INFLUENCES OF LOW-FREQUENCY MOISTURE TRANSPORTATION ON LOW FREQUENCY PRECIPITATION ANOMALIES IN THE ANNUALLY FIRST RAINY SEASON OF SOUTH CHINA IN 2010

85-station daily precipitation data from 1961-2010 provided by the National Meteorological Information Center and the NCEP/NCAR 2010 daily reanalysis data are used to investigate the low-frequency variability on the precipitation of the first rain season and its relationships with moisture transport in South China,and channels of low-frequency water vapor transport and sources of low-frequency precipitation are revealed.The annually first raining season precipitation in 2010 is mainly controlled by 10-20 d and 30-60 d oscillation.The rainfall is more(interrupted) when the two low-frequency components are in the same peak(valley) phase,and the rainfall is less when they are superposed in the inverse phase.The 10-20 d low-frequency component of the moisture transport is more active than the 30-60 d.The10-20 d water vapor sources lie in the South India Ocean near 30° S,the area between Sumatra and Kalimantan Island(the southwest source),and the equatorial middle Pacific region(the southeast source),and there are corresponding southwest and southeast moisture transport channels.By using the characteristics of 10-20 d water vapor transport anomalous circulation,the corresponding low-frequency precipitation can be predicted 6 d ahead.

Modeling Rainfall Intensity-Duration-Frequency (IDF) and Establishing Climate Change Existence in Uyo-Nigeria Using Non-Stationary Approach

This study aims at establishing if climate change exists in the Niger Delta environment using non-stationary rainfall Intensity-Duration-Frequency (IDF) modelling incorporating time-variant parameters. To compute the intensity levels, the open-access R-studio software was used based on the General Extreme Value (GEV) distribution function. Among the four linear parameter models adopted for integrating time as a covariate, the fourth linear model incorporating scale and location with the shape function constant produced the least corrected Akaike Information Criteria (AICc), varying between 306.191 to 101.497 for 15 and 1440 minutes, respectively, selected for calibration of the GEV distribution equation. The non-stationary intensities yielded higher values above those of stationary models, proving that the assumption of stationary IDF models underestimated extreme events. The difference of 13.71 mm/hr (22.71%) to 14.26 mm/hr (17.0%) intensities implies an underestimation of the peak flood from a stationary IDF curve. The statistical difference at a 95% confidence level between stationary and non-stationary models was significant, confirming evidence of climatic change influenced by time-variant parameters. Consequently, emphasis should be on applying shorter-duration storms for design purposes occurring with higher intensities to help reduce the flood risk and resultant infrastructural failures.

Dynamic Stability Analysis of Caisson Breakwater in Lifetime Considering the Annual Frequency of Severe Storm

In the dynamic stability analysis of a caisson breakwater, most of current studies pay attention to the motion characteristics of caisson breakwaters under a single periodical breaking wave excitation. And in the lifetime stability analysis of caisson breakwater, it is assumed that the caisson breakwater suffers storm wave excitation once annually in the design lifetime. However, the number of annual severe storm occurrence is a random variable. In this paper, a series of random waves are generated by the Wen Sheng-chang wave spectrum, and the histories of successive and long-term random wave forces are built up by using the improved Goda wave force model. It is assumed that the number of annual severe storm occurrence is in the Poisson distribution over the 50-year design lifetime, and the history of random wave excitation is generated for each storm by the wave spectrum. The response histories of the caisson breakwater to the random waves over 50-year design lifetime are calculated and taken as a set of samples. On the basis of the Monte Carlo simulation technique, a large number of samples can be obtained, and the probability assessment of the safety of the breakwater during the complete design lifetime is obtained by statistical analysis of a large number of samples. Finally, the procedure of probability assessment of the breakwater safety is illustrated by an example.

RELATIONSHIPS BETWEEN ZONAL WIND ANOMALIES IN HIGH AND LOW TROPOSPHERE AND ANNUAL FREQUENCY OF NW PACIFIC TROPICAL CYCLONES

Relationships between large-scale zonal wind anomalies and annual frequency of NW Pacific tropical cyclones and possible mechanisms are investigated with the methods of correlation and composition. It is indicated that when A U2oo- A U850 〉0 in the eastern tropical Pacific and A U2oo- A U850 〈0 in western tropical Pacific, the Walker cell is stronger in the Pacific tropical region and the annual frequency of NW Pacific tropical cyclone are above normal. In the years with zonal wind anomalies, the circulation of high and low troposphere and the vertical motions in the troposphere have significant characteristics. In the time scale of short-range climate prediction, zonal wind anomalies in high and low troposphere are useful as a preliminary signal of the annual frequency prediction of NW Pacific tropical cyclones.

