兰江流域水文动力参数变化与兰江防洪

本文根据钱塘江重要干流兰江的地面蓄水累计曲线SPER、流域入渗曲线Holton公式参数(入渗率f、稳定入渗率fc、入渗比例系数k)、Maskingum指数(流水河段传播时间k、楔蓄系数x)、水位与水量等近30年的抽样数据,分析了兰江流域河槽导流环境、植被条件、土地性质、气象因素的变化,指出了该河段近年来洪水频发的原因,提出了治理建议.     

基于投影寻踪的洪水灾情评价插值模型

为解决单项洪水灾情等级评价指标评价结果的不相容问题,提高综合评价各层次的分辩力和评价模型的精度,本文利用投影寻踪、遗传算法、插值型曲线,为洪水灾情评价提供了一种新模型--遗传投影寻踪插值模型.通过最佳投影向量和评价指标向量的内积可把洪水灾情多维评价样本指标综合成一维投影指标,根据该投影指标值和对应等级的分布,可建立洪水灾情评价的插值模型,解决了各单项洪水灾情评价指标评价结果的不相容问题,提高了洪水灾情综合评价问题各层次的分辩力.作为示例,对中国部分省市的洪水灾情进行了综合评价.     

太湖流域水灾演变与环境变迁的相关分析

新石器时期以来,太湖地区的水灾发生机制和表现形式严格受控于海、地、气系统的能量均衡和转换过程,具有明显的阶段性特征,遵循由海洋优势性向海面控制基准下陆源洪水的演变过程.愈接近现代,成灾和干扰因素愈趋复杂,逐渐呈现出水灾与环境相互反馈使水灾加深(岗身体系形成并完善,太湖形成并扩张以来),以及人类活动、水灾与环境三者间相互反馈使水灾频度加大等趋势(尤其自南宋以来).提出了相对高海面的水灾控制基面效应和太湖水灾扩张效应等观点.     

土壤水分对沙尘暴的阈值反应--以内蒙古中西部地区为例

以2001年4月至2003年6月内蒙古中西部地区逐时观测的土壤体积含水百分率资料为基础,论述了土壤体积含水百分率的时间变化规律及其对沙尘暴的阈值反应.得到的主要结论是:(1)土壤体积含水百分率有着单峰型日波动反应,最高和最低值分别出现在午后4时和午前9时.(2)土壤体积含水百分率的月际变化基本遵循以1a为周期作简单振动的变化规律,最低值出现在3～4月.土壤体积含水百分率全年波动介于18.5%～37.3%之间,年平均值为26.5%.(3)沙尘暴的发生在土壤体积含水百分率含量一定范围内并不随土壤含水量的降低而发生明显变化,但当土壤体积含水百分率低于19.5%时,则随着土壤体积含水百分率的降低而明显增加,表现为土壤体积含水百分率有明显的阈值反应.(4)引进沙尘暴时度的概念研究了沙尘暴发生的持续时间,由沙尘暴时度与土壤体积含水百分率的指数关系发现,在时度大于200min和小于120min的两类沙尘暴中,土壤体积含水百分率每降低1%,沙尘暴时度将分别增加19.94min和10.14min.     

珠江三角洲腹地洪水位异常变化及成因分析

珠江三角洲是我国东南沿海的经济发达地区.三角洲地区的防洪安全保障对区域的社会、经济发展具有举足轻重的作用.由于三角洲地区复杂的网河及口门构成,以及径流和潮汐共同影响的水动力条件,使三角洲的洪水水势表现出随时间和空间复杂变化的动态特征.20世纪80年代以来,三角洲地区受水土资源无序开发的人类活动的影响,90年代的洪水表现出了网河腹地河段洪水位异常壅高的现象,使区域的防洪安全受到严重威胁.结合"94.6","98.6"洪水期间三角洲腹地洪水水位异常壅高现象,综合分析了区域洪水位异常壅高的外部及内在成因,为科学制订三角洲地区防洪对策提供技术依据.     

