Mechanism of Thermal Features over the Indo-China Peninsula and Possible Effects on the Onset of the South China Sea Monsoon

The thermal characteristics during the South China Sea (SCS) summer monsoon onset period near the Indo-China Peninsula are analyzed by using the South China Sea Monsoon Experiment (SCSMEX) reanalysis data from 1 May to 31 August 1998 and the NCEP/ NCAR pentad-mean reanalysis data from January 1980 to December 1995. The possible relationships between the anomaly of thermal features near the Indo-China Peninsula and the SCS monsoon onset are investigated, and the mechanism causing the SCS summer monsoon onset is also discussed. Results from the 1998 SCSMEX reanalysis data show that there exists a strong persistent surface sensible heating near the Indo-China Peninsula prior to the SCS monsoon onset, which has apparent low frequency oscillation features. This sensible healing leads lo a warmer center in the lower atmosphere near the Indo-China Peninsula and strong local horizontal temperature and geopotential height gradients which are favorable to strengthening the southwest wind over the Indo-China Peninsula. It is also found that stronger convergent winds at lower levels and stronger divergent winds at high levels appear, which provide a favorable configuration for the development of vertical motion, enhancement of precipitation, and onset of the SCS monsoon. These results can be verified by analysis of the multi-year mean data. Additionally, it is found that the temperature at 850 hPa increases more rapidly over the Indo-China Peninsula than the South China Sea prior to the SCS monsoon onset, which leads to a strengthening of the temperature difference between the Indo-China Peninsula and the South China Sea. Moreover, results from the analysis of the longitudinal temperature and geopotential height differences show that the eastern retreat of the subtropical high over the Indo-China Peninsula during the period of SCS monsoon onset is associated with the temperature increase over the Indo-China Peninsula and the eastern extension of low trough over the Bay of Bengal.

Establishment of the South Asian High over the Indo-China Peninsula During Late Spring to Summer

The establishment of the upper-level South Asian high （SAH） over the Indo-China Peninsula （ICP） during late boreal spring and its possible causes are investigated using long-term NCEP-NCAR and ERA-40 reanalysis and satellite-observed OLR data. Results show that, from early March to mid-April, deep convection stays south of -6°N over the northern Sumatran islands. As the maximum solar radiation moves over the latitudes of the ICP （10-20°N） in late April, the air over the ICP becomes unstable. It ascends over the ICP and descends over the adjacent waters to the east and west. This triggers deep convection over the ICP that induces large latent heating and strong updrafts and upper-level divergence, leading to the formation of an upper-level anticyclonic circulation and the SAH over the ICE During early to mid-May, deep convection over the ICP intensifies and extends northwards to the adjacent waters. Strong latent heating from deep convection enhances and maintains the strong updrafts and upper-level divergence, and the SAH is fully established by mid-May. Thus, the seasonal maximum solar heating and the land-sea contrast around the ICP provide the basic conditions for deep convection to occur preferentially over the ICP, which leads to the formation of the SAH over the ICP from late April to mid-May. Simulations using RegCM4 also indicate that the diabatic heating over the ICP is conducive to the generation and development of upper-level anticyclonic circulation, which leads to an earlier establishment of the SAH.

Enhanced Seasonal Predictability of Spring Soil Moisture over the Indo-China Peninsula for Eastern China Summer Precipitation under Non-ENSO Conditions

