共查询到19条相似文献，搜索用时 218 毫秒
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对中国北方243个站点1958—2009年逐月降水资料,采用小波分析和奇异谱分析(SSA)方法,在分4区基础上,对北方不同地区降水的周期和趋势进行分析,并进行比较。结果表明,西北地区(青海区、干旱区)降水的趋势性比北方中、东部区的明显。北方中、东部区在20世纪50年代末到60年代相对多雨,而青海区、干旱区在20世纪50年代末到70年代末或80年代中相对少雨。在20世纪80年代,北方中部区降水由偏多转为偏少,而其余3个区域(北方东部区、青海区、干旱区)的降水由偏少转为偏多,发生和持续时间各不相同。近几年,北方东部区、北方中部区、青海区的降水增加,而干旱区降水下降。北方东部区、中部区、干旱区存在10年以上的长周期,北方东部区为准22年,北方中部区为准15年,干旱区为准11年,这种长周期在20世纪80年代之后变得规则且稳定。北方降水普遍存在准2～3年周期和准5年周期,其振幅有明显的年际、年代际变化,具有一定的周期性。 相似文献
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1961-2010年西北干旱区极端降水指数的时空变化分析 总被引：3，自引：0，他引：3
结合绝对阈值和百分位法定义极端降水事件的优点,提出了一种更灵敏的检测极端降水事件的方法. 该方法不仅能检测出常用降水指数无法检测到的降水量稀少地区尤其干旱区的极端降水事件,同时也能过滤掉其检测到的降水量丰富地区的虚假极端降水事件. 此方法首次被应用于统计1961年1月至2010年2月西北干旱区72个气象站点的年和季节的极端降水指数（大降水和强降水指数）,并分析了极端降水指数的时间变化趋势及其空间分布特征. 结果表明：西北干旱区春（3-5月）、秋（9-11月）、冬（12月至次年2月）三季极端降水指数无显著（P>0.05）变化趋势,夏季（6-8月）大降水的频率和降水量以及大降水降水量占总降水量的比重都显著增加;新疆地区极端降水指数为增加趋势的区域基本都分布在海拔较高（约海拔1 000 m以上）的地区;西北干旱区东部极端降水指数变化趋势的空间分布有明显的季节差异,表现为夏、秋季大部分地区为增加趋势,冬、春季大部分地区为减小趋势. 相似文献
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将秦岭淮河以北、90°E以东的广大地区呈现“多雨” 格局的年份称为“北方多雨年”,其中105°N以东地域降水偏多的年份称为“北方东部多雨年”。综合利用历史文献记录、树木年轮代用记录和降水量资料来确定近五百年间的北方多雨年份和北方东部多雨年份,并建立历史年表(1470～2007年)。指出,在过去的538年间有北方多雨年97年(发生率18.0%)和北方东部多雨年174年(发生率32.3%),二者均呈现阶段性集中出现的特点,各有6个长约 20～40年的频繁发生时段。在北半球和东亚气候相对温暖的时段内,北方多雨年和北方东部多雨年的发生频率明显地高于气候相对寒冷的时段,这意味着在未来气候变暖的背景下,我国的降水分布将可能出现北方多雨年频繁出现的情形。在最近百年的全球大范围急剧升温时段,北方多雨年的发生频率仅表现为高于冷时段而已,并未呈现随增温速率的加快而同步增高,这表明北方多雨年的发生率与温度背景并非简单的线性关系。 相似文献
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基于线性倾向估计、小波分析、Mann-Kendall检验及空间插值等方法,对1962—2013年28个均匀分布在青海省内的气象站点数据近50 a(1962—2013年)极端降水事件的时空特征进行了分析。结果表明,在长期趋势上青海省极端降水事件呈上升趋势,其强度与频数变化分别具有28 a和15 a±的主周期,并且少数站点在20世纪90年代发生突变;青海省内的极端降水事件在空间上存在明显差异,整体呈自西向东逐渐增强的特征,极端降水事件在南部地区发生频率总体高于北部地区,东南部发生极端降水的频率最高;近50 a青海省内大部分地区极端降水事件的强度与频数均呈上升趋势,其中东北部地区极端降水事件的强度上升趋势较为明显,仅有东南端与西北端呈现下降趋势,极端降水事件频数的上升趋势由东南端及西北端分别向中部加强。 相似文献
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西北干旱区近50年气候变化特征与趋势 总被引：1，自引：0，他引：1
20世纪后期全球增暖趋势越来越明显，受全球增暖的影响，西北地区的气候也将受到不同程度的影响。选取了西北干旱区1951-2000年的21个代表站点气温、降水量资料，采用趋势系数法对西北干旱区近50年气温和降水变化进行分析，找出各分区的变化趋势。结果表明：近50年西北干旱区气温呈上升趋势（0．22℃／10a），1986年后气温明显升高；柴达木盆地和新疆北部升温较大；各季都有增温趋势，贡献最大的是秋冬两季。降水变化有增加的趋势（3．2mm／10a），年降水量贡献最大的是夏季；各区降水都有增加，其中新疆北部降水增加最多。西北干旱区近50年气温升高趋势是南北高，中间低；降水量增加趋势从东南向西北呈现递增的格局。 相似文献
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1981-2006年西北干旱区NDVI时空分布变化对水热条件的响应 总被引：5，自引：1，他引：4
气候是植被变化的重要驱动因子. 利用1981-2006年GIMMS归一化植被指数（NDVI）时间序列数据,结合68个气象站降水、气温数据和DEM地形数据等资料,研究分析了西北干旱区植被活动的年、季变化和空间差异. 结果显示：在1981-2006年的26 a,西北干旱区植被的覆盖率增加了4.5%,年平均NDVI增加了3.2%;植被的生长季延长,主要表现在生长季的推迟. 从总体来说,植被覆盖率、生长季和NDVI值在2000年以前显著增加,而在2000年以后都呈现减小的趋势;其中,减少明显的区域是在伊犁河谷、中天山及平原区,在河流上游山区或源头以及部分河流两岸呈现增加态势;在年际变化上,大部分区域的气温、降水与NDVI相关性不强. 而年平均气温在4.58 ℃以下低温区和年降水在180 mm以上的相对湿润区,气温和降水都呈现正相关;在季节变化上,NDVI值在春季和秋季与温度相关显著,而夏季与降水相关性强. 2000年以后,植被覆盖率和NDVI值开始出现降低趋势与气温持续升高、降水量增幅下降有关. 相似文献
