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441.
In arid regions, mountains fulfill important ecological and economic functions for the surrounding lowlands. In the scenario of global warming, mountain ecosystems change rapidly, especially in the arid region of northwestern China. This paper provides an assessment of the changes in temperature and precipitation in the historical records of climate on the northern slopes of the eastern Tianshan Mountains. A Mann-Kendall nonparametric trend and Sen's tests are employed to analyze the interannual changes and innerannual variability in temperature and precipitatiofi in the regions of low to high altitude. The present study finds that the largest increases in annual temperature are observed at stations in the low altitude regions. The significant increasing trends in temperature tend to occur mainly in late winter and early spring at stations from middle to high altitude, but in summer and autumn at stations of low altitudes. The increasing trends in annual precipitation are found from the middle to high altitude areas, but decreasing trends are found in the low altitude areas. The significant increasing trends in precipitation occur mostly in winter and earlier spring at stations from the middle to high altitudes, while the increasing and decreasing trend coexists at stations of low altitude with most of the significant trend changes occurring in March, June and August. 相似文献
442.
气候因子影响天山北坡植被指数时空分布研究 总被引:7,自引:0,他引:7
利用2000—2004年逐月的MODIS归一化植被指数(NDVI)数字影像,计算了天山北坡NDVI动态变化与气温、降水变化的相关关系。在此基础上,分析了NDVI变化的区域分布规律,探讨气温、降水对NDVI动态变化的驱动作用,研究了NDVI变化的气候因子驱动的区域分布规律,并据此对天山北坡植被NDVI变化的气候因子驱动进行了分区。结果表明,研究区的植被状况主要受气温和降水的复合影响,气温主导影响区域主要分布在天山中高覆盖度林区和绿洲农区过渡带以及NDVI≤0.25的荒漠区区域内。 相似文献
443.
444.
近30 年渤海水文和气象状况的长期变化及其相互关系 总被引:20,自引:3,他引:20
利用线性回归方法对渤海和北黄海西部沿岸 7个海洋站 1 965— 1 997年实测海洋表层水温和盐度及地面气温和降水等 4个水文气象要素的长期变化趋势作了分析 ,得出渤海在这 32年期间海表温度年变率为 0 .0 1 5℃ /a ,由此推算得出 32年升高 0 .48℃ ;海表盐度年变率为 0 .0 4 2 /a ,32年升高 1 .34;气温年变率为 0 .0 34℃ /a ,32年升高 1 .0 9℃ ;降水年变率为- 2 .73mm/a,32年减少 87mm。这 4个要素之间及其与厄尔尼诺指数之间的超前 /滞后线性回归分析表明 ,海温与气温的年际变化相关关系最密切 ,相关系数达到 76.5 % ,置信度高于0 .99。其次是盐度与降水 ,它们之间亦有良好关系。同年盐度和降水之间的相关系数为- 43.6% ,盐度落后降水一年时相关系数为 - 39.2 % ,置信度均高于 0 .95。由此可推知 ,盐度变化平均落后降水约半年。渤海水文气象状况变化与厄尔尼诺有一定关系 ,其中以降水与厄尔尼诺关系最密切 ,1 982— 1 983年厄尔尼诺期间渤海气温和水温较高 ,降水显著偏少且海水盐度显著偏高。 相似文献
445.
J. Sjöström 《Environmental Geology》1993,21(4):219-226
The groundwater chemistry of 14 shallow wells and 10 springs in Halland, southwest Sweden, and precipitation have been studied in trilinear diagrams. Ionic strength and saturation index (SI) for selected minerals have been calculated. Five springwaters have similar chemical composition to that of the precipitation, which indicates surficial and rapidly recharged water. The SI of the groundwaters is out of equilibrium (undersaturated) with respect to primary silicates such as mafic minerals, feldspar, K-mica and chlorite, but in equilibrium with solid SiO2 (quartz, cristobalite, or chalcedony). The SI shows oversaturation conditions for kaolinite, hydroxy-Al interlayered vermiculite, Na,K,Mg-beidellite, Mg-montmorillonite, and AB-montmorillonite. Concentrations of soluble Al and Si can be governed by Mg,Fe-beidellite, BF-montmorillonite, or Ca-montmorillonite at four springs, and by halloysite at two wells on the coastal plain. For these groundwaters, clay minerals may act as H+ buffers and thus have an influence on pH and toxic Al, i.e., parameters affecting the drinking water quality and environment. The study shows that the soil catena are intensily weathered at the investigated sites. It is further concluded that neither cation exchange nor primary silicate weathering will keep up with buffering the acidic loads into the soils. A general prediction of groundwater quality is presented. 相似文献
446.
