Variability in Latent Heat Flux over the Tropical Pacific in Association with Recent Two ENSO Events

This paper analyzed the variations of latent heat flux (LHF) over the tropical Pacific in the period 1978-1988 by using COADS (Comprehensive Ocean and Atmospheric Data Set). It has been founded that the interannual variabili ty of LHF exhibits strong ENSO signal, with the significant increasing LHF during the recent two warm events, i.e., 1982 / 83 and 1986 / 87 and decreasing LHF in the cold episodes. However the longitudinal distribution of the LHF departures varies from event to event. In the eastern Pacific, the specific humidity difference at air-sea interface (qs -qa) makes a dominant contribution to the interannual variability of LHF ( r = 0.73 ), while in the western Pacific the surface wind speed, W and the qs - qa make nearly equal contribution to that of LHF.

Antarctic sea ice and ENSO event

The characteristic low-frequency oscillation of the sea surface temperature anomaly (SSTA) of ENSO related regions, Nino 1 + 2, Nino 3, Nino 4 and Nino West, and the Southern Oscillation index (SOI) is analyzed with the method of maximum entropy spectrum. Antarctic sea ice is divided into 4 regions, i. e. East Antarctic is Region Ⅰ (0°-120° E), the region dominated by Ross Sea ice is Region Ⅱ (120° E-120° W), the region dominated by Ross Sea ice is Region Ⅲ (120° W-0°), and the whole Antarctic sea ice area is Region Ⅳ. Also, the month-to-month correlation series of the sea ice with ENSO from contemporary to 5-years lag is calculated. The optimum correlation period is selected from the series. The characteristics and the rules obtained are as follows.1. There are a common 4-years main period of the SSTA of Ninos 1 + 2,3 and 4, a rather strong 4-years secondary period and a quasi-8-years main period of that of Nino West. There are also 1. 5 and 2 to 3-years secondary periods of that of all 4 Nino regions.2. As another indicator of El Nino, the SOI represents the feature of the atmosphere in low latitude area, having a quasi-5-years main period; it also has secondary periods, 1, 1. 5 and 2 to 3 years, among them, the 2 to 3-years one is prominent.3. There is a close relationship between Antarctic sea ice and ENSO event. In the long-range correlation from contemporary up to 60 months of the SSTA in Ninos 1 + 2,3 and 4 and Antarctic sea ice area index, or the time series of 16 correlation coefficients made of each one of the 4 sea ice regions with that of the 4 Nino regions, there is a prominent common characteristic that all correlations are negative from contemporary to 34-months lag of the SSTA of the 4 Nino regions behind Antarctic sea ice, the optimum correlation periods with the confidences equal to or more than 5 % , 1 % lagging in 13-19, 24-34 month are the most. The correlations of sea ice in Regions Ⅱ , Ⅲ and W with the SSTA of Ninos 3 and 4 are the strongest. The correlation of the sea ice in Region Ⅰ with Nino West in 4 - 5-years lag becomes a very strong positive one. The correlations of the sea ice in Regions Ⅱ and Ⅲ with Ninos 1 + 2, 3 and 4 become strong positive ones during the quasi-4-years lag. The variation of the correlation series of the SOI and the 4 sea ice regions is the opposite of that of the 4 Nino regions. The correlations with the sea ice in Regions Ⅱ , Ⅲ and Ⅳ are strong, with the strong positive correlations of 6, 10 and 24-months lag being the optimum correlation periods. And the strong negative correlation period is 40-months lag.4. The characteristic variation of the correlation time series reflects the low-frequency oscillation feature of Antarctic sea ice and ENSO. In the periodic variation, the correlation becomes the strongest when the ice and ENSO are inresonance. Specifically,the Antarctic sea ice influences ENSO most in an earlier period of its own variation. Moreover, it is also related with the period of variation of ENSO itself, i. e. the correlation of sea ice and ENSO gets the best in a period lag of ENSO its own variation.

