剧烈侵蚀面积比例高于农田. 海拔高度范围与土壤流失量之间的关系与植被的海拔分布范围明显相关; 土壤平均侵蚀模数随坡度的增加而增大, 土壤侵蚀量主要分布在15°～45°的坡度范围, 不同植被覆盖下土壤流失随坡度变化的趋势可在一定程度上反映该类植被对土壤流失的防止作用. 相似文献
9.
M. Antonellini P. Mollema B. Giambastiani K. Bishop L. Caruso A. Minchio L. Pellegrini M. Sabia E. Ulazzi G. Gabbianelli 《Hydrogeology Journal》2008,16(8):1541-1556
Saltwater has invaded the coastal aquifer along the southern Adriatic coast of the Po Plain in Italy. The topography, morphology and land use of the region is complex: rivers, canals, wetlands, lagoons, urban, industrial and agricultural areas and tourist establishments all coexist in a small area. Water table and iso-salinity maps show that in four study areas (Ancona-Bellocchio, Marina Romea, San Vitale Forest, Cervia) out of five, the water tables are below sea level and saltwater has replaced freshwater in the aquifer. The fifth area (Classe Forest) has a relatively pristine freshwater aquifer thanks to an average water-table height of 2 m above sea level, a lower hydraulic conductivity (< 7.7 m/day) and a continuous dune system along the coast. Only in this area is the topography high enough to maintain freshwater heads that can counteract saltwater intrusion according to the Ghyben-Herzberg principle. Furthermore, the climate, with an average yearly precipitation of 606 mm and an average temperature of 14.4°C, allows for little recharge of the aquifer. Ongoing subsidence, encroachment of sea water along rivers and canals, as well as drainage from agricultural land also enhance the salinization process. 相似文献
10.
Densely populated coastal zones of India are highly exposed to natural environment. These are impacted by episodic natural events, continuous coastal process, gradually rising sea levels and coexisting human interventions. The present study is an attempt to assess the implication of the sea level rise and coastal slope in the coastal erosion for entire mainland of India. In this regard, two methods were employed to estimate the shoreline change rate (SCR): (1) satellite-derived SCR using the Landsat TM and ETM+ acquired during 1989–2001 and (2) SCR derived by Bruun Rule using the parameters coastal slope and sea level trend derived from satellite altimetry. Satellite-derived SCR has been compared with the shoreline change estimated based on Bruun Rule, revealing a better agreement with each other in terms of trend. Peaks of shoreline retreat calculated using Bruun model and satellite-observed SCR offset by 25–50 km. Offset in these peaks was observed due to net drift towards north in the east coast and south in the west coast of India, revealing the applicability of the Bruun Rule along the Indian coast. The present study demonstrates that coastal slope is an additional parameter responsible for the movement of shoreline along with sea level change. The results of satellite-derived SCR reveal the highest percentage of erosion along West Bengal coast with 70% followed by Kerala (65%), Gujarat (60%) and Odisha (50%). The coastlines of remaining states recorded less than 50% of coasts under erosion. Results of this study are proving critical inputs for the coastal management. 相似文献
11.
Nalin Prasanna Ratnayake Amila Sandaruwan Ratnayake P. V. Keegle M. A. K. M. Mallawa Arachchi H. M. R. Premasiri 《Environmental Earth Sciences》2018,77(1):24
Man-made coastal structures directly affect sediment balance and sediment dynamics on the surrounding beaches. The Colombo Harbor Expansion Project has created about 5-km-long breakwater nearly perpendicular to the beach. The present study is focused on quantitatively and qualitatively analyzing the effect of the Colombo Harbor Expansion Project on economically important beaches in and around Colombo city area. In this study, the authors measured monthly variations of beach width, beach profile and the mean grain-size of the sediments at mean sea level for complete annual monsoon cycle. Data were analyzed to establish site-specific erosion vulnerability. Monitoring results show that cumulative beach erosion has increased after the construction of the breakwater (rate = 0.7 m/year from May 2000 to April 2011 and rate = 28.2 m/year from April 2011 to June 2012). In addition, the cumulative and site-specific sand accretion and erosion patterns have a clear relationship with the monsoon seasonality. Beaches were narrower during the stormy southwestern monsoon, whereas beaches were wider during fair weather of northeast monsoon and inter-monsoon periods. In contrast, the constructed breakwater obstructs natural longshore sediment dynamics. For example, a significant amount of sediments from the Kelani-Ganga River were buried in the Colombo Harbor due to alteration of prominent longshore sediments transportation on the western coast of Sri Lanka. Therefore, this study shows enhancement of coastal erosion in the studied southern beaches due to a lack of sediment deposition. 相似文献
12.