Seasonal prediction of summer precipitation over eastern China is closely linked to the East Asian monsoon circulation,which is largely affected by the El Niño-Southern Oscillation(ENSO).In this study,results show that spring soil moisture(SM)over the Indo-China peninsula(ICP)could be a reliable seasonal predictor for eastern China summer precipitation under non-ENSO conditions.When springtime SM anomalies are present over the ICP,they trigger a structured response in summertime precipitation over most of eastern China.The resultant south-to-north,tri-polar configuration of precipitation anomalies has a tendency to yield increased(decreased)precipitation in the Yangtze River basin and decreased(increased)in South and North China with a drier(wetter)spring soil condition in the ICP.The analyses show that ENSO exerts a powerful control on the East Asian circulation system in the ENSO-decaying summer.In the case of ENSO forcing,the seasonal predictability of the ICP spring SM for eastern China summer precipitation is suppressed.However,in the absence of the influence of ENSO sea surface temperature anomalies from the preceding winter,the SM anomalies over the ICP induce abnormal local heating and a consequent geopotential height response owing to its sustained control on local temperature,which could,in turn,lead to abnormal eastern China summer precipitation by affecting the East Asian summer monsoon circulation.The present findings provide a better understanding of the complexity of summer climate predictability over eastern China,which is of potential significance for improving the livelihood of the people.

Seismic Hazard Assessment in the Boundary Region of Indo-China:First Phase of Implementation of the Global Seismic Hazard Assessment Program (GSHAP) in Continental Asia

The primary goal of the demonstration project endorsed by the Scientific and Technical Committee for IDNDR in 1992 is to ensure that national agencies are able to assess seismic hazard in a regionally coordinated fashion by using advanced methods.China,as a Regional Center of Central Southern Asia,has contacted with countries of the region to realistically practice seismic hazard assessments of Continental Asia.A test area located in the collision boundary between the Indian and Eurasian plates was chosen to examine the seismic hazard assessment approach in the regional coordinates.The seismotectonics and three versions of seismic sources of the test area are described in this paper and under the Global Seismic Hazard Assessment Program(GSHAP),guidelines an earthquake catalogue of the test area was assembled.Because of the incompleteness of earthquake data in different countries,we adopt different time windows for different magnitude intervals in order to obtain the seismicity parameters of sources.By

Witnessing the Development of Indo-China,and Promoting People-to-People Understanding and Cooperation——Sidelights on Visits to Cambodia and Laos

At the invitation of Union Youth Federation of Cambodia and the International Department of the Lao People’s Revolutionary Party’s Central Committee,a Chinese NGO Delegation headed by Mr.Ni Jian,Secretary-General of the Chinese Association for International Understanding paid visit to Cambodia and Laos from October 21 to 28.As a member of the delegation,I set my feet on

Impact of Antecedent Soil Moisture Anomalies over the Indo-China Peninsula on the Super Meiyu Event in 2020

In the summer of 2020,a super Meiyu event occurred in the Yangtze River basin(YRB),causing enormous economic losses and human casualties.Recent studies have investigated the possible causes of this super Meiyu event from the perspective of anomalous atmospheric circulation activities and sea surface temperature(SST)anomalies;however,the influence of land surface processes has not garnered considerable attention.This study investigates the possible contributions of land surface processes to this extreme event based on observational analysis and numerical simulations,and shows that antecedent soil moisture(SM)anomalies over the Indo-China Peninsula(ICP)may have had a vital influence on the super Meiyu in 2020.Negative SM anomalies in May over the ICP increased the surface temperature and sensible heat flux.The“memory”of soil allowed the anomalies to persist into the Meiyu period.The heating of the lower atmosphere by the surface strengthened the western Pacific subtropical high,which caused an anomalous anticyclone from the ICP to Northwest Pacific and thus enhanced the southwesterly winds and vertical motion over the YRB.Consequently,the water vapor flux and convergence were strengthened.Sensitivity experiments based on the Weather Research and Forecasting(WRF)model further confirmed the results of observational analysis and indicated that the warm air heated by the ICP surface significantly warmed the lower troposphere from the ICP to Northwest Pacific under the influence of the background wind,thus increasing the geopotential height and inducing an anticyclone.The results of the sensitivity experiments showed that the SM anomalies in May over the ICP increased the precipitation by 10.6%from June to July over the YRB.These findings can improve our understanding of the mechanism of the super Meiyu event in 2020 and facilitate the prediction of extreme Meiyu events.

