Sea surface temperature anomaly in the tropical North Atlantic during El Niño decaying years

Based on reanalysis data from 1979 to 2016, this study focuses on the sea surface temperature (SST) anomaly of the tropical North Atlantic (TNA) in El Niño decaying years. The TNA SST exhibits a clear warm trend during this period. The composite result for 10 El Niño events shows that the TNA SST anomaly reaches its maximum in spring after the peak of an El Niño event and persists until summer. In general, the anomaly is associated with three factors—namely, El Niño, the North Atlantic Oscillation (NAO), and a long-term trend, leading to an increase in local SST up to 0.4°C, 0.3°C, and 0.35°C, respectively. A comparison between 1983 and 2005 indicates that the TNA SST in spring is affected by El Niño, as well as the local SST in the preceding winter, which may involve a long-term trend signal. In addition, the lead–lag correlation shows that the NAO leads the TNA SST by 2–3 months. By comparing two years with an opposite phase of the NAO in winter (i.e., 1992 and 2010), the authors further demonstrate that the NAO is another important factor in regulating the TNA SST anomaly. A negative phase of the NAO in winter will reinforce the El Niño forcing substantially, and vise versa. In other words, the TNA SST anomaly in the decaying years is more evident if the NAO is negative with El Niño. Therefore, the combined effects of El Niño and the NAO must be considered in order to fully understand the TNA SST variability along with a long-term trend.摘要基于1979年到2016年多种再分析资料, 本文分析了El Niño衰减年热带北大西洋的海温异常. 结果表明, 热带北大西洋海温在此期间呈显著变暖趋势. 10次El Niño事件的合成结果表明热带北大西洋海温异常在El Niño事件峰值之后的春季达到最大值, 并持续到夏季. 一般而言, 这种异常与三个因子有关, 即El Niño, 北大西洋涛动和长期趋势, 能分别导致局地海温上升0.4°C, 0.3°C和0.35°C. 1983年和2005年的对比分析表明, 尽管El Niño强度对春季北大西洋海温起到决定性作用, 与长期趋势密切相关的前冬海温也很重要. 此外, 超前-滞后相关结果表明北大西洋涛动超前海温约2–3个月. 比较两个冬季相反位相北大西洋涛动的年份 (即1992年和2010年) , 表明北大西洋涛动也能调制北大西洋海温异常. 冬季负位相北大西洋涛动能显著增强El Niño的强迫影响, 反之亦然. 换言之, 如果北大西洋涛动与El Niño位相相合, 衰减年北大西洋海温异常才更为显著. 因此, 为全面理解热带北大西洋海温变化, 除长期趋势外, 还必须考虑El Niño和北大西洋涛动的综合影响.     

Impact of the Equatorial Atlantic on the El Ni?o Southern Oscillation

Observations indicate that the Atlantic zonal mode influences El Ni?o Southern Oscillation (ENSO) in the Pacific, as already suggested in previous studies. Here we demonstrate for the first time using partial coupled experiments that the Atlantic zonal mode indeed influences ENSO. The partial coupling experiments are performed by forcing the coupled general circulation model (ECHAM5/MPI-OM) with observed sea surface temperature (SST) in the Tropical Atlantic, but with full air-sea coupling allowed in the Pacific and Indian Ocean. The ensemble mean of a five member simulation reproduces the observational results well. Analysis of observations, reanalysis, and coupled model simulations all indicate the following mechanism: SST anomalies associated with the Atlantic zonal mode affect the Walker Circulation, driving westward wind anomalies over the equatorial Pacific during boreal summer. The wind stress anomalies increase the east-west thermocline slope and enhance the SST gradient across the Pacific; the Bjerknes positive feedback acts to amplify these anomalies favouring the development of a La Ni?a-like anomalies. The same mechanisms act for the cold phase of Atlantic zonal mode, but with opposite sign. In contrast to previous studies, the model shows that the influence on ENSO exists before 1970. Furthermore, no significant influence of the Tropical Atlantic on the Indian Monsoon precipitation is found in observation or model.     