STUDY OF A COMPREHENSIVE MONITORING INDEX FOR TWO TYPES OF ENSO EVENTS

Some recent studies presented two existing types of ENSO events, one is the Eastern-Pacific(EP) type and the other the Central-Pacific(CP) type. This study examined the monitoring ability of several current operational ENSO indices. The results indicated that a single index could not distinguish the EP and CP in the historical ENSO events during 1950-2009. The Nio 3 index may only be suitable for monitoring the EP-type ENSO, while the Nio 4 index works only for the CP-type ENSO. In order to capture the occurrence of ENSO events and distinguish the type, we considered a new monitoring index group using Nio 3 and Nio 4 indices. Further analysis confirmed that this index group can monitor different types of historical ENSO events with different spatial distribution of sea surface temperature. It has a good performance in determining the characteristics of the ENSO events, including peak intensity, onset,decay, and mature phase.

AN ANALYSIS ON LARGE-SCALE AIR-SEA INTERACTIVE LINKAGES BETWEEN THE TROPICAL INDIAN OCEAN AND THE PACIFIC OCEAN DURING ENSO EVENTS

By utilizing a 3-D atmospheric circulation resolving method, the authors studied the air-sea interactive linkages between the tropical Indian Ocean and the Pacific Ocean in 1979-2008 E1 Nifio-Southern Oscillation （ENSO） events. Their findings showed that evident 3-D gear-coupling characteristics existed in the 1979-2008 ENSO events. Their resolving analyses also suggested that the general circulation showed stronger and wider sinking motions over the eastern Indian Ocean-western Pacific during the mature phase of 1979-2008 ENSO events, compared with the vertical velocities from the U.S. National Centers for Enviornmental Prediction （NCEP） reanalysis data. With their 3-D analysis method, the vertical velocity was resolved by two components, i.e. zonal and meridional components. It was found that the zonal component of the vertical velocities showed a strong sinking motion while the meridional components showed an upward motion during the prevailing phases of the ENSO events. In the tropics, the zonal component of the vertical velocities was found greater than the meridional component, reflecting the dominant characteristics of the vertical velocity, and the overall outcomes showed a strong sinking motion, although the two components also partially offset each other in the processes. Compared with the vertical velocities from NCEP reanalysis, the vertical motions calculated with the 3-D resolving analysis method demonstrate some advantages.

RELATION BETWEEN SUMMER TYPHOON FREQUENCY ANOMALIES IN WEST PACIFIC AND ENSO EVENTS AND THE ANOMALOUS ATMOSPHERIC CIRCULATION CHARACTERISTICS

By using data of serially numbered typhoons in northwestem Pacific and NOAA OLR data and NCEP/NCAR reanalysis data of wind field, based on the statistics and study of the relationship between the calendar years with more （or fewer） summer typhoons and ENSO events, we compared the composites of OLR eigenvectors and tropical summer wind fields during E1 Nino and La Nino events with more or fewer than normal summer typhoons, respectively. The results show that, in summer, without remarkable systematic anomalies of Mascarene High and Australia High in South Hemisphere, the anomaly of Walker circulation will dominate and follow the rule of ENSO impacts to atmospheric circulation and typhoon frequency. Otherwise, when systematic anomalies of Australia High appear during the El Nino events, circulation anomalies in the South Hemisphere will dominate, and many more typhoons will occur. In 1999, which is a special year of La Nina events, northward and eastward monsoon was induced by the stronger Mascarene High, and fewer typhoons arose. The typhoon source are regions where weak vertical wind shear, warm pool in westem Pacific and the area with monsoon troughs are overlapping with each other. Finally, this paper analyzes and compares the source locations and ranges of more （fewer） typhoons in the events of El Nino and La Nino, respectively.