Effects of the Thermal Contrast Between Indo-China Peninsula and South China Sea on the SCS Monsoon Onset

The seasonal and interannual variations of the thermal contrast between Indo-China Peninsula （ICP） and South China Sea （SCS） were analyzed using the pentad mean NCEP/NCAR reanalysis data during 1958-1998 and the pentad mean outgoing long-wave radiation （OLR） data during 1975-1998, along with the effects of such a thermal contrast on the SCS monsoon onset （SCSMO）. It is shown that there exists significant seasonal evolution for such a thermal contrast. The surface temperature of ICP is higher than that of SCS from pentad 3 to pentad 25 due to the sensible heating of the ICP. After pentad 25, such a thermal gradient reverses due to the temperature decrease resulted from the convection and rainfall over the ICP from pentad 22 to pentad 23. Furthermore, the above seasonal evolution of the discussed thermal contrast also demonstrates a remarkable interannual change which plays an important role in the SCSMO. On one hand, the reversion happens prior to （or simultaneously with） the SCSMO each year during 1958- 1998, thus becoming a precondition for the SCSMO. On the other hand, the earlier （later） the date when the surface temperature of ICP becomes higher （lower） than that of the SCS, the later the SCSMO.

Tracing Escaping Structure in the Northern Indo-China Peninsula by Openness and Remote Sensing

The Openness based on DEM emphasizes the terrain convexity and concavity. It facilitates the interpretation of detailed landforms on the Earth＇s surface. Compared with the layer stacking of ETM＋ with less three-dimensionality and visualizability and with indefinite details of linear images in the deep cutting or deep covered region, the Openness is used for accurate interpretation of tectonic geomorphic units and linear structures. In this paper, the ETM＋ images（741 RGB） and RRIM based on Openness combined with the field geological investigation are used to trace the escaping structure in SE Asia. The east boundary is Ailaoshan shear zone and the west boundary is Uttaradit-Dien Bien Phu fault, which together form the southwards extruding wedge block. The arc boundary surface of the southern Khorat Plateau is jutted to the north. The NW and NE sides of Khorat Plateau are traversed by Uttaradit-Dien Bien Phu fault and Thakhek-Da Nang fault, respectively, resulting in a blocked escaping structure. The SE margins of Truong Son structure belt and Song Ma structure belt are both arcs jutting to SE. These arc structures clamped by faults or related to the fault on one side indicating the material flow direction obviously, are the most specific manifestation of escaping structures. Moreover, these push units are extruded from south to north successively.

冷战结束以来美国的东南亚政策:演进、特征与前景

作为全球战略的重要组成部分,冷战结束以来美国的东南亚政策不断调整演进,经历了重塑、深化和战略升级三个主要发展阶段。整体来看,美国的东南亚政策演进呈现出延续性与阶段性兼具、双边与多边并进的特点,并受到美国与域内外大国关系发展变化的直接影响,具有明显的针对第三方的政策指向性。受制于其全球战略调整以及地区和国际环境变化等多种因素,尤其是服务于制华遏华战略意图的需要,美国将依托“印太战略”框架,从战略布局、议题设置、机制平台等方面强化其东南亚政策。

地位焦虑视角下澳大利亚对华政策的嬗变

21世纪以来,中澳关系在较长时期内保持了良好发展的态势。但自2016年下半年始,在中美战略竞争背景下,澳大利亚开始逐渐产生地位焦虑情绪。澳大利亚认为,中国的迅速崛起将会冲击印太地区既有的权势结构和秩序,而一旦中国主导印太秩序,它将无法在新秩序中维系既有的国家地位。因此,在地位焦虑情绪的驱使下,澳大利亚对中国实施了一系列强硬政策,两国关系进入剧烈动荡期。不过,自2022年5月阿尔巴尼斯领导的工党政府上台后,澳大利亚的地位焦虑情绪有所缓解,两国关系实现破冰、转圜,经贸合作企稳回升,但在安全层面澳大利亚联美制华的趋势短期恐难改变。

