太行山南段符山高镁闪长岩的成因 —— 拆沉陆壳物质熔融的熔体与地幔橄榄岩反应的结果

本文对太行山南段符山高镁闪长岩进行了年代学与地球化学研究,结合其中地幔橄榄岩包体的研究,对符山高镁闪长岩的成因和中生代岩石圈地幔的性质进行了探讨.研究表明,符山闪长岩体是由一套含橄榄石角闪闪长岩-角闪闪长岩-闪长岩构成.含橄榄岩包体的寄主岩--角闪闪长岩中的锆石可划分为两种:一是代表寄主岩浆结晶的锆石:内部结构均匀、呈条带状吸收、自形-半自形晶形,具有较高的Th/U比值(1.10～4.08),其206Pb/238U年龄介于123～128Ma之间,12个点的加权平均值为125±1Ma,这表明岩体的形成时代为早白垩世;二是捕获或继承锆石:具有核边结构、吸收程度不均匀、呈浑圆状和自形-半自形两种,它们的Th/U比值介于0.32～2.03之间,构成了3组207Pb/206Pb加权平均年龄:2503±11Ma、2181±26Ma和1778±36Ma.该类岩石的SiO2和MgO含量分别介于56.69%～59.21%和3.60%～6.33%之间;且以高:Mg#(0.51～0.64)、富Na(Na2O/K2O大于1)、高Cr(93.1×10-6～420×10-6)、Ni(35.1×10-6～137×10-6)为特征.该类岩石强烈富集轻稀土元素和大离子亲石元素、明显亏损高场强元素,(87Sr/86Sr)I、εNd(t)值和(206Pb/204Pb)I分别变化于0.70581～0.70641、-8.30～-16.56和17.052～17.512之间.综合上述特征,同时结合地幔橄榄岩包体的特征和古元古代捕获锆石的大量存在,认为符山高镁闪长岩的原始岩浆起源于拆沉陆壳物质的部分熔融,其后经历了与地幔橄榄岩的反应过程.     

西藏松西地区辉绿玢岩岩石化学、地球化学特征及构造环境

青藏高原南羌塘石炭纪-二叠世地层中侵入大量的辉绿玢岩岩墙群，其侵位时代为晚古生代。区域资料显示，这一时期该地区处于冈瓦纳大陆北部边缘。岩石化学、地球化学特征表明，辉绿玢岩与洋脊型、洋岛型及典型的大陆裂谷玄武岩都有明显区别，显示出大陆拉张带（或初始裂谷）的拉斑玄武岩特征。辉绿玢岩是冈瓦纳被动陆缘在晚古生代裂解的产物。     

基于奇异谱分析的南方涛动指数短期气候预测试验

The Southern Oscillation Index (SOI) time series is analyzed by means of the singular spectrum analysis (SSA) method with 60-month window length. Two major oscillatory pairs are found in the series whose pe riods are quasi-four and quasi-two years respectively. The auto-regressive model, which is developed on the basis of the Maximum Entropy Spectrum Analy sis, is fitted to each of the 9 leading components including the oscillatory pairs. The prediction of SOI with the 36-month lead is obtained from the reconstruction of these extrapolated series. Correlation coefficient between predicted series and 5 months running mean of observed series is up to 0.8. The model can successfully predict the peak and duration of the strong ENSO event from 1997 to 1998. It＇s also shown that the proper choice of reconstructed components is the key to improve the model prediction.     

ENSO发生前与发展初期赤道西太平洋西风异常的爆发问题

利用 NCEP/NCAR再分析资料 ,通过对 El Nino与 La Nina发生前与发展初期低层风场的合成分析 ,发现在赤道中东太平洋增暖当年的春季与夏季 ,赤道西太平洋存在两次显著的西风局地 ( 1 40°E～ 1 80 )增强过程。其原因并不仅仅在于印度洋的西风异常东移 ,更在于南北半球的经向风在该地区强烈辐合 ,造成局地气压梯度增强 ,促进西风加强并向东爆发 ;同时由于地球自转效应的作用 ,来自北半球的东北风到达赤道附近后转西北风 ,南半球的东南风转西南风 ,直接加强了西风的强度。对比分析南北半球经向风的作用表明 ,南半球东南风的强度与位置更稳定 ,对赤道西风两次增幅过程的贡献更大。这支南半球的经向气流来自高纬极区 ,与中高纬度气压场异常有直接的关系。     

