Evolution of meteorological drought characteristics in Vietnam during the 1961–2007 period     

Hang Vu-Thanh  Thanh Ngo-Duc  Tan Phan-Van 《Theoretical and Applied Climatology》2014,118(3):367-375

The drought conditions over the seven sub-climatological regions in Vietnam are examined using three meteorological drought indices: de Martonne J, PED, and Standardized Precipitation Index (SPI). According to the seasonal probabilities of drought occurrence estimated by the de Martonne index, droughts mainly occur between November and March in all the sub-regions. The PED index and the SPI index generally show high probabilities of drought occurrence from April to August and from May to October, respectively. In the southern sub-regions of Vietnam, droughts more frequently occur in El Niño years and wet conditions are more frequently observed in La Niña years. However, such El Niño–Southern Oscillation influences are not clearly observed in the northern sub-regions. During 1961–2007, droughts significantly increased in the northern part of Vietnam. In the southern regions, PED shows increasing drought conditions while J and SPI show decreasing drought trends for almost all the stations.  相似文献   

广东省能见度自动观测系统资料评估分析与订正     

夏冬  吴志权  谭浩波  袁志扬  陈玲  黄培光  尹淑娴  罗鵾 《气象科技》2014,42(1):68-72

利用广东省能见度自动观测系统22个站点2011年的人工观测和自动观测的能见度资料,分析了人工观测与自动观测的能见度资料的相关系数、均方根误差等,并对自动观测资料进行了订正。分析结果显示:人工观测与自动观测能见度的分布大致相同,表现为沿海的能见度高于内陆,粤东高于粤西,主要低能见度区域集中在珠江三角洲和粤西的内陆地区;自动观测能见度的准确性主要受到仪器工作原理局限性、气溶胶类型和气象条件的影响。对能见度自动观测资料订正结果显示:订正后,在低能见度时,大部分站点的均方根误差在3km以内;在高能见度时,大部分站点均方根误差在8km以内,平均为6km左右。利用统计方法对器测能见度值作数据订正,能有效减小测量误差,使能见度自动观测系统能基本满足能见度自动化观测需要,特别是低能见度事件的服务需求。  相似文献   

Copula函数在广西洪涝灾害的降水概率预测中的应用     

倪增华  刘合香  罗彦丽  谭金凯 《气象研究与应用》2014,(2):32-39

为了研究洪涝的重要致灾源因子降水的概率,利用广西从1970年-2012年的降水数据,以年降水均值（X）和年降水极值均值（Y）为研究变量,通过Copula函数构建其联合分布.经过OLS,AIC拟合优度评价,采用Copula函数中拟合效果较好的Gumbel-Hougaard Copula函数建立边缘分布为Pearson-Ⅲ型的两变量的联合分布.随后,进行相应的重现期计算,计算结果表明,在联合重现期下的两变量降水设计值比单变量设计值和同现重现期下的设计值都要高,故采用联合重现期下的联合设计值作为防洪标准会更加安全.最后,对比降水数据与灾情数据,研究降水重现期与洪涝灾情的关系.结果表明,降水的重现期越长,洪涝灾害也越严重.  相似文献   

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王伟  杨少敏  谭凯  赵斌  黄勇  张彩红  王迪晋 《大地测量与地球动力学》2014,34(3):75-80

?????й??????????????1999~2013????й?????????????????2009~2013???GPS????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????1????????????????????????????????????????????????????????????й????????????????????????????????????????????????Σ?77°E?????????45×10^-9/a???????????Σ?86°E?????????10×10^-9/a;2)???????????????????????????????????????????????????????????????????50~60??×10^-9/a??????????????40~50??×10^-9/a????????GPS?????????????10~15??mm/a??????????????????;3)?????????????????????????????????38°N?????????????????????????????????????????????????????????к?????????????????????????????????????????????Σ??????????????10~20??×10^-9/a???????????????;4)??????????????????????????????????б??Σ???????????????????????????????????????????????????????????40×10^-9/a??5)????????????????λ???????????78°E??????????????30×10^-9/a??  相似文献   

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邹舟  杜瑞林  卢海燕  胡国庆  马武刚  吴艳霞  谭业春 《大地测量与地球动力学》2014,34(4):172-174

???????У???????????????????μ????б??????á?????????????е?VP??б?????У???????????????9.414 mV/ms??  相似文献   

Effect of dietary potassium on growth,nitrogen metabolism,osmoregulation and immunity of pacific white shrimp (Litopenaeus vannamei) reared in low salinity seawater     

LIU Hongyu  ZHANG Xinjie  TAN Beiping  LIN Yingbo  CHI Shuyan  DONG Xiaohui  and YANG Qihui 《中国海洋大学学报(英文版)》2014,13(2):311-320

