江淮流域夏季降水异常及与全球中低纬海温异常关系的诊断研究

对1951－1999年中国夏季江淮流域降水异常与海温异常关系的分析表明,前期及同期各季节三大洋海表温度异常（SSTA）与长江流域降水异常的关系是非常显著的,而对淮河流域降水异常总体上的影响较小,前期冬季SSTA的影响显著区主要有：热带印度洋、黑潮、热带中东太平洋和大西洋,各关键区海温异常对亚洲夏季风的影响特征为：当前期冬季赤道印度洋、黑潮、赤道大西洋和热带东太平洋海表温度异常升高（降低）,当年夏季印度西南季风和东亚热带辐合带减弱（加强）,副热带高压位置偏南（北）,副热带辐合带加强（减弱）,长江流域易发生洪涝（干旱）,相关显著性分析表明,前冬赤道印度洋和黑潮区的海温异常对中国夏季降水的影响更为显著。     

Indian Ocean temperature dipole and SSTA in the equatorial Pacific Ocean

The observed sea surface temperature (SST) data of recent 100 years are analyzed and the existence of the Indian Ocean temperature dipole in the equatorial region is exposed further. It is very clear that the amplitude of the positive phase (higher SST in the west and lower SST in the east than normal) is larger than that of the negative phase (higher SST in the east and lower SST in the west). The dipole is stronger in September-November and weaker in January-April than in other months and it also appears obviously inter-annual and inter-decadal variations. Although the Indian Ocean dipole in the individual year seems to be independent of ENSO in the equatorial Pacific Ocean, in general, the Indian Ocean dipole has obviously negative correlation with the Pacific Ocean dipole (similar to the inverse phase of ENSO mode). The atmospheric zonal (Walker) circulation over the equator is fundamental to relate the two dipoles to each other.     

热带太平洋和印度洋海温对东南亚降水的影响

 应用谱分析的方法,讨论了东南亚降水分别与热带印度洋和太平洋海温的关系.得出热带印度洋和太平洋海温变化对东南亚降水影响的最佳落后时间长度.同时找出了上述2片海域对东南亚降水影响的几个关键区,它可以作为东南亚旱涝预报的强信号因子.     

热带印度洋偶极子区域海表面温度特征与海流相关性分析

为了研究热带印度洋偶极子(IOD)爆发年其耦合作用迅速消亡是否由海流异常引起,利用1958—2007年热带印度洋月均海表面温度(SST)和海流数据,分析IOD的主要特征,并探讨IOD与ENSO和海流异常之间的相关关系。通过对印度洋偶极子指数(DMI)及其经Hilber-t Huang变换后得到的固有模态函数(IMF)与南方涛动指数(SOI)的相关性分析,指出IOD与ENSO之间可能存在相关性,其中,表现出准2a周期振荡的IMF-3与ENSO相关性最好。通过对IOD爆发年DMI的进一步分析,证实IOD具有季节锁相的重要特征,并探讨该季节变化与海流异常的相关关系。结果表明,海流异常在热带印度洋SST的耦合振荡中起重要作用,但是它可能不是引起IOD迅速消亡的原因。     

Interconnections between the Asian monsoon, ENSO, and high northern latitude climate during the Holocene

The International Geosphere Biosphere Program (IGBP), which promotes better understanding of the living environment, was initiated in the early 1990s. IGBP and other programs have uncovered much evi-dence that the Earth system is complex and nonlinear, ex…     

太平洋海温演变的时空结构

运用转动复自然正交展开(RCEOF)分析近50年太平洋海温场的时空结构,得出在赤道中、东太平洋和40°N 附近有两个海温异常强信号中心;赤道东海岸太平洋海温异常信号(对应ENSO信号)在几个月到半年左右传播到赤道西太平洋;海温主要周期大部分落在3～10d的范围内,还存在年和准两年变化。     

亚澳季风区内水汽汇的准两年振荡及其与大气环流的关系

利用1950-2000年大气视水汽汇资料,分析了亚澳季风区内水汽汇准两年振荡的变化特征及其与大气环流的关系.亚澳季风区内水汽汇有显著的准两年振荡,其关键区位于西太平洋暖池、孟加拉湾、东南印度洋和西南印度洋,它们对应3种遥相关型.当暖池水汽汇偏强时,我国华南为偏北风距平,东亚季风区水汽汇偏弱;印度洋水汽汇距平呈现为偶极子分布,东南印度洋附近水汽汇偏强时,东南印度洋至赤道西印度洋为偏西风距平,赤道西印度洋水汽汇偏弱;孟加拉湾水汽汇偏强时,孟加拉湾至西南印度洋为偏南风距平,西南印度洋的水汽汇偏弱.反之亦然.     

