流域水文年及丰枯水期划分方法

研究流域水文年及丰、枯水期划分方法,为水文水利计算提供科学依据。通过分析流域径流变化特点,提出径流累计距平法。将该方法用于黑河上游流域,结果表明:该方法为黑河上游流域确定了合理的水文年及丰、枯水期;在不同水文年起讫日下,黑河上游流域年径流时间序列的统计特性和典型年的径流年内分配特征发生显著变化。因此,径流累计距平法可用于划分流域水文年及丰、枯水期,统一水文年划分方式对水文水利计算十分必要。     

基于“水文频率-水质”拟合曲线的河流水质变异与等级特征值分析方法

时空特征分析对全面掌握水质变异规律具有重要意义,但现有的水质时空特征分析方法仍存在水质变异次序不分、水质变幅极值不清、水质评价特征值不明等不足。为更加清晰地探析水质时空特征信息,以秦淮河为研究对象,参考工程水文学经验频率法,建立“水文频率-水质”拟合曲线用于探索流域内高/低活动区不同时间段和丰/枯水期不同河段水质变异特征,并与传统的箱线图法进行对比。结果表明:与箱线图相比,“水文频率-水质”拟合曲线可量化关键水质评判点与特征值信息,使水质时空变异过程更为清晰。在时间上“水文频率-水质”拟合曲线的最佳形式为线性曲线,水质浓度一般不会发生突变;在空间上“水文频率-水质”拟合曲线的最佳形式为指数曲线,水质浓度有较大可能发生突增。各时间段高活动区氮磷浓度大于低活动区,各水体断面丰水期氮磷浓度低于枯水期。该方法分析过程简单方便,结果直观有序,能将水质信息以统计规律自动反映出来,在水质采样点、采样时间和采样频率典型时可作为优选方法用于河流水质时空特征研究。     

陕北定边盐湖卤水水位历史演变及其气候指示意义(1265—1949年)

受自然环境和资料限制的原因,中国西北的季风边缘区内的湖泊千-百年时间尺度演变序列重建工作存在不足.历史文献中的湖泊演变信息丰富,有效利用可较好地解决这一问题.本文通过梳理历史文献记录的定边盐湖采盐方式资料,反演历史时期定边盐湖卤水水位,重建公元1265-1949年陕北定边盐湖卤水水位演变序列,该序列较好地指示出公元12...     

Evidence of Self‐Organized Criticality in riverbank mass failures: a matter of perspective?

A growing body of field, theoretical and numerical modelling studies suggests that predicting river response to even major changes in input variables is difficult. Rivers are seen to adjust rapidly and variably through time and space as well as changing independently of major driving variables. Concepts such as Self‐Organized Criticality (SOC) are considered to better reflect the complex interactions and adjustments occurring in systems than traditional approaches of cause and effect. This study tests the hypothesis that riverbank mass failures which occurred both prior to, and during, an extreme flood event in southeast Queensland (SEQ) in 2011 are a manifestation of SOC. Each wet‐flow failure is somewhat analogous to the ‘avalanche’ described in the initial sand‐pile experiments of Bak et al. (Physical Review Letters, 1987, 59(4), 381–384) and, due to the use of multitemporal LiDAR, the time period of instability can be effectively constrained to that surrounding the flood event. The data is examined with respect to the key factors thought to be significant in evaluating the existence of SOC including; non‐linear temporal dynamics in the occurrence of disturbance events within the system; an inverse power‐law relation between the magnitude and frequency of the events; the existence of a critical state to which the system readjusts after a disturbance; the existence of a cascading processes mechanism by which the same process can initiate both low‐magnitude and high‐magnitude events. While there was a significant change in the frequency of mass failures pre‐ and post‐flood, suggesting non‐linear temporal dynamics in the occurrence of disturbance events, the data did not fit an inverse power‐law within acceptable probability and other models were found to fit the data better. Likewise, determining a single ‘critical’ state is problematic when a variety of feedbacks and multiple modes of adjustment are likely to have operated throughout this high magnitude event. Overall, the extent to which the data supports a self‐organized critical state is variable and highly dependent upon inferential arguments. Investigating the existence of SOC, however, provided results and insights that are useful to the management and future prediction of these features. Copyright © 2014 John Wiley & Sons, Ltd.     

近60 a来西秦岭及周边地区降水的分布格局

基于西秦岭及周边地区15个气象站点的降水、气温等月值、年值资料,采用相关统计分析及检验的方法,研究了1951年以来该区域近60 a干湿变化的时空特征。结果表明:西秦岭及周边地区1951年以来降水量呈下降趋势,秋季降水量减少趋势最明显,速率为-18.6 mm· (10 a)^-1;而近60 a年平均气温呈上升趋势,升温速率为0.28℃· (10 a)^-1。对比气温和降水要素,西秦岭及周边地区年平均温度每升高1℃,则年降水减少37 mm,表明该区近60 a由冷湿向暖干转变。同时将气候要素与Niño3.4指数进行相关分析,结果显示在厄尔尼诺事件发生当年该区降水少,气温高,容易发生干旱。利用改进的经验正交函数法分析西秦岭及其周边地区15个气象站点的气候要素,发现该区年降水距平百分率的第一模态解释方差为49.0%,整个区域呈同向变化,而年平均温度距平第一模态解释方差为78.8%,在整个区域内亦呈现同向变化。对比两个要素第一模态显示西秦岭近60 a东部地区与西部地区相比,呈现降水减少幅度大,气温升高速率小的分布格局。     

