El Nino and anti-El Nino events in 1854-1987

-Using the COADS data set of sea surface temperature in the Equatorial Eastern Pacific, thirty one El Nino events and twenty four anti -El Nino events were identified for the period from 1854 to 1987. The results were compared with those of the other authors. The El Nino events (or anti -El Nino events ) are classified into two groups according to the timing of occrrence of the events: one starts at the first half of a year, another begins at the second half of a year. Both 1982-1983 and 1986-1987 events fall into the second group, which are characterized by the eastward migration of the positive anomaly of the sea surface temperature and the significant increasing of the anomaly in September or October.

Threshold autoregression models for forecasting El Nino events

-In this paper, monthly mean SST data in a large area are used. After the spacial average of the data is carried out and the secular monthly means are substracted, a time series (Jan. 1951-Dec. 1985) of SST anomalies of the cold tongue water area in the eastern tropical Pacific Ocean is obtained. On the basis of the time series, an autoregression model, a self-exciting threshold autoregression model and an open loop autoregression model are developed respectively. The interannual variations are simulated by means of those models. The simulation results show that all the three models have made very good hindcasting for the nine El Nino events since 1951. In order to test the reliability of the open loop threshold model, extrapolated forecast was made for the period of Jan. 1986-Feb. 1987. It can be seen from the forecasting that the model could forecast well the beginning and strengthening stages of the recent El Nino event (1986-1987). Correlation coefficients of the estimations to observations are respectively 0. 84, 0. 88 and 0. 89. It is obvious that all the models work well and the open loop threshold one is the best. So the open loop threshold autoregression model is a useful tool for monitoring the SSTinterannual variation of the cold tongue water area in the Eastern Equatorial Pacific Ocean and for estimating the El Nino strength.

Analysis of the air-sea heat exchange during the El Nino event in 1983

In this paper,by using the ECMWF objective analysed data as well as CAC and NOAA grid point data of 1981 and 1983,the sensible and latent heat fluxes at the air and sea boundary surface within the range of 45°E-75°W, 35°N-35°S over the Pacific and the Indian Ocean are calculated. The purpose is to analyse the different revealing features during the mature stage and at the end of the 1982 -1983 El Nino event and to compare the difference of the features between thd El Nino and the normal. The result shows that the air and sea heat exchange west of the dateline over the central tropical Pacific during the EJ Nino period is more intense than that of the normal. However,the fluxes of the sensible and latent heat on the sea surface with strong warming of SSTneat by and on the south side of the equator east of 170°W are low and even negative,and the patterns of the sensible and latent heat fluxes over the Indian Ocean during the year of 1983 are similer to that of normal. Spatial patterns of the sensible heat ,the latent heat,SST,OLR and the wind speed exhibit large anomalies during the El Nino event. The corresponding relationships of the spatial distribution of the streng exchange of heat fluxes with regions of high SST and action convection or negative anomalies of OLR are relatively complicated. But the region of maximum air and sea heat exchange is in good coincidence with that of high value of the Vs. The strong heat exchange is weakened with the declining and the finishing of the El Nino event in the central tropical Pacific.

The heat balance on the sea surface in the mature phase of 1982/83 El Nino event

Using the air-sea data set of January, 1983 (the mature phase of the 1982/83 El Nino event), the net radiation on the sea surface, the fluxes of the latent and the sensible heat from ocean to the atmosphere and the net heat gain of the sea surface are calculated over the Indian and the Pacific Oceans for the domain of 35°N-35°S and 45°E-75°W. The results indicate that the upward transfer of the latent and the sensible heat fluxes over the winter hemisphere is larger than that over the summer hemisphere. The sensible heat over the tropical mid Pacific in the Southern Hemisphere is transported from the atmosphere to the ocean, though its magnitude is rather small. The latent heat flux gained by the air over the eastern Pacific is less than the mean value of the normal year. The net radiation, on which the cloud amount has considerable impact, is essentially zonally distributed. Moreover, the sea surface temperature (SST) has a very good correlation with the net radiation, the region of warm SST coinciding with that of the low net radiation. The net radiation obtained by the mid Pacific Ocean is reduced by the SST anomaly during the El Nino event, whereas the atmosphere over there get more latent heat flux, and this results in the diminution of the net heat gain of the ocean. The overview of the heat budget is that the ocean over the winter hemisphere is the energy source of the atmosphere, and that over the summer hemisphere its energy sink.