夏季长江淮河流域异常降水事件环流差异及机理研究

长江、淮河同处东亚中纬度,天气过程的大尺度环流背景相似,大量相关研究基本是把江淮流域天气气候事件作为一个整体研究,然而对长江、淮河流域夏季降水的时空变化进行分析发现,长江、淮河流域夏季异常降水事件有各自不同的年际、年代际变化特征,但环流差异及成因并不十分清楚。本文根据中国台站降水资料及NCEP/NCAR再分析资料,利用物理量诊断和现代统计学等方法,重点分析长江、淮河流域梅雨期降水异常事件发生时南北半球大气环流内部动力过程的差异及成因。研究指出:长江（淮河）流域梅雨期降水异常偏多年500 hPa位势高度场亚洲中高纬度环流呈现为南北向（东西向）的波列与东亚中高纬鄂霍茨克海阻塞频次增多（减少）以及200 hPa高度场上东亚副热带高空西风急流强度加强（减弱）、稳定（移动）有关;长江（淮河）流域梅雨期降水异常偏多年主要水汽来源与南半球澳大利亚高压、马斯克林高压位置偏东（西）造成西太平洋150°E～180°（阿拉伯海50°E～60°E）地区越赤道气流加强有关。长江（淮河）流域梅雨期异常降水事件大气环流内部动力过程最显著的差异表现为:东亚副热带高空西风急流加强（减弱）以及南半球澳大利亚高压、马斯克林高压位置偏东（西）。     

南大洋淡水强迫对南半球环状模的影响分析

南半球环状模是南半球热带外大气环流变异的主导模态,对南半球海洋—大气—海冰耦合系统有重要的影响。冰川融化激发的淡水强迫是南大洋的一种重要外强迫。在历史气候记录中,南大洋淡水通量异常曾引发数次全球性气候异常事件。基于海—气完全耦合模式FOAM,在60°S以南的海洋中施加强度为1.0 Sv的理想化淡水通量异常,分析南半球环状模的响应。结果表明：南大洋淡水通量异常可使局地西风增强,且西风的增强在垂向各个层次上均有体现。西风强度的变化导致对流层中大气斜压性增强,平流层中大气斜压性减弱。此外,淡水强迫使环状模的年际变率振幅显著减弱,而年代际变率开始增强,谱能量的变化具有垂向一致性。海温和海冰等外强迫因子的变化对环状模年代际振幅的增强具有重要意义。     

东亚地区北方气旋和南方气旋活动频数的时空特征

利用1953-2007年NCEP／NCAR再分析逐日海平面气压场资料,统计分析东亚地区北方气旋和南方气旋的时间和地域分布特征。结果表明：南、北气旋活动频数存在明显的年际和年代际变化,伴随着一次全球性的年代际气候跃变,20世纪80年代初期北方气旋活动频数出现了显著的突变。从月际分布可知,5月北方气旋频数最多,8月南方气旋频数最多;春季北方气旋活动频繁,存在着明显的两个高值中心,分另Ij位于蒙古国中部和中国东北地区北部;夏季南方气旋活动频繁,主要集中在中国东部沿海及日本南部海面。南北气旋活动频数的季节变化与大气环流的变化密切相关。相关统计结果可增加对东亚温带气旋活动规律的认识和了解,并为预测和预报提供参考。     

Planetary-Scale Wave Structures of the Earth’s Atmosphere Revealed from the COSMIC Observations

