scholarly journals Northern Hemisphere Stratospheric Pathway of Different El Niño Flavors in Stratosphere-Resolving CMIP5 Models

2017 ◽  
Vol 30 (12) ◽  
pp. 4351-4371 ◽  
Author(s):  
N. Calvo ◽  
M. Iza ◽  
M. M. Hurwitz ◽  
E. Manzini ◽  
C. Peña-Ortiz ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
El Niño ◽  
El Nino ◽  
Cmip5 Models ◽  
Eastern Canada ◽  
Central Pacific ◽  
Cp El Niño ◽  
El Niño Events ◽  
Ep El Niño ◽  
El Nino Events

The Northern Hemisphere (NH) stratospheric signals of eastern Pacific (EP) and central Pacific (CP) El Niño events are investigated in stratosphere-resolving historical simulations from phase 5 of the Coupled Model Intercomparison Project (CMIP5), together with the role of the stratosphere in driving tropospheric El Niño teleconnections in NH climate. The large number of events in each composite addresses some of the previously reported concerns related to the short observational record. The results shown here highlight the importance of the seasonal evolution of the NH stratospheric signals for understanding the EP and CP surface impacts. CMIP5 models show a significantly warmer and weaker polar vortex during EP El Niño. No significant polar stratospheric response is found during CP El Niño. This is a result of differences in the timing of the intensification of the climatological wavenumber 1 through constructive interference, which occurs earlier in EP than CP events, related to the anomalous enhancement and earlier development of the Pacific–North American pattern in EP events. The northward extension of the Aleutian low and the stronger and eastward location of the high over eastern Canada during EP events are key in explaining the differences in upward wave propagation between the two types of El Niño. The influence of the polar stratosphere in driving tropospheric anomalies in the North Atlantic European region is clearly shown during EP El Niño events, facilitated by the occurrence of stratospheric summer warmings, the frequency of which is significantly higher in this case. In contrast, CMIP5 results do not support a stratospheric pathway for a remote influence of CP events on NH teleconnections.

scholarly journals Impact of two different types of El Niño events on runoff over the conterminous United States

2015 ◽  
Vol 12 (9) ◽  
pp. 8977-9002
Author(s):  
T. Tang ◽  
W. Li ◽  
G. Sun
Keyword(s):  
Water Resource ◽  
El Niño ◽  
El Nino ◽  
Cmip5 Models ◽  
Great Loss ◽  
Cp El Niño ◽  
Different Types ◽  
El Niño Events ◽  
Ep El Niño ◽  
El Nino Events

Abstract. The responses of river runoff to shifts of large-scale climatic patterns are of increasing concerns to water resource planners and managers for long-term climate change adaptation. El Niño is one of the most dominant modes of climate variability that is closely linked to hydrologic extremes such as floods and droughts that cause great loss of lives and properties. However, the different impacts of the two types of El Niño-Central Pacific (CP) and Eastern Pacific (EP)-El Niño on runoff across the conterminous US (CONUS) are not well understood. This study characterizes the impacts of the CP- and EP-El Niño on seasonal and annual runoff using observed historical streamflow data from 658 reference gaging stations and NCAR-CCSM4 model. We found that surface runoff responds similarly to the two types of El Niño events in Southeast, Central, South and Western coastal regions, but differently in Northeast (NE), Pacific Northwest (PNW) and West North Central (WNC) climatic zones. Specifically, EP-El Niño events tend to bring above-average runoff in NE, WNC, and PNW throughout the year while CP-El Niño events cause below-than normal runoff in the three regions. Similar findings were also found by analyzing NCAR-CCSM4 model outputs that captured both the CP- and EP-El Niño events representing the best datasets among selected CMIP5 models. The CCSM4 model simulates lower runoff values during CP-El Niño years than those in EP-El Niño in all of the three climatic regions (NE, PNW and WNC) during 1950–1999. In the future (2050–2099), for both types of El Niño years, runoff is projected to increase over the NE and PNW regions, mainly due to increased precipitation (P). In contrast, the increase of future evapotranspiration (ET) is higher than that of future P, leading to a projected decrease in runoff over the WNC region. In addition, model analysis indicates that all of the three regions (NE, PNW and WNC) are projected to have lower runoff values during CP-El Niño years than EP-El Niño. Our study suggests that US water resources may be distributed more unevenly in space and time with more frequent and intense flood and drought events. The findings from this study have important implications to water resource management at the regional scale. Information generated from this study is useful for water resource planners to anticipate the influence of two different types of El Niño events on droughts and floods across the CONUS.