The inversion of the Equatorial Undercurrent in the western tropical Pacific during 1986/1987 El Nino event

On the basis of time series measurements of winds, currents, temperature and salinity from equatorial current meter mooring and acoustic Doppler current profiler during the PRC/USA joint air-sea interaction studies in the western tropical Pacifc Ocean and sea level data provided by Prof. Wyrtki, analyses are made of the physical process and mechanism for the exceptionally inverse phenomenon (westward) of the Equatorial Undercurrent (EUC) in the western tropical Pacific after entering the mature stage of 1986/1987 ENSO event, and the numerical simulation is also conducted by 'cross section' model. The results indicate that the inversion of the EUC is related to that of pressure gradient force near the equator under the influence of non-local permanent westerlies.

STUDY ON MECHANISM OF EL NINO EVENT OCCURRENCE

A possible mechanism is put forward in this paper for El Nino events from the viewpoint of plate tec- tonics and oceanic geology.A number of the data are cited to illustrate the views that sea-bottom volcanic ac- tivities and hot springs may cause El Nino events.

Premonitory phenomenon of El Nino event reflected in the observations of LOD and sea level

Data sets of the changes of the length of day, the sea surface temperature in the eastern Pacific and of the sea level in Hong Long from tide gauge observations are used to analyze and reveal the reflections in the observations of the length of day and the sea level changes concerned with the premonitory phenomenon of next El Nino event. The results from this study indicate that a new El Nino event has been brewing with the ending of the strong La Nina event that started in early summer of 1998. The estimated formation period of the new El Nino event will begin before the end of 2000, and the peak period may be reached at around the end of 2001.

PREDICTION OF EL NINO EVENTS BY THE ASTRONOMICAL OBSERVATION OF THE LENGTH OF DAY

Ⅰ. INTRODUCTIONSince the strong El Nio event occurred at the end of 1982, which was characterized by the anomalous warming up of the sea surface water in equatorial area of eastern Pacific, the relationship between the variation of the rate of Earth rotation and the El Nio event has attracted more and more attention and some significant studies have been made. How-

Propagation Route of the Impact of El Nino Event on Atmospheric Circulation

El Ni(?)o event is a kind of global-scale atmospheric-oceanic interaction, i. e. couple impact event. In China, many studies recognized that

El Nino事件的概率预测研究

根据1854～1993年期间的El Nino事件资料序列,通过正态性、独立性等统计检验,确定序列的性质。利用Markov随机过程和一阶自回归建立预测模式,给出了下次发生El Nino事件的时间可能在2002年前后。2001年发生的概率为44 %;2002年发生的概率为61 %。

北太平洋SST的时空分布特征及其与黑潮大弯曲和El—Nino的关系

用EOF分析方法对北太平洋及赤道太平洋地区1949～1979年31年海表面温度距平场进行分解,得到几个主要距平海温模态(EOF1～3),分析了EOF1～3的时空分布特征。得到海温距平场的EOF1和EOF2～3模态分别对E1—Nino事件和黑潮大弯曲有很显著的相关性,指出SST第三模态场对黑潮大弯曲的影响具有很好的持续性,持续时间为1～2年。最后讨论了相互的影响过程,为黑潮大弯曲和E1—Nino事件的预报的可能性提供了依据。

两类El Nino事件对Hadley环流及中国气候的影响分析

利用1979-2014年的NCEP/NCAR再分析资料,分析了两类El Ni?o事件对Hadley环流及中国地区降水和气温的影响.结果表明,无论在冷季还是暖季,El Ni?o事件使得Hadley环流增强但并未改变Hadley环流中上升支及下沉支的位置;在暖季El Ni?o Modoki事件使得Hadley环流的上升支和下沉支均发生北移,在冷季则没有这种特征.El Ni?o对Hadley环流的影响较El Ni?o Modoki要大,是由两类El Ni?o事件下海温异常分布型的不同造成的.El Ni?o事件下中国南方易出现低温、洪涝,北方易发生高温、干旱,东北易出现冷夏,且易导致暖冬现象.当发生El Ni?o Modoki事件时,在冷季,中国地区气温分布表现为北部和东部地区偏低,西部及西南部地区较高;在暖季,中国东北地区表现为较强的增温现象,长江以南地区的降水较气候平均态偏少.选择两类El Ni?o事件对Hadley环流影响最大的个例,发现中国气温、降水的异常特征与两类El Ni?o事件影响中国气候变化的统计规律基本相符,表明两类El Ni?o事件对中国气候影响的不同,很大程度上是由于其对Hadley环流的影响不同造成的,其他环流系统的作用使得最终影响更为复杂.