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1961-2016年四川地区不同量级不同持续时间降水的 时空特征分析 总被引：1，自引：0，他引：1
利用四川地区122站逐日降水数据,采用均值、气候趋势系数等统计方法,对1961-2016年不同量级不同持续时间降水的空间和时间变化特征进行了分析,结果表明：盆地和攀西地区小雨、中雨、大雨和总暴雨所占年降水量比例接近,高原地区小雨降水量约占50%以上,中雨约40%,大雨约10%;整个四川地区小雨日数占总降水日数75%以上,量级越高降水日数越少。年降水量在盆地和攀西地区为减少趋势,高原则相反,年降水日数除了在高原局部微弱增加外其他地区皆减少且大部分区域减少趋势通过99%的显著性水平检验,这种趋势显著性主要体现在小雨量级降水。随着降水量级的增加,高原、盆地东北、攀西和盆地东南的部分地区出现了降水量和降水次数增加趋势,这可能说明高原地区年降水量的增加由小雨量级降水效率以及中雨和大雨降水次数增加导致,盆地和攀西部分地区年降水量的增加主要由降水量级大的降水次数增加导致。 相似文献
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降水观测误差修正对降水变化趋势的影响 总被引：4，自引：2，他引：2
依据中国气象局国家气候数据中心提供的660个气象站1951-2004年逐日气温、降水、风速资料, 以及雨雪类型资料, 在乌鲁木齐河源降水误差对比观测试验基础上, 对我国的降水资料进行了系统的修正计算. 这一修正不仅使降水量在数量上增加, 更接近实际值, 同时由于相关气象要素的变化, 还会对降水的长期变化趋势产生影响, 通过对比分析原始观测降水系列和修正后的降水系列的长期变化趋势, 结合理论分析估计这一影响的大小.结果表明: 我国观测和修正后的全国面积加权平均降水量分别为565.2 mm和654.9 mm, 平均修正量为89.7 mm (16%);修正后的降水系列, 绝对趋势大于实际观测系列趋势, 而相对趋势则小于观测系列. 全部台站统计结果表明, 实际的降水变化趋势被低估了6%, 而相对变化趋势被高估了约10%. 同时, 由于我国大部分地区风速呈减少趋势, 导致降水观测误差减小, 结果实际的降水变化趋势远小于观测资料显示的趋势值, 1955-2004年全国实测降水的变化趋势为-1.9 mm·(10a)-1, 而修正后降水的变化趋势高达-6.0 mm·(10a)-1. 目前依据实测的降水观测资料得出的降水变化趋势远远小于实际的变化趋势. 相似文献
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ZHU Jun 《中国地球化学学报》2005,24(4):352-360
The distribution of nutrients (N, P, Si, C) in the Wujiang River surface water was studied during the high-flow and low-flow periods in 2002. The results showed that nitrate nitrogen (NO3-N) is the main form of dissolved inorganic nitrogen (DIN) in the Wujiang River Basin. It accounts for about 90% of DIN. The average NO3-N concentrations in the mainstream are 147.5 μM in the high-flow period and 158.0 μM in the low-flow period, respectively. The average concentrations of total phosphorus (TP) are 6.43 μM in the high-flow period and 4.18 μM in the low-flow period, respectively. Of the various forms of phosphorus, particulate phosphorus (PP) has the highest percentage ( 62.9%) of TP in the high-flow period. In the low-flow period, however, phosphate is the main form of phosphorus, which accounts for 49% of TP. With the Wujiangdu Reservoir as the boundary, the concentrations of DIN and phosphorus in the upper reaches are different from those in the lower reaches of the Wujiang River. As a whole, the concentrations of DIN and phosphorus are both higher in the low-flow period than in the high-flow period. The spatial and temporal variations of DIN and phosphorus concentrations suggested that DIN and phosphorus come from agricultural and domestic wastewaters and groundwaters and that the Wujiangdu Reservoir has an important impact on the concentrations and distribution of DIN and phosphorus in the Wujiang River. The distribution patterns of dissolved silica (DSi) and dissolved organic carbon (DOC) are similar. Both of them maintain no change in the whole course of the river and their concentrations (with the