Factor analysis for El Niño signals in sea surface temperature and precipitation

Maximum likelihood factor analysis (MLFA) is applied to investigate the variables of monthly Tropical Pacific sea surface temperatures (SST) from Niño 1+2, Niño 3, Niño 3.4, and Niño 4 and precipitation over New South Wales and Queensland of eastern Australia, Kalimantan Island of Indonesia, and California and Oregon of the west coast of the United States. The monthly data used were from 1950 to 1999. The November-February SST with time leads of 0, 1, 2, and 3 months to precipitation are considered for both El Niño warm phases and non El Niño seasons. Interpretations of the factor loadings are made to diagnose relationships between the SST and precipitation variables. For El Niño signals, the rotated FA loadings can efficiently group the SST and precipitation variables with interpretable physical meanings. When the time lag is 0 or 1 month, the November–February El Niño SST explains much of the drought signals over eastern Australia and Kalimantan. However, when the time lag is 2 or 3 months, the same SST cannot adequately explain the precipitation during January–May over the two regions. Communality results of five factors for precipitation indicate nearly 100% explanation of variances for Queensland and California, but the percentages are reduced to only about 30% for Oregon and Kalimantan. Factor scores clearly identify the strongest El Niño relevant to precipitation variations. Principal component factor analysis (PCFA) is also investigated, and its results are compared with MLFA. The comparison indicates that MLFA can better group SST data relevant to precipitation. The residuals of MLFA are always smaller than the PCFA. Thus, MLFA may become a useful tool for improving potential predictability of precipitation from SST predictors.     

North Atlantic sea surface temperatures and their relation to the North Atlantic Oscillation during the last 230?years

August Sea Surface Temperatures (aSSTs) based on fossil diatom assemblages are generated with 2?year average resolution from a 230-year-long sediment core (Rapid 21-12B), from the Reykjanes Ridge in the subpolar North Atlantic. The results indicate a warming trend of ~0.5°C of the surface waters at the Reykjanes Ridge for the last 230?years. Superimposed on this warming trend there is a multidecadal to decadal aSST variability of up to 1°C. The interval from the 1770s to the 1830s represents the coldest period, whereas ~1860?C1880 represents the warmest period during the last 230?years. The last 25?years is characterized by a warming trend showing strong decadal aSST variability with several warm years, but also the coldest years since the 1820s. The time of these cold years in the mid-1970s, -1980s and -1990s correspond with the documented great salinity anomalies (GSA) in the North Atlantic suggesting increased fluxes of cold, low-salinity waters from the Arctic during the last decades. The aSST record and the August North Atlantic Oscillation (aNAO) index show similar multidecadal-scale variability indicating a close coupling between the oceanic and atmospheric patterns. The aSST record shows a negative correlation with the aNAO indicating cold aSST during the positive aNAO trend and vice versa. Results suggest that the wind driven variation in volume fluxes of the North Atlantic surface waters could be the major mechanism behind the observed relationship.     

Impact of El Niño onset timing on the Indian Ocean: Pacific coupling and subsequent El Niño evolution

A relation between the timing of the El Niño onset and its subsequent evolution is examined by emphasizing its association with the Indian Ocean (IO) SST variation. Two types of El Niño events based on the timing of their onset are classified and their characteristics are examined and compared. In general, spring onset (SP) events grow greater in magnitude and their evolutions have a faster transition. On the contrary, summer onset (SU) events are relatively weaker in magnitude and have a slower transition. Moreover, in contrast to the SU events, the SP events have a strong tendency for accompanying an IO dipole and basin-wide type of warming pattern in the El Niño developing and mature phases, respectively. It is demonstrated here that the distinctive evolutions in transition phase of the two events are resulted from the difference in IO SST. The warm IO SST in the SP El Niño event, lead an anomalous easterlies over the western Pacific, which forces a fast termination of El Niño events.     

