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.

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 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 Nio 3 index may only be suitable for monitoring the EP-type ENSO, while the Nio 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 Nio 3 and Nio 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 El Nio-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.

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.

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 northwestern Pacific and NOAA OLR data andNCEP/NCAR reanalysis data of wind field, based on the statistics and study of the relationship between thecalendar years with more (or fewer) summer typhoons and ENSO events, we compared the composites of OLReigenvectors and tropical summer wind fields during El Nio and La Nio events with more or fewer thannormal summer typhoons, respectively. The results show that, in summer, without remarkable systematicanomalies of Mascarene High and Australia High in South Hemisphere, the anomaly of Walker circulation willdominate and follow the rule of ENSO impacts to atmospheric circulation and typhoon frequency. Otherwise,when systematic anomalies of Australia High appear during the El Nio events, circulation anomalies in theSouth Hemisphere will dominate, and many more typhoons will occur. In 1999, which is a special year of LaNia events, northward and eastward monsoon was induced by the stronger Mascarene High, and fewertyphoons arose. The typhoon source are regions where weak vertical wind shear, warm pool in western Pacificand the area with monsoon troughs are overlapping with each other. Finally, this paper analyzes and comparesthe source locations and ranges of more (fewer) typhoons in the events of El Nio and La Nio, respectively.

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。

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.

ENSO对安徽省旱涝灾害和粮食产量的影响

为防御旱涝灾害,保障粮食安全,利用1971—2018年ENSO的特征量、不同位相及安徽省78个站点的气象数据和全省灾情、作物产量数据,采用比较法、x^(2)拟合检验法,分析ENSO的特征量、不同位相与安徽省典型干旱和涝渍年的关系及ENSO对安徽省主要粮食作物产量的影响。结果表明:(1)厄尔尼诺和拉尼娜事件均发生在春季到秋季(4—10月),结束在初夏之前(1—6月),其峰值大部分出现在冬季(1月和11—12月)。(2)典型干旱和涝渍年各发生11年,平均2~3年出现1次,大多集中在20世纪80年代初到90年代中期。(3)安徽省典型干旱年出现在厄尔尼诺事件对涝渍的当年或拉尼娜事件的次年的概率大,厄尔尼诺、拉尼娜事件对安徽省旱灾的影响相当;典型涝渍年出现在厄尔尼诺事件对涝渍的次年或拉尼娜事件的当年的概率大,且厄尔尼诺事件对涝渍的影响远大于拉尼娜事件的影响。(4)ENSO持续时间越长、强度越大,越易发生干旱和涝渍灾害,干旱和涝渍灾害易发生在ENSO的衰减年或波峰后。(5)厄尔尼诺事件的衰减年,主要粮食作物以减产为主;拉尼娜事件的衰减年,小麦增减产年份相当,而一季稻、玉米则以增产为主。

ENSO事件对山东苹果生产的影响Ⅱ:不同ENSO年型下农业气象灾害变化及对苹果产量的影响

苹果作为山东优势果品之一,其生产受农业气象灾害影响较大。探究厄尔尼诺-南方涛动(ENSO)事件下山东农业气象灾害演变规律及其对山东苹果产量的影响,对指导当地苹果生产具有重大意义。本文基于山东1991-2019年逐日气象观测数据、地市级苹果种植统计数据及ENSO事件数据,利用数理统计分析和ArcGIS空间表达,得出以下结论:1)1991-2019年不同ESNO年型下农业气象灾害发生情况区域差异显著。6-8月果实膨大期厄尔尼诺年干旱灾害发生较为频繁,共计78次,干旱频率最高约50%;中性年雨涝灾害较为严重,高达60次。鲁西、鲁中等热量资源充足地区,干旱发生较为频繁;鲁南降水资源较为充沛地区,雨涝灾害发生频繁。鲁东、胶东半岛等地3-5月苹果花期极端低温灾害发生较为频繁,发生日数约7~9 d·a^(-1),频率约为60%-100%。鲁西等地是6-8月苹果果实膨大期高温热害的高发区,发生天数11~15 d·a^(-1)。2)不同ESNO年型下,干旱与厄尔尼诺年呈正相关,与拉尼娜年呈负相关。3-10月苹果可生长期厄尔尼诺年南方涛动指数与雨涝呈正相关,拉尼娜年、中性年南方涛动指数与雨涝呈负相关。3-5月苹果花期低温灾害与厄尔尼诺年南方涛动指数呈负相关;与拉尼娜年、中性年南方涛动指数呈正相关。3)3-10月苹果可生长期,厄尔尼诺年,胶东半岛地区干旱加剧,导致苹果减产率上升;中性年,雨涝灾害使得苹果减产减收的影响加重。6-8月苹果果实膨大期,拉尼娜年、中性年,鲁西地区干旱与苹果减产率呈正相关;中性年,山东大部分地区雨涝与苹果减产率呈正相关。厄尔尼诺年苹果减产率受极端低温灾害影响较小,高温热害影响较大;拉尼娜年、中性年山东大部分地区低温冷害、冻害天数增加,导致苹果减产率上升,风险加大。苹果生产中谨防厄尔尼诺年高温、干旱,拉尼娜年、中性年应预防低温、雨涝灾害对苹果产量、品质的损害,确保苹果产业健康可持续的生产。

