黄土高原西部土壤水分时空变化模拟研究——以安家坡流域为例   总被引：3，自引：2，他引：1  

赵传燕  冯兆东  南忠仁 《冰川冻土》2007,29(5):785-794

土壤水作为陆地水循环和水量平衡的一个重要组成部分,在土壤-植被-大气连续体物质与能量转化中起着重要的作用,成为陆面过程研究中的重要参量.选择黄土高原西部的安家坡流域,采用多点长序列观测方法,对该区域土壤水分的时空变化规律进行研究.结果表明:坡向和土地利用类型是小流域土壤水分变异的重要影响因素,得出了不同立地条件下土壤水分的剖面变化与时间的动态规律.在此基础上,利用土壤湿度指数结合主要影响因素预测土壤水分的时空变化,旨在为黄土高原大中尺度的土壤水分模拟提供思路.  相似文献   

珠穆朗玛峰地区雪冰中重金属浓度与季节变化   总被引：4，自引：0，他引：4  

段建平  任贾文  秦翔  李月芳 《地理学报》2007,62(1):22-29

对2005 年9 月采自珠穆朗玛峰北坡海拔6523 m 的东绒布冰川积累区一批雪坑样品中重金属Ba, Co, Cu, Zn 和Pb 的浓度利用电感耦合等离子体质谱仪进行了测试, 重金属浓度范围分别为(pg/ml); Ba2~227、Co2.8~15.7、Cu 10~120、Zn29~4948、Pb14~142。并利用气体稳 定同位素质谱仪MAT-252 对样品稳定氧同位素比率(δ¹⁸O) 进行了测试, 雪坑样品对应的时间为2004 年夏到2005 年秋, δ¹⁸O和重金属元素的浓度都存在着季节变化特征。在夏季风期间δ¹⁸O 值和重金属元素的浓度都很低,而在非夏季风期间δ¹⁸O值和重金属元素浓度升高,反映了不同的水汽来源对重金属浓度季节变化的影响及其环境意义。Co, Cu, Pb, Zn 的地壳富集系数(EF_c) 分别为: 3.6、27、33、180, 表明该地区Pb, Cu, Zn 已经受到了人类活动的污染, 其中Zn 受到的污染最大。  相似文献   

2000-2012年陕甘宁黄土高原区地表蒸散时空分布及影响因素     

王鹏涛  延军平  蒋冲  曹永旺 《中国沙漠》2016,36(2):499-507

分析陕甘宁黄土高原区地表蒸散变化特征及其影响因素,可以为区域水资源规划、生态环境改善提供依据。本文利用MOD16蒸散数据,统计分析了陕甘宁黄土高原区2000-2012年地表实际蒸散量的时空变化特征,并结合国家气象站点观测数据和基于像元的相关分析法探讨了其影响因素。结果表明:(1) 2000-2002年蒸散量迅速上升,在2003年达到最高值378.6 mm, 2003-2006年蒸散量呈下降趋势,2006年之后蒸散量呈现缓慢上升趋势。(2) 近13年来,陕甘宁黄土高原区多年平均蒸散量具有明显的空间差异,蒸散量自西北至东南递增,最南部的六盘山、子午岭、黄龙山地是3个主要的高值区;年蒸散量以夏季最多,其次是春季,秋季和冬季最少,且季节蒸散的分布与年蒸散的空间分布格局基本一致。(3) 陕甘宁黄土高原区蒸散量草地和耕地的贡献率最高,密灌丛、疏灌丛次之,常绿针叶林、森林草原贡献率则较小。(4) 陕甘宁黄土高原区动力因素对地表蒸散量影响以正相关为主,风速对该区影响较大;热力因素对地表蒸散量影响以负相关为主,其中气温与蒸散在空间上呈负相关的区域较大,日照时数与蒸散在空间上的负相关区域的面积次之;水分条件(降水量、相对湿度)对蒸散的影响也以正相关为主。  相似文献   

北太平洋波浪输运和西边界流的季节变化     

张坤兰  吴克俭  胡保全  毕凡 《海洋湖沼通报》2009,(4)

西边界流输运可以用Sverdrup理论推算出来.本文首先利用ECMWF再分析风场数据,计算了44年的月平均的风应力旋度及Sverdrup体积输运,在北太平洋3条纬度上对Sverdrup体积输运进行积分,得到Sverdrup体积输运的季节变化,从中发现,在向赤道流动的方向上,Sverdrup体积输运在冬季存在最大值,夏季存在最小值;同样利用ECMWF再分析波浪数据,计算了44a的月平均的Stokes体积输运,在相同纬度上对Stokes体积输运进行积分,得到Stokes体积输运的季节变化,从结果中发现,在向赤道流动的方向上,Stokes输运在冬季存在最大值,在夏季存在最小值.在本文中设定R=T_(st)/T_(sv)×100%,T_(st)为Stokes体积输运,T_(sv)为Sverdrup体积输运,发现Stokes输运和Sverdrup输运存在同位相的季节变化,并且(-R)冬季平均值在5%以上,年平均值在2%～3%左右,从而推断出波浪诱导的输运对Sverdrup输运,既对西边界流有不可忽视的贡献.  相似文献   

Long-term stability of the fish assemblages in a warm-temperate South African estuary     

Nicola C. James  Alan K. Whitfield  Paul D. Cowley 《Estuarine, Coastal and Shelf Science》2008,76(4):723-738