Regional Frequency Analysis of Observed Sub-Daily Rainfall Maxima over Eastern China

Based on hourly rainfall observational data from 442 stations during 1960-2014, a regional frequency analysis of the annual maxima （AM） sub-daily rainfall series （1-, 2-, 3-, 6-, 12-, and 24-h rainfall, using a moving window approach） for eastern China was conducted. Eastern China was divided into 13 homogeneous regions： Northeast （NE1, NE2）, Central （C）, Central North （CN1, CN2）, Central East （CE1, CE2, CE3）, Southeast （SE1, SE2, SE3, SE4）, and Southwest （SW）. The generalized extreme value performed best for the AM series in regions NE, C, CN2, CE1, CE2, SE2, and SW, and the generalized logistic distribution was appropriate in the other regions. Maximum return levels were in the SE4 region, with value ranges of 80-270 mm （1-h to 24-h rainfall） and 108-390 mm （1-h to 24-h rainfall） for 20- and 100 yr, respectively. Minimum return levels were in the CN1 and NE1 regions, with values of 37-104 mm and 53-140 mm for 20 and 100 yr, respectively. Comparing return levels using the optimal and commonly used Pearson-III distribution, the mean return-level differences in eastern China for 1-24-h rainfall varied from -3-4 mm to -23-11 mm （- 10%-10%） for 20-yr events, reaching -6-26 mm （-10%-30%） and -10-133 mm （-10%-90%） for 100-yr events. In view of the large differences in estimated return levels, more attention should be given to frequency analysis of sub-daily rainfall over China, for improved water management and disaster reduction.

Low Frequency Characteristics of Tropical Pacific Wind Stress Anomalies in Observations and Simulations from a Simple and a Comprehensive Models

Low frequency characteristics of tropical Pacific wind stress anomalies in observation and simulations from the CZ simple atmospheric model and COLA R15 AGCM are analyzed.The results show that ENSO event may be a multi-scale process,that is,ENSO time scale has the period longer than three years; biennial oscillation and annual variability.Dynamical characteristics are involved in the evolution process of wind stress anomaly with ENSO time scale: 1) the development and eastward movement of a cyclonic anomaly circulation in subtropical northwestern Pacific and weakening of Southern Oscillation result in the eastward propagation of westerly anomaly along the equator,therefore,interactions between flows in subtropics and in tropics play an important role in the evolution of wind stress anomaly with ENSO time scale; 2) easterly and westerly anomalies with ENSO time scale are one kind of propagating wave,which differs from Barnett's (1991).It is interesting that the evolution of observed and simulated wind stress anomalies with biennial time scale bears a strong resemble to that with ENSO time scale although their period is different.Observed annual variability is weak during 1979-1981 and intensified after 1981,especially it reaches to maximum during 1982-1984,and the spatial structure of the first mode is the ENSO-like pattern.

基于物元可拓法的高潜水位煤矿区土地损毁程度评价

高潜水位煤矿区井工开采造成了地面塌陷积水、农田减产等情况,但积水农田的损毁程度、损毁范围较难获取;加之高潜水位煤矿区采煤沉陷土地具有典型的不确定性和模糊性,因此,科学进行土地损毁程度评定成为矿区土地复垦方案编制和受损农民补偿标准制定的理论基础。采用熵权法确定积水时长、下沉深度、倾斜变形(东西方向,南北方向)、曲率(东西方向,南北方向)、水平变形(东西方向,南北方向)和水平移动(东西方向,南北方向)10种指标的权重,将极限条件法和可拓评价方法相结合,对芡实地、水稻玉米田和莲藕池共计34个评价单元的土地损毁程度进行评价。研究结果表明:芡实地总面积为444.7hm^(2),中度损毁面积为135.7hm^(2),占比30.51%;水稻玉米田总面积为747.2hm^(2),整体属于轻度损毁状态;莲藕池总损毁面积为562.6 hm^(2),中度损毁面积为151.8 hm^(2),占比26.98%;研究区整体土地损毁程度较好。研究结论为科学确定土地损毁程度及范围提供理论支撑,对地区土地复垦方案编制及损毁补偿标准制定具有重要意义。