scholarly journals Impact of two different types of El Niño events on runoff over the conterminous United States

2016 ◽  
Vol 20 (1) ◽  
pp. 27-37 ◽  
Author(s):  
T. Tang ◽  
W. Li ◽  
G. Sun
Keyword(s):  
Water Resource ◽  
El Niño ◽  
El Nino ◽  
Cmip5 Models ◽  
Great Loss ◽  
Cp El Niño ◽  
Different Types ◽  
El Niño Events ◽  
Ep El Niño ◽  
El Nino Events

Abstract. The responses of river runoff to shifts of large-scale climatic patterns are of increasing concerns to water resource planners and managers for long-term climate change adaptation. El Niño, as one of the most dominant modes of climate variability, is closely linked to hydrologic extremes such as floods and droughts that cause great loss of lives and properties. However, the different impacts of the two types of El Niño, i.e., central Pacific (CP-) and eastern Pacific (EP-)El Niño, on runoff across the conterminous US (CONUS) are not well understood. This study characterizes the impacts of the CP- and EP-El Niño on seasonal and annual runoff using observed streamflow data from 658 reference gaging stations and the NCAR-CCSM4 model. We found that surface runoff responds similarly to the two types of El Niño events in southeastern, central, southern, and western coastal regions, but differently in northeast (NE), Pacific northwest (PNW) and west north central (WNC) climatic zones. Specifically, EP-El Niño events tend to bring above-average runoff in NE, WNC, and PNW throughout the year while CP-El Niño events cause below-than normal runoff in the three regions. Similar findings were also found by analyzing NCAR-CCSM4 model outputs that captured both the CP- and EP-El Niño events, representing the best data set among CMIP5 models. The CCSM4 model simulates lower runoff values during CP-El Niño years than those in EP-El Niño over all of the three climatic regions (NE, PNW, and WNC) during 1950–1999. In the future (2050–2099), for both types of El Niño years, runoff is projected to increase over the NE and PNW regions, mainly due to increased precipitation (P). In contrast, the increase of future evapotranspiration (ET) exceeds that of future P, leading to a projected decrease in runoff over the WNC region. In addition, model analysis indicates that all of the three regions (NE, PNW, and WNC) are projected to have lower runoff in CP-El Niño years than in EP-El Niño years. Our study suggests that the US water resources may be distributed more unevenly in space and time with more frequent and intense flood and drought events. The findings from this study have important implications to water resource management at regional scales. Information generated from this study may help water resource planners to anticipate the influence of two different types of El Niño events on droughts and floods across the CONUS.

scholarly journals Changes in Independency between Two Types of El Niño Events under a Greenhouse Warming Scenario in CMIP5 Models

2015 ◽  
Vol 28 (19) ◽  
pp. 7561-7575 ◽  
Author(s):  
Yoo-Geun Ham ◽  
Yerim Jeong ◽  
Jong-Seong Kug
Keyword(s):  
Global Warming ◽  
El Niño ◽  
El Nino ◽  
Western Pacific ◽  
Cmip5 Models ◽  
Greenhouse Warming ◽  
Central Pacific ◽  
El Niño Events ◽  
The Western Pacific ◽  
El Nino Events