黄河三角洲滨海地区植物生长季大气氮沉降动态

利用SCJ-302型降水降尘自动采样器在植物生长季对黄河三角洲滨海湿地的大气氮沉降进行监测,对沉降物中水溶性离子、干、湿沉降氮输入量、铵态氮和硝态氮在总沉降量中的贡献率及月变化动态等分析表明：黄河三角洲植物生长季,大气干、湿沉降中SO₄^2-和NO₃^-占阴离子总量的92%以上,和Na⁺和Ca²⁺占阳离子总量的80%以上,总N沉降量约为2 264.24 mg/m²,且69%集中在降雨量较丰沛的6-8月。其中干沉降氮贡献率约为32.02%,主要集中在春季。N的湿沉降量与降雨量呈显著正线性相关（R²=0.82）,在降雨量丰沛的8月,达到最大值675.64 mg/m²。该地区大气干沉降的氮素形态以硝态氮为主,约占氮素输入量的57.21%,湿沉降中以铵态氮为主,约占氮素输入量的56.51%。植物生长季中,大气沉降中的硝态氮与铵态氮含量对表层10 cm土壤的月平均贡献率分别为约31.38%和20.50%,可见大气氮沉降是黄河三角洲滨海区域土壤主要氮素来源之一。     

Recycling of Coastal Dredged Sediments from the Northern Nile Delta,Egypt, for Heavy Minerals Exploitation

Mineralogical and textural analyses of 45 undisturbed short cores and 80 grab sediment samples, collected from five frequently dredged navigational areas within harbors and water pathways of the Nile delta littoral system, were utilized for evaluation of these sediments as potential source of economic heavy minerals (EHMs). Results of mineralogical characterization indicate that the average total heavy mineral (HM) concentrations are as follows: Abu Qir Bay (1.7%), Rosetta estuary (3.1%), Burullus fishing port (4.5%), Damietta Harbor (2.9%), and El Gamil lagoon inlet (1.9%). Assessment of HM grades indicates predominance of magnetite, ilmenite, hematite, leucoxene, garnet, zircon, and rutile. Results of the feasibility analysis indicate that dredged sediments at these study areas are considered as a potential source of EHMs and economically promising to be mined for HMs. The present study suggests a practical operative plan of two successive phases for HMs recycling: (1) in-situ initial separation of HMs on the dredger deck using wet-gravity spirals, then (2) transportation of the recovered HM concentrates to an onshore processing plant to selectively separate individual HMs via wet and dry magnetic and electrostatic separators. Alternatively, dredged sediments can be directly pumped to a nearby onshore area as stockpile to be recycled afterward in inland processing plant.     

2010年2月辽宁地区冻雨天气诊断分析

应用常规天气资料,从天气、气候及大气物理量场等方面,对2010年2月下旬发生在辽宁地区历史罕见的冰冻雨雪灾害性天气发生发展的成因、主要特征以及造成严重灾害的主要原因进行诊断分析。结果表明：500 hPa低涡分裂的小槽东移是冻雨天气的环流背景;700 hPa源源不断的水汽输送和低层辐合作用是降水产生的基本条件。地面强冷空气是冻雨天气的触发机制;高层为冷的冰晶层,对流层中低层有温度t>0℃的暖的融化层,近地面1-2 km为气温t<0℃的冷层,同时地面达到 0℃以下,这种复杂的逆温层是冻雨产生的天气条件。高层暖平流是维持中空暖层结构的重要条件之一,对暖层的建立和破坏起较大作用,暖层消失冻雨天气也随之结束。中低空水汽饱和度、地面温度和中低空上升、下沉运动与冻雨的强度有密切关系。     

GPS气象预报的可行性分析

基于中国区域5个IGS跟踪站的实测GPS数据,利用Bernese 4.2软件反演了部分典型测站上空的可降水量,并分析了该降水量变化与降雨之间的关系,探讨了将GPS应用于气象预报的可行性.     

基于太平洋海温的冬小麦春季湿渍害预测模型

为了进一步开展冬小麦春季湿渍害的预测预报业务工作,利用江苏省1969-2008 年60 个气象站常规观测资料和冬小麦产量资料,根据场相关分析原理,将江苏省春季湿渍害3 个风险区的湿渍害指数与太平洋海温资料进行相关普查,结果表明:3 个风险区的小麦春季湿渍害指数和西太平洋海温均存在高相关区,主要位于Nino 区和西太平洋北部海区,其相关程度随时间具有一定的变化趋势;挑选出与湿渍害指数相关的强信号海区作为预报因子,通过最优化相关处理提高预报因子相关性;经稳定性和独立性检验,创建了对应3 个风险区的冬小麦湿渍害指数预测模型,所有模型均通过0.01 显著性水平检验,拟合及试报结果理想,表明预测模型具有一定应用价值。