Space-Time Characteristic Analysis of Wind Field over the South Indian Ocean

According to the ship observation data over the South Indian Ocean during 1950 1995, taking 1°× 1° and 5°× 5°grid, the characteristics and variation rule of wind are analyzed. Through analyzing the chart of isopleths of the monthly elements, the conclusion that the seasonal variation of the wind field over the South Indian Ocean is less remarkable than that in the oceans of the Northern Hemisphere is got. The seasonal variation of the wind field is also obvious in this region, but the seasonal difference is little. The wind in winter is stronger than in summer, correspondingly, the average wind speed is higher, and the frequencies of gale of forces ≥ 6 and 8 are also higher. The north of 10°S is a monsoon area; Southeast wind prevails all over the year in the rest of the trade wind area; Westerly wind dominates in the south of 40°S. This paper provides specific data of wind field and variation for ship ocean transportation, ocean-going visits and scientific experiment.

MEDIUM-RANGE OSCILLATION AND TELECONNECTION OF THE ATMOSPHERIC CIRCULATION SYSTEMS OVER THE NORTHWEST PACIFIC AND SOUTH INDIAN OCEANS

This paper aims to demonstrate some characteristics of the 20-50 day oscillations of certain circulation systems in low latitudes during the northern summer seasons.The teleconnection between the variations of the Mascarene high and the Northwest Pacific high and its physical mechanism are studied.How the Mas- carene high plays an important role in the interaction between the atmospheric circulations of both hemispheres is discussed.

Covariability of Subantarctic Mode Water and the Southern Branch of the Subtropical Indian Ocean Countercurrent in Argo Observations

The Subantarctic Mode Water(SAMW)forms in the deep mixed layer north of the Antarctic Circumpolar Current and spreads northward into the subtropical gyre.The subtropical South Indian Countercurrent(SICC)flows eastward on the north flank of the thick SAMW layer within 22°-32°S from south of Madagascar at around 25°S,50°E toward western Australia.The dynamical relation of the SAMW and the southern branch of the SICC(30°-32°S)is investigated in this work based on the monthly mean Argo data from 2004 to 2019.The physical properties of the SAMW and its pathway from the formation region are described.Most of the SAMW in the Indian Ocean sector originates from the deep mixed layers of the southeastern Indian Ocean(about 40°S,85°-105°E)and moves along the subtropical gyre.It takes around ten years to arrive east of Madagascar Island preserving its low potential vor-ticity characteristics.As a thick layer with homogeneous vertical properties,the SAMW forces the upper pycnocline to shoal,and the associated eastward shear results in the surface-intensified SICC.The SAMW forms a tongue-shaped thickness pattern,which influ-ences the southern branch of the SICC above the northern flank of the thickest SAMW layer between 24°S and 32°S.The seasonal,interannual,and decade variations of the southern branch of the SICC are closely related to the meridional gradient of the underlying SAMW thickness.The SAMW thickened and strengthened from 2005 to 2015,thereby anchoring a strengthened SICC.The interan-nual covariability of the SAMW and SICC further supports the SAMW’s role in driving SICC variability.

The Impact of the Tropical Indian Ocean on South Asian High in Boreal Summer

The tropical Indian Ocean （TIO） is warmer than normal during the summer when or after the El Nio decays. The present study investigates the impact of TIO SST on the South Asian High （SAH） in summer. When the TIO is warmer, the SAH strengthens and its center shifts southward. It is found that the variations in the SAH cannot be accounted for by the precipitation anomaly. A possible mechanism is proposed to explain the connection between the TIO and SAH： warmer SST in the TIO changes the equivalent potential temperature （EPT） in the atmospheric boundary layer （ABL）, alters the temperature profile of the moist atmosphere, warms the troposphere, which produces significant positive height anomaly over South Asia and modifies the SAH. An atmospheric general circulation model, ECHAM5, which has a reasonable prediction skill in the TIO and South Asia, was selected to test the effects of TIO SST on the SAH. The experiment with idealized heating over the TIO reproduced the response of the SAH to TIO warming. The results suggest that the TIO-induced EPT change in the ABL can account for the variations in the SAH.