The relationship between sea surface temperature anomaly and wind energy input in the Pacific Ocean

The relationship between sea surface temperature anomaly (SSTA) and wind energy input in the Pacific Ocean over the period of 1949–2003 is studied by using daily-mean NOAA/NCEP wind stress and monthly mean Reynolds SST data. The results indicate the strong negative correlation between SSTA and local wind energy input to surface waves in most of the domain at low and middle latitudes. The SST is low (high) during the years with more (less) wind energy input. The correlation coefficients are high in the central and eastern tropical Pacific and the central midlatitude North Pacific at the decadal scale, and in the central tropical Pacific at the interannual scale. Vertical mixing processes in the upper ocean are closely associated with wind energy input, indicating that wind energy input may play an important role in interannual and decadal variability in the Pacific Ocean via regulating vertical mixing.     

Decadal variability of the IOD-ENSO relationship

Using three kinds of over 100-year sea surface temperature （SST） datasets as well as three-dimensional wind data from NCEP/NCAR, this paper documents the decadal variability of the Indian Ocean Dipole （IOD）-EI Nino/Southern Oscillation （ENSO） relationship. During 1948--1969, positive （negative） IOD and warm （cold） ENSO events were more independent of each other. But after 1970, they tended to occur in the same year. ENSO would influence the whole life span of IOD, and IOD also affects the developing phase of ENSO. Considering the climatological background SST, low-level winds and also equatorial vertical circulations, it is revealed that the decadal variability of the IOD-ENSO relationship may be caused by the enhanced Walker circulation with increased rising motion over the Maritime Continent after 1970. Warmer SST around the Maritime Continent gives rise to anomalous low-level convergence and intensified convection there, which apparently increases the SST linkage between the eastern Indian Ocean and the western Pacific and thereby the interaction between the IOD and ENSO event.     

导致西太平洋海温异常的主要因素研究

通过对不同区域海表面温度(SST)资料做超前/滞后相关性分析, 研究导致西太平洋SST异常的主要因素。基于东、西太平洋相互作用理论和印度洋电容器效应理论, 将热带西太平洋SST异常的变化分别与热带东太平洋和印度洋SST异常做超前/滞后相关性分析, 得到每个格点与强迫场之间相关性最显著的月份, 从时间的角度研究西太平洋SST异常变化与东太平洋和印度洋之间的关系。按照上述两种理论, 由于海洋的比热大, 热响应时间较长, 西太平洋SST变化应滞后于东太平洋或印度洋2~3个月。分析结果显示, 在El Nino和La Nina事件下, 西太平洋SST异常变化均超前于东太平洋1~2个月时相关性最显著; 同时, 西太平洋SST异常变化超前于印度洋3~4个月时相关性最显著。 这表明热带东太平洋和印度洋都不是导致西太平洋SST异常变化的主要因素, 西太平洋SST异常可能由多种因素共同作用所导致。     

Indonesian Throughflow in an eddy-permitting oceanic GCM

An eddy-permitting quasi-global oceanic GCM was driven by wind stresses from reanalysis data for the period of 1958-2001 to get the time series of the upper circulation in the Indonesian Sea. The model represents a reasonable pathway of Indonesian Throughflow (ITF) with Makassar Strait making the major passage transfer the North Pacific water southward. The simulated annual mean ITF transport is 14.5 Sv, with 13.2 Sv in the upper 700 m. Annual cycle is the dominant signal for the seasonal climatology of the upper layer transport. Both the annual mean and seasonal cycle agree well with the observation. The overall correlation between the interannual anomaly of the ITF transport and Nino 3.4 index reaches -0.65 in the simulation,which indicates that ENSO-related interannual variability in the Pacific is dominant in controlling the ITF transport. The relationship between the interannual anomalies of ITF and sea surface temperature in the Pacific, the Indian Ocean is not fixed in the simulation. In 1994, for instance, the intensive Indian Ocean sea surface temperature anomaly plays a dominant role in the formation of an impressive large transport of ITF.     