exception of the reservoir itself) are higher in the high-flow period than in the low-flow period. The average DSi and DOC concentrations in the mainstream are 85.4, 84.6 μM in the high-flow period and 60.8, 53.9 μM in the low-flow period, respectively. The concentrations of nutrients in most of the major tributaries are lower than in the mainstream. This suggested that the contributions of most tributaries are relatively small but importance should be attached to the influence of some individual tributaries such as the Qingshuijiang River and the Weng'an River on the mainstream. 相似文献
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Jing Liu Siliang Li Jun Zhong Xuetao Zhu Qingjun Guo Yunchao Lang Xiaokun Han 《中国地球化学学报》2017,36(4):611-618
While it is critical to accurately understand the sources and transformation of sulfate based on time-series analysis, there are limited studies on temporal variation of sulfate in rivers and on rock weathering by sulfuric acids. We conducted a monthly sampling campaign in the Beipan, Nanpan, and Hongshui Rivers over the course of one hydrological year. This study examined seasonal variations in riverine sulfate impacted by the monsoon climate in the upper reaches of the Xijiang River basin. In general, the SO4 2? contents in these rivers dropped from relatively high levels to low values during the high-flow season, in response to increasing discharge. The sulfate was generally enriched in heavy isotopes during the low-flow season compared to the high-flow season. The calculated results indicate that the riverine sulfate was mainly derived from sulfide oxidation, but that evaporite dissolution could be an important source during the low-flow season, based on isotopic evidence. Mine drainage is likely an important source of sulfate to these rivers during the high-flow season due to contributions from fast surface flow, which responds to frequent heavy rain in monsoonal climate regions. A relatively high proportion of HCO3 ? was found to be derived from rock weathering by sulfuric acid during the high-flow season when compared to that observed during the low-flow season. The results suggest that approximately one quarter of the HCO3 ? in the Hongshui River originated from carbonate weathering by sulfuric acid derived from the oxidation of sulfide. Such information on the specific dual isotopic characteristics of riverine sulfate throughout a hydrological year can provide unique evidence for understanding the temporal variability of sulfate concentrations and weathering processes in rivers. 相似文献
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研究干旱半干旱典型区域降水的动态变化及未来走向有助于应对气候变化。采取线性回归、Mann-Kendall趋势检验、小波分析的方法探讨青藏高原1961—2019年降水量的变化特征。结论如下：（1）降水量整体上均呈现增长趋向,春冬季上升趋势最强,且春季降水对年降水量贡献率存在骤增现象。（2）春冬两季的降水量和年降水量的趋势检验均为显著增加,降水量分别于1996年、1982年和1998年起快速上升,夏秋两季检验结果不显著。（3）年降水量震荡最显著的周期为1 a,结果亦显示未来降水处于偏高期。研究显示：青藏高原降水量增加势头不变,春冬季降水量将持续增加并显著影响年降水量,全球需发展低碳经济以减缓冰川消融进程。 相似文献