Bottom water temperature measurements in the South China Sea,eastern Indian Ocean and western Pacific Ocean

文章报道了一批新的海底底水温度(BWT)数据,其中南海(SCS)158个站位、东印度洋(EIO)30个站位及西太平洋(WPO)37个站位。基于这批新的BWT数据,获得南海和西太平洋海域底水温度与水深经验关系,可为地球物理和物理海洋提供准确、可靠的海底温度边界。这将有助于海底油气资源调查与评估。同时,这批实测数据表明:1)水深超过3500m的海域,其底水温度在南海约为2.47℃,比东印度洋(～1.34℃)和西太平洋(～1.60℃)稍微偏高。这与大洋传送带模式所预测的情况比较吻合。该模式认为:低温高盐的海水,从北大西洋格陵兰岛和冰岛附近海域下沉到深层,然后向南流动,再与南极洲周围海域的低温高盐海水一同向北进入印度洋和太平洋。而南海是一个相对比较封闭的热带边缘海,其内部海水与印度洋和菲律宾海交换有限,导致海水温度整体高于印度洋和太平洋。2)台西南盆地水深在2700～3000m的部分站位,其底水温高达约3.00℃,明显高于其周边同水深海域底水温度(平均值约为2.33℃)。这可能是台西南盆地海底水热活动导致的结果。3)在东印度洋和西太平洋水深超过4800m海域,底水温度随着水压增大稍有升高,其升高率分别为10.6mK·MPa^(-1)和12.0mK·MPa^(-1)。这与理论估算的深层底水绝热压力温度梯度范围较为吻合。这也意味着东印度洋和西太平洋深层底水,主要由绝热自压作用导致其温度随着深度的增大而升高。

Rapid Climatic Change during Past 60 ka Recorded in NE Indian Ocean and Its Correspondence from South China Land

According to the marine records from the Bay of Bengal, northeastern Indian Ocean, and the continental records from the South China, the authors make a detailed discussion in this paper about the correlation between them and their implication of rapid climatic change. The marine records show its good response to the high latitudes both for cold events and for warm ones while the continental records mainly mirror those cold Heinrich events corresponding to the North Atlantic but bear strongly a local color in reflecting warm events. The authors assume that the heat transmission style may cause the unbalanced coupling relationship.

Relationship between Indian Ocean dipole and ENSO and their connection with the onset of South China Sea summer monsoon

Using Reynolds and Smith 1950 - 1998 re-constructed monthly-mean SST to discuss the relationship between the ENSO and Indian Ocean dipole （IOD） and their possible connection with the onset of South China Sea summer monsoon（ SCSSM）, the results are obtained as follows ： Most of IOD events have a closely positive relation to simultaneous ENSO events in summer and autumn. IOD events in autumn （ mature phase） are also closely related to ENSO events in winter （ mature phase）. When these two kinds of events happen in phase, i.e. , positive （negative） IOD events are coupled with E1 Nifío （La Nifía） events, they are always followed by late （ or early） onsets of SCSSM. On the contrary, when these two kinds of events happen out of phase, i.e. positive （negative） IOD events are coupled with La Nifia （ E1 Nifío） events, they are followed by normal onsets of SCSSM. In addition, single IOD events or single ENSO events cannot correspond well to the abnormal onset of SCSSM.

Comparisons of surface Chl a and primary productivity along three transects of the southern South China Sea, northern Java Sea and eastern Indian Ocean in April 2011

Results are presented about the changes in chlorophyll a density, carbon fixation and nutrient levels in the surfacewaters of three transects of the southern South China Sea （SCS）, northern Java Sea （JS） and eastern Indian Ocean （IO） duringApril 5-16 of 2011. The in situ Chl a concentration and carbon fixation showed decreasing trends from high to low latitudealong the three transects, while the photosynthetic rate of phytoplankton estimated from 14C incorporation displayed no simplevariation with latitude. Chl a concentration and carbon fixation in the IO water was lower than that in the JS water. Highersalinity and lower contents of dissolved inorganic nitrogen （DIN） and silicate （SiO3^2-） characterized the IO water as comparedto the SCS or JS water, and the PO4^3- content was lower in the IO water than in the SCS or JS water in most cases. Our resultsalso indicate the importance of DIN and SiO3^2- concentrations for the geographical changes in phytoplankton biomass andprimary productivity among the three regions.

Southern and Tropical Indian Ocean SST: A Possible Predictor of Winter Monsoon Rainfall over South India

