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11.
利用1980~2010年月平均Hadley中心海表温度、美国全球海洋资料同化系统(GODAS)海洋温度和NCEP/NCAR大气环流再分析资料,通过对2个海洋要素(海表温度SST、上层热含量HC)和5个大气要素(海平面气压SLP、850 hPa风场、200hPa速度势和对外长波辐射OLR)的多变量经验正交函数展开(multivariate EOF,简称MV-EOF)探讨了热带太平洋的主要海气耦合特征.结果表明,MV-EOF分析的前两个耦合模态分别很好地对应了传统型El Ni(n)o和ElNiloModoki的海气耦合特征:传统型El Ni(n)o期间,伴随着赤道中东太平洋SST的异常增温,HC、SLP、200 hPa速度势等要素总体呈东西反相的“跷跷板”变化,低层850hPa赤道中太平洋出现较强西风距平,西北太平洋上空为反气旋性异常环流;ElNi(n)o Modoki期间,SST持续增温和HC正异常中心均显著西移至中太平洋,低层SLP和高空200 hPa速度势均呈现纬向三极型异常分布,低层异常强西风向西移至暖池东部,西北太平洋上空呈现气旋性异常环流.两类El Ni(n)o的海气耦合特征存在显著差异,较优的El Ni(n)o指数应不仅可以客观描述和区分El Ni(n)o现象本身,更要紧密联系两类事件所产生的大气响应.以往定量表征El Ni(n)o年际变化的指标大多立足于SST或SLP,本文选取HC作为研究指标,定义了一组新的El Ni(n)o指数HCEI和HCEMI.较以往基于SST的El Ni(n)o指数,HCEI和HCEMI不仅能更清楚地表征和区分两类El Ni(n)o(如1993年的传统型El Ni(n)o和2006年的El Ni(n)o Modoki),而且能更好地反映和区分两类El Ni(n)o与大气间的海气耦合特征,为ElNi(n)o的监测和短期气候预测工作提供了一个新工具. 相似文献
12.
The Impacts of Two Types of El Ni(n)o on Global Ozone Variations in the Last Three Decades 总被引:1,自引:0,他引:1
The effects of E1Nifio Modoki events on global ozone concentrations are investigated from 1980 to 2010 E1 Nifio Modoki events cause a stronger Brewer-Dobson (BD) circulation which can transports more ozone-poor air from the troposphere to stratosphere, leading to a decrease of ozone inthe lower-middle stratosphere from 90~S to 90~N. These changes in ozone concentrations reduce stratospheric column ozone. The reduction in stratospheric column ozone during E1 Nifio Modoki events is more pronounced over the tropical eastern Pacific than over other tropical areas because transport of ozone-poor air from middle-high latitudes in both hemispheres to low latitudes is the strongest between 60°W and 120°W. Because of the decrease in stratospheric column ozone during E1 Nifio Modoki events more UV radiation reaches the tropical troposphere leading to significant increases in tropospheric column ozone An empirical orthogonal function (EOF) analysis of the time series from 1980 to 2010 of stratospheric and tropospheric ozone monthly anomalies reveals that: E1 Nifio Modoki events are associated with the primary EOF modes of both time series. We also found that E1 Nifio Modoki events can affect global ozone more significantly than canonical E1 Nifio events. These results imply that E1 Nifio Modoki is a key contributor to variations in global ozone from 1980 to 2010. 相似文献
13.
In the summers of 1998 and 2010, severe floods occurred in the middle and lower reaches of the Yangtze
River. Although an El Ni~no event took place preceding each of the summer floods, significant differences
between the two summer floods and the two El Ni~no events were identified. The 1997/98 El Ni~no is a
conventional one with strongest warming in the central-eastern Pacific, whereas the 2009/10 event is an El
Ni~no Modoki with strongest warming in the central Pacific. In this study, summer rainfall anomalies (SRA)
in the two years were first compared based on the rainfall data at 160 stations in mainland China, and a
significant difference in SRA was found. To understand the underlying mechanism for the difference, the
atmospheric circulation systems, particularly the western North Pacific anticyclone (WNPAC), the western
Pacific subtropical high (WPSH), and the low-level air flows, were compared in the two years by using the
NCEP/NCAR reanalysis data. The results display that the WNPAC was stronger in 2010 than in 1998, along
with a northwestward shift, causing weakened southwesterly from the Bay of Bengal to the South China Sea
but intensified southerly in eastern China. This resulted in less water vapor transport from the tropical Indian
Ocean and the South China Sea but more from the subtropical western Pacific to East Asia. Subsequently,
the rainband in 2010 shifted northward. The difference in the WNPAC was caused by the anomalous
ascending motion associated with the warming location in the two El Ni~no events. Furthermore, the role
of tropical sea surface temperature (SST) in modulating these differences was investigated by conducting
sensitivity experiments using GFDL AM2.1 (Geophysical Fluid Dynamics Laboratory Atmospheric Model).
Two experiments were performed, one with the observed monthly SST and the other with June SST persisting
through the whole summer. The results suggest that the model well reproduced the primary differences in
the atmospheric circulation systems in the two years. It is found that the difference in El Ni~no events has
shaped the rainfall patterns in the two years of 1998 and 2010. At last, the case of 2010 was compared
with the composite of historical El Ni~no Modoki events, and the results indicate that the impact of El Ni~no
Modoki varies from case to case and is more complicated than previously revealed. 相似文献
14.
