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 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.

Effects of Climate Modes on Interannual Variability of Upwelling in the Tropical Indian Ocean

2020 ◽  
Vol 33 (4) ◽  
pp. 1547-1573 ◽  
Author(s):  
Xiaolin Zhang ◽  
Weiqing Han
Keyword(s):  
Wave Propagation ◽  
Indian Ocean ◽  
Interannual Variability ◽  
El Niño ◽  
El Nino ◽  
Tropical Indian Ocean ◽  
Strong Impact ◽  
Central Pacific ◽  
El Niño Events ◽  
El Nino Events

AbstractThis paper investigates interannual variability of the tropical Indian Ocean (IO) upwelling through analyzing satellite and in situ observations from 1993 to 2016 using the conventional Static Linear Regression Model (SLM) and Bayesian Dynamical Linear Model (DLM), and performing experiments using a linear ocean model. The analysis also extends back to 1979, using ocean–atmosphere reanalysis datasets. Strong interannual variability is observed over the mean upwelling zone of the Seychelles–Chagos thermocline ridge (SCTR) and in the seasonal upwelling area of the eastern tropical IO (EIO), with enhanced EIO upwelling accompanying weakened SCTR upwelling. Surface winds associated with El Niño–Southern Oscillation (ENSO) and the IO dipole (IOD) are the major drivers of upwelling variability. ENSO is more important than the IOD over the SCTR region, but they play comparable roles in the EIO. Upwelling anomalies generally intensify when positive IODs co-occur with El Niño events. For the 1979–2016 period, eastern Pacific (EP) El Niños overall have stronger impacts than central Pacific (CP) and the 2015/16 hybrid El Niño events, because EP El Niños are associated with stronger convection and surface wind anomalies over the IO; however, this relationship might change for a different interdecadal period. Rossby wave propagation has a strong impact on upwelling in the western basin, which causes errors in the SLM and DLM because neither can properly capture wave propagation. Remote forcing by equatorial winds is crucial for the EIO upwelling. While the first two baroclinic modes capture over 80%–90% of the upwelling variability, intermediate modes (3–8) are needed to fully represent IO upwelling.

Impacts of Central Pacific El Niño on Southern China Spring Precipitation Controlled by its Longitudinal Position

2019 ◽  
Vol 32 (22) ◽  
pp. 7823-7836 ◽  
Author(s):  
Feng Jiang ◽  
Wenjun Zhang ◽  
Xin Geng ◽  
Malte F. Stuecker ◽  
Chao Liu
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern China ◽  
Spring Precipitation ◽  
Central Pacific ◽  
Cp El Niño ◽  
El Niño Events ◽  
Longitudinal Position ◽  
El Nino Events ◽  
The Tropical Pacific

ABSTRACT Here we investigate the response of boreal spring precipitation over southern China (SPSC) to central Pacific (CP) El Niño based on observational datasets. While there is enhanced precipitation over southern China during the decaying boreal spring of eastern Pacific (EP) El Niño events, so far no clear precipitation response has been detected during the same decaying stage for CP El Niño composites. Here we show that around half of the CP El Niño events coincide with enhanced SPSC (wet CP El Niño), while the other half are accompanied by reduced SPSC (dry CP El Niño). These two types of CP El Niño events bear dramatically different evolution features in their respective tropical sea surface temperature anomaly (SSTA) patterns. Wet CP El Niño events are characterized by an SSTA longitudinal position confined to the tropical central-eastern Pacific. In contrast, dry CP El Niño events exhibit a clear westward propagation of SSTAs during their evolution, with maximum SSTAs located to the west of the date line after their mature phase. These different longitudinal positions of positive SSTAs during their decaying phase result in distinct meridional structures of the tropical Pacific convection anomalies as well as the ENSO combination mode (C-mode) response. An anomalous low-level anticyclone is evident over the western North Pacific during wet CP El Niño events during their decaying phase, while an anomalous cyclonic circulation is found for dry CP El Niño events. We emphasize that the impacts of CP El Niño on the SPSC depend crucially on the simultaneous zonal location of warm SSTAs in the tropical Pacific.

The Initiation and Developing Mechanisms of Central Pacific El Niños

2014 ◽  
Vol 27 (12) ◽  
pp. 4473-4485 ◽  
Author(s):  
Jingzhi Su ◽  
Tim Li ◽  
Renhe Zhang
Keyword(s):  
El Niño ◽  
El Nino ◽  
Ocean Dynamics ◽  
Central Pacific ◽  
Cp El Niño ◽  
Thermocline Feedback ◽  
El Niño Events ◽  
Sst Warming ◽  
Sst Anomaly ◽  
El Nino Events