The complexities in the relationship between winter monsoon rainfall (WMR) over South India and Sea Surface temperature (SST) variability in the southern and tropical Indian Ocean (STIO) are evaluated statistically. The data of the time period of our study (1950-2003) have been divided exactly in two halves to identify predictors. Correlation analysis is done to see the effect of STIO SST variability on winter monsoon rainfall index (WMRI) for South India with a lead-lag of 8 seasons (two years). The significant positive correlation is found between Southern Indian Ocean (SIO) SST and WMRI in July-August-September season having a lag of one season. The SST of the SIO, Bay of Bengal and North Equatorial Indian Ocean are negatively correlated with WMRI at five, six and seven seasons before the onset of winter monsoon. The maximum positive correlation of 0.61 is found from the region south of 500 S having a lag of one season and the negative correlations of 0.60, 0.53 and 0.57 are found with the SST of the regions SIO, Bay of Bengal and North Equatorial Ocean having lags of five, six and seven seasons respectively and these correlation coefficients have confidence level of 99%. Based on the correlation analysis, we defined Antarctic Circumpolar Current Index A and B (ACCIA (A) & ACCIB (B)), Bay of Bengal index (BOBI (C)) and North Equatorial Index (NEI (D)) by averageing SST for the regions having maximum correlation (positive or negative) with WMRI index. These SST indices are used to predict the WMRI using linear and multivariate linear regression models. In addition, we also attempted to detect a dynamic link for the predictability of WMRI using Nino 3.4 index. The predictive skill of these indices is tested by error analysis and Willmott’s index.

Pacific-Indian interocean circulation of the Antarctic Intermediate Water around South Australia

On the basis of the salinity distribution of isopycnal（σ_0=27.2 kg/m^3） surface and in salinity minimum, the Antarctic Intermediate Water（AAIW） around South Australia can be classified into five types corresponding to five regions by using in situ CTD observations. Type 1 is the Tasman AAIW, which has consistent hydrographic properties in the South Coral Sea and the North Tasman Sea. Type 2 is the Southern Ocean（SO） AAIW, parallel to and extending from the Subantarctic Front with the freshest and coldest AAIW in the study area. Type 3 is a transition between Type 1 and Type 2. The AAIW transforms from fresh to saline with the latitude declining（equatorward）. Type 4, the South Australia AAIW, has relatively uniform AAIW properties due to the semienclosed South Australia Basin. Type 5, the Southeast Indian AAIW, progressively becomes more saline through mixing with the subtropical Indian intermediate water from south to north. In addition to the above hydrographic analysis of AAIW, the newest trajectories of Argo（Array for real-time Geostrophic Oceanography） floats were used to constructed the intermediate（1 000 m water depth） current field, which show the major interocean circulation of AAIW in the study area. Finally, a refined schematic of intermediate circulation shows that several currents get together to complete the connection between the Pacific Ocean and the Indian Ocean. They include the South Equatorial Current and the East Australia Current in the Southwest Pacific Ocean, the Tasman Leakage and the Flinders Current in the South Australia Basin, and the extension of Flinders Current in the southeast Indian Ocean.

Circulation Patterns Linked to the Positive Sub-Tropical Indian Ocean Dipole

The positive phase of the subtropical Indian Ocean dipole(SIOD)is one of the climatic modes in the subtropical southern Indian Ocean that influences the austral summer inter-annual rainfall variability in parts of southern Africa.This paper examines austral summer rain-bearing circulation types(CTs)in Africa south of the equator that are related to the positive SIOD and the dynamics through which specific rainfall regions in southern Africa can be influenced by this relationship.Four austral summer rain-bearing CTs were obtained.Among the four CTs,the CT that featured(i)enhanced cyclonic activity in the southwest Indian Ocean;(ii)positive widespread rainfall anomaly in the southwest Indian Ocean;and(iii)low-level convergence of moisture fluxes from the tropical South Atlantic Ocean,tropical Indian Ocean,and the southwest Indian Ocean,over the south-central landmass of Africa,was found to be related to the positive SIOD climatic mode.The relationship also implies that positive SIOD can be expected to increase the amplitude and frequency of occurrence of the aforementioned CT.The linkage between the CT related to the positive SIOD and austral summer homogeneous regions of rainfall anomalies in Africa south of the equator showed that it is the principal CT that is related to the inter-annual rainfall variability of the south-central regions of Africa,where the SIOD is already known to significantly influence its rainfall variability.Hence,through the large-scale patterns of atmospheric circulation associated with the CT,the SIOD can influence the spatial distribution and intensity of rainfall over the preferred landmass through enhanced moisture convergence.

A Note on the South China Sea Shallow Interocean Circulation

The existing estimates of the volume transport from the Pacific Ocean to the South China Sea are summarized, showing an annual mean westward transport, with the Taiwan Strait outflow subtracted, of 3.5±2.0 Sv （1 Sv=-0^6 ma s^-1）. Results of a global ocean circulation model show an annual mean transport of 3.9 Sv from the Pacific to the Indian Ocean through the South China Sea. The boreal winter transport is larger and exhibits a South China Sea branch of the Pacific-to-Indian Ocean throughflow, which originates from the western Philippine Sea toward the Indonesian Seas through the South China Sea, as well as through the Karimata and Mindoro Straits. The southwestward current near the continental slope of the northern South China Sea is shown to be a combination of this branch and the interior circulation gyre. This winter branch can be confirmed by trajectories of satellite-tracked drifters, which clearly show a flow from the Luzon Strait to the Karimata Strait in winter. In summer, the flow in the Karimata Strait is reversed. Numerical model results indicate that the Pacific water can enter the South China Sea and exit toward the Sulu Sea, but no observational evidence is available. The roles of the throughiiow branch in the circulation, water properties and air-sea exchange of the South China Sea, and in enhancing and regulating the volume transport and reducing the heat transport of the Indonesian Throughflow, are discussed.