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A major assumption of the Empirical Transport Model (ETM), widely adopted by both electric utilities and regulatory agencies
for estimating the effects of entrainment mortality on fish populations in estuaries, is that the fraction of ichthyoplankton
entrained varies only in response to changes in water withdrawals, not to changes in freshwater flow. We evaluated this assumption
using a particle-tracking model to estimmate the probability of entrainment at power plants on the Hudson River during low
and high freshwater flow periods and comparing those probabilities with estimates calculated from the ETM. We found that freshwater
flow had a profound effect on the probability of entrainment. Both the number of river regions from which particles were entrained
and the probabilities of entrainment for particles in those river regions differed between low-flow and high-flow periods.
During high flow, particles spent less time in the grid box next to the intakes, reducing the probability of entrainment for
particles released in the river region of each power plant and the average probability of entrainment across all regions at
three power plants. The reduced probability of entrainment for particles released in the river regions of two power plants
was offset by higher entrainment for particles upriver of these power plants. Although the average probabilities of entrainment
across all river regions estimated with the particle-tracking model and the ETM were relatively similar for some power plants
at high flow, low flow, or both, the probabilities for each river region differed considerably between the models. The number
of river regions from which particles were entrained using the ETM was consistently undersestimated, resulting in probabilities
for regions where entrainment occurred that were biased high compared with the particle-tracking model. 相似文献
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Surface water gross primary production potential (pGPP), respiration (RESP), metabolism potential (pMET), and CO2 fluxes in Hilo Bay, Hawai’i, USA, were examined along two river plumes during storm (high-flow) and non-storm (low-flow)
conditions. Significant differences in pGPP, RESP, and pMET were found between low- and high-flow conditions, with lowest
rates of all processes occurring during high-flow conditions. CO2 fluxes were influenced by metabolic processes at all but one site, with the bay’s surface waters being autotrophic and a
sink for atmospheric CO2 during low-flow conditions and less autotrophic and a source of atmospheric CO2 during high-flow conditions. Significant differences in pMET were found between the two river plumes during low-flow conditions