1970—2019年河南省气温变化特征及其对ENSO事件的响应

利用河南省19个气象站点的逐日气温数据,并辅以海表温度距平指数(Sea Surface Temperature Anomaly,SSTA)和南方涛动指数,运用多项式拟合、相关性分析等方法,分析了1970—2019年河南省气温变化特征及其与厄尔尼诺-南方涛动(ENSO)的关系。结果表明:(1)1970—2019年河南省年、季节气温均呈明显的波动上升趋势,其中年均温以0.24℃/10a的速率递增,且春季气温增温速率最大,冬季气温增温速率最小。(2)过去50年,河南省的气温变化与ENSO事件的强度存在一定的相关关系,20世纪90年代以来,随着厄尔尼诺(El Nino)事件的增多和强度的加大,对应的河南省气温也显著增加。(3)在ENSO事件发生年份,河南省气温变化与SSTA值呈现比较明显的相关关系,且存在一定的滞后性。因此,河南省在强ENSO事件发生的当年或次年易发生极端灾害事件,需要提高警惕,加强防范。

ENSO事件对长江源区径流演变的影响

以长江源区为研究对象,采用沱沱河站、直门达站实测径流系列,分析两站近60年来径流演变趋势,利用海洋尼诺指数分析ENSO事件的强度与时间特征,研究两站径流丰枯变化对ENSO事件的响应规律,从海-气耦合影响大气环流角度分析ENSO事件对径流的影响机制。研究结果表明,两站均呈现震荡上升的趋势,尤其在2000年以后径流呈现显著增加的趋势。分析ENSO事件发生期间长江源区径流丰枯变化响应规律可知,1960—2000年期间,暖事件发生年份,无论是当年还是次年,长江源区出现径流偏枯的概率较高;冷事件发生年份,两站均呈现出在当年偏枯、次年丰枯概率基本相当的态势。2000年以后,长江源区径流偏丰态势尤为显著。在1970年以前和2000年以后,长江源区径流与ENSO事件之间的时频结构具有一定程度的正相关性。ENSO事件发生后,引起纬向和经向大气环流异常,使得海洋向高原热量和水汽输送产生变化,从而影响青藏高原降水和径流。

1960年以来ENSO事件对贺州市气候的影响

基于贺州市4个国家地面气象观测站1960—2021年降水和气温等气候观测资料以及同期的ENSO事件,采用统计学方法分析研究ENSO事件对贺州市气候的影响。结果表明,El Niño事件对贺州市年降水量、汛期降水量和暴雨日数有增多的作用,La Niña事件则对上述三个气候要素有减少的作用,但El Niño事件的增幅较La Niña事件的减幅稍偏大。El Niño事件强度与年降水量距平呈正相关关系。同样,El Niño年贺州市春季、冬季降水量增多,而La Niña年春季降水量基本持平而冬季降水量明显偏少;El Niño年贺州市春季、冬季和年平均气温均较多年平均偏高,且El Niño事件强度越强,年平均、春季平均气温和冬季平均气温偏高幅度越大;La Niña年贺州市年平均气温则偏低,尤其春季、冬季的平均气温偏低更明显;ENSO事件对贺州市高温天气日数存在一定的抑制效应。

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。