GPS radio occultation（GPS RO） method,an active satellite-to-satellite remote sensing technique,is capable of producing accurate,all-weather,round the clock,global refractive index,density,pressure,and temperature profiles of the troposphere and stratosphere.This study presents planetary-scale equatorially trapped Kelvin waves in temperature profiles retrieved using COSMIC（Constellation Observing System for Meteorology,Ionosphere,and Climate） satellites during 2006-2009 and their interactions with background atmospheric conditions.It is found that the Kelvin waves are not only associated with wave periods of higher than 10 days（slow Kelvin waves） with higher zonal wave numbers（either 1 or 2）,but also possessing downward phase progression,giving evidence that the source regions of them are located at lower altitudes.A thorough verification of outgoing longwave radiation（OLR） reveals that deep convection activity has developed regularly over the Indonesian region,suggesting that the Kelvin waves are driven by the convective activity.The derived Kelvin waves show enhanced（diminished） tendencies during westward（eastward） phase of the quasi-biennial oscillation（QBO） in zonal winds,implying a mutual relation between both of them.The El Nino and Southern Oscillation（ENSO） below 18 km and the QBO features between 18 and 27km in temperature profiles are observed during May 2006-May 2010 with the help of an adaptive data analysis technique known as Hilbert Huang Transform（HHT）.Further,temperature anomalies computed using COSMIC retrieved temperatures are critically evaluated during different phases of ENSO,which has revealed interesting results and are discussed in light of available literature.     

What Drives the Decadal Variability of Global Tropical Storm Days from 1965 to 2019?

The tropical storm day(TSD)is a combined measure of genesis and lifespan.It reflects tropical cyclone(TC)overall activity,yet its variability has rarely been studied,especially globally.Here we show that the global total TSDs exhibit pronounced interannual(3-6 years)and decadal(10 years)variations over the past five-to-six decades without a significant trend.The leading modes of the interannual and decadal variability of global TSD feature similar patterns in the western Pacific and Atlantic,but different patterns in the Eastern Pacific and the Southern Indian Ocean.The interannual and decadal leading modes are primarily linked to El Ni?o-Southern Oscillation(ENSO)and Pacific Decadal Oscillation(PDO),respectively.The TSDs-ENSO relationship has been steady during the entire 55-year period,but the TSDs-PDO relationship has experienced a breakdown in the 1980 s.We find that the decadal variation of TSD in the Pacific is associated with the PDO sea surface temperature(SST)anomalies in the tropical eastern Pacific(PDO-E),while that in the Atlantic and the Indian Ocean is associated with the PDO SST anomalies in the western Pacific(PDO-W).However,the PDO-E and PDO-W SST anomalies are poorly coupled in the 1980 s,and this"destructive PDO"pattern results in a breakdown of the TSDs-PDO relationship.The results here have an important implication for seasonal to decadal predictions of global TSD.     

Recurrent daily OLR patterns in the Southern Africa/Southwest Indian Ocean region,implications for South African rainfall and teleconnections

A cluster analysis of daily outgoing longwave radiation (OLR) anomalies from 1979 to 2002 over the Southern Africa/Southwest Indian Ocean (SWIO) region for the November to February season reveals seven robust and statistically well separated recurrent patterns of large-scale organized convection. Among them are three regimes indicative of well defined tropical–temperate interactions linking the hinterland parts of Southern Africa to the mid-latitudes of the SWIO. Preferred transitions show a tendency for an eastward propagation of these systems. Analysis of daily rainfall records for South Africa shows that six of the OLR regimes are associated with spatially coherent and significant patterns of enhanced or reduced daily rainfall over the country. Atmospheric anomalies from the NCEP/DOE II reanalysis dataset show that the OLR regimes are associated with either regional or near-global adjustments of the atmospheric circulation, the three regimes representative of tropical–temperate interactions being in particular related to a well-defined wave structure encompassing the subtropical and temperate latitudes, featuring strong vertical anomalies and strong poleward export of momentum in the lee of the location of the cloud-band. The time-series of OLR regimes seasonal frequency are correlated to distinctive anomaly patterns in the global sea-surface-temperature field, among which are shown to be those corresponding to El Nino and La Nina conditions. The spatial signature of El Nino Southern Oscillation’s (ENSO) influence is related to the combination of an increased/decreased frequency of these regimes. It is shown in particular that the well-known “dipole” in convection anomalies contrasting Southern Africa and the SWIO during ENSO events arises as an effect of seasonal averaging and is therefore not valid at the synoptic scale. This study also provides a framework to better understand the observed non-linearities between ENSO and the seasonal convection and rainfall anomalies over the region.