Southern Ocean origin for the resumption of Atlantic thermohaline circulation during deglaciation

During the two most recent deglaciations, the Southern Hemisphere warmed before Greenland. At the same time, the northern Atlantic Ocean was exposed to meltwater discharge, which is generally assumed to reduce the formation of North Atlantic Deep Water. Yet during deglaciation, the Atlantic thermohaline circulation became more vigorous, in the transition from a weak glacial to a strong interglacial mode. Here we use a three-dimensional ocean circulation model to investigate the impact of Southern Ocean warming and the associated sea-ice retreat on the Atlantic thermohaline circulation. We find that a gradual warming in the Southern Ocean during deglaciation induces an abrupt resumption of the interglacial mode of the thermohaline circulation, triggered by increased mass transport into the Atlantic Ocean via the warm (Indian Ocean) and cold (Pacific Ocean) water route. This effect prevails over the influence of meltwater discharge, which would oppose a strengthening of the thermohaline circulation. A Southern Ocean trigger for the transition into an interglacial mode of circulation provides a consistent picture of Southern and Northern hemispheric climate change at times of deglaciation, in agreement with the available proxy records.     

January temperature anomalies over Northeast China and precursors

This paper analyzes the large-scale atmospheric circulation characteristics of anomalous cases of January temperatures that occurred in Northeast China during 1960-2008 and precursory oceanic conditions.The January monthly mean surface air temperature(SAT) anomalies and the duration of low temperature are used to define temperature anomaly cases.The anomalous cyclonic circulation over northeast Asia strengthens the northerly flow in cold Januarys,while the anomalous anticyclonic circulation weakens the northerly flow in the warm Januarys.The negative(positive) North Pacific sea surface temperature anomaly(SSTA) and increased(decreased) sea ice concentration in the Barents-Kara seas in the preceding month are probably linked to the cyclonic(anticyclonic) circulation pattern over northeast Asia in the cold(warm) cases.Further analyses indicate that the preceding oceanic conditions play distinct roles in the SAT anomalies over Northeast China on different time scales.Strong relationships exist between North Pacific SSTA and the SAT in Northeast China on the interannual time scale.On the other hand,the sea ice concentration is more closely associated with the interdecadal variations of SAT in Northeast China.     

大西洋热盐环流减弱对热带太平洋气候平均态及年际变率的影响

利用一个完全耦合的海气模式, 通过对比分析两组试验中海表温度、盐度、风应力等气候态变化特征以及ENSO强度和频率的变化, 研究热带太平洋气候平均态及年际变率对热盐环流减弱的响应。在北大西洋高纬地区注入1 Sv淡水后, 大西洋经向翻转流(AMOC)减弱约90%, 这直接导致向北的经向热量输送减少, 使北大西洋有明显降温, 南大西洋略有升温。这些变化会经过大气和海洋的远程传播以及局地海气反馈作用, 影响热带太平洋气候平均态: 赤道东西太平洋的SST都略有增温, 但纬向温度梯度和纬向风应力并没有太大变化, 赤道太平洋温跃层的深度和倾斜度也基本保持不变。相应地, ENSO强度和频率也没有明显变化。由此得出结论: 热盐环流减弱会引起全球气候平均态的变化, 但对热带太平洋的年际变率没有太大影响。     

热带印度洋海温与海表面高度相关关系分析

为了研究热带印度洋偶极子(IOD)与海平面异常之间的相关性,采用经验正交函数分析方法(EOF)及Hilbert-Huang变换等统计方法,分析热带印度洋的海表面温度(SST)与海平面高度异常(SLA)的相关关系。通过对热带印度洋偶极子指数(DMI)与南方涛动指数(SOI)和SLA的相关性分析,得出IOD与El Nio-Southern Oscillation(ENSO)之间可能存在一定相关关系,此外,IOD与海平面变化有很好的相关性。通过对IOD爆发年的DMI以及海平面变化的分析,证实IOD具有季节锁相的重要特征,并探讨了该季节变化与海平面变化的相关关系。结果表明,IOD事件与海平面的变化这两者之间存在很强的一致性。     

黄河上游汛期水量丰枯的气候因子分析

利用EOF、相关、合成等分析方法,对兰州以上黄河上游五测站的月平均流量、东半球的500hPa高度距平场及太平洋海温场资料进行了分析。结果表明：典型丰（枯）同期和前期500hPa高度距平场有着明显的差异,主要反映在极涡、西太平洋副高、中高纬西风带低槽等系统的强度和位置上;该流域流量的丰枯与太平洋海温距平场的分布关系密切,典型丰（枯）年前期（前一年9月至当年的2月）和同期太平洋海温场距平场的分布亦存在很大的差异。     

