A Theoretical Explanation of Anomalous Atmospheric Circulation Associated with ENSO Modoki during Boreal Winter          下载免费PDF全文

XING Nan  LI Jian-Ping  LI Yao-Kun 《大气和海洋科学快报》2014,(4):352-357

Based on a linear model, the present study provides analytical solutions for ideal triple forcing sources similar to sea surface temperature anomaly （SSTA） pat- terns associated with El Nino-Southern Oscillation （ENSO） Modoki in winter. The ideal triple pattern is composed of an equatorially symmetric heat source in the middle and equatoriaUy asymmetric cold forcing in the southeast and northwest. The equatorially symmetric heat source excites low-level cyclonic circulation anomalies associated with Rossby waves in both hemispheres, while the northwest- ern and southeastern equatorially asymmetric cold sources induce low-level anomalous anticyclones associated with Rossby waves in the hemisphere where the forcing source is located. Low-level zonal winds converge toward the heat sources associated with Kelvin and Rossby waves. Due to unequal forcing intensity in the northwest and southeast, atmospheric responses around the equatorially symmetric forcing become asymmetric, and low-level cyclonic circulation anomalies in the Southern Hemisphere become greater than those in the Northern Hemisphere. Ascending （descending） flows coincide with heat （cold） sources, resulting in a double-cell structure over the regions of forcing sources. Ideal triple patterns similar to SSTA patterns associated with La Nina Modoki produce opposite atmospheric responses. The theoretical atmospheric responses are consistent with observed circulation anomalies associated with ENSO Modoki. Therefore, the theoretical solutions can explain the dynamics responsible for atmospheric circulation anomalies associated with ENSO Modoki events.  相似文献   

pCO2增加引起的海洋酸化对造礁珊瑚光合效率的影响研究     

周洁  余克服  施祺 《海洋与湖沼》2014,45(1):39-50

海洋酸化是近年来人类所遇到的重大全球环境问题之一,它指的是大气CO2浓度增加引起的海水pH降低的现象。海洋酸化已经威胁到珊瑚礁及其它钙质生物的生存与发展。近期的预测模型与野外实验均表明,海洋酸化的后果可能比以前想象的更为严峻。本研究采用叶绿素荧光技术,选取3种鹿回头珊瑚礁区常见的珊瑚种类（Acropora valida、Galaxea astreata和Favites abdita）,分别设置海水环境为450 μatm、650 μatm（IPCC预测的2065年的水平）和750 μatm（IPCC预测的2100年的水平）的3个pCO2浓度梯度,监测珊瑚在不同CO2浓度背景下10天内的光合荧光参数的变化。实验结果表明,水体pCO2为650μatm时,珊瑚的总体光合效率最高,但随着时间的延长,珊瑚荧光参数在3个浓度梯度下都会显示不同程度的下降趋势。虽然3种珊瑚对不同浓度CO2响应的程度不同,但基本上显示出,在低浓度pCO2时,pH下降引起的酸化作用控制着珊瑚共生藻的光合效率;而随着浓度的增加,CO2增加引起的施肥效应愈加明显,与酸化作用竞争,共同作用于珊瑚共生藻,使得光合荧光参数在波动中变化。  相似文献   

Diagnosis of physical and biological controls on phytoplankton distribution in the Sargasso Sea     

WANG Caixia  and Paola Malanotte-Rizzoli 《中国海洋大学学报(英文版)》2014,13(1):32-44

The linkage between physical and biological processes is studied by applying a one-dimensional physical-biological coupled model to the Sargasso Sea. The physical model is the Princeton Ocean Model and the biological model is a five-component system including phytoplankton, zooplankton, nitrate, ammonium, and detritus. The coupling between the physical and biological model is accomplished through vertical mixing which is parameterized by the level 2.5 Mellor and Yamada turbulence closure scheme. The coupled model investigates the annual cycle of ecosystem production and the response to external forcing, such as heat flux, wind stress, and surface salinity, and the relative importance of physical processes in affecting the ecosystem. Sensitivity experiments are also carried out, which provide information on how the model bio-chemical parameters affect the biological system. The computed seasonal cycles compare reasonably well with the observations of the Bermuda Atlantic Time-series Study (BATS). The spring bloom of phytoplankton occurs in March and April, right after the weakening of the winter mixing and before the establishment of the summer stratification. The bloom of zooplankton occurs about two weeks after the bloom of phytoplankton. The sensitivity experiments show that zooplankton is more sensitive to the variations of biochemical parameters than phytoplankton.  相似文献   

基于流强度的中国城市对外服务能力时空演变特征   总被引：2，自引：2，他引：0  

柯文前  陆玉麒  俞肇元  王晗  陈伟  马颖忆 《地理科学》2014,(11):1369-1376

综合运用城市流强度模型、改良Theil系数和K-means时空聚类法对2004~2010年中国地级以上286个城市对外服务能力的时空演变特征进行探讨,得到以下结论:1城市流强度值的绝对量均有明显上升,但存在显著的区域非均衡现象,并与城市经济实力有较高的相关性。2省内差异对城市对外服务能力的差异贡献率在58%~72%,是其空间尺度差异的主要来源。3时空演变表现出明显的阶段性和等级性规律,且空间等级性特征随阶段演进更趋明显。4对外服务能力的强弱和集聚强化趋势与城市流强度基数值大小和增速快慢有着紧密关系,一定程度上体现了基础乘数效应和循环累积效应配置下的非均衡特征。  相似文献   