A Further Study on an Extended Nonlinear Ocean-Atmosphere Coupled Hydrodynamic Characteristic System and the Abrupt Feature of ENSO Events

An extended ocean-atmosphere coupled characteristic system including thermodynamic physical processes in ocean mixed layer is formulated in order to describe SST explicitly and remove possible limitation of ocean-atmosphere coupling assumption in hydrodynamic ENSO models. It is revealed that there is a kind of abrupt nonlinear characteristic behaviour, which relates to rapid onset and intermittency of El Nino events, on the second order slow time scale due to the nonlinear interaction between a linear unstable low-frequency primary eigen component of ocean-atmosphere coupled Kelvin wave and its higher order harmonic components under a strong ocean-atmosphere coupling background. And, on the other hand, there is a kind of finite amplitude nonlinear characteristic behaviour on the second order slow time scale due to the nonlinear interaction between the linear unstable primary eigen component and its higher order harmonic components under a weak ocean-atmosphere coupling background in this model system.

A Diagnostic Analysis of Winter Atmospheric Circulation during the 1982-1983 ENSO Event

In this paper, the winter atmospheric circulation, the convection along the equator and their variations of 1982 and 1983 are investigated. It is suggested that there was a well organized three dimensional structure of anomalies of the atmospheric circulations during 1982 winter which may be related to the variations of the convection in the equatorial region.

Abnormality of the monsoon wind in the sea area along the southeasterncoast of China and the response of the northern areaof the South China Sea during the ENSO events

-Variations of monsoon wind field in the sea area along the southeastern coast of China during the ENSO events and its influence on the sea level and sea surface temperature (SST) are explored mainly on the basis of the data of monthly mean wind at 850 hPa and five coastal stations during 1973-1987. The results from the analyses of the data and theoretical estimation show that the southwest wind anomalies appeared in the study area during the events, and northeast wind anomalies occurred in general before the events. With the coastline of the area being parallel basically to the direction of the wind, an Ekman transport will result in an accumulation of the water near the coast or a departure of the water from the coast. As a result , the sea level and SST there will be affected markedly. During the events, southwest wind will intensify in the summer, and northeast wind will weaken in the winter. Their total effect is that a large negative anomaly of the sea level and SST will occur. The estimations indicate that the monsoon wind is stronger in the summer and weaker in the winter than the normal by 1-1. 5 m/s during the events, and this anomaly will cause a decrease of the sea level by 7-11 cm . Changes of the wind field, therefore, is mainly responsible for a large negative anomalies of the sea level and SST there during the ENSO events.

The ENSO event and rice planthopper occurrence in China

The rice planthopper,including brown planthopper(Nilaparvata hugens Stal)and white—backed planthopper(Sogata furcifera Hor-vath),is one kind of tropical pests.They im-migrate with the southeast monsoon from low—latitude area into China at March of April.The global climatic anomaly especially the ElNi (?)o event and the Southern Oscillation(theENSO event)directly influence the rice plan-

STUDY OF ANOMALOUS SST FIELD IN TROPICAL PACIFIC IN PRECEDING YEARS OF TWO PATTERNS OF ENSO EVENTS

Analyzing the anomalous field of SST over the tropical Pacific for two kinds of ENSO events after 1956. we find that in the preceding year before the eastern pattern of El Nino event there is the La Nina event and large negative anomalies of SST in the tropical central and eastern Pacific; the preceding year before the eastern pattern of La Nina event witnesses the prevalence of the El Nino event and large positive anomalies of SST in the same waters: the preceding year before the central patterns of the El Nino (La Nina) events are generally marked by significant positive (negative) SST anomalies in central/western (eastern) tropical Pacific. The fields are just the opposite for two patterns of ENSO events. For waters in the warm pool in the western tropical Pacific, the central (eastern) pattern of El Nino event is with a warm (cool) preceding year of the pool. The warmer conditions in the western Pacific warm pool are a necessity for the occurrence of the central pattern of El Nino event.