本文利用EOF展开,对我国西部树轮指数和降水场进行了讨论,分别计算了降水和树轮的第一、第二主成份的周期。结果表明我国西部树轮和降水在空间与时间上都有着较好的对应关系。在此基础上,通过稳健回归方法对树轮和降水的传输函数进行了研究。 相似文献
447.
The paper analyses the causes of flood occurrence in the Gran La Plata, Buenos Aires Province, Argentina, and the changes
that have occurred since the 1970s. The area is characterized by serious deficiencies in the use and management of water resources.
The main factors are: (1) flood risk information is not updated; (2) urban building organization does not consider the flood
risk; (3) the topography and other physical features are not taken into account in urban development. This research considers
some specific problems, especially in data availability, and suggests ways to solve them, including improved analytical methodology.
One of the main objectives is to analyse flood risk in social terms, producing a map of flood risk from the “human social
vulnerability” point of view. The results suggest that flood risk has increased since the 1980s and that this is associated
with changes in precipitation patterns that have also been aggravated by lack of controls on urban development. The poorer
areas with the lowest level of infrastructure and public services, many of them developed over the last quarter-century, are
especially vulnerable. 相似文献
448.
449.
本文是祁连山夏季地形云结构和微物理过程模拟的第II部分。文中利用第I部分中祁连山夏季两个地形云降水个例的模拟结果,详细分析了地形云及其降水发展期间云微物理过程的特征及变化,并通过与平坦地面条件下模拟结果的对比,研究了云发展过程中的地形影响。研究表明,地形云中微物理过程的发展受地形影响很大,冰相微物理过程明显增强;地形影响下云的主要降水机制也受到影响甚至被改变。 相似文献
450.
Melanie Louise Inez Witt Stephen Skrabal Robert Kieber Joan Willey 《Journal of Atmospheric Chemistry》2007,58(2):89-109
Significant quenching of fluorescence by Cu in rainwater samples from southeastern North Carolina demonstrates that chromophoric
dissolved organic matter (CDOM) is an effective ligand for Cu in rainwater. A strong inverse correlation between the decrease
in fluorescence upon Cu addition and CDOM abundance suggests the presence of excess binding sites for Cu in high CDOM samples.
Electroanalytical studies indicate that CDOM extracted from C18 cartridges formed Cu complexes with concentrations and conditional stability constants similar to ligands found in ambient
rainwater. When authentic rainwater samples were photolyzed with simulated sunlight both photoproduction and photodestruction
of ligands were observed, suggesting the photochemical response of Cu-complexing ligands in rainwater is the result of two
competing reactions. The rate of CDOM photobleaching was directly related to changes in strong ligands (KCuL ∼ 1015) whereas weaker ligands (KCuL < 1013) were not correlated, suggesting the photolabile CDOM resides in the strong ligand class. A photolysis study comparing filtered
and unfiltered rainwater samples indicated that Cu-complexing ligands adsorbed onto or otherwise associated with particles
are photodegraded much more rapidly than dissolved ligands. Photolysis with UV radiation appears to be most effective at engendering
changes in Cu ligands, however a significant photochemical response was also observed when samples were exposed to photosynthetically
active radiation with wavelengths greater than 400 nm. Results from this study demonstrate that complexation of Cu by CDOM
has important ramifications for controlling both the speciation of the metal and the reactivity of CDOM in rainwater. 相似文献