Coupled ocean-atmosphere dynamics in the Indian Ocean during 1997-98

Climate variability in the Indian Ocean region seems to be, in some aspects, independent of forcing by external phenomena such as the El Ni?o/Southern Oscillation. But the extent to which, and how, internal coupled ocean-atmosphere dynamics determine the state of the Indian Ocean system have not been resolved. Here we present a detailed analysis of the strong seasonal anomalies in sea surface temperatures, sea surface heights, precipitation and winds that occurred in the Indian Ocean region in 1997-98, and compare the results with the record of Indian Ocean climate variability over the past 40 years. We conclude that the 1997-98 anomalies--in spite of the coincidence with the strong El Ni?o/Southern Oscillation event--may primarily be an expression of internal dynamics, rather than a direct response to external influences. We propose a mechanism of ocean-atmosphere interaction governing the 1997-98 event that may represent a characteristic internal mode of the Indian Ocean climate system. In the Pacific Ocean, the identification of such a mode has led to successful predictions of El Ni?o; if the proposed Indian Ocean internal mode proves to be robust, there may be a similar potential for predictability of climate in the Indian Ocean region.     

A dynamic view of the tropospheric teleconnection between IOD and the Pacific Ocean

The tropospheric teleconnection pattern between the Indian Ocean Dipole （IOD） and the Pacific Ocean was studied using GISST and NECP/NCAR reanalysis data. Results show that a structure of Rossby wave train extends from the tropical Indian Ocean over southern subtropical regions of Australia and Pacific Ocean to the tropical Pacific Ocean, where a strong correlation between IOD and geopotential height （GH） anomaly of Pacific Ocean exists. Energy propagating pathways of the planetary wave with wave numbers 1-3 are qualitatively in agreement with the Rossby wave train, which implies that the energy propagation of the stationary planetary wave could be responsible for the tropospheric teleconnection between IOD and tropical Pacific Ocean.     

Eastern Pacific cooling and Atlantic overturning circulation during the last deglaciation

Surface ocean conditions in the equatorial Pacific Ocean could hold the clue to whether millennial-scale global climate change during glacial times was initiated through tropical ocean-atmosphere feedbacks or by changes in the Atlantic thermohaline circulation. North Atlantic cold periods during Heinrich events and millennial-scale cold events (stadials) have been linked with climatic changes in the tropical Atlantic Ocean and South America, as well as the Indian and East Asian monsoon systems, but not with tropical Pacific sea surface temperatures. Here we present a high-resolution record of sea surface temperatures in the eastern tropical Pacific derived from alkenone unsaturation measurements. Our data show a temperature drop of approximately 1 degrees C, synchronous (within dating uncertainties) with the shutdown of the Atlantic meridional overturning circulation during Heinrich event 1, and a smaller temperature drop of approximately 0.5 degrees C synchronous with the smaller reduction in the overturning circulation during the Younger Dryas event. Both cold events coincide with maxima in surface ocean productivity as inferred from 230Th-normalized carbon burial fluxes, suggesting increased upwelling at the time. From the concurrence of equatorial Pacific cooling with the two North Atlantic cold periods during deglaciation, we conclude that these millennial-scale climate changes were probably driven by a reorganization of the oceans' thermohaline circulation, although possibly amplified by tropical ocean-atmosphere interaction as suggested before.     

El Niño/Southern Oscillation and tropical Pacific climate during the last millennium

Any assessment of future climate change requires knowledge of the full range of natural variability in the El Ni?o/Southern Oscillation (ENSO) phenomenon. Here we splice together fossil-coral oxygen isotopic records from Palmyra Island in the tropical Pacific Ocean to provide 30-150-year windows of tropical Pacific climate variability within the last 1,100 years. The records indicate mean climate conditions in the central tropical Pacific ranging from relatively cool and dry during the tenth century to increasingly warmer and wetter climate in the twentieth century. But the corals also document a broad range of ENSO behaviour that correlates poorly with these estimates of mean climate. The most intense ENSO activity within the reconstruction occurred during the mid-seventeenth century. Taken together, the coral data imply that the majority of ENSO variability over the last millennium may have arisen from dynamics internal to the ENSO system itself.