An 8 weeks feeding experiment was conducted to determine the effect of dietary potassium on the growth and physiological acclimation of Pacific white shrimp(Litopenaeus vannamei) reared in diluted seawater(salinity 4). Six semi-purified practical diets containing 0.59, 0.96, 1.26, 1.48, 1.74, and 2.17+ g potassium K per 100 g diet were formulated, respectively. The survival and feed conversion rate did not show significant difference among groups of shrimps given these diets(P0.05). The shrimps fed the diets containing 0.96-1.48 g K+ per 100 g diet gained the highest weight, specific growth rate, and protein efficiency ratio. Their ammonium-N excretion rate as well as hemolymph concentration of Na+ and Cl- were significantly lower than those of the control(P0.05), but a reverse trend was observed for their gill Na+/K+-ATPase. Moreover, the shrimps fed with 1.48 g K+ per 100 g diet were the highest in hemolymph urea level, and the phenoloxidase and lysozyme activities were significantly higher than those of the control(P0.05). The growth and physiological response of the test shrimps suggested that diet containing 1.48 g K+ per 100 g diet improved the growth of L. vannamei in low-salinity seawater, and enhanced the physiological acclimation of the organism.  相似文献   

数据中心内网核心业务运行环境升级改造实践     

何俊  吴洪桥  谈夭林等 《国土资源信息化》2014,(1):9-13

运行环境升级改造是国土资源部数据中心建设与完善过程中必不可少的重要工作。本文以部数据中心内网核心业务运行环境升级改造项目为例,介绍了该项目实施过程中的主要任务、实施原则、实施方案和过程安排等内容。对类似的数据中心生产环境升级改造工作,具有一定的参考借鉴意义。  相似文献   

Oceanic crustal structure and tectonic origin of the southern Kyushu-Palau Ridge in the Philippine Sea     

Xiongwei Niu  Pingchuan Tan  Weiwei Ding  Wei Wang  Yao Wei  Xiaodong Wei  Aiguo Ruan  Jie Zhang  Chunyang Wang  Yong Tang  Jiabiao Li 《海洋学报(英文版)》2022,41(1):39-49

A new high-resolution velocity model of the southern Kyushu-Palau Ridge(KPR) was derived from an activesource wide-angle seismic reflection/refraction profile. The result shows that the KPR crust can be divided into the upper crust with the P-wave velocity less than 6.1 m/s, and lower crust with P-wave velocity between 6.1 km/s and 7.2 km/s. The crustal thickness of the KPR reaches 12.0 km in the center, which gradually decreases to 5.0–6.0 km at sides. The velocity structure of the KPR is simil...  相似文献   

自适应非局部均值地震随机噪声压制(英文)   总被引：2，自引：1，他引：1  

尚帅  韩立国  吕庆田  谭尘青 《应用地球物理》2013,10(1):33-40

非局部均值滤波是一种基于图像信息冗余的去噪方法,其认为图像自身的有效结构具有一定的重复性,而随机噪声则不具备这一特点,通过利用图像本身的自相似性来达到压制随机噪声的目的,是一种全局的去噪方法。本文把这一思想引入地震数据随机噪声压制中,针对传统非局部均值滤波计算量过大的问题,文章采用分块非局部均值的方式来减少计算量;针对滤波参数选取会影响非局部均值滤波效果的问题,提出一种简单的自适应滤波参数地震数据分块非局部均值算法。模型和实际数据处理结果表明:相对于传统的去噪算法(如f-x反褶积),该方法在压制随机噪声的同时对有效信号保护地更好,具有更高的保真度,更有利于后续的处理和解释工作。  相似文献   

Ground roll attenuation using a time-frequency dependent polarization filter based on the S transform     

Tan Yu-Yang  He Chuan  Wang Yan-Dong  Zhao Zhong 《应用地球物理》2013,10(3):279-294

The ground roll and body wave usually show significant differences in arrival time, frequency content, and polarization characteristics, and conventional polarization filters that operate in either the time or frequency domain cannot consider all these elements. Therefore, we have developed a time-frequency dependent polarization filter based on the S transform to attenuate the ground roll in seismic records. Our approach adopts the complex coefficients of the S transform of the multi-component seismic data to estimate the local polarization attributes and utilizes the estimated attributes to construct the filter function. In this study, we select the S transform to design this polarization filter because its scalable window length can ensure the same number of cycles of a Fourier sinusoid, thereby rendering more precise estimation of local polarization attributes. The results of applying our approach in synthetic and real data examples demonstrate that the proposed polarization filter can effectively attenuate the ground roll and successfully preserve the body wave.  相似文献