Little is known about long-term changes in estuarine fish populations and related environmental variations. Fishes in the temporarily open/closed East Kleinemonde Estuary were sampled bi-annually, in summer and winter, using seine and gill nets between December 1994 and July 2005. A total of 18 families, represented by 33 species, were recorded. The 10 most abundant species caught were consistently recorded in catches each year, but CPUE of individual species varied on an annual basis and this can often be related to mouth state. Multivariate analyses of the annual marine fish community identified two distinct groups, with more species recorded during years that succeeded spring (September to November) mouth-opening events than in years following no mouth-opening events in spring. Interannual community stability (IMD) and seriation (IMS) also increased from the years following no opening events in spring to the years that succeeded spring opening events. These results highlight the importance of the timing of mouth opening to the marine fish community in a temporarily open/closed estuary. This study reinforces the importance of long-term studies to understanding community changes in estuaries caused by environmental variations over different time scales.  相似文献   

Seasonal and spatial variation in abundance and egg production of Paracalanus parvus (Copepoda: Calanoida) in/out Jiaozhou Bay, China     

X.H. Sun  S. Sun  C.L. Li  G.T. Zhang 《Estuarine, Coastal and Shelf Science》2008,79(4):637-643

The spatial distribution of stage-specific abundance and reproduction of the copepod Paracalanus parvus were studied from October 2005 to September 2006 in the Jiaozhou Bay. This copepod occurred continuously in this bay throughout the year. The species reached the lowest abundance in April and peaked in June. From October to December, distribution center mainly occurred in offshore water and at the mouth of the bay. In winter, early copepodites and adults gradually decreased and till February, most of the population was only comprised of CIV–CV stages. Overwintering copepodites matured in March and males tended to mature before female. From May to September, each stage occurred in the population and gradually reached high abundance. Temperature and chlorophyll a (Chl-a) concentration in the three stations can't clearly explain the seasonal variation in stage-specific abundance, so we surmised the important effect of the Yellow Sea. Egg production rate (EPR) reached its lowest in winter and peaked in June at 60.8 eggs female⁻¹ day⁻¹ in nearshore water. In the warming period, EPR in nearshore water was statistically higher and EPR > 10 eggs female⁻¹ day⁻¹ lasted longer than that in offshore water, showing the importance of nearshore water for recruitment of P. parvus. Our study showed that EPR was positively related to temperature and total chlorophyll a in offshore water and mouth of the bay. In nearshore water, the relationships between EPR and temperature and Chl-a in three size fractions were not the same as those in offshore water, suggesting complicated ecosystem in such a eutrophic area in warming period.  相似文献   

Geomagnetic secular variations 0-2700 yr BP recorded by lake sediments from Waginger See (southeastern Bavaria)     

J. Werner  G. Michler  A. Schult 《Geophysical Journal International》1990,101(2):479-485

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Inter-annual variability in phytoplankton summer blooms in the freshwater tidal reaches of the Schelde estuary (Belgium)   总被引：1，自引：1，他引：0  

Marie Lionard  Koenraad Muylaert  Abdel Hanoutti  Tom Maris  Michle Tackx  Wim Vyverman 《Estuarine, Coastal and Shelf Science》2008,79(4):694-700

The inter-annual variability in phytoplankton summer blooms in the upper reaches of the Schelde estuary was investigated between 1996 and 2005 by monthly sampling at 10 stations. The large inter-annual variations of the chlorophyll a concentration in the freshwater tidal reaches were independent from variations in chlorophyll a in the tributary river Schelde. Summer mean chlorophyll a concentrations were significantly negatively correlated with flushing rate (Spearman correlation: r = −0.67, p = 0.05, n = 9) but not with temperature, irradiance and suspended particulate matter or dissolved silica (DSi) concentrations. During dry summers, low flushing rates permitted the development of dense phytoplankton populations in the upper part of the estuary, while during wet summers high flushing rates prevented the development of dense phytoplankton blooms. Flushing rate was also found to be important for the phytoplankton community composition. At low flushing rates, the community was dominated by diatoms that developed within the upper estuary. At high flushing rates, chlorophytes imported from the tributary river Schelde became more important in the phytoplankton community. The position of the chlorophyll a maximum shifted from the head of the estuary when flushing rates were low, to more downstream when flushing rates were high. Although DSi concentrations tended to be lower during years of high phytoplankton (mainly diatom) biomass, the relation with flushing rate was not significant.  相似文献   

广利港河道水位变化及河口拦门沙地形变化分析研究     

林维田  吴永亭  刘建立 《海岸工程》2008,27(3):9-14

根据1984年和2007年两次对广利港航道水深测量的结果，分析研究了广利港航道内的水位变化规律，以及河口拦门沙的地形特征。结果表明广利港航道内水位变化复杂，拦门沙形态改变，水深变浅，原有的航道已经消失。  相似文献   

大洋调查中海山地磁测量的静日变化校正方法   总被引：2，自引：1，他引：1       下载免费PDF全文

刘保华  刘晨光  裴彦良  阚光明 《海洋学报》2008,30(6):94-98

针对大洋调查中海山地磁测量时难以设立静日变化观测站的问题,提出了一种基于多项式拟合最小二乘算法的日变校正方法,即假设静日变化磁场可以用一个关于时间的高阶多项式来拟合,利用主测线和联络测线交点误差的最小二乘估计求得多项式的系数,从而得到静日变化曲线。从调查测得的磁场中减掉静日变化磁场即可得消除静日变化影响后的海山地磁异常。理论模型和实际资料处理都表明,这种方法不仅可以较好地消除静日变化的影响,而且用计算机实现也简单。为了提高静日变化校正结果,讨论了为提高静日变化校正效果,在大洋调查中测量海山地磁时应注意的几个问题。  相似文献