Abstract This study uses archives from phase 5 of the Coupled Model Intercomparison Project (CMIP5) to investigate changes in independency between two types of El Niño events caused by greenhouse warming. In the observations, the independency between cold tongue (CT) and warm pool (WP) El Niño events is distinctively increased in recent decades. The simulated changes in independency between the two types of El Niño events according to the CMIP5 models are quite diverse, although the observed features are simulated to some extent in several climate models. It is found that the climatological change after global warming is an essential factor in determining the changes in independency between the two types of El Niño events. For example, the independency between these events is increased after global warming when the climatological precipitation is increased mainly over the equatorial central Pacific. This climatological precipitation increase extends convective response to the east, particularly for CT El Niño events, which leads to greater differences in the spatial pattern between the two types of El Niño events to increase the El Niño independency. On the contrary, in models with decreased independency between the two types of El Niño events after global warming, climatological precipitation is increased mostly over the western Pacific. This confines the atmospheric response to the western Pacific in both El Niño events; therefore, the similarity between them is increased after global warming. In addition to the changes in the climatological state after global warming, a possible connection of the changes in the El Niño independency with the historical mean state is discussed in this paper.

scholarly journals Contrasting behaviors of the atmospheric CO<sub>2</sub> interannual variability during two types of El Niños

2018 ◽  
Author(s):  
Jun Wang ◽  
Ning Zeng ◽  
Meirong Wang ◽  
Fei Jiang ◽  
Jingming Chen ◽  
...  
Keyword(s):  
Interannual Variability ◽  
El Niño ◽  
El Nino ◽  
Ecosystem Respiration ◽  
Atmospheric Co2 ◽  
Occurrence Rate ◽  
Central Pacific ◽  
Cp El Niño ◽  
El Niño Events ◽  
El Nino Events

Abstract. El Niño has two different flavors: eastern Pacific (EP) and central Pacific (CP) El Niños, with different global teleconnections. However, their different impacts on carbon cycle interannual variability remain unclear. We here compared the behaviors of the atmospheric CO2 interannual variability and analyzed their terrestrial mechanisms during these two types of El Niños, based on Mauna Loa (MLO) CO2 growth rate (CGR) and Dynamic Global Vegetation Models (DGVMs) historical simulations. Composite analysis shows that evolutions of MLO CGR anomaly have three clear differences in terms of (1) negative and neutral precursors in boreal spring of El Niño developing years (denoted as “yr0”), (2) strong and weak amplitudes, and (3) durations of peak from December (yr0) to April of El Niño decaying year (denoted as “yr1”) and from October (yr0) to January (yr1) during EP and CP El Niños, respectively. Models simulated global land–atmosphere carbon flux (FTA) is able to capture the essentials of these characteristics. We further find that the gross primary productivity (GPP) over the tropics and extratropical southern hemisphere (Trop+SH) generally dominates the global FTA variations during both El Niño types. Regionally, significant anomalous carbon uptake caused by more precipitation and colder temperature, corresponding to the negative precursor, occurs between 30° S and 20° N from January (yr0) to June (yr0), while the strongest anomalous carbon releases, due largely to the reduced GPP induced by low precipitation and warm temperature, happen between equator and 20° N from February (yr1) to August (yr1) during EP El Niño events. In contrast, during CP El Niño events, clear carbon releases exist between 10° N and 20° S from September (yr0) to September (yr1), resulted from the widespread dry and warm climate conditions. Different spatial patterns of land temperature and precipitation in different seasons associated with EP and CP El Niños account for the characteristics in evolutions of GPP, terrestrial ecosystem respiration (TER), and resultant FTA. Understanding these different behaviors of the atmospheric CO2 interannual variability along with their terrestrial mechanisms during EP and CP El Niños is important because CP El Niño occurrence rate might increase under global warming.

scholarly journals Contrasting interannual atmospheric CO<sub>2</sub> variabilities and their terrestrial mechanisms for two types of El Niños

2018 ◽  
Vol 18 (14) ◽  
pp. 10333-10345 ◽  
Author(s):  
Jun Wang ◽  
Ning Zeng ◽  
Meirong Wang ◽  
Fei Jiang ◽  
Jingming Chen ◽  
...  
Keyword(s):  
El Niño ◽  
El Nino ◽  
Ecosystem Respiration ◽  
Regional Analysis ◽  
Atmospheric Co2 ◽  
Occurrence Rate ◽  
Central Pacific ◽  
Cp El Niño ◽  
El Niño Events ◽  
El Nino Events