Impacts of El Nino on the somatic condition of Humboldt squid based on the beak morphology

The Humboldt squid Dosidicus gigas has a short life span, and environmental variability plays a significant role in regulating its population dynamics and distribution. An analysis of 1 096 samples of D. gigas collected by the Chinese commercial fishing vessels during 2013, 2014, and 2016 off the Peruvian Exclusive Economic Zone, was conducted to evaluate the impacts of El Nino events on the somatic condition of D. gigas. This study indicates that the slopes of all beak variables in relation to mantle length (ML) for females were greater than those of males during 2013, 2014, and 2016, and slopes of the upper crest length and the lower rostrum length significantly differed between females and males in 2013 (P<0.05). Variation in the slopes for beak variables among years was studied;no significant difference was observed (ANCOVA, P>0.05). The Fulton's condition coefficients (K) of females and males in 2013 and 2014 were significantly greater than those in 2016 (P<0.01). The K values of females were greater than those of males in 2013, 2014, and 2016, and K values significantly differed between females and males in 2013. In normal years, the chlorophyll a (Chl a) concentration showed an N-shaped variability from January to December. However, in the El Nino period, it tended to weaken the upwelling coupled with warm and low Chl a concentration waters. We suggest that the poor somatic condition of D. gigas during the El Nino year was resulted from the low Chl a concentration in the waters, and the abundance of D. gigas would decrease due to the unfavourable environment and the lack of prey items in the El Nino year.

A Comparative Study on the Dominant Factors Responsible for the Weaker-than-expected El Ni?o Event in 2014

Anomalous warming occurred in the equatorial central-eastern Pacific in early May 2014, attracting much attention to the possible occurrence of an extreme E1 Nifio event that year because of its similarity to the situation in early 1997. However, the subsequent variation in sea surface temperature anomalies （SSTAs） during summer 2014 in the tropical Pacific was evidently different to that in 1997, but somewhat similar to the situation of the 1990 aborted E1 Nifio event. Based on NCEP （National Centers for Environmental Prediction） oceanic and atmospheric reanalysis data, the physical processes responsible for the strength of E1 Nifio events are examined by comparing the dominant factors in 2014 in terms of the preceding instability of the coupled ocean-atmosphere system and westerly wind bursts （WWBs） with those in 1997 and 1990, separately. Although the unstable ocean-atmosphere system formed over the tropical Pacific in the preceding winter of 2014, the strength of the preceding instability was relatively weak. Weak oceanic eastward-propagating downwelling Kelvin waves were forced by the weak WWBs over the equatorial western Pacific in March 2014, as in February 1990. The consequent positive upper-oceanic heat content anomalies in the spring of 2014 induced only weak positive SSTAs in the central-eastern Pacific-unfavorable for the subsequent generation of summertime WWB sequences. Moreover, the equatorial western Pacific was not cooled, indicating the absence of positive Bjerknes feedback in early summer 2014. Therefore, the development of E1 Nifio was suspended in summer 2014.

厄尔尼诺(ElNino)事件与东南沿海热带气旋活动的相关分析

统计分析了近50 a(1949～1998年)厄尔尼诺(ELNINO)事件以及我国东南沿海热带气旋历史资料,得出了厄尔尼诺(ELNINO)事件与我国东南沿海热带气旋的活动频数、移动路径、强度以及相关灾害的关系。

近57年来El Nino/La Nina事件对鄂尔多斯高原东缘气候的影响

根据1955年～2011年期间发生的El Nino／LaNina事件和鄂尔多斯高原东缘3个站点（兴县，绥德和榆林）的气象资料，利用统计分析的方法研究了1955年以来该区的降水量、温度、旱涝灾害与El Nino／LaNina事件之间的关系，揭示了El Nino／LaNina事件对鄂尔多斯高原东缘气候的影响.结果表明，鄂尔多斯高原东缘近57年降水量呈减少趋势而气温呈升高的趋势；厄尔尼诺年降水量比正常年平均降水量少87.6mm，年平均气温比正常年高0.2℃；拉尼娜年降水量比正常年均降水量少22.3mm，年平均气温比正常年低0.1℃，且其年降水量递减率和增温率略高于全国.厄尔尼诺事件对鄂尔多斯高原东缘降水量减少的影响和气温上升的影响要大于拉尼娜事件对鄂尔多斯高原东缘的影响.由小波分析可知，鄂尔多斯高原东缘降水变化在30a尺度内存在2a、8a、20a、27a的变化周期，而气温变化在30a尺度内存在3a、5a,7a、29a的变化周期.El Nino／LaNina事件对该区的旱涝灾害影响显著，旱灾年份出现厄尔尼诺的概率为63％，出现拉尼娜的概率为25％，厄尔尼诺年易于发生旱灾.

