NUMERICAL STUDY ON DOMINATING FACTOR AND KEY AREA OF EL NINO CYCLE FORMATION*

A coupled model,which is employed to study the dominating factor and key area of El Nino cycle formation,consists of a dynamical ocean model and a statistical atmospheric model.The coupled model with seasonal forcing successfully reproduces the El Nino event cycle which exhibits quasi-regular oscillations with a preferred period of about 4 years.The results show that the heat content(HC) is transported between the eastern and the western tropical Pacific areas.The spatial distribution of HC anomalies for four phases of the whole cycle clearly shows a possible formation mechanism of El Nino.Experiments further suggest that sea surface temperature in the tropical Pacific and HC in the central tropical Pacific are the most important factors and the central tropical Pacific is the most important area for determining formation of El Nino cycle.     

Variability of the Intertropical Convergence Zone recorded in coral isotopic records from the central Indian Ocean (Chagos Archipelago)

We have analyzed the stable oxygen isotopic composition of two Porites corals from the Chagos Archipelago, which is situated in the geographical center of the Indian Ocean. Coral δ¹⁸O at this site reliably records temporal variations in precipitation associated with the Intertropical Convergence Zone (ITCZ). Precipitation maxima occur in boreal winter, when the ITCZ forms a narrow band across the Indian Ocean. The Chagos then lies within the center of the ITCZ, and rainfall is strongly depleted in δ¹⁸O. A 120-yr coral isotopic record indicates an alternation of wet and dry intervals lasting 15 to 20 yr. The most recent 2 decades are dominated by interannual variability, which is tightly coupled to the El Niño-Southern Oscillation (ENSO). This is unprecedented in the 120 yr of coral record. As the ITCZ is governed by atmospheric dynamics, this provides evidence of a major change in the coupled ENSO-monsoon system.     

On the Mechanism of the Locking of the El Nio Event Onset Phase to Boreal Spring

1. Introduction The observed facts show that the ENSO cycle has obvious phase-locking and oscillates irregularly (An and Wang, 2001; Kaplan et al., 1998). Based on Zibiak and Cane's (1987) model (hereafter, the Z-C model) and simple, coupled ocean-atmosph…     

The Application of ARGO Data to the Global Ocean Data Assimilation Operational System of NCC

1. Introduction It is well-known that the state of ocean plays very important role in the climate change. But there is a paucity of the ocean observation data. The data distri- bution in the space, time and different components is very inhomogeneous, even in some areas, there are no any observation data. Hence, it brings some diffcul- ties to the scientists to study many problems relevant to ocean. This situation has been being changed since ARGO (Array for Real-time Geostrophic Oceanogra-…     

新疆哈密地区近54a日照时数的均一性分析及其影响因素

以新疆哈密地区1961-2014年6个气象观测站地面气象观测资料为依据,利用线性趋势分析、相关性分析、M-K突变检验分析等方法,对哈密地区近54a四季及年平均日照时数的变化趋势、异常年份、突变检验及影响因子进行分析,得出以下结论：近54a哈密地区春季与年平均日照时数均呈上升趋势,而夏、秋、冬季变化比较平稳;年日照时数异常偏少出现在1998年,但从未出现过异常偏多年;年日照时数在1973年和2008年发生两次突变,减少、增加趋势不显著;年、春季日照时数增加与低云量的减少关系密切。     

LINKAGE BETWEEN INDIAN OCEAN DIPOLE AND TWO TYPES OF El NI?O AND ITS POSSIBLE MECHANISMS

After compositing three representative ENSO indices,El Nio events have been divided into an eastern pattern(EP) and a central pattern(CP).By using EOF,correlation and composite analysis,the relationship and possible mechanisms between Indian Ocean Dipole(IOD) and two types of El Nio were investigated.IOD events,originating from Indo-Pacific scale air-sea interaction,are composed of two modes,which are associated with EP and CP El Ni o respectively.The IOD mode related to EP El Nio events(named as IOD1) is strongest at the depth of 50 to 150 m along the equatorial Indian Ocean.Besides,it shows a quasi-symmetric distribution,stronger in the south of the Equator.The IOD mode associated with CP El Nio(named as IOD2) has strongest signal in tropical southern Indian Ocean surface.In terms of mechanisms,before EP El Nio peaks,anomalous Walker circulation produces strong anomalous easterlies in equatorial Indian Ocean,resulting in upwelling in the east,decreasing sea temperature there;a couple of anomalous anticyclones(stronger in the south) form off the Equator where warm water accumulates,and thus the IOD1 occurs.When CP El Nio develops,anomalous Walker circulation is weaker and shifts its center to the west,therefore anomalous easterlies in equatorial Indian Ocean is less strong.Besides,the anticyclone south of Sumatra strengthens,and the southerlies east of it bring cold water from higher latitudes and northerlies west of it bring warm water from lower latitudes to the 15° to 25°S zone.Meanwhile,there exists strong divergence in the east and convergence in the west part of tropical southern Indian Ocean,making sea temperature fall and rise separately.Therefore,IOD2 lies farther south.     