at spatial scales of 1.5 km; however, no differences between river plumes were found during high-flow conditions. Our study
suggests that an increase in storms associated with global climate change could impact surface water metabolic dynamics of
tropical estuaries. 相似文献
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西北干旱区和黄土高原大气边界层特征对比及其对气候干湿变化的响应 总被引：5，自引：2，他引：3
利用西北干旱区民勤、 黄土高原平凉和榆中3站2006-2009年1、 4、 7月和10月逐日08:00时和20:00时探空资料、 降水和日最高气温, 计算和对比分析了最大混合层厚度(ML)、 逆温层特征和垂直温湿场及其对干湿气候变化形成的影响. 结果表明: 最大混合层厚度与最高地气温差关系较为密切, 呈显著正相关, 干旱区民勤较密切其相关系数达0.92. 最大混合层厚度4月最深厚, 干旱区民勤高达2 871 m, 明显高于黄土区两站200~400 m左右, 平凉最为浅薄, 1月不足1 000 m; 但日降水量≥5 mm的降水发生时榆中较深厚, 高于其他两站300~400 m. 强降水发生前后干旱区湿度变化大, 发生时高低空湿度迅速增大, 而黄土高原变化湿度小, 榆中中低层增湿较明显. 干旱区近地层较干, 但有降水时中高层增湿较黄土高原显著. 干湿气候变化与最大混合层厚度、 逆温层的频数和强度、 近地面层的干湿程度关系密切, 混合层越深厚, 逆温层多而强, 近地层越干, 干旱加剧. 相似文献
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中国东部季风区和西北干旱区分别受控于季风和西风环流,是全球变化响应的敏感区域.过去50年全球升温,西北干
旱区降水显著增加,而东部季风区的降水变化不明显.在未来全球继续变暖的情况下,两个地区降水将如何变化尚不清楚.利
用湖北神农架三宝洞和新疆特克斯科桑洞的石笋生长速率记录,考察它们对降水变化的响应,研究冰期-间冰期旋回中两地
的降水变化及其差异,为未来气候变暖下的中国降水模型预测提供一个验证实例.研究表明,500ka以来中国东部季风区和西
部干旱区降水呈现冰期-间冰期波动变化,气温偏高的间冰期降水量大.但是,中国西北干旱区降水的响应滞后于东部季风
区,指示两地降水对温度变化的响应可能并非完全同步. 相似文献
19.
Groundwater recharge in natural dune systems and agricultural ecosystems in the Thar Desert region, Rajasthan, India 总被引：2，自引：1，他引：1
Bridget R. Scanlon Abhijit Mukherjee John Gates Robert C. Reedy Amarendra K. Sinha 《Hydrogeology Journal》2010,18(4):959-972
Water and nutrient availability for crop production are critical issues in (semi)arid regions. Unsaturated-zone Cl tracer data and nutrient (NO3 and PO4) concentrations were used to quantify recharge rates using the Cl mass balance approach and nutrient availability in the Thar Desert, Rajasthan, India. Soil cores were collected in dune/interdune settings in the arid Thar Desert (near Jaisalmer) and in rain-fed (nonirrigated) and irrigated cropland in the semiarid desert margin (near Jaipur). Recharge rates were also simulated using unsaturated zone modeling. Recharge rates in sparsely vegetated dune/interdune settings in the Jaisalmer study area are 2.7–5.6 mm/year (2–3% of precipitation, 165 mm/year). In contrast, recharge rates in rain-fed agriculture in the Jaipur study area are 61–94 mm/year (10–16% of precipitation, 600 mm/year). Minimum recharge rates under current freshwater irrigated sites are 50–120 mm/year (8–20% of precipitation). Nitrate concentrations are low at most sites. Similarity in recharge rates based on SO4 with those based on Cl is attributed to a meteoric origin of SO4 and generally conservative chemical behavior in these sandy soils. Modeling results increased confidence in tracer-based recharge estimates. Recharge rates under rain-fed agriculture indicate that irrigation of 20–40% of cultivated land with 300 mm/year should be sustainable. 相似文献