Linear trends in sea surface temperature of the tropical Pacific Ocean and implications for the El Niño-Southern Oscillation

A principal component decomposition of monthly sea surface temperature (SST) variability in the tropical Pacific Ocean demonstrates that nearly all of the linear trends during 1950–2010 are found in two leading patterns. The first SST pattern is strongly related to the canonical El Niño-Southern Oscillation (ENSO) pattern. The second pattern shares characteristics with the first pattern and its existence solely depends on the presence of linear trends across the tropical Pacific Ocean. The decomposition also uncovers a third pattern, often referred to as ENSO Modoki, but the linear trend is small and dataset dependent over the full 61-year record and is insignificant within each season. ENSO Modoki is also reflected in the equatorial zonal SST gradient between the Niño-4 region, located in the west-central Pacific, and the Niño-3 region in the eastern Pacific. It is only in this zonal SST gradient that a marginally significant trend arises early in the Northern Hemisphere spring (March–May) during El Niño and La Niña and also in the late summer (July–September) during El Niño. Yet these SST trends in the zonal gradient do not unequivocally represent an ENSO Modoki-like dipole because they are exclusively associated with significant positive SST trends in either the eastern or western Pacific, with no corresponding significant negative trends. Insignificant trends in the zonal SST gradient are evident during the boreal wintertime months when ENSO events typically mature. Given the presence of positive SST trends across much of the equatorial Pacific Ocean, using fixed SST anomaly thresholds to define ENSO events likely needs to be reconsidered.     

Influence of Intraseasonal Oscillation on the Asymmetric Decays of El Ni?o and La Ni?a

Warm and cold phases of El Nino–Southern Oscillation (ENSO) exhibit a significant asymmetry in their decay speed. To explore the physical mechanism responsible for this asymmetric decay speed, the asymmetric features of anomalous sea surface temperature (SST) and atmospheric circulation over the tropical Western Pacific (WP) in El Nino and La Nina mature-to-decay phases are analyzed. It is found that the interannual standard deviations of outgoing longwave radiation and 850 hPa zonal wind anomalies over the equatorial WP during El Nino (La Nina) mature-to-decay phases are much stronger (weaker) than the intraseasonal standard deviations. It seems that the weakened (enhanced) intraseasonal oscillation during El Nino (La Nina) tends to favor a stronger (weaker) interannual variation of the atmospheric wind, resulting in asymmetric equatorial WP zonal wind anomalies in El Nino and La Nina decay phases. Numerical experiments demonstrate that such asymmetric zonal wind stress anomalies during El Nino and La Nina decay phases can lead to an asymmetric decay speed of SST anomalies in the central-eastern equatorial Pacific through stimulating di erent equatorial Kelvin waves. The largest negative anomaly over the Nino3 region caused by the zonal wind stress anomalies during El Nino can be threefold greater than the positive Nino3 SSTA anomalies during La Nina, indicating that the stronger zonal wind stress anomalies over the equatorial WP play an important role in the faster decay speed during El Nino.     

Intraseasonal variability of western North Pacific subtropical high based on the El Ni?o influence and its relationship with East Asian summer monsoon

The boreal summer season could be divided into two periods in terms of the variability of western North Pacific subtropical high (WNPSH) based on the El Ni?o influence. The correlation analysis indicates that the WNPSH in the period of pentad 32?C37 (June 5 to July 4, first period) is not affected by El Ni?o, while that in the period of pentad 40?C45 (July 15 to August 13, second period) is strongly affected by sea surface temperature in the equatorial eastern Pacific in the previous winter. The different response of low-level circulation over the western North Pacific (WNP) to the El Ni?o forcing between two periods seems to be due to the difference of mean climatological fields over the WNP and the East Asian regions. The WNPSH in the first period is closely connected to the variability of North Pacific subtropical High. In the second period, on the other hand, the WNPSH variability is dominantly controlled by the convective activity over the WNPSH region and it is related with the El Ni?o forcing. The composite analysis on the relationship between the WNPSH and the East Asian summer monsoon exhibits distinct contrasts between two periods. In the first period, the East Asian stationary front exists all the time regardless of the strength of the WNPSH. On the other hand, in the second period the East Asian stationary front appears only when the WNPSH is strong, while there is no obvious East Asian frontal zone when it is weak.     