北约印太转向:战略逻辑演进、新动向与前景

近年来,在中美战略竞争深化和俄乌冲突两大战略背景下,在美国压力下,北约积极推动印太转向。北约不仅视中国为“系统性挑战”,强调“印太地区对北约重要”和欧亚安全不可分割,还高度“关切”印太海洋安全,加强与日本、韩国、澳大利亚和新西兰“印太四国”机制化联系,推进防务及新兴科技领域务实合作。这一基于“一体化威慑”战略逻辑的北约印太转向,与20世纪90年代及“9·11”事件后基于“合作安全”的战略逻辑大异其趣,表现出新形势下北约印太转向的新动向与新特点。展望未来,受制于北约核心战略利益、军事能力、北约内部分歧及美国国内政治变化等诸多因素限制,北约印太转向始终存在“天花板”,也具有较大不确定性。

美国“印太战略”背景下的美日韩安全合作

在中美战略博弈态势下,美国在亚太地区南北双向推动集团化对抗,对其亚太同盟体系进行升级。拜登政府着力调解日韩在历史及领土问题上的矛盾,将三方安全合作作为推动“印太战略”的外交重点。美日韩安全合作范围和定位发生根本转变,直指中国。三方走近不仅意味着亚太地区安全架构重大变化,也严重冲击亚太区域经济合作与发展。美日韩为不平等的三边关系,难以发展成为真正的三边同盟。东北亚局势事关中国战略安全。中国要保持多边沟通与合作,维护区域和平稳定,避免陷入美日韩挑起的阵营对抗。

“印太经济框架”数字规则:区域合作影响与中国-东盟应对策略

数字经济业已成为改变全球竞争格局的关键力量,数字规则的制定和推广则成为各国提升国际影响力,抢占全球数字市场的重要手段。美国在亚洲和大洋洲启动“印太经济框架”,期望通过广泛的经济合作框架或合作委员会拓展美式规则影响力,从而主导未来数字经济发展走向,持续数字时代的美式霸权。“印太经济框架”数字经济领域涵盖数字环境、新兴技术、基础设施、监管措施和可持续发展等5个方面的内容,既是对美国此前《印度太平洋战略报告》内容的承继,也是与《美日数字贸易协定》为主的美式高标准数字贸易规则的联动,其倡导高标准合作的同时忽视东盟国家市场准入需求和实际承受能力,实质上是为了坚持贸易保护、阻碍亚太一体化和推广美式规则。“印太经济框架”下美国与东盟数字经济合作的达成,不仅会利用投资和数字技术输出阻碍中国与东盟的数字合作,而且会向东盟输出数字发展理念,加剧中国与东盟的“数字鸿沟”,破坏围绕《区域全面经济伙伴关系协定》形成的数字经济合作伙伴关系。因此,中国应当统筹国内国际两个大局,完善中国数字经济规则;全面对接国际标准,巩固数字合作伙伴关系;细化合作内容,共谋数字发展全球规则,共建数字发展新格局。