Abstract. El Niño has two different flavors, eastern Pacific (EP) and central Pacific (CP) El Niños, with different global teleconnections. However, their different impacts on the interannual carbon cycle variability remain unclear. Here we compared the behaviors of interannual atmospheric CO2 variability and analyzed their terrestrial mechanisms during these two types of El Niños, based on the Mauna Loa (MLO) CO2 growth rate (CGR) and the Dynamic Global Vegetation Model's (DGVM) historical simulations. The composite analysis showed that evolution of the MLO CGR anomaly during EP and CP El Niños had three clear differences: (1) negative or neutral precursors in the boreal spring during an El Niño developing year (denoted as yr0), (2) strong or weak amplitudes, and (3) durations of the peak from December (yr0) to April during an El Niño decaying year (denoted as yr1) compared to October (yr0) to January (yr1) for a CP El Niño, respectively. The global land–atmosphere carbon flux (FTA) simulated by multi-models was able to capture the essentials of these characteristics. We further found that the gross primary productivity (GPP) over the tropics and the extratropical Southern Hemisphere (Trop + SH) generally dominated the global FTA variations during both El Niño types. Regional analysis showed that during EP El Niño events significant anomalous carbon uptake caused by increased precipitation and colder temperatures, corresponding to the negative precursor, occurred between 30° S and 20° N from January (yr0) to June (yr0). The strongest anomalous carbon releases, largely due to the reduced GPP induced by low precipitation and warm temperatures, occurred between the equator and 20° N from February (yr1) to August (yr1). In contrast, during CP El Niño events, clear carbon releases existed between 10° N and 20° S from September (yr0) to September (yr1), resulting from the widespread dry and warm climate conditions. Different spatial patterns of land temperatures and precipitation in different seasons associated with EP and CP El Niños accounted for the evolutionary characteristics of GPP, terrestrial ecosystem respiration (TER), and the resultant FTA. Understanding these different behaviors of interannual atmospheric CO2 variability, along with their terrestrial mechanisms during EP and CP El Niños, is important because the CP El Niño occurrence rate might increase under global warming.

scholarly journals Historical change of El Niño properties sheds light on future changes of extreme El Niño

2019 ◽  
Vol 116 (45) ◽  
pp. 22512-22517 ◽  
Author(s):  
Bin Wang ◽  
Xiao Luo ◽  
Young-Min Yang ◽  
Weiyi Sun ◽  
Mark A. Cane ◽  
...  
Keyword(s):  
El Niño ◽  
El Nino ◽  
Historical Change ◽  
Western Pacific ◽  
Intensity Change ◽  
Cmip5 Models ◽  
Central Pacific ◽  
El Niño Events ◽  
Extreme El Niño ◽  
El Nino Events

El Niño’s intensity change under anthropogenic warming is of great importance to society, yet current climate models’ projections remain largely uncertain. The current classification of El Niño does not distinguish the strong from the moderate El Niño events, making it difficult to project future change of El Niño’s intensity. Here we classify 33 El Niño events from 1901 to 2017 by cluster analysis of the onset and amplification processes, and the resultant 4 types of El Niño distinguish the strong from the moderate events and the onset from successive events. The 3 categories of El Niño onset exhibit distinct development mechanisms. We find El Niño onset regime has changed from eastern Pacific origin to western Pacific origin with more frequent occurrence of extreme events since the 1970s. This regime change is hypothesized to arise from a background warming in the western Pacific and the associated increased zonal and vertical sea-surface temperature (SST) gradients in the equatorial central Pacific, which reveals a controlling factor that could lead to increased extreme El Niño events in the future. The Coupled Model Intercomparison Project phase 5 (CMIP5) models’ projections demonstrate that both the frequency and intensity of the strong El Niño events will increase significantly if the projected central Pacific zonal SST gradients become enhanced. If the currently observed background changes continue under future anthropogenic forcing, more frequent strong El Niño events are anticipated. The models’ uncertainty in the projected equatorial zonal SST gradients, however, remains a major roadblock for faithful prediction of El Niño’s future changes.