Hypothesis on a possible role of El Ni?o in the occurrence of influenza pandemics

The El Ni?o phenomenon is the Earth??s strongest climatic fluctuation on an interannual timescale and has a quasi-global impact, although originating in the tropical Pacific Ocean. A very strong El Ni?o is recognized to cause extreme dryness and wetness in different parts of the world. We show that all the eight well-documented influenza pandemics, starting from the first certain one documented in ad 1580, originated in China and in Russia, a few years after the occurrence of a very strong or after a prolonged strong/moderate El Ni?o event. At present, the next El Ni?o will probably occur at the beginning of 2013 (Mazzarella et al. Theor Appl Climatol 100:23?C27, 2010), and this forecast may suggest to be well prepared to take appropriate precautionary epidemiological measures.     

Dependency of typhoon intensity and genesis locations on El Ni?o phase and SST shift over the western North Pacific

The effects of the El Ni?o-Southern Oscillation (ENSO) phase and the shifting of the ENSO sea surface temperature (SST) on the intensity of tropical cyclones (TC) have been extensively investigated in terms of TC genesis locations in the western North Pacific (WNP). To advance the hypothesis for a relation of genesis location–intensity that the TC formation location hints its intensity, two cases have been compared, which include the phase of the decaying El Ni?o turning over to La Ni?a (type I) and the phase that recovers to a neutral condition (type II). In addition, the shift of ENSO SST to the central Pacific warming (CPW) from the East Pacific warming (EPW) has been examined. The genesis potential index (GPI) and the accumulated cyclone energy have been applied to compare the differences between the ENSO phase and the TC formation location. It was apparent that ENSO influences the WNP typhoon formation location depending on the cycle of the ENSO phase. In addition, the typhoon activity was affected by the zonal shift of the El Ni?o SST. The CPW, which has maximum SST over the central Pacific, tends to have a persistently high GPI over the WNP in September–November and June–August, demonstrating that the formation locations of strong TCs significantly shift southeastward compared with the EPW having SST maximum over the eastern Pacific. CPW years revealed a distinguishable relationship between the TC formation location and the TC between the tropical depression (TD) + tropical storm (TS) and the intense typhoon of category 4?+?5.     

The impact of solar activity on the 2015/16 El Ni?o event

最近的海洋表面温度和大气环流异常的数据表明此次2015/16厄尔尼诺事件正在快速衰退。一些研究者预测紧随的拉尼娜事件将在2016年夏季或早秋到来。从太阳活动对热带海洋表面温度的调制作用出发,作者研究了发生在太阳活动峰值年(2014)之后的2015/16厄尔尼诺事件的演变过程。统计和合成分析的结果表明,当厄尔尼诺Modoki指数滞后太阳黑子数两年时,二者存在显著的正相关。在过去的126年(1890–2015)里,每一个太阳活动峰值年之后的1–3年内均明确存在厄尔尼诺Modoki事件的演变过程。这说明可能在太阳活动峰值期,异常强的太阳活动有利于激发产生厄尔尼诺Modoki事件。自2014年以来,季节平均的海洋表面温度异常和风场异常的空间特征更像是两类厄尔尼诺事件的混合物(即东太平洋型厄尔尼诺和厄尔尼诺Modoki),其空间特征受到太阳活动的调控。因此,2015/16 El Ni?o事件中的厄尔尼诺Modoki组分可能是太阳活动的结果,其衰退速度比东太平洋型厄尔尼诺组分较慢。因此,在2016年下半年,微弱的海洋表面温度正异常可能持续存在于赤道中太平洋(日界线附近)和北美西边界附近。     