中南半岛野火变化特征及其与土壤水分的相互作用

[目的]分析野火变化特征并探讨火点数与不同深度土壤水分的关联性,为评价生态文明建设和人类生产生活提供科学依据。[方法]基于SNPP/ⅦRS卫星火点监测、火烧迹地和SMAP土壤水分等数据,使用统计方法多角度对2016—2021年中南半岛野火变化特征进行分析,探讨不同干湿条件下火点数与0—5cm和0—100cm2个不同深度土壤水分的相互作用。[结果]①中南半岛火点数和火烧迹地年内主要出现在2—4月,二者在时空分布上具有较高的一致性,多集中在缅甸西部与印度接壤区域、缅甸中部以东和老挝北部。②2—4月火点主要出现在林地、灌木地和耕地,而易发生在归一化植被指数(NDVI)为如下3个等级的区域:0.2<NDVI≤0.4,0.4<NDVI≤0.6,0.6<NDVI≤0.8,但其所占比例随地表覆盖类型和月份的不同存在一定差异。③特旱和重旱条件下火点区明显较无火点区广,火点数集中程度更高;土壤水分随火点数的增加整体呈减少趋势,但极端干湿条件下,土壤水分随火点数变化存在由减转增的“拐点”,且“拐点”值随时间延后而减小。④滞后1~2个月的火点数与土壤水分相关程度最高;日时间尺度上土壤水分对火点数变化同期响应快,且土壤水分和NDVI高的区域关联性更强。[结论]土壤水分亏缺是中南半岛火点高发的重要驱动力。火点数与土壤水分之间相互作用,二者之间存在显著负向关联性。

美国“印太”海域态势感知体系的构建路径分析

“9·11”事件后,通过制定《国家海域态势感知计划》及其配套措施,美国采取国家统筹、自上而下和全政府的方式,构建了完整、全面的海域态势感知体系。美国“印太战略”提出后,拜登政府努力构建美国主导的、地区盟友和伙伴参与的“印太”海域态势感知网络体系。美国构建这一体系的路径主要包括开放式框架和小范围网络两种模式,并通过以下途径提升“印太”海域态势感知能力:增强自身能力,强化盟伴体系间合作,通过海上军演提升能力和互操作性,以及加强区域内外国家的协调与合作。中国应进一步提升自身海域态势感知能力建设,并加强国际合作,以应对新的安全挑战。

中南半岛春季气溶胶直接辐射强迫时空演变特征分析

中南半岛国家春季存在大量的生物质燃烧活动,生成的气溶胶会通过大气环流影响我国西南地区大气辐射收支,探究其对大气加热率的影响可为研究它对天气和气候的影响提供依据。基于MERRA-2再分析数据中逐时的气溶胶和晴空下的辐射通量等资料,首先分析其时空特征,其次利用EOF、合成分析等统计方法,讨论中南半岛气溶胶光学厚度(AOD)、地表气溶胶直接辐射强迫(ADRF)的时空演变特征及其与大气短波加热率的关系。结果表明:(1)在3-4月生物质燃烧季节,中南半岛与云南省均存在AOD极大值,它们的时间序列变化趋势具有较高的一致性,主要表现为老挝和越南北部地区AOD中心值超过1,受其影响云南省的AOD由北向南逐渐增强。(2)3-4月中南半岛生物质燃烧AOD与总AOD的高值中心一致,说明该区域气溶胶主要来源于生物质燃烧,老挝北部存在高达28 kg·m^(-1)·d^(-1)的生物质燃烧气溶胶的水平通量散度,能将气溶胶向东北方向输送至中国。(3)地表ADRF与AOD时空分布存在较高的一致性,3-4月老挝和越南的北部地区同样存在地表ADRF高值中心,其值可达-36 W·m^(-2)。EOF第一模态中,印度东北角与我国西藏东南部交界处、老挝、越南和泰国地区均为正位相区域,主要在3-4月出现极大值,2017-2018年间极值减弱,2019年再次增大。云南省地表ADRF时间变化趋势与中南半岛变化一致。(4)地表负ADRF和大气短波加热率的统计关系为:地表的净辐射通量减少越多,低层大气吸收短波辐射造成的加热越大,表明大气内气溶胶截留的短波辐射通量越多,该现象在700 hPa上最为明显,尤其是3-4月。

日本对华安全战略的调整及其影响

在中美战略博弈加剧的大背景下,以遏制中国为目标,日本调整安全政策,积极配合美国“印太战略”,支持美在亚太地区谋取核心地位;以日美同盟为基础,着力配合美国共同联合韩菲印澳等盟友遏制中国;拉拢非美日盟友的亚太国家作为外围补充,助推“核心—主力—外围”的遏华结构。日本将中俄朝视为现实挑战,更将中国视为首要威胁,通过强化自身防卫能力和日美同盟,构建双边及小多边安全合作机制,着力介入台海问题,加强对华战略围堵。安全战略的调整并不能使日本实现“绝对安全”,其将加大对华干扰,阻碍中日关系发展,恐使外围国家处于选择困境中,严重影响地区稳定。