日本钢筋混凝土结构抗震加固技术现状与发展趋势   总被引：1，自引：0，他引：1  

曲哲  张令心 《地震工程与工程振动》2013,33(4)

既有钢筋混凝土结构的丰富而可靠的抗震加固技术是提升我国建筑物抗震性能,实现社会可持续发展的重要保障.在长期工程实践的积累中,日本建筑界逐渐发展出一套行之有效的抗震性能评估、加固设计体系和多种多样的抗震加固技术,值得我国借鉴.文章在简要回顾日本抗震加固设计方法之后,介绍了日本钢筋混凝土结构抗震加固的传统方法,总结了近年来在传统加固方法基础上所做的改良,并在此基础上,从外附子结构、消能减震化和自复位技术等3个方面归纳了日本新一代钢筋混凝土结构抗震加固技术的发展趋势.  相似文献   

Estimating Climate-Change Impacts on Colorado Plateau Snowpack Using Downscaling Methods     

《The Professional geographer》2013,65(1):117-125

This study develops observed climate-based downscaling transfer functions that are used with general circulation model (GCM) output to assess potential global-change impacts on Upper Colorado Plateau, USA, water resources. Daily automated snow water equivalent stations are used with 700 mb atmospheric circulation to determine empirical transfer functions. Downscaling methodologies using multiple regression and neural networks are evaluated, with the neural network results explaining approximately 70%of the daily snowfall variance. The neural network-based transfer functions are used with the GENESIS GCM to simulate snowfall characteristics in both a 1xCO₂ and a 2xCO₂ climate. While the total precipitation simulated by the 2xCO₂ analysis remains nearly the same as today, less will fall as snow; specifically, snow water equivalence shows significant reduction (except in the Green River Basin) as the snow season is reduced by 58 days on average.  相似文献   

Latitude-Dependent Response of East Asian Summer Monsoon to External Forcing in the Last Millennium     

GU Yajin  WANG Hongli  LIU Jian 《Acta Meteorologica Sinica》2010,24(6):671-679

Response of the East Asian summer monsoon(EASM) rainfall to external forcing(insolation,volcanic aerosol,and greenhouse gases) is investigated by analysis of a millennium simulation with the coupled climate model ECHO-G.The model reproduces reasonably realistic present-day EASM climatology.The simulated precipitation variation in East Asia over the last millennium compares favorably with the observed and proxy data.It is found that the features and sensitivity of the forced response depend on latitude.On...  相似文献   

基于LSDYNA的射流式液动锤回程动力 外传机构研究          下载免费PDF全文

张鹏飞  程靖清  葛东  彭枧明 《探矿工程》2019,46(2):71-74,85

设计一种改变冲击应力波在射流式液动锤内传播途径的结构,分析在不同传播途径中应力波衰减程度的改变,基于LSDYNA显式动力学分析方法,对冲锤回程阶段进行仿真分析,探究冲锤回程冲击在液动锤内两种不同传播途径的模型中射流元件受到的应力变化。研究表明,动力外传机构通过避免对缸体上部的刚性碰撞,能大大降低射流元件所受到的冲击应力,并且外传机构的几何参数对应力的衰减也有一定的影响。  相似文献   

仿刺参不同体外标记方法效果的比较     

孙璐  邱天龙  许强  刘辉  林承刚  杨红生 《海洋科学》2013,37(7):1-6

为筛选出仿刺参(Apostichopus japonicus)体外标记方法,研究了体腔植入标记物法、体壁半包埋法、棘部及体壁穿刺法、体壁胶粘法和石灰环嵌套法。研究结果表明,前4种方法标记保留时间均未超过2 d,且有严重排异反应,影响活动和摄食,难以满足标记要求,体壁胶粘法保留时间可达2 d,且活动摄食正常,可用于短期标记。使用石灰环嵌套法标记小规格仿刺参10 d后标签保留率达到75.8%,标记大规格仿刺参3个月后标签保留率可达93%,初步确定石灰环嵌套法可作为仿刺参体外长效标记的方法。  相似文献   

海湾扇贝混交家系中优先受精以及自然选择压力下杂合子过剩的研究     

张守都  许飞  李莉  张国范 《海洋科学》2013,37(3):1-5

以中国海湾扇(Argopecten irradians)贝养殖群体为亲本分别构建了5个配对混交的海湾扇贝混交系,通过5对微卫星分子标记为手段对海湾扇贝卵子在同一个体和不同个体精子间的优先受精问题和不同生命阶段的海湾扇贝混交系杂合子比例的变化进行了研究。结果发现在受精后6 h的担轮幼虫期3个混交系中有2个混交系杂合子显著过剩。5个混交系的1d D形幼虫、20d稚贝、40d稚贝、3个月稚贝以及成贝在自然选择压力下杂合子比例逐渐上升,以壳长计算的杂交优势率也呈逐渐上升趋势,并且各个阶段的杂合子比例同杂交优势率的变化成显著正相关。  相似文献