Effects of El Ni?o Modoki on winter precipitation in Korea

This study compares the impacts of El Ni?o Modoki and El Ni?o on precipitation over Korea during the boreal winters from 1954 to 2009. Precipitation in Korea tends to be equal to or greater than the normal level during an El Ni?o Modoki winter, whereas there is no significant change during an El Ni?o winter. Greater than normal precipitation during El Ni?o Modoki was also found over the lower reaches of the Yangtze River, China and much of southern Japan. The latitudes of these regions are 5–10° further north than in southern China, where precipitation increases during El Ni?o. The following two anomalous atmospheric circulations were found to be causes that led to different precipitation distributions over East Asia. First, an atmospheric wave train in the lower troposphere, which propagated from the central tropical Pacific (cyclonic) through the southern Philippine Sea (anticyclonic) to East Asia (cyclonic), reached the southern China and northern Philippine Sea during El Ni?o, whereas it reached Korea and southern Japan during El Ni?o Modoki. Second, an anomalous local meridional circulation, which consists of air sinking in the tropics, flowing poleward in the lower troposphere, and rising in the subtropics, developed between the southern Philippine Sea and northern Philippine Sea during El Ni?o. During El Ni?o Modoki, however, this circulation expanded further to the north and was formed between the southern Philippine Sea and regions of Korea and southern Japan.     

Influence of the pace of El Niño decay on tropical cyclone frequency over the western north pacific during decaying El Niño summers

This study investigated the distinct responses of western North Pacific (WNP) tropical cyclone (TC) activity during different decaying El Niño summers. The El Niño events were classified into two types according to the periodicity of the ENSO cycle, with positive SST anomalies in the equatorial central-eastern Pacific maintaining positive values into the following summer as the slow decaying (SD) cases, but transforming to negative values in the following summer as the rapid decaying (RD) cases. Compared with that in SD El Niño summers, the TC occurrence frequency over the WNP is significantly lower in RD El Niño summers, led by a much weaker WNP monsoon trough with more unfavorable environmental factors for TC genesis and development. Further examination showed that the apparent warming over the tropical Indian Ocean basin and cooling over the equatorial central-eastern Pacific contribute together to an enhanced lower-tropospheric anticyclone through modulation of the descending branch of the large-scale Walker circulation over the WNP, which may play a crucial role in suppressing the TC activity during the decaying summer of RD El Niño cases. In contrast, the warming equatorial central-eastern Pacific and remote western Indian Ocean induce a weakening WNP anticyclone and less suppressed deep convection during the decaying summer of SD El Niño cases. Thus, the different evolution of SST anomalies associated with different paces of El Niño decay results in the linkage between the preceding winter El Niño and the decreased WNP TC frequency in summer being more (less) robust for RD (SD) El Niño cases.摘要本文分析了El Niño事件衰减速度的差异对衰退年夏季西北太平洋热带气旋 (tropical cyclone, TC) 频数的不同影响. 按照El Niño事件衰减速度不同, 将其划分为迅速衰减 (rapid decaying, RD) 和缓慢衰减 (slow decaying, SD) 的El Niño事件. SD (RD) El Niño事件的衰退年夏季, 赤道中东太平洋海温仍维持正异常 (衰减为负异常) . 与SD El Niño事件相比, RD El Niño事件衰退年夏季西北太平洋TC频数显著减少. 进一步的分析揭示了导致TC频数差异的大尺度环境要素, 指出热带印度洋-太平洋海温异常密切相关的西北太平洋低层反气旋异常在其中起到了关键作用.     

