南印度洋海温偶极子型振荡及其气候影响

印度洋海表温度（Sea Surface Temperature，简称SST）的方差分析和相关分析表明南印度洋也存在一个海温偶极子型振荡，并定义了一个南印度洋海表温度异常偶极子指数.夏、秋季（南半球冬、春）的南印度洋偶极子指数与后期热带500hPa和100hPa高度场异常有显著而持续的相关，在冬、春达到最大，并可以持续到次年夏、秋.前期夏、秋季节的南印度洋偶极模对次年我国大陆东部夏季降水异常有显著的影响，对应偶极子正位相，次年夏季印度洋、南海（东亚）夏季风偏弱；副高加强且南撤、西伸，南亚高压偏强且位置偏东，易形成我国长江流域降水偏多，华南降水偏少；负位相年反之.后期冬季西太平洋暖池是联系南印度洋偶极子与次年我国夏季降水异常关系的一条重要途径.南印度洋偶极子表现出了明显的独立于ENSO（El Nio Southern Oscillation，简称ENSO）的特征.     

谐变磁偶极激发下层状介质中球的电磁响应

本文在前人基础上,从理论计算角度研究了两层大地下球形导电体的偶极激发音频电磁场。探讨了电模式、磁模式场的耦合及其意义,并列出了剖面数据和频率响应数据,以适应移动源音频电磁法的实际需要。     

The Subsurface and Surface Indian Ocean Dipoles and Their Association with ENSO in CMIP6 models

This study assesses the reproducibility of 31 historical simulations from 1850 to 2014 in the Coupled Model Intercomparison Project phase 6(CMIP6) for the subsurface(Sub-IOD) and surface Indian Ocean Dipole(IOD) and their association with El Ni?o-Southern Oscillation(ENSO). Most CMIP6 models can reproduce the leading east-west dipole oscillation mode of heat content anomalies in the tropical Indian Ocean(TIO) but largely overestimate the amplitude and the dominant period of the Sub-IOD. Associat...     

印度洋海表温度的变化及其对印度夏季季风降水影响的诊断研究

对印度洋海表温度(SST)的主要特征及变化趋势进行分析,并研究了其与印度夏季季风降水(ISMR)和季风环流的关系,揭示出:从北印度洋到南半球中高纬度印度洋,SST最显著的变化模态是全海盆一致的变化,近50 a来总体趋势是上升的,在1976,1986年以及1996年间分别有一次跳跃性增温,与太平洋SST变化趋势基本一致.除了长期变化趋势外,南印度洋中高纬度比热带地区有更显著的模态分布.在印度洋SST升温的背景下,ISMR具有逐渐减少的趋势,但两者相关较弱.印度洋SST发生跳跃后的不同阶段,许多海区SST与ISMR相关均发生变化,但在春季,热带外南印度洋具有一对相对稳定区,其分布与EOF分析的第2模态相似.根据它们的分布,文中定义了春季南半球偶极子(SIOD),在正SIOD(PSIOD)情况下印度降水偏多,而负SIOD(NSIOD)则反之.环流分析表明,PSIOD(NSIOD)通过与大气的相互作用,对夏季马斯克林高压具有增强(减弱)作用,进而使得索马里越赤道气流增强(减弱),在印度地区低空产生异常的辐合(辐散),高层辐散(辐合),从而影响印度季风环流,使得印度季风降水偏多(少).     

Tanzanian rainfall responses to El Niño and positive Indian Ocean Dipole events during 1951–2015

The relative impacts of Indian and Pacific Ocean processes on Tanzanian rainfall was evaluated using composite and correlation analyses. It was found that the seasonal responses of rainfall to positive Indian Ocean Dipole (pIOD) and El Niño events are substantial from September–October–November (SON) to December–January–February (DJF), whereas the Indian Ocean Dipole (IOD) exerts more control than El Niño–Southern Oscillation (ENSO) in both seasons. The associated relationship with the sea surface temperature (SST) and large-scale atmospheric circulations revealed distinct features. For the pure pIOD years, there is above-normal rainfall over the entire country. A strong rainfall condition is evident over the Lake Victoria basin and coastal and northeastern highland parts of the country during SON, while areas of the central and southern highlands exhibit substantial rains during DJF. For the pure El-Niño events, Tanzania has suffered from insignificant, weak, and non-coherent rainfall conditions during SON. However, a contrasting insignificant rainfall signature is found between the northern and southern parts of the country during the subsequent DJF season. For the co-occurrence of pIOD and El Niño, significant, excessive rainfall conditions are restricted to over the northern coast and northeastern areas of the country during SON, consistent with the rainfall pattern for pIOD. A weak, positive rainfall condition is observed over the entire country in the following season of DJF. Generally, in terms of Tanzanian rainfall, the IOD/ENSO variability and the associated impacts can be explained by the anomalous SST and circulation anomalies.     