CLIMATE ANOMALY RECORDED IN GULIYA ICE CORE AND ENSO EVENTS

Examination of ENSO events and the accumulated precipitation and δ^(18)O values recorded in the Guliya ice core,China,shows that the relationship between the occurrence of ENSO events and the precipitation anomaly in Guliya is significant.In the years of El Nino events,the anomalies of precipitation and δ^(18)O values in the Guliya ice core were negative anomalies,that is,the ENSO events are related to the deficit of precipitation as well as low temperature in the western China.

Interannual variations in the length of day and ENSO events in 1982-1983 and 1997-1998

The length of day series during the period of 1962.0-2000.0, the atmospheric angular momentum and the Southern Oscillation Index are adopted to analyze the relationships among the EN-SO events that have occurred since 1960, the changes in the length of day and the atmospheric angular momentum. Attention is particularly given to the different effects of the 1982-1983 and 1997-1998 ENSO events on the variations of Earth rotation. The synthetic excitation effects of multi-scale atmospheric oscillations on the anomalous variations of the interannual rates of Earth rotation are revealed by means of the time-frequency spectrum of the wavelet transform.

1962—2021年闽江流域干湿演变特征及其对ENSO事件的响应

基于1962—2021年闽江流域29个气象观测站的日降水量数据,运用标准化降水指数(standard precipitation index,SPI),Mann-Kendal趋势检验(M-K检验)以及Morlet小波分析等多种方法,深入分析不同时间尺度下闽江流域干湿演变特征,同时,结合海温异常指数(sea surface temperature anomaly,SSTA),进一步探究闽江流域干湿对厄尔尼诺-南方涛动(El Ni?o-Southern Oscillation,ENSO)事件的响应。结果表明:近60年来,闽江流域整体呈不显著湿润化趋势,夏季在20世纪90年代后显著湿润化,秋季在1995年后有干旱化倾向,冬季比其他季节更容易出现极端干湿事件;从空间上看,流域东南部湿润化趋势明显,具有春季流域中部干旱化,夏季北部以及东南部湿润化,秋季南部干旱化的态势;全流域各级湿润和干旱事件均呈增加趋势,湿润事件多出现在夏季,干旱事件多出现在秋、冬季;闽江流域在20~30 a的范围内存在干—湿—干的周期变化。ENSO对闽江流域干湿有显著影响,且具有一定的滞后性,暖、冷事件的影响分别在滞后1~4个月和3~5个月最显著。

ENSO事件对东莞气候特征的影响

利用1963—2021年东莞国家气象观测站的气象观测资料,运用数理统计、趋势分析和Mann-Kendall突变检测等方法从台风、降水和气温等角度进行分析,研究厄尔尼诺和拉尼娜事件对东莞气候特征的影响,分析表明:(1)2000年以前发生厄尔尼诺事件概率更大,2000年以后ENSO事件持续时间变短,厄尔尼诺和拉尼娜事件发生概率基本相当;(2)厄尔尼诺(或拉尼娜)年影响东莞的台风频数减少(或增多);拉尼娜年台风季偏长,初台偏早、终台偏晚;(3)厄尔尼诺事件发生当年东莞非汛期和次年汛期降水偏多,当年汛期和次年非汛期降水偏少;拉尼娜事件发生当年汛期和非汛期降水都偏少;厄尔尼诺和拉尼娜事件都对后汛期降水影响更明显,ENSO事件强度越强,对降水影响越大;(4)东莞气温受ENSO事件影响较小,厄尔尼诺年东莞气温偏高,拉尼娜年东莞气温偏低;高低温日数受ENSO事件影响较小,有明显的年代变化特征。