The trivariate seasonal analysis of couplings between El Niño,North Atlantic Oscillation,and Indian monsoon

Interdependencies between the El Niño-Southern Oscillation (ENSO), North Atlantic Oscillation (NAO), and Indian monsoon (IM) phenomena are investigated from data over the period of 1871-2013. Along with the bivariate analysis of directional couplings between ENSO, NAO, and IM, their trivariate analysis was carried out. To detect the seasonal features of directional couplings using Wiener-Granger causality, various temporal resolutions of the data ranging from a month to a half-year are used. Taking into account the seasonality of the processes, the influence of ENSO on NAO is detected which has different signs in winter and summer. The influence of NAO on ENSO is revealed only in the trivariate analysis. The strongest couplings are observed between ENSO and IM. All the detected couplings can be divided into two groups: the "fast" (with the characteristic time from a month to several months) and "slow" (with the characteristic time of a half-year or longer) ones. The fast couplings include bidirectional couplings between IM and ENSO in summer and autumn when the summer pattern of NAO influences the patterns of ENSO and IM in the next season. The slow couplings include the effects of ENSO on NAO and on the winter pattern of IM as well as the influence of IM on the summer pattern NAO.     

A diagnostic study of the impact of El Niño on the precipitation in China

The impact of El Niño on the precipitation in China for different seasons are investigated diagnostically. It is found that El Niño can influence the precipitation in China significantly during its mature phase. In the Northern winter, spring and autumn, the positive precipitation anomalies are found in the southern part of China during the El Niño mature phase. In the Northern summer, the patterns of the precipitation anomalies in the El Niño mature phase are different from those in the other seasons. The negative precipitation anomalies appear in both southern and northern parts of China, while in between around the lower reaches of the Yangtze River and the Huaihe River valleys the precipitation anomalies tend to be positive. In the Northern winter, spring and autumn, the physical process by which El Niño affects the precipitation in the southern part of China can be explained by the features of the circulation anomalies over East Asia during the El Niño mature phase (Zhang et al., 1996). The appearance of an anticyclonic anomaly to the north of the maritime continent in the lower troposphere during the El Niño mature phase intensifies the subtropical high in the western Pacific and makes it shift westward. The associated southwesterly flow is responsible for the positive precipitation anomalies in the southern part of China. In the Northern summer, the intensified western Pacific subtropical high covers the southeastern periphery of China so that the precipitation there becomes less. In addition, the weakening of the Indian monsoon provides less moisture inflow to the northern part of China.     

Theories on Formation of an Anomalous Anticyclone in Western North Pacific during El Ni?o: A Review

The western North Pacific anomalous anticyclone(WNPAC) is an important atmospheric circulation system that conveys El Ni?o impact on East Asian climate. In this review paper, various theories on the formation and maintenance of the WNPAC, including warm pool atmosphere–ocean interaction, Indian Ocean capacitor, a combination mode that emphasizes nonlinear interaction between ENSO and annual cycle, moist enthalpy advection/Rossby wave modulation, and central Pacific SST forcing, are discussed. It is concluded that local atmosphere–ocean interaction and moist enthalpy advection/Rossby wave modulation mechanisms are essential for the initial development and maintenance of the WNPAC during El Ni?o mature winter and subsequent spring. The Indian Ocean capacitor mechanism does not contribute to the earlier development but helps maintain the WNPAC in El Ni?o decaying summer.The cold SST anomaly in the western North Pacific, although damped in the summer, also plays a role. An interbasin atmosphere–ocean interaction across the Indo-Pacific warm pool emerges as a new mechanism in summer. In addition, the central Pacific cold SST anomaly may induce the WNPAC during rapid El Ni?o decaying/La Ni?a developing or La Ni?a persisting summer. The near-annual periods predicted by the combination mode theory are hardly detected from observations and thus do not contribute to the formation of the WNPAC. The tropical Atlantic may have a capacitor effect similar to the tropical Indian Ocean.     