scholarly journals Differences in the Initiation and Development of the Madden–Julian Oscillation over the Indian Ocean Associated with Two Types of El Niño

2017 ◽  
Vol 30 (4) ◽  
pp. 1397-1415 ◽  
Author(s):  
Pang-Chi Hsu ◽  
Ting Xiao
Keyword(s):  
Indian Ocean ◽  
El Niño ◽  
El Nino ◽  
Radiative Heating ◽  
Madden Julian Oscillation ◽  
Cp El Niño ◽  
El Niño Events ◽  
The Indian Ocean ◽  
Ep El Niño ◽  
El Nino Events

Abstract The influences of different types of Pacific warming, often classified as the eastern Pacific (EP) and central Pacific (CP) El Niño events, on Madden–Julian oscillation (MJO) activity over the Indian Ocean were investigated. Accompanied by relatively unstable (stable) atmospheric stratification induced by enhanced (reduced) moisture and moist static energy (MSE) in the lower troposphere, strengthened (weakened) MJO convection was observed in the initiation and eastward-propagation stages during CP (EP) El Niño events. To examine the key processes resulting in the differences in low-level moistening and column MSE anomalies over the Indian Ocean associated with the two types of El Niño, the moisture and column MSE budget equations were diagnosed using the reanalysis dataset ERA-Interim. The results indicate that the enhanced horizontal advection in the CP El Niño years plays an important role in causing a larger moisture and MSE growth rate over the MJO initiation area during CP El Niño events than during EP El Niño events. The increases in horizontal moisture and MSE advection primarily result from advection by mean flow across the enhanced intraseasonal moisture and MSE gradient, as well as by intraseasonal circulation across the mean moisture and MSE gradient associated with the CP El Niño. In the eastward development stage, the enhanced preconditioning comes from positive moisture and MSE advection anomalies in the CP El Niño events. Meanwhile, the strengthened MJO-related convection over the central-eastern Indian Ocean is maintained by increased atmospheric radiative heating and surface latent heat flux during the CP El Niño compared to the EP El Niño events.

scholarly journals The North Equatorial Countercurrent East of the Dateline, Its Variations, and Its Relationship to the El Niño Event

2021 ◽  
Vol 9 (10) ◽  
pp. 1041
Author(s):  
Yusuf Jati Wijaya ◽  
Ulung Jantama Wisha ◽  
Yukiharu Hisaki
Keyword(s):  
El Niño ◽  
El Nino ◽  
Thermocline Depth ◽  
Central Pacific ◽  
Ocean Reanalysis ◽  
Central Pacific El Niño ◽  
The North ◽  
El Niño Events ◽  
Ep El Niño ◽  
El Nino Events

Using forty years (1978–2017) of Ocean Reanalysis System 4 (ORAS4) dataset, the purpose of this study is to investigate the fluctuation of the North Equatorial Countercurrent (NECC) to the east of the dateline in relation to the presence of three kinds of El Niño events. From spring (MAM) through summer (JJA), we found that the NECC was stronger during the Eastern Pacific El Niño (EP El Niño) and the MIX El Niño than during the Central Pacific El Niño (CP El Niño). When it comes to winter (DJF), on the other hand, the NECC was stronger during the CP and MIX El Niño and weaker during the EP El Niño. This NECC variability was affected by the fluctuations of thermocline depth near the equatorial Pacific. Moreover, we also found that the seasonal southward shift of the NECC occurred between winter and spring, but the shift was absent during the CP and MIX El Niño events. This meridional shift was strongly affected by the local wind stress.

scholarly journals The Annual-Cycle Modulation of Meridional Asymmetry in ENSO’s Atmospheric Response and Its Dependence on ENSO Zonal Structure