A Review of Ocean-Atmosphere Interaction Studies in China

A large number of papers have been published and great efforts have been made in the recent 20 years by the Chinese oceanographic and meteorological scientists in the ocean-atmosphere interaction studies. The present paper is an overview of the major achievements made by Chinese scientists aad their collaborators in studies of larger scale ocean-atmosphere interaction in the following oceans： the South China Sea, the Tropical Pacific, the indian Ocean and the North Pacific. Many interesting phenomena and dynamic mechanisms have been discovered and studied in these papers. These achievements have improved our understanding of climate variability and have great implications in climate prediction, and thus are highly relevant to the ongoing international Climate Variability and Predictability （CLIVAR） efforts.

基于青藏高原和印度洋区域热力状况的气候预测先兆信号

围绕青藏高原和印度洋区域热力状况对南亚季风、水汽输送和区域气候的影响,本文梳理总结了相关研究进展,重点聚焦在青藏高原和印度洋区域热力状况和热力差异与季风活动、水汽输送等重要气候指标的联系,并据此提出了印度洋和高原区域在次季节、季节尺度的气候预测指标和方法。对认识青藏高原和印度洋区域热力状况对气候的影响,改善该区域气候预测的能力具有参考意义。

Connection of sea level variability between the tropical western Pacific and the southern Indian Ocean during recent two decades

Based on the merged satellite altimeter data and in-situ observations, as well as a diagnosis of linear baroclinic Rossby wave solutions, this study analyzed the rapidly rise of sea level/sea surface height （SSH） in the tropical Pacific and Indian Oceans during recent two decades. Results show that the sea level rise signals in the tropical west Pacific and the southeast Indian Ocean are closely linked to each other through the pathways of oceanic waveguide within the Indonesian Seas in the form of thermocline adjustment. The sea level changes in the southeast Indian Ocean are strongly influenced by the low-frequency westward-propagating waves originated in the tropical Pacific, whereas those in the southwest Indian Ocean respond mainly to the local wind forcing. Analyses of the lead-lag correlation further reveal the different origins of interannual and interdecadal variabilities in the tropical Pacific. The interannual wave signals are dominated by the wind variability along the equatorial Pa- cific, which is associated with the El Nifio-Southern Oscillation; whereas the interdecadal signals are driven mainly by the wind curl off the equatorial Pacific, which is closely related to the Pacific Decadal Oscillation.

青藏高原—印度洋热力差对南亚季风活动的多尺度影响

海陆热力差异是季风形成和演变的根本驱动力,青藏高原与印度洋热力差异是影响南亚季风活动的重要因素。本文围绕次季节、季节、年际和年代际等不同时间尺度上青藏高原与印度洋的热力差异对南亚季风活动的影响,回顾和总结了相关研究成果。在次季节尺度上,主要聚焦在两者的热力差异对南亚季风爆发的影响;在年际尺度上,着重阐释了其对南亚季风强度年际变化的指示意义;在年代际尺度上,考察了热力差异和南亚季风降水关系的年代际变化。同时,本文对该领域一些需要进一步研究的问题进行了讨论。

Differences in Atmospheric Heat Source between the Tibetan Plateau–South Asia Region and the Southern Indian Ocean and Their Impacts on the Indian Summer Monsoon Outbreak