Influence of the strongest positive Indian Ocean Dipole and an El Niño Modoki event on the 2019 Indian summer monsoon

The year 2019 experienced an excess monsoon season over the Indian region, with the seasonal rainfall being 110 % of the long period average (LPA). Several zones across the country suffered multiple extreme rainfall events and flood situations resulting in a massive loss of life and property. The first half of 2019 experienced a moderate El Niño Modoki event that lasted till mid-summer. Another important feature of 2019 was the strongest recorded positive Indian Ocean Dipole (IOD) that lasted approximately seven months from May to November. This study has examined the reasons for the intra-seasonal variability of rainfall over India during the 2019 monsoon using available remote sensing and reanalysis data. Our analysis has shown that the presence of El Niño and the formation of a very severe cyclonic storm (VSCS) in the Arabian Sea were unfavorable for the monsoon onset and its northward advancement during June. However, the Walker circulation associated with El Niño helped strengthen the IOD developed early in the Indian Ocean, much before the monsoon onset. The anomalously strong IOD strengthened the monsoon circulation during July-September and resulted in excess rainfall over India.     

印度洋偶极子向海盆一致模转变的年代际变化及其成因

利用3种百年时间尺度的海温资料,探讨了印度洋偶极子(India Ocean Dipole,IOD)向海盆一致模(Indian Ocean Basin,IOB)年际转变的年代际变化,结果发现1940—1970年几乎不存在这一转变现象,1970年以后该现象则十分显著。研究表明,IOD与ENSO之间海气耦合作用的年代际变化是这一转变现象的主要原因,1940—1970年IOD与ENSO之间发生发展相互独立,而1970年以后联系密切。通过进一步对物理量场的诊断分析,揭示了其中主要的动力机理:1970年以前,热带印度洋上空形成的季风环流异常无法与热带太平洋的沃克环流异常进行耦合,IOD事件发生时无法与热带太平洋产生联系。反之,1970年以后,热带两大洋上空两个纬圈环流异常之间耦合作用强烈,正(负) IOD事件发生时,通过海气相互作用,促进El Niño (La Niña)发展,印度洋又会受到来自ENSO的正反馈作用。因此这种“齿轮式”耦合模型能一直持续到冬季和次年春季,热带印度洋上空持续受到东(西)风异常的影响和低层环流的引导,西印度洋有次表层暖水的流入(出),加上印度洋本身海盆尺度较小,西边的暖(冷)水区显著增大,东西海温异常差异迅速减小并向海盆一致变暖(冷)转变,导致了后期冬季、春季正(负) IOB事件的出现。     

偶层位曲面位场数据处理及转换方法

本文在文献［１］［２］的基础上，进一步完善了偶层位曲面位场数据处理及转换方法。克服了三角函数曲面位场数据处理及转换方法不能适应于所有＂强地形＂的弱点。提出了曲面位场处理及转换的两个基本类型（纯位场型和磁力场型）及其相应的计算公式；提出了简单快速的数值积分方法；提出了分块处理技术。编制了相应方法软件，并通过理论模型试算和实际资料处理，检验了方法的正确性和有关技术措施的有效性。该套方法软件具有适应性强，计算速度快和精度高等特点。     

Impact of the Preceding Boreal Winter Southern Annular Mode on the Summertime Somali Jet

One of the major high-latitude circulation systems in the Southern Hemisphere is the Southern Annular Mode（SAM）. Its effect on the Somali Jet（SMJ）, which connects the Southern and Northern hemispheres, cannot be ignored. The present reported results show that time series of both the Southern Annular Mode Index（SAMI） during the preceding winter and the summertime Somali Jet intensity Index（SMJI） display a significant increasing trend and have similar interdecadal variation. The latter was rather strong around 1960, then became weaker up to the mid-1980 s, before starting to strengthen again. The lead-lag correlations of monthly mean SAMI with the following summertime SMJI showed significant positive correlations in November, December, and January. There are thus connections across two seasons between the SAM and the SMJ. The influence of the winter SAM on the summer SMJ was explored via analyses of SST anomalies in the Southern Indian Ocean. During strong（weak） SAM/SMJ years, the SST east of Madagascar is colder（warmer） while the SST west of Australia is warmer（colder）, corresponding to the positive（negative） Southern Indian Ocean Dipole-like（SIODL） event. Subsequently, the SIODL excites an anticyclone located over the Arabian Sea in summer through air-sea coupling from winter to summer, which causes an increase in the summer SMJ intensity. The anticyclone/high branch of the SAM over the Southern Hemisphere subtropics and the cyclone/low over the east coast of Madagascar play an important role in the formation of Southern Indian Ocean ＂bridge＂ from winter to summer.     

不同偏振方向的偶极子声源在HTI地层井孔中激发声场的实验研究

本文首先制作了TI地层模型井,对模型井的速度、密度等物理参数进行了测量,通过快速模拟退火算法得到了该介质的五个TI刚性系数,然后采用缩尺的偶极子探头在HTI地层井孔内进行超声测量实验模拟了实际的偶极子声波测井,并结合数值模拟的结果,研究了不同偏振方向的声源在HTI地层井孔中进行偶极子声波测井的响应特征.模拟结果表明,弯曲波的幅度和速度随声源的偏振方向不同而不同.正交分量的波形幅度在声源偏振方向平行或垂直于快横波面方位时最小,在与快横波面方位呈一定夹角时较大;同向分量波形幅度随声源的偏振方向的变化规律同正交分量相反.弯曲波速度在声源的偏振方向与快横波面方位的夹角小于30°或者大于60°时,分别接近于快弯曲波和慢弯曲波的速度,对于夹角的变化不敏感;当夹角在30°和60°之间时,弯曲波的速度对该夹角变化非常敏感,由接近快弯曲波速度快速变化到接近慢弯曲波速度.