T. K. Mallik M. Samsuddin T. N. Prakash V. Vasudevan Terry Machado 《Environmental Geology》1987,10(2):105-110
The thickly populated coastal zone of Kerala, India is facing severe problems due to attack of high waves during the southwest
monsoon. Systematic beach profiling at 5-km intervals was carried out along the 560-km stretch of the Kerala coast during
the pre-and postmonsoon seasons in 1984. Beach volume changes were calculated at each profile station, and the erosional and
accretional trends for the entire coastal tract were demarcated in a map. Total erosion along 55 stations is 1276 m3/m. The general erosional and acceretional trends were also found to coincide with diverging and converging littoral currents
deduced from the wave refraction diagrams. Such study at periodic intervals will be highly useful for proper management of
the coastal zone. 相似文献
13.
利用1979-2016年ERA-Interim再分析资料提供的1°×1°水汽通量和大气可降水量（PWV）数据,采用相关性分析、趋势分析法、累积距平及反距离加权（IDW）等方法,研究三江源地区PWV与水汽通量的时空分布特征和降水转化率（PCE）。结果表明:①过去38年来,经、纬向多年平均水汽通量分别为2.0 kg/（m·s）、10.3 kg/（m·s）,水汽通量纬向增幅高于经向,水汽在纬向汇入为主,经向输出为主;② PWV呈微弱增多趋势,年平均PWV为1 791.6~2 278.9 mm,季节平均PWV为122.2~1 134.2 mm,不同季节内空间差异明显;③三江源区多年平均PCE为24.6%,1989年最高,达32.8%;季节与多年平均PCE空间分布一致,都表现出由东南向西北递减的变化特征,季节分布变化差异大;④该地区空中水资源丰富但自然PCE低,开发潜力大,应用前景广阔。 相似文献
14.
Branka Ivančan-Picek Kristian Horvath Nataša Strelec Mahović Marjana Gajić-Čapka 《Natural Hazards》2014,72(2):1231-1252
The aim of this study was to identify the main mesoscale features and mechanisms responsible for the generation of an extreme precipitation event as a contribution to improving the modelling of processes that produce HPEs. The event occurred during the morning hours on 22 November 2010 over the Dubrovnik coast in Croatia and the hinterland mountain range of the southern Dinaric Alps and caused severe flash floods and landslides and consequent interruption of traffic and electricity supply as well as other infrastructural damage. The analysis is geographically focused on the southern portion of the eastern Adriatic region, which is prone to relatively frequent heavy precipitation events that occur mostly in autumn. This area is one of the rainiest in Europe with expected annual amounts of precipitation greater than 5,000 mm in the mountainous hinterland. The mechanisms responsible for the formation of convection were analysed using synop measurements, satellite data and numerical experiments performed with the WRF model, which was set up at the convection-permitting resolution in the innermost domain. Satellite data were used to identify the precipitation systems and to estimate the intensity of the precipitation during the period of interest. The development of the precipitation system was connected to a strong large-scale ascent over the southern Italy and southern Adriatic due to the advection of warm air and cyclonic vorticity advection, which increases with height. The numerical simulations highlighted the essential role of a southerly low-level jet stream in the transport of warm and moist air towards the affected area. The convergence of two branches of low-level marine air favoured convection triggered over the coast and sea. Furthermore, numerical sensitivity experiments suggested that the orography of the Dinaric Alps plays an essential role in the precipitation maximum over the mountainous hinterland, but also that the orography was not the crucial factor in the heavy precipitation near Dubrovnik. This study highlights the need for a dense network of observations, especially radar measurements, to validate the simulated mechanisms and improve numerical forecasts via data assimilation. 相似文献
15.
Angeliki Mentzafou Chrysa Vamvakaki Ierotheos Zacharias Areti Gianni Elias Dimitriou 《Environmental Earth Sciences》2017,76(6):259
The Spercheios river basin—coastal marine area is a complex natural and interdependent ecosystem, highly affected by human activities and interventions. Such sensitive systems are even more vulnerable to alterations of the hydrological cycle components and it is likely to be rapidly and severely affected by climate change. In order to examine the climate change impacts on water resources of the study area, the interaction between the hydrology of the river basin and the hydrodynamic of the coastal marine area was examined using two models. Based on the results, although the irrigation needs decrease for the years 2050 and 2100 due to corresponding decrease in cultivated areas, temperature increase and precipitation decrease are both expected to influence the water resources of the Spercheios river basin, which will directly affect the Maliakos Gulf hydrodynamics. The necessity to adopt a holistic approach which will treat river basins and coastal marine areas as an integrated whole, with regard to environmental, socio-economic and political framework, is evident. 相似文献
16.