ENSO与中国夏季降水年际变化关系的不稳定性特征

根据1951～2007年中国160站月降水量资料和Nin～o3区月平均海表温度资料,采用滑动相关分析和合成分析等方法,探讨了中国夏季降水与前期冬季Nin～o3区海温年际变化关系的不稳定性问题。结果表明,它们之间年际变化关系的长期变化具有明显的地域性,东北和西北地区相关的不稳定性比东部地区大,与预测经验吻合。同时也有明显的阶段性,1951～2007年据滑动相关系数序列可分成1962～1977年、1978～1992年和1993～至今三个时期。各个时期平均约为16年。它们从一个阶段向另一个阶段过渡的时间很短,是以气候跃变的形式来完成的。近50多年来在1960年代初、1970年代末和1980年代末1990年代初共发生了3次明显的跃变过程。跃变前后某些地区滑动相关系数的符号或强度都有显著的差异。研究还表明,不同时期,尽管同样是ElNin～o事件,它们对中国夏季降水的影响有不同的表现。1962～1977年时间的相关模型有两条多雨带:一条位于华北、东北平原和内蒙古东部一线,另一条在长江中游地区。秦岭大巴山区和江淮流域降水偏少。1978～1992年时期只有一条多雨带,位于秦岭大巴山区、长江中游和下游一线。黄淮地区及华北至东北南部降水偏少。目前我们所处的时期(1993～至今)雨带分布与1962～1977年时期的模型基本相似,也为南、北两条多雨带,但其北支雨带南移,位于从川渝地区经黄淮地区、黄河下游至东北平原一带,湖北北部和长江下游降水偏少。呈现北方降水偏多、南方降水相对偏少的分布。所以,利用ENSO事件做我国汛期降水预报,不能只考虑其平均情况的年际变化关系,还应注意它们之间关系的不稳定性问题。

ENSO影响下安徽省旱涝灾害及农业生产损失时空变化特征

基于1961—2014年25个气象站资料,采用线性趋势法、标准化降水蒸散指数(SPEI)、M-K趋势检验以及皮尔逊相关分析法,分析了ENSO影响下安徽省1961—2014年近54年旱涝时空特征及对农业生产影响。研究表明:(1)与ENSO事件有关的中度以上干旱(洪涝)发生次数占中度以上干旱(洪涝)总次数的68%(83%),且干旱事件受厄尔尼诺次年及拉尼娜年影响大,洪涝受厄尔尼诺当年影响更大;(2)春、秋季SPEI波动幅度大于夏季和冬季,洪旱灾害风险增大。春季呈干旱化趋势,冬季在20世纪90年代湿润化达到最大,随后趋向于干旱化。与皖北地区相比较,皖南地区各月份趋势变化大;(3)安徽各地区的旱涝指数与SSTA的相关性在ENSO冷暖事件中不同,ENSO暖事件对皖南地区相关系数最大达0.32,超过99%置信度检验,影响更为显著,而ENSO冷事件对皖北地区相关系数最大达0.28,超过99%置信度检验,影响更为显著。随着滞后性月份的增加,安徽各区域的旱涝指数与SSTA的相关系数逐渐增大,皖南地区与SSTA相关性大于皖北地区,SSTA对未来3个月皖南旱涝有明显的影响;(4)近20年皖北、皖南地区稻、麦减产主要发生在ENSO事件年或者前一年,且减产率高。皖北地区和江淮地区的小麦减产发生次数较少,小麦减产率较大,而皖南地区小麦减产发生年份较多,小麦减产率较小。ENSO对农业生产的影响与旱涝分布状况有关,江淮地区良好的灌溉条件会降低ENSO年农业旱涝受灾风险。

黄河源区降水与径流过程对ENSO事件的响应特征

根据最新季分辨率ENSO指数序列所确认的近 40多年来所发生的 2 0次ENSO事件 ,并确定了每次ENSO事件强度及其影响年 ,通过对相应年份黄河源区降水与径流距平变化值的对比 ,分析了降水与径流过程对ENSO事件响应的统计规律 :ENSO事件与黄河源区降水与径流年际波动变化有很好的相关性 ,这种相关性与ENSO事件的性质强弱、发生季节以及持续时间等有关 ,一般夏秋季暖事件无论强弱均使影响年降水减少 ,发生于春季的中等强度暖事件使发生年降水呈负距平 ,影响年降水呈增加趋势 ;冷事件与暖事件对降水的影响正好相反 ;暖事件对应年份黄河源区径流量减少 ,而冷事件则使其增加 .随着 2 0世纪 90年代以来暖事件发生频率的增加 。