两类中太平洋El Nio特征的对比分析

利用1979—2012年逐月Hadley中心海表温度、欧洲中期天气预报中心次表层海温、NCEP/NCAR风场再分析资料,对两类中太平洋(CP)El Nio及耦合的大气环流特征进行分析。结果表明,第一类CP El Nio(CP-ⅠEl Nio)增暖中心位于Nio4区且关于赤道对称;第二类CP El Nio(CP-ⅡEl Nio)的Nio4区与热带东北太平洋区域(NEP,130~110°W、15~25°N)同位相变化,冬季成熟后形成关于赤道非对称的带状增暖结构。进一步的研究表明,两类CP El Nio次表层结构存在差异:CP-ⅠEl Nio冬季次表层海温异常(SOTA)在中东太平洋与西太平洋呈显著偶极分布;CP-ⅡEl Nio在中、西太平洋位相相反但东太平洋异常较弱,且经向异常主要在赤道及其以北。两类CP El Nio耦合的大气环流特征不同:CP-ⅠEl Nio冬季异常Walker环流上升中心位于赤道上空,经向风向赤道辐合,低纬地区Hadley环流加强;CP-ⅡEl Nio冬季低层向北越赤道气流加强,Walker环流上升中心移到赤道以北,低纬地区Hadley环流减弱。     

闽西北5月雨量特多年份环流特征及其成因分析

利用闽西北三明市的11个县、市1961—2014年5月降雨量资料、常规气象观测资料和NCEP 2.5×2.5°再分析资料等对闽西北历史上5月雨量特多年的降雨量时空分布特征和大气环流特征及其成因进行了分析,结果表明:5月区域性、全区性雨量特多年的环流异常特征是500hPa欧亚中高纬度自西向东环流呈"+-+"的波列分布,鄂霍次克海北侧高度正距平区的稳定少动,起到阻挡冷空气东移的作用,冷空气沿乌拉尔山西侧高度正距平中心前的偏北气流不断南下,使萨彦岭一带高度负距平中心加强,其底部不断分裂小槽东移影响闽西北。925hPa华南北部维持一条稳定切变线;对于2014年5月特例的环流形势分析结果可知,500hPa东亚大槽明显偏东,引导冷空气南下与强大副高西北侧西南暖湿气流交绥在闽西北上空。925hPa闽西北处于气旋式辐合区内。北支槽、南支槽均非常活跃,东移影响闽西北,是导致该地5月区域性降雨量特多的主要原因。     

Sulfur speciation with high performance liquid chromatography as a tool for El Chichón volcano,crater lake monitoring

The monitoring of sulfur species in crater lakes has proven to be useful for forecasting episodes of volcanic unrest in certain active volcanoes, including Poás, Costa Rica; Kusatsu-Shirane, Japan; and Mt. Ruapehu, New Zealand. In this study, we have improved the current geochemical monitoring of El Chichón volcano through the setting of optimal high-performance liquid chromatography conditions (HPLC) for the analysis of S²⁻, SO₃²⁻, S₂O₃²⁻, S₄O₆²⁻ and SO₄²⁻ using a common chromatographic system. The procedure was applied to the analysis of lake samples taken in March, July and October of 2014 and April of 2015. The results were promising, since nearly all species were detected (with the exception of S₂O₃²⁻) in measurable amounts, including S²⁻ (<0.85–5.05 mg/L), SO₃²⁻ (<2.77–26.1 mg/L), S₄O₆²⁻ (108.27–303.82 mg/L) and SO₄²⁻ (489.58–676.26 mg/L). The spatial distribution of these species along the lakeshore showed zones of increased concentrations to the east and southeast of the lake, which provides information on the distribution of faults or cracks that feed hydrothermal fluids to the lake. This method thus provides additional information linked to the volcanic and hydrothermal activity of the volcano.     

近年来厄尔尼诺期间北赤道流输运的年际变化

为了研究近年来厄尔尼诺期间北赤道流输运的年际变化,本文利用海洋客观分析数据MOAA GPV(Grid Point Value of the Monthly Objective Analysis)以及P-vector方法计算了北太平洋绝对地转流,探讨了2001~2013年期间厄尔尼诺与北赤道流输运之间的关系。在此期间发生的4次厄尔尼诺事件中,北赤道流输运在2002~2003、2006~2007、2009~2010年的厄尔尼诺成熟期都出现了明显的增强,但是在2004~2005年的厄尔尼诺成熟期并没有明显的增强。进一步分析发现,在2002~2003年、2006~2007年、2009~2010年的厄尔尼诺成熟期,10°N以南的热带西北太平洋区域出现了负的海面高度异常和气旋式环流异常,这主要是由热带环流区域出现的西风异常和正的Ekman抽吸通过Rossby波西传到热带西太平洋区域所致;但是在2004~2005年厄尔尼诺成熟期,海面温度异常的分布明显不同,西风异常和正的Ekman抽吸异常明显北移,导致负的海面高度异常和气旋式环流异常出现在了10°N以北的西北太平洋区域,使得北赤道流输运在2004~2005年的厄尔尼诺成熟期没有明显的增强。