2001-2018年石羊河流域植被变化及其对流域管理的启示 总被引：1，自引：0，他引：1
植被是流域生态系统的重要指标,植被景观管理也是流域综合管理的重要内容。综合利用长时间序列MODIS反射率和归一化差值植被指数（NDVI）产品及Landsat卫星遥感影像,基于谷歌地球引擎（GEE）平台,利用计算机自动分类的方法,监测了2001-2018年间石羊河流域的植被（包括灌溉土地）的逐年变化,结合降水、径流量和地下水位地面监测数据,分析了全流域植被指数、植被面积、灌溉土地范围的变化特征及其与水循环之间的互馈关系。研究发现,2001-2018年间,石羊河流域的植被面积以每年约135 km2的速率增加,其中,自然植被和灌溉土地分别以每年60.5 km2和74.6 km2的速率增加。除了金昌区的植被增加以灌溉土地为主外,其他区域都以自然植被的增加为主。特别是民勤地区,由于十多年的持续调水和有效退耕,地下水位近年来开始抬升,自然植被开始恢复。但与此同时,中游凉州区和永昌县的生态风险加大。未来可从灌溉规模控制、地表与地下水统一调度、景观分级和配置技术发展、优化产业结构、强化与流域外的连通性等方面加强流域综合管理,提高流域社会系统弹性,增强可持续发展能力。 相似文献
17.
中国西北C-3植物的碳同位素组成与年降雨量关系初探 总被引：13，自引：0，他引：13
本文对不同年降雨量环境下生长的藜、独行菜、魁蓟和平车前这4种常见C-3植物的δ13C进行了分析,发现这4种C-3植物的δ13C组成都表现出随年降雨量减少而变重的趋势,其中藜和独行菜的碳同位素组成对降水变化的响应相对要较其它2种植物强烈得多。藜、独行菜和魁蓟的δ13C组成与年降雨量有显著的线性关系,平车前碳同位素组成与年降雨量没有显著的相关性,表明藜、独行菜和魁蓟的δ13C组成可作为年降雨量的替代性指标,平车前的δ13C组成不能作为年降水的替代性指标。 相似文献
18.
《China Geology》2018,1(4):512-521
Shandong has more than 70% of natural coasts are under erosion. Coastal erosion started from the 1970’s and became a very serious problem at 1990’s. The dramatic decrease of sediment supplies from rivers caused rapid erosion at the delta and estuary areas, especially in the abandoned Yellow River Delta. Most sandy coasts along the Peninsula were eroded due to lack of sand supply and interruption of alongshore sediment drift, sand dredging from the beach or the offshore area caused serious erosion during short time. Sea-level rise causes slow but constant shoreline retreats and became a more serious threat. Different types of hard solutions for coastal protection against erosion were used in Shandong. Seawalls are most widely used, especially at the Yellow River Delta and city center waterfront. Groynes, jetties and breakwater are used on the north and east sandy coast of the Peninsula. Hard approaches are effective to protect the coast erosion but not change the erosion causes and led secondary impact on the coast. Soft engineering solution or the combined solutions are taken into acts. Beach nourishment is mostly considered as the better soft solution, especially to those tourists attracting sandy beaches along the Shandong coast. Long term monitoring and continuous lessons learning from the coastal erosion management will be adaptive for better coast solution in the future. 相似文献
19.
G. Muthusankar C. Lakshumanan V. Pradeep-Kishore S. Eswaramoorthi M. P. Jonathan 《Natural Hazards》2013,65(3):2401-2409
A study on the possible inundation limit in SE coast of India was carried out using various physical, geological and satellite imageries. The coastal inundation hazard map was prepared for this particular region as it was affected by many cyclones, flooding, storm surge and tsunami waves during the last six decades. The results were generated using various satellite data (IRS-P6 LISS3; LANDSAT ETM; LANDSAT-5 ETM; LANDSAT MSS) and digital elevation models (ASTER GLOBAL DEM), and a coastal vulnerability index was generated for the entire coastal stretch of Nagapattinam region in SE coast of India. The coastal area which will be submerged totally due to a 1–5 m rise in water level due to any major natural disaster (tsunami or cyclone) indicates that 56–320 km2 will be submerged in this particular region. The results suggest that nearly 7 towns and 69 villages with 667,477 people will be affected and indicate that proper planning needs to be done for future development. 相似文献
20.
为了分析和评价气候变化对水文水资源的影响,根据中国东部地区1956～2000年实测年降水量系列数据,采用多年均值、系列趋势变化指标和反映系列可持续特性的Hurst系数等3项指标,对CGCMA3、MPI-ECHAM5和平均GCM等3种气候模式模拟的同期年降水系列数据进行了检验。检验结果表明,3种气候模式模拟结果与实测值之间,以及不同模式模拟结果之间,不仅定量方面差异很大,而且在定性方面甚至出现相悖的结果,不确定性十分显著。同样,根据3种气候模式预测的未来2001～2050年年降水量和季平均气温推得的未来年径流量系列数据,其多年均值、系列趋势变化指标和干旱年年径流量多项指标也存在明显的不确定性。据此对气候模式及其应用提出了相应的建议。 相似文献