欧盟“印太战略”的调整与中欧关系

2021年9月,欧盟观望多年后正式出台了欧版“印太战略”,有意将印太事务置于其对外政策的优先位置,实现促进经济复苏与发展转型、扩大外交空间与地缘政治影响、协调成员国立场并加强对外政策自主性这三大关键战略目标。2022年2月乌克兰危机升级后,欧盟为应对诸多本土与周边挑战投入大量精力与资源,推进“印太战略”内在动能与面临的资源限制进一步增加。然而,欧盟主观上无意削弱上述三大目标,客观上加强与印太接触的经济、政治乃至安全需要实际上还有所上升。受此影响,欧盟调整了“印太战略”的实施方式,呈现出强化价值观色彩并与俄罗斯因素挂钩、更加突出防务安全议题以及对美协调加强的趋势。此外,欧盟还试图将其“印太战略”塑造为“双向”战略,开始要求印太行为体,尤其是澳大利亚、日本、韩国、新加坡等国积极参与欧洲事务。在此背景下,欧盟对华政策的失衡性与复杂性进一步增加,进入深度调整时期,中欧关系由此面临新的挑战。尽管如此,危机并未改变欧盟在中美之间寻求平衡和自主性的根本逻辑。欧盟仍有意维持对华关系总体稳定,在乌克兰问题上的对华预期也渐趋理性。

从敌人到战略伙伴:越美关系发展的原因与限度

2023年9月,越南与美国领导人在河内宣布建立全面战略伙伴关系,越美关系进入历史最好时期。为何越南与美国能从曾经的生死敌手演变为如今的战略伙伴?在越美关系的演变历程中,两国关系的发展受到多重因素的综合影响。首先,越美两国对解决越战遗留问题的积极态度有助于消解双方对彼此负面的历史记忆,为两国关系改善提供了前提条件。其次,大国关系变化也催化了越美关系发展。冷战后期越南跟随苏联主动改善与美国关系,实现了关系正常化并开展初步合作。自2009年起,随着美国发起对华竞争并拉拢越南,越美关系进入战略合作阶段。最后,越南对美国的发展需求、安全需求与美国对越南的经济战略需求和安全战略需求相交织,共同推动了越美合作水平的不断提升。然而,越美战略合作进一步发展仍存在制约因素,包括两国意识形态分歧、美国可靠性不足及越南避免“选边站队”的政策倾向。对此,中国在大国竞争的变局下应未雨绸缪,通过理性审慎的对越政策,管控分歧、推进合作,妥善处理好中越关系。

“全球大国”定位与英国对东南亚的政策调整

2016年“脱欧”公投后,英国重塑其外交战略布局,确定了“全球大国”定位。东南亚既事关英国切身利益,又是其配合美国实施“印太战略”的重点地区。基于此,英国对其东南亚政策作出了一系列调整:双边与多边并进,打造多层级的伙伴关系网络;以构建自贸网络与援助为抓手,强化对东南亚的经济外交;扩大防务合作,加大在东南亚的军事部署;在南海问题上的立场由谨慎中立转为“选边站”,拉拢当事国并挑动南海对立。英国对东南亚政策的调整一定程度上提升了其在东南亚的影响力,进一步推动其深度介入印太,加剧了地区局势的复杂化,恶化了中国地缘安全环境。同时,由于对东南亚投入的有限性、东南亚国家奉行的大国平衡战略以及中国在东南亚的影响力,英国拟在该地区重建大国地位也面临一系列挑战。针对英国对东南亚政策的调整,中国应保持清醒认知并妥善处理。