Indices of El Nio and El Nio Modoki:An Improved El Nio Modoki Index

In recent years, El Nio Modoki (a type of pseudo-El Nio) has been distinguished as a unique large-scale ocean warming phenomenon happening in the central tropical Pacific that is quite different from the traditional El Nio. In this study, EOF analysis was used to successfully separate El Nio and El Nio Modoki. The abilities of the NINO3 index, NINO3.4 index, NINO1+2 index and NINO4 index in characterizing El Nio were explored in detail. The resulting suggestion was that, comparatively, NINO3 is the op...     

Revisiting Asymmetry for the Decaying Phases of El Ni?o and La Ni?a

This study investigated the relationship between the asymmetry in the duration of El Ni?o and La Ni?a and the length of their decaying phases. The results suggested that the duration asymmetry comes from the long decaying ENSO cases rather than the short decaying ones. The evolutions of short decaying El Ni?o and La Ni?a are approximately a mirror image with a rapid decline in the following summer for the warm and cold events. However, a robust asymmetry was found in long decaying cases, with a prolonged and re-intensified La Ni?a in the following winter. The asymmetry for long decaying cases starts from the westward extension of the zonal wind anomalies in a mature winter, and is further contributed to by the air-sea interaction over the tropical Pacific in the following seasons.     

Statistical simulations of the future 50-year statistics of cold-tongue El Niño and warm-pool El Niño

Recent extensive studies have suggested that the occurrence of warm-pool El Niño has increased since the late 1970s and will increase in future climate. Occurrence frequencies of cold-tongue and warm-pool El Niño have been investigated in the observational record (1980–2006) and in the future 50 years (2007–2056) based on 100 synthetic SST datasets with estimates of statistical confidence. In the observational record, 80% of the warm-pool El Niño occurred since 1980 over a period of 27 years; only 20% of the warm-pool El Niño occurred prior to 1980 over a period of 110 years. The 100 synthetic datasets, on average, produce 142 months of cold-tongue El Niño in 2007–2056 as opposed to an average 107 months in the same length of the observational data; this is a 20.7% increase in the occurrence of cold-tongue El Niño compared with the observational period. Warm-pool El Niño occurred for 112 months in 2007–2056 as opposed to an average occurrence of 42 months in the observational record; this is 2.5 times the occurrence frequency in the 1980–2006 period in the synthetic datasets. As a result, occurrence frequencies of cold-tongue and warm-pool El Niño in the period of 2007–2056 become quite comparable to each other in the synthetic datasets. It is expected in the next 50 years that warm-pool El Niño will be nearly as frequent as cold-tongue El Niño.     

An Introduction to the Integrated Climate Model of the Center for Monsoon System Research and its simulated influence of El Niño on East Asian-western North Pacific climate

This study introduces a new global climate model--the Integrated Climate Model （ICM）--developed for the seasonal prediction of East Asian-western North Pacific （EA-WNP） climate by the Center for Monsoon System Research at the Institute of Atmospheric Physics （CMSR, IAP）, Chinese Academy of Sciences. ICM integrates ECHAM5 and NEMO2.3 as its atmospheric and oceanic components, respectively, using OASIS3 as the coupler. The simulation skill of ICM is evaluated here, including the simulated climatology, interannual variation, and the influence of E1 Nifio as one of the most important factors on EA-WNP climate. ICM successfully reproduces the distribution of sea surface temperature （SST） and precipitation without climate shift, the seasonal cycle of equatorial Pacific SST, and the precipitation and circulation of East Asian summer monsoon. The most prominent biases of ICM are the excessive cold tongue and unrealistic westward phase propagation of equatorial Pacific SST. The main interannual variation of the tropical Pacific SST and EA-WNP climate E1 Nifio and the East Asia-Pacific Pattern--are also well simulated in ICM, with realistic spatial pattern and period. The simulated E1 Nifio has significant impact on EA-WNP climate, as in other models. The assessment shows ICM should be a reliable model for the seasonal prediction of EA-WNP climate.