In this paper, the NCEP-NCAR daily reanalysis data are used to investigate the characteristics of the atmospheric heat source/sink （AHSS） over South Asia （SA） and southern Indian Ocean （SIO）. The thermal differences between these two regions and their influence on the outbreak of the Indian summer monsoon （ISM） are explored. Composite analysis and correlation analysis are applied. The results indicate that the intraseasonal variability of AHSS is signi- ficant in SA but insignificant in the SIO. Large inland areas in the Northern Hemisphere still behave as a heat sink in March, similar to the situation in winter. Significant differences are found in the distribution of AHSS between the ocean and land, with distinct land-ocean thermal contrast in April, and the pattern presents in the transitional period right before the ISM onset. In May, strong heat centers appear over the areas from the Indochina Peninsula to the Bay of Bengal and south of the Tibetan Plateau （TP）, which is a typical pattern of AHSS distribution during the monsoon season. The timing of SA-SIO thermal difference turning positive is about 15 pentads in advance of the onset of the ISM. Then, after the thermal differences have turned positive, a pre-monsoon meridional circulation cell develops due to the near-surface heat center and the negative thermal contrast center, after which the meridional circulation of the ISM gradually establishes. In years of early （late） conversion of the SASIO thermal difference turning from neg- ative to positive, the AHSS at all levels over the TP and SIO converts later （earlier） than normal and the establish- ment of the ascending and descending branches of the ISM＇s meridional circulation is later （earlier） too. Meanwhile, the establishment of the South Asian high over the TP is later （earlier） than normal and the conversion of the Mas- carene high from winter to summer mode occurs anomalously late （early）. As a result, the onset of the ISM is later （earlier） than normal. However, the difference in vorticity between early and late conversion only shows in the changes of strong vorticity centers＇ location in the upper and lower troposphere.

NUMERICAL EXPERIMENTS FOR THE INFLUENCES OF SST ANOMALIES OVER THE SOUTH CHINA SEA-EASTERN TROPICAL INDIAN OCEAN ON THE SOUTH CHINA SEA SUMMER MONSOON ONSET

Numerical experiments with a low resolution atmospheric general circulation model (AGCM) were conducted to investigate the influences of SST anomalies (SSTA) over the South China Sea- tropical eastern indian Ocean (SCS-TEIO) on the onset of the South China Sea summer Monsoon (SCSM).With positive SSTA over the SCS-TEIO,the anomalous cyclones appear over both sides of the equator at low layer,which weakens the Somali and Australian cross-equatorial SW flow. The anomalous anticyclone in the east of Phillips strengthens the subtropical high with its ridge southwestward shifted.The anomalous anticyclones over both sides of equator at high layer strengthen the South Asia high,thus weaken the SCSM and delay its onset.With negative SSTA over the SCS-ETIO,the anomalous anticyclones appear over both sides of the equator at low layer,which strengthen the Australian but weaken the Somali cross-equatorial SW flow.The anomalous cyclone in northeast of Phillips will weaken the subtropical high.The stronger monsoon meridional circulation over the tropical western Pacific will strengthen the cross-equatorial southerly flow,and the anomalous cyclones over both sides of equator at high layer will weaken the South Asia high,hence strengthen the SCSM and advance its onset.

印度洋变局中的大国竞争与合作

印度洋海上贸易和海上交通要道对于世界各国的重要性再强调也不为过。其中,中国90%和印度80%的石油进口需要通过该地区的阿拉伯海。更为重要的是,印度洋海床承载着的光纤电缆网络是当代数字连接和通信系统在东西方之间联通的基石,不仅具有战略重要性,而且已经引起了区域大国的关注,并正在加剧着该地区地缘政治紧张局势,凸显全球治理模式转变的迫切性和必要性。同时,印度洋地区位于“全球南方”的中心,这里拥有许多地区性组织,如东盟、非洲联盟、海合会和环孟加拉湾多领域技术经济合作倡议(BIMSTEC)等。然而,如何防止竞争演变为全面冲突和战争,则是一个真正的挑战。和平共处原则和致力于共同发展的理念再次成为构建多边主义的要义。

南印度洋中国中山站至澳大利亚费里曼特尔断面海洋锋位置及其年际变化

根据中国第 1 8次南极科学考察队 2 0 0 2年 1～ 3月在南印度洋从中山站外普里兹湾到澳大利亚费里曼特尔断面的走航XBT/XCTD资料和CTD资料及 1 998年1月、1 999年 2月和 2 0 0 0年 3月等其他航次的调查资料 ,分析了该航线上海洋锋的位置及其年际变化 :( 1 )在 75°～ 78°E南极陆坡锋的位置在 6 4 5°～ 6 5 5°S ;在 84°～1 0 0°E范围极地锋在 53 5°～ 54 3°S附近 ;在 96°～ 1 0 3°E亚南极锋在 4 6°S～ 4 7 0°S附近 ;在 1 1 0°E附近亚热带锋在 37 2～ 38 0°S之间 ;( 2 )在南极极锋区存在显著等温线、等盐线的上凸和下凹 ,不同年份发生位置有变化 ;( 3)在亚南极锋北侧 ,等温线、等盐线呈垂直排列的状态 ,温度、盐度垂直方向上分布均匀一致 ;( 4 )与 1 979,1 991和 1 992年该区域同期的资料相比 ,近 4a观测到的极地锋显著偏南 1个纬距以上 .