Traditional El Nino and El Nino Modoki Revisited: Is El Nino Modoki Linearly Independent of Traditional El Nino? 总被引:1,自引:0,他引:1 下载免费PDF全文
The present study revisited the first two leading modes of tropical Pacific sea surface temperature anomalies (SSTA) during the period of 1979-2008. It is suggested that the so-called El Nino Modoki, which is captured by the second mode, exists objectively and exhibits obvious differences from traditional El Nino, which is captured by the first mode, in terms of its spatial characteristics. Furthermore, the authors found that El Nino Modoki is linearly independent of traditional El Nino; hence, it cannot be described as part of the traditional El Nino evolution, and vice versa. 相似文献
15.
Anomalous winter climate conditions in the Pacific rim during recent El Niño Modoki and El Niño events 总被引:2,自引:1,他引:1
Present work compares impacts of El Niño Modoki and El Niño on anomalous climate in the Pacific rim during boreal winters of 1979–2005. El Niño Modoki (El Niño) is associated with tripole (dipole) patterns in anomalies of sea-surface temperature, precipitation, and upper-level divergent wind in the tropical Pacific, which are related to multiple “boomerangs” of ocean-atmosphere conditions in the Pacific. Zonal and meridional extents of those “boomerangs” reflect their independent influences, which are seen from lower latitudes in the west to higher latitudes in the east. In the central Pacific, more moisture is transported from the tropics to higher latitudes during El Niño Modoki owing to displacement of the wet “boomerang” arms more poleward toward east. Discontinuities at outer “boomerang” arms manifest intense interactions between tropical and subtropical/extratropical systems. The Pacific/North American pattern and related climate anomalies in North America found in earlier studies are modified in very different ways by the two phenomena. The seesaw with the dry north and the wet south in the western USA is more likely to occur during El Niño Modoki, while much of the western USA is wet during El Niño. The moisture to the southwestern USA is transported from the northward shifted ITCZ during El Niño Modoki, while it is carried by the storms traveling along the southerly shifted polar front jet during El Niño. The East Asian winter monsoon related anticyclone is over the South China Sea during El Niño Modoki as compared to its position over the Philippine Sea during El Niño, causing opposite precipitation anomalies in the southern East Asia between the two phenomena. 相似文献
16.
中部型ENSO和平流层准两年振荡对冬季北半球平流层臭氧的联合调制作用 总被引:1,自引:0,他引:1
利用观测和再分析资料通过合成分析方法,研究了中部型ENSO和平流层准两年振荡(QBO)对冬季北半球平流层臭氧的独立影响和联合调制作用。研究表明,北半球平流层臭氧在中部型厄尔尼诺年增加,而在中部型拉尼娜年减少;准两年振荡东风位相年份,北半球平流层臭氧增加,准两年振荡西风位相结果则相反。相比之下,北半球中、高纬度平流层臭氧异常对准两年振荡活动的响应明显小于其对ENSO活动的响应。进一步研究发现,准两年振荡东风位相会加强中部型厄尔尼诺事件引起的北半球平流层臭氧的增加,而减弱中部型拉尼娜事件造成的平流层臭氧的减少。在准两年振荡西风位相下,中部型厄尔尼诺事件仅导致北半球平流层臭氧含量少量升高,而中部型拉尼娜事件期间臭氧会大幅度减少。因此,准两年振荡东风位相会加强中部型厄尔尼诺事件对北半球平流层臭氧的影响,而减弱中部型拉尼娜事件对北半球平流层臭氧的影响。准两年振荡西风位相会减弱中部型厄尔尼诺而加强中部型拉尼娜事件对北半球平流层臭氧的影响。 相似文献
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In recent years, El Nino Modoki (pseudo-El Nino) 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 Nino. Empirical Orthogonal Function (EOF) analysis is used to successfully separate El Nino and El Nino Modoki. The abilities of the NINO3 index, NINO3.4 index, NINO1+2 index and NINO4 index in characterizing the El Nino are explored in detail. It is suggested that the NINO3 index is comparatively optimal to monitor the El Nino among the four NINO indices, since other NINO indices either cannot well distinguish El Nino and El Nino Modoki signals or are easily disturbed by El Nino Modoki signals. Further, an improved El Nino Modoki index (IEMI) is introduced to better represent the El Nino Modoki that is captured by the second leading EOF mode of monthly tropical Pacific sea surface temperature anomalies (SSTA). The IEMI is an improvement of the El Nino Modoki index (EMI) through adjusting the inappropriate weight coefficients of the three boxes of EMI, and it effectively overcomes the lack of EMI in monitoring the two historical El Nino Modoki events and also avoids the possible risk of EMI in excluding the interference of El Nino signal, indicating the realistic and potential advantages. 相似文献
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El Nio Modoki,similar to but different from canonical El Nio,has been observed since the late1970s.In this paper,using HadISST and NCEP/NCAR wind data,we analyze the relationship between El Nio Modoki and Sea Surface Temperature(SST)in the offshore area of China and its adjacent waters for different seasons.Our results show a significant negative correlation between El Nio Modoki in summer and SST in autumn in the offshore area of China and its adjacent waters,particularly for regions located in the east of the Kuroshio.It is also found that during El Nio Modoki period,anomalous northerlies prevail over the regions from the northern part of the Philippines to the offshore area of China,indicating that the northerlies are unfavorable for the transport of warm water from the western tropical Pacific to the mid-latitude area.Consequently,El Nio Modoki in summer may play a substantial role in cold SST anomalies in the offshore area of China and its adjacent waters in autumn through the influence of the Kuroshio,with a lagged response of the ocean to the atmospheric wind field. 相似文献