关于变频多联机APF能效试验中针对低温制冷实测时准确性的检讨和建议

目前我国多联机变频空调机组均采用全年性能系数(APF)替代IPLV作为评价指标。基于现有多联变频空调器的调节范围广的特点,指出了现有APF中对于选择性试验即低温制冷工况实测时,会出现不符合实际的情况,利用实测数据和理论分析产生的原因,水平展开,并给出了针对实测的改进建议。

WAVELET ANALYSIS OF INTERANNUAL VARIATION OF TROPICAL CYCLONES IN GUANGDONG

Climatological laws are studied for the annual frequency of tropical cyclone occurrence and the date of the yearly first landfall, which take place in the Guangdong province or pose serious threats on it from 1951 to 1999, using the data in the Yearly Book on Typhoons. A new method that has developed over recent years for the study of temporal sequences, the wavelet analysis, is used, in addition to more common statistical approaches. By analyzing two wavelet functions, MHAT and MORLET, we have compared the results of transformation of the wavelets provided that other conditions remain unchanged. It is discovered that the variance of MORLET wavelet has better indication of primary periods; period-time sequence charts can reflect major affecting periods for individual sections of time; when compared with the original sequence, the chart shows a little shift. On the other hand, such shift is absent in the MHAT wavelet, but its higher frequency part of variance covers up the primary periods to make its variance less predominant as compared to the MORLET wavelet. Besides, the work compares two different assumptions of an amplifying factor a. It is found that primary periods can be shown more clearly in the variance when a takes the exponential of 2 than it takes values continuously. Studying the annual frequency of tropical cyclones and the date of first appearance for periodic patterns, we have found that the primary periods extracted by this approach are similar to those obtained by wavelet transformation.

时序数据年变信息提取及地震预测指标评估方法研究

针对时序数据中的破年变异常,基于S变换时频方法构建信息提取流程,在提取常规短周期破年变信号(ONA)的同时分析背景年变信号(ANA)的演化过程。在此基础上,基于双向非对称阈值策略,结合R值评分及Molchan图表法构建预测指标确定和效能定量评估方法。新疆库尔勒水平摆倾斜北南测项的实际应用结果显示,该测项的ANA信息对台站周边250 km内6级以上地震具有较好的预测效能,ONA信息对200 km范围内5级以上地震的预测效果相对更优。

麻街水文站年径流量频率密度和频率分布规律分析

利用频率密度和频率分布分析方法,对丹江上游麻街水文站实测径流系列进行频率密度和频率分布分析,得出该河段年径流量的概率分布规律在0.5 m^(3)/s~3.0 m^(3)/s之间占76%,特别大、特别小的年径流量出现的机会较少。

基于改进物元分析法的疏勒河中上游生态流量计算与评价

适宜生态流量是保障河流水生态系统健康的重要变量,合理评估适宜生态流量具有现实意义。以河西走廊内流水系的第二大河疏勒河为研究对象,基于疏勒河干流中上游昌马堡水文站64年的长时间径流资料,选取年内展布法、NGPRP法、最小生态流量法、逐月频率法及Tennant法5种计算方法对疏勒河干流中上游生态流量进行计算,并建立基于博弈论的改进物元分析模型对计算结果进行评价分析。结果表明:采用年内展布法与逐月最小流量法确定的疏勒河干流中上游最小生态流量,以及采用逐月频率法取法Ⅰ与逐月频率法取法Ⅲ确定的疏勒河干流中上游适宜生态流量符合该流域的生态水文特征,同时表明基于博弈论的改进物元分析模型适用性较高。研究可为疏勒河干流中上游生态修复提供科学参考,也为计算并评价河道生态流量过程提供新方法。

廊坊市风力资源分析

以廊坊市9个国家气象观测站2013~2022年的测风资料为基础,依据相关国家标准计算廊坊地区的各项风能参数,包括平均风功率密度、年有效时数、威布尔参数、风速频率、风能频率,并对廊坊地区风力资源的时空变化特征进行分析评价。通过研究可知,廊坊地区2013~2022年距地10m高度的平均风速在北部和中部均呈现减小趋势,而南部变化较平稳。历年平均风速有从廊坊东南部到西北部递减,再从西北部向东北部递增的空间分布规律。各观测站80m高度的平均风速为2.1~3.4m/s,平均风功率密度为30.7~115.4W/m2。南部的霸州市、大城县、文安县和北部的香河县、大厂县风力资源较丰富,平均风功率密度为72.5~115.4W/m2,年有效小时数为2858~3813h,具有一定开发价值。廊坊地区中部平均风速、风功率密度、年有效时数均较小,不利于风力资源的开发利用。