一种综合监测两类不同分布类型ENSO事件指标的研究

针对1950—2009年的东部型(EP)和中部型(CP)ENSO事件,比较了目前国际上常用的ENSO监测指数对它们的监测能力。结果表明:单一的指数无法同时区分EP和CP型ENSO事件,其中Ni o 3指数只能有效识别EP型ENSO事件,而Ni o 4指数则对CP型事件具有较强的监测能力。据此提出同时以Ni o 3和Ni o 4指数构建指数组的形式来监测不同类型的ENSO事件,结果表明,该指标组能够较全面监测历史上发生的不同分布类型ENSO事件,且能准确判定事件的峰值强度、起止时间和成熟期等其他特征。

2005—2017年两次强ENSO事件对中国区域陆地水储量变化影响的卫星重力观测

近年来极端气候事件的频发对全球和区域性水循环产生了重大影响,特别是2005—2017年间两次强ENSO(El Nino-Southern Oscillation)事件使得全球陆地水储量出现了较大的年际波动.GRACE(Gravity Recovery and Climate Experiment)重力卫星随着数据质量的提高、后处理方法的完善和超过十年的连续观测,捕捉陆地水储量异常的能力明显提高,这为研究2005—2017年间两次强ENSO事件对中国区域陆地水储量变化的影响提供了观测基础.本文综合利用GRACE卫星重力数据、GLDAS水文模型和实测降水资料分析了中国区域陆地水储量年际变化和与ENSO的关系.研究发现:长江流域中、下游地区和东南诸河流域与ENSO存在较高的相关性,与ENSO的相关系数最大值分别为0.55、0.78、0.70,较ENSO分别滞后约7个月、5个月和5个月.其中长江流域下游地区与ENSO的相关性最强,2010/11 La Nina和2015/16 El Nino两次强ENSO事件使得陆地水储量分别发生了约-24.1亿吨和27.9亿吨的波动.在2010/11 La Nina期间,长江流域下游地区和东南诸河流域陆地水储量异常约在2011年4—5月达到谷值,而长江流域中游地区晚1~2月达到谷值.在2015/16 El Nino期间,长江流域中、下游地区和东南诸河流域陆地水储量从2015年9月到2016年7月持续出现正异常信号.其中,2015年秋冬季(2015年9月至2016年1月)陆地水储量异常明显是受此次El Nino同期影响的结果;2016年春季(4—5月)陆地水异常是受到此次厄尔尼诺峰值的滞后影响所致;2016年7月的陆地水储量异常则与西北太平洋存在的异常反气旋环流有关.

淮河流域降水过程时空特征及其对ENSO影响的响应研究

基于淮河流域35个站点1961~2008年日降水资料,从成因角度研究不同厄尔尼诺-南方涛动事件（ENSO）事件对流域降水过程时空演变特征的影响。研究表明：1流域降水过程出现沂沭泗河水系变干、淮河水系降水量缓慢增大的特征。2 CPW年,年最长连续降水日数、年最长连续降水量的距平变化幅度大且为负值;EPC年,年最长连续无降水日数较常年明显增多;EPW年,连续降水日数变长、连续降水量减少。3 ENSO对流域强降水影响较大,在CPW和EPW年淮河水系暴雨、大雨日数较常年多,而沂沭泗河水系暴雨、大雨日数比常年少;EPC年与此相反。4 ENSO对连续4 d以上降水影响显著,其中EPC年影响最大。