历史上的一次溃决洪水--1482年沁河流域大洪水

据沁河流域九女台洪水题刻水位及相关历史文献记载,沁河流域1482年洪水洪峰流量极大,历时甚长,与该流域一般洪水过程的差异迥然.通过地貌调查,并利用14C测年等方法,对沁河九女台河段进行了详细研究,发现其1482年高洪水位是梯沟口泥石流-崩塌堆积物堰塞沁河主河道的结果.当年由于降雨,使梯沟流域发生泥石流,并导致沟口右岸岩壁崩塌,形成堰塞坝,造成沁河河道阻塞,过水断面减小,九女台附近河段水位壅高,并保持了近40天的时间,堰塞坝最终溃决,导致沁河下游怀庆府发生严重的洪水灾害.     

单一重现期非线性暴雨强度模型参数的确定--新型混合加速遗传算法的构建与应用

对浮点编码遗传算法进行了改进,并嵌入Powell方向加速局部搜索算法与加速循环操作,从而构建了新型混合加速遗传算法.确定单一重现期的非线性暴雨强度模型参数的应用实例表明,该方法兼顾了改进浮点编码遗传算法和Powell算法的优点,是一种既可以较大概率、快速地搜索全局近似最优解,又能进行局部细微搜索的出色的非线性优化方法.该法在其它工程问题的非线性模型参数的确定中也具有广阔的应用前景.     

试论洪涝对水稻的影响

洪涝灾害是我国主要的农业气象灾害之一，水稻遭受洪涝灾害的概率较大，研究洪涝对水稻的影响具有重要的意义。通过现场试验，对水稻不同生长阶段遭受洪涝灾害的影响和不同温度下遭受淹浸后的影响进行了研究，并用数理统计方法对水稻遭受淹浸后，其产量的一系列变化作了定量的分析。     

Anthropogenic Calcium Particles Observed in Beijing and Qingdao, China

Analysis of individual particles collected at Beijing in northern China revealed that particles abundant in calcium (Ca) always constituted a large fraction of mineral particles in the urban atmosphere. The particles were characterized by cubic morphologies. The major mineral element in the particles was Ca and few or no other mineral elements were detected. A large number of the particles were in the range of diameter <1 μm, where common natural mineral particles were rarely detected. The contribution of the Ca particles to the volume of total mineral particles greatly exceeded that of other mineral particles during non-dust-storm periods and was comparable to that during dust-storm periods. Reagent film tests showed that particulate sulfate and nitrate formation on the Ca particles was similar to that on common mineral particles. These results indicate that a large portion of Ca in the atmospheric particulate matter in Beijing was from anthropogenic sources rather than from natural sources, and the anthropogenic Ca particles acted as a significant medium for the formation of sulfate and nitrate. Similar particles were also detected at Qingdao, a coastal city in northern China. Data of a dust storm event showed that Ca-abundant particles from East China arrived there and moved out of the continent, similarly to Asian dust storm particles, suggesting possible contributions of anthropogenic Ca even in Asian dust storm samples in the downstream areas. Therefore, Ca may not be a good indicator of Asian dust from natural sources. However, the Ca particles, due to their unique shapes and elemental compositions, may provide an indicator for the atmospheric dispersion of anthropogenic particulate matters in East Asia.     

Climatic and Environmental Changes in the Source Areas of Dust Storms in Xinjiang, China, during the Last 50 Years

The desert environmental changes in the source areas of dust storms occurring in Xinjiang are discussed based on the climate changes and the impacts of human activities in Xinjiang during the past 50 years. The results show that the climate in Xinjiang is changing from a warm-dry type to a warm-wet one. The warm-wet climate has been obvious since the mid-1970's, and especially the sensitivity of the regional climate change in this arid area is obviously revealed by many factors, such as the characteristics of the local climate change in south Xinjiang and north Xinjiang, the difference of climate change in the alpine zones and the basins, and the change of areas of the waters bodies. Furthermore, these factors also reveal the difference in the regional climate change between Xinjiang and central and eastern areas of China. The occurrence and development of dust storms are directly affected by the precipitation, air humidity, status of underlying surface, etc. in the arid areas. The frequency and intensity of dust storms are closely related to the natural conditions, changes of climate and desert environment, as well as the dynamic conditions (i.e., weather systems) in the source areas of dust storms. Therefore, global warming is one of the main causes resulting in the degradation of the ecological environment and the frequent occurrence of natural disasters, especially the disasters of sand drift and dust storms in the arid areas since the late-1980's, which reveals that the inland arid areas are sensitive regions to climate changes.