The Influence of Two Kinds of El Ni?o Events on the Strong Tropical Cyclone Generation and Strength in the Pacific Ocean

This paper focuses on the effects of two types of El Nino events on tropical cyclone activity. We classified El Nino events from 1961 to 2015 according to their sea surface temperature （SST） anomalies into an eastern type and a central type. Then we selected strong tropical cyclones to statistically analyze the tropical cyclone characteristics during different events and their effects, as well as to study the possible mechanisms related to thermodynamic and dynamic factors. The tropical cyclone generation areas were found to be very similar during the two kinds of events. The average number of tropical cyclone in the eastern event is more than that in central event, and the hurricane in northeastern Pacific （HNP） has more energy than the typhoon in northwestern Pacific （TNP） in all cases. The seasonal distribution of the TNP high-incidence centers during central El Nifio events is opposite to that of the HNP. The TNP accumulated cyclone energy （ACE） intensity is similar in the fall and summer, and the HNP ACE intensity in the summer is greater than that in the fall. The SSTs are consistent with the TNP and HNP movement trends. The Walker circulation intensity was strongly affected by the eastern events, but it quickly returned to its normal state, while the intensity was slightly reduced in the central events, and it slowly returned to its normal state. The vertical velocity distributions in the Pacific are different at different stages of both events, and the distributions of vertical velocity anomalies for typhoons and hurricanes are consistent.

Contribution of El Nino amplitude change to tropical Pacific precipitation decline in the late 1990s

Equatorial central Pacific precipitation experienced a prominent decline in the late 1990 s.This change was previously attributed to a La Nina-like mean sea surface temperature(SST)change in the Pacific Ocean associated with a phase switch of the Interdecadal Pacific Oscillation.Here,using a series of model experiments,the authors reveal that the El Nino-related interannual SST anomalies contributed largely to the precipitation decrease over the equatorial central Pacific.This El Nino SST effect was due to the change in the amplitude of El Nino events in the late 1990 s.The 1980-98 decade had more large-amplitude El Nino events than the 1999-2014 decade.The nonlinear precipitation response to SST anomalies resulted in a larger decadal mean precipitation in the 1980-98 decade than in the 1999-2014 decade.The results highlight the importance of El Nino amplitude change in future climate change related to global warming.

试论El nino事件对沈阳气候的影响

通过对1951~2005年沈阳温度、降水、暴雨日数资料及1951~2005年沈阳气候极值分析,探讨El Nino事件对沈阳气候的影响。结果发现,在El nino当年沈阳地区温度呈偏低趋势,当El nino过后沈阳地区温度呈现偏高趋势。通常在E l nino发生前一直到接近El nino峰期这一段时间,沈阳地区雨水充沛,有的年份会洪涝灾害发生;温度偏低,冬季容易出现冷冬,有的年份会发生低温冷害。El nino事件次年,沈阳地区雨量偏少,日照充足,偏暖,一般会出现暖冬,有的年份会有干旱、高温少雨等灾害性天气发生。

两类El Nino事件对中国近海及毗邻海域海表温度的影响

为研究东部型和中部型两类厄尔尼诺(El Nino)事件与中国近海海表温度(sea surface temperature,SST)变化间的联系,基于中国科学院大气物理研究所连续80年(1940—2019年)的SST再分析数据,采用EOF分解、合成分析等方法做了初步分析,发现中国近海及毗邻海域近80年SST变化与全球变暖密切相关。并且两类El Nino事件对中国近海SST变化的影响存在显著差异。东部型El Nino事件发展过程中,中国近海及毗邻海域SST在发展年主要为负异常,衰退期为正异常;中部型El Nino事件发展过程中, SST变化区域差异大,发展年日本附近海域为正异常, 28°N以南为弱的负异常。两类El Nino事件引发西太平洋风场反气旋涡的时间、位置与强度等的不同,是造成中国近海风场与海表温度异常(sea surface temperature anomaly, SSTA)差异的主要原因。