2015 ◽  
Vol 28 (14) ◽  
pp. 5795-5812 ◽  
Author(s):  
Wenjun Zhang ◽  
Haiyan Li ◽  
Fei-Fei Jin ◽  
Malte F. Stuecker ◽  
Andrew G. Turner ◽  
...  
Keyword(s):  
Annual Cycle ◽  
El Niño ◽  
El Nino ◽  
Warm Pool ◽  
Atmospheric Response ◽  
Central Pacific ◽  
Cp El Niño ◽  
El Niño Events ◽  
Sst Anomalies ◽  
El Nino Events

Abstract Previous studies documented that a distinct southward shift of central Pacific low-level wind anomalies occurring during the ENSO decaying phase is caused by an interaction between the western Pacific annual cycle and El Niño–Southern Oscillation (ENSO) variability. The present study finds that the meridional movement of the central Pacific wind anomalies appears only during traditional eastern Pacific El Niño (EP El Niño) events rather than in central Pacific El Niño (CP El Niño) events in which sea surface temperature (SST) anomalies are confined to the central Pacific. The zonal structure of ENSO-related SST anomalies therefore has an important effect on meridional asymmetry in the associated atmospheric response and its modulation by the annual cycle. In contrast to EP El Niño events, the SST anomalies of CP El Niño events extend farther west toward the warm pool region with its climatological warm SSTs. In the warm pool region, relatively small SST anomalies are thus able to excite convection anomalies on both sides of the equator, even with a meridionally asymmetric SST background state. Therefore, almost meridionally symmetric precipitation and wind anomalies are observed over the central Pacific during the decaying phase of CP El Niño events. The SST anomaly pattern of La Niña events is similar to CP El Niño events with a reversed sign. Accordingly, no distinct southward displacement of the atmospheric response occurs over the central Pacific during the La Niña decaying phase. These results have important implications for ENSO climate impacts over East Asia, since the anomalous low-level anticyclone over the western North Pacific is an integral part of the annual cycle–modulated ENSO response.

scholarly journals Thermocline Fluctuations in the Equatorial Pacific Related to the Two Types of El Niño Events

2017 ◽  
Vol 30 (17) ◽  
pp. 6611-6627 ◽  
Author(s):  
Kang Xu ◽  
Rui Xin Huang ◽  
Weiqiang Wang ◽  
Congwen Zhu ◽  
Riyu Lu
Keyword(s):  
El Niño ◽  
El Nino ◽  
Heat Budget ◽  
Equatorial Pacific ◽  
Central Pacific ◽  
Cp El Niño ◽  
Function Decomposition ◽  
Subsurface Ocean ◽  
El Niño Events ◽  
El Nino Events

The interannual fluctuations of the equatorial thermocline are usually associated with El Niño activity, but the linkage between the thermocline modes and El Niño is still under debate. In the present study, a mode function decomposition method is applied to the equatorial Pacific thermocline, and the results show that the first two dominant modes (M1 and M2) identify two distinct characteristics of the equatorial Pacific thermocline. The M1 reflects a basinwide zonally tilted thermocline related to the eastern Pacific (EP) El Niño, with shoaling (deepening) in the western (eastern) equatorial Pacific. The M2 represents the central Pacific (CP) El Niño, characterized by a V-shaped equatorial Pacific thermocline (i.e., deep in the central equatorial Pacific and shallow on both the western and eastern boundaries). Furthermore, both modes are stable and significant on the interannual time scale, and manifest as the major feature of the thermocline fluctuations associated with the two types of El Niño events. As good proxies of EP and CP El Niño events, thermocline-based indices clearly reveal the inherent characteristics of subsurface ocean responses during the evolution of El Niño events, which are characterized by the remarkable zonal eastward propagation of equatorial subsurface ocean temperature anomalies, particularly during the CP El Niño. Further analysis of the mixed layer heat budget suggests that the air–sea interactions determine the establishment and development stages of the CP El Niño, while the thermocline feedback is vital for its further development. These results highlight the key influence of equatorial Pacific thermocline fluctuations in conjunction with the air–sea interactions, on the CP El Niño.

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