透水混凝土压缩试验及劈裂试验三维离散元分析

为研究透水混凝土细观力学参数与宏观力学性能的关系,通过PFC3D三维颗粒流建立平行粘结模型,对所建立方体透水混凝土进行单轴压缩试验模拟,得到砂浆粘结力提高倍数低于2.0时,两者呈y=x趋势增长,高于2.0时,呈y=1.54 ln(x)+0.90非线性趋势增长;三轴压缩试验模拟,得到围压从5 MPa~20 MPa,透水混凝土抗压强度提高了约2~3倍,表明结构可显著增强透水混凝土力学性能,并计算得透水混凝土的c、φ值分别为0.8 MPa、24°;压条劈裂试验模拟结果得透水混凝土劈裂抗拉强度为2.43 MPa,与试验结果相差0.08 MPa,提供了一种较为可靠的劈裂试验替代方法。

年预计雷击频次GUI计算程序的设计与探讨

文章以肇庆市某区X波段双极化相控阵天气雷达塔为例,介绍了基于Python语言开发的年预计雷击频次GUI计算程序,阐述了应用AutoCAD软件进行可视化三维建模的要点。使用三维模型结合程序计算的方式,使年预计雷击频次的确定更为准确和直观,为防雷技术人员的实际工作提供支持。

变化环境下非一致性年径流序列的水文频率计算原理

由于受频繁人类活动和气候变化的影响,用于水资源评价计算的天然年径流量序列失去了一致性.为了适应变化环境对水文频率计算的要求,提出了基于时间序列分析的非一致性年径流序列的水文频率计算原理,包括假设前提和一般方法.该方法假设非一致性水文序列由相对一致的随机性成分和非一致的确定性成分两部分组成,采用成因分析法与统计分析法分别对确定性成分和随机性成分进行识别与检验,并对确定性成分进行拟合计算,对随机性成分进行频率计算;根据时间序列分析的分解与合成理论,将确定性的预测值和随机性的设计值进行合成,得到过去、现在和未来不同时期合成序列的频率分布.

Copula联结函数在多变量水文频率分析中的应用

介绍了Copula联结函数的定义、属性和构造方法.在应用实例中,针对位于同一河流上下游的两个水文站点采用Copula联结函数建立起两个站点的年最大洪水联合分布函数.结果表明,Copula联结函数能够比较好的模拟这两个站点的年最大洪水联合分布概率.由于Copula联结函数可以采用各种各样的边际函数来推求联合分布函数,具有灵活性和应用范围广等特点,因此在多变量水文频率分析中具有广泛的应用前景.

从潮白河年径流频率分布变化看北京市水资源安全问题

密云水库是北京市生活供水的唯一地表水源,而潮白河流域又是密云水库的径流形成区,因此,潮白河流域年径流量的变化直接关系到北京市的水资源安全。根据变化环境下非一致性年径流序列的水文频率计算原理,对潮白河水资源分区年径流序列的确定性成分和随机性成分进行分解,并分别对确定性成分进行拟合计算,对随机性成分进行频率计算;将确定性的预测值和随机性的设计值进行合成,得到潮白河水资源分区在过去、现在和未来年径流量的频率分布;从年径流量的频率分布变化上,分析了北京市所面临的水资源安全问题。分析结果表明潮白河流域年径流量变化的总体趋势是逐年减小,密云水库在平水年和枯水年的入库径流量也将随之减小,因此密云水库不能成为北京21世纪可持续发展的水资源保障。

我国西北地区降水强度、频率和总量变化

利用西北地区120个测站1954-2003年逐日降水观测资料,采用REOF将我国西北地区降水变化划分为东西两部分进行研究,分析了近50年来西北地区东西部降水强度、频率和总降水量变化趋势以及它们之间的联系。结果表明:西北地区降水量的增多主要是西北西部降水量的增多引起的;西北西部年降水频率呈增加趋势,年平均降水强度也呈增强趋势,而西北东部年平均降水强度增强,年降水频率却呈显著减少趋势。

基于低定量取样的枯水频率分析

概述了枯水频率分析的研究进展,采用低定量取样,应用泊松和指数(Po-Ex)分布分别拟合低定量系列的年发生次数和量级,并与皮尔逊III型(P3)模型进行比较.实测枯水流量系列和统计试验的计算结果表明,Po-Ex模型的拟合和预测效果较好,要优于采用年最小流量取样和P3模型的枯水频率分析.基于低定量取样的模型可利用更多枯水流量信息,具有更强的物理相关性.为枯水频率分析提供了一条新的途径.