Abstract The initiation and developing mechanisms of four major central Pacific (CP) El Niño events in 1994, 2002, 2004, and 2009 were investigated by analyzing oceanic and atmospheric reanalysis data. A mixed layer heat budget analysis was conducted and the result shows that the initiation mechanism of the 1994 CP El Niño is very different from other CP El Niños in 2000s, while the developing mechanisms are similar among these events. The initial sea surface temperature (SST) warming of the 1994 El Niño was caused by enhanced solar radiation, which was related to atmospheric meridional overturning circulation in association with positive SST anomaly forcing in the subtropical Pacific. The subtropical SST anomalies also induced anticyclonic surface wind stress curl anomalies, which caused the formation of subsurface warmer waters in the off-equatorial regions. The off-equatorial subsurface warmer waters were transported farther equatorward by the mean subsurface ocean currents, leading to the subsurface warming in the central equatorial Pacific. The deepened thermocline anomaly at the equator further promoted a positive advective and thermocline feedback so that the SST anomaly grew. During the initiation phase of the 2000s El Niños, ocean dynamics played a dominant role, while the effect of surface heat flux anomalies was minor. Preexisting subsurface warmer waters appeared in the equatorial region during their initiation phases. Such subsurface anomalies can cause the SST warming in the central Pacific through induced anomalous eastward zonal currents that advect high mean SST eastward. This positive zonal advective feedback, along with a positive thermocline feedback, continued to warm the local SST throughout the developing phase of the 2000s El Niño events.

scholarly journals Time-Spatial Features of Mix El Niño

Atmosphere ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 476
Author(s):  
Zhiyuan Zhang ◽  
Gen Li
Keyword(s):  
El Niño ◽  
El Nino ◽  
Sea Surface ◽  
Eastern Pacific ◽  
Central Pacific ◽  
Cp El Niño ◽  
Spatial Features ◽  
El Niño Events ◽  
Far Eastern ◽  
El Nino Events

The diversity of El Niño is a critical field of the climate research. The eastern Pacific (EP) and central Pacific (CP) types of El Niño have been identified in the previous studies. However, the extreme El Niño event that occurred in 2015–2016 is quite different from both the EP and CP El Niño events. The sea surface temperatures anomalies (SSTA) for this event widely spread in both the central and eastern Pacific and have a small zonal gradient in the central-eastern Pacific. Many researchers regarded this event as a mixed type of El Niño. Using the regression-EOF method, the Mix El Niño pattern is extracted from the tropical Pacific SSTA field during the period from 1900 to 2019. Here, we reveal that the Mix El Niño is a very usual rather than a new type of El Niño, it is just that the EP and CP El Niño events are more frequent since the 1980s, while the Mix El Niño events frequently appear before the 1980s. The time-spatial features of the Mix El Niño are further investigated. The results demonstrate a unique westward propagation of the maximum SSTA for the Mix El Niño from the far eastern Pacific to the central Pacific. In contrast, the SSTA center is locked in the far eastern Pacific region for the EP El Niño and the central Pacific region for the CP El Niño. The evolutions of subsurface ocean temperature anomalies and sea surface height anomalies are also examined to support this. The ocean–atmosphere interaction plays an important role in the evolution of the Mix El Niño. The anomalous atmospheric Walker circulation for the Mix El Niño is mainly in the western and central Pacific as well as very weak in the eastern Pacific. In contrast, there are significant westerlies/easterlies in the eastern Pacific for the EP/CP El Niño. The small gradient of SSTA in the central-eastern Pacific for the Mix El Niño leads to weak zonal wind anomalies, which further weaken the zonal gradient of SSTA. All this suggests that the Mix El Niño is not unusual and fundamentally different from the EP and CP El Niño with important implications for global climate effects.

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 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 Decadal Change of Combination Mode Spatiotemporal Characteristics due to an ENSO Regime Shift

2020 ◽  
Vol 33 (12) ◽  
pp. 5239-5251
Author(s):  
Feng Jiang ◽  
Wenjun Zhang ◽  
Malte F. Stuecker ◽  
Fei-Fei Jin
Keyword(s):  
El Niño ◽  
Regime Shift ◽  
El Nino ◽  
Surface Wind ◽  
Climate Impacts ◽  
Decadal Change ◽  
Central Pacific ◽  
El Niño Events ◽  
Combination Mode ◽  
El Nino Events

AbstractPrevious studies have shown that nonlinear atmospheric interactions between ENSO and the warm pool annual cycle generates a combination mode (C-mode), which is responsible for the termination of strong El Niño events and the development of the anomalous anticyclone over the western North Pacific (WNP). However, the C-mode has experienced a remarkable decadal change in its characteristics around the early 2000s. The C-mode in both pre- and post-2000 exhibits its characteristic anomalous atmospheric circulation meridional asymmetry but with somewhat different spatial structures and time scales. During 1979–99, the C-mode pattern featured prominent westerly surface wind anomalies in the southeastern tropical Pacific and anticyclonic anomalies over the WNP. In contrast, the C-mode-associated westerly anomalies were shifted farther westward to the central Pacific and the WNP anticyclone was farther westward extended and weaker after 2000. These different C-mode patterns were accompanied by distinct climate impacts over the Indo-Pacific region. The decadal differences of the C-mode are tightly connected with the ENSO regime shift around 2000; that is, the occurrence of central Pacific (CP) El Niño events with quasi-biennial and decadal periodicities increased while the occurrence of eastern Pacific (EP) El Niño events with quasi-quadrennial periodicity decreased. The associated near-annual combination tone periodicities of the C-mode also changed in accordance with these changes in the dominant ENSO frequency between the two time periods. Numerical model experiments further confirm the impacts of the ENSO regime shift on the C-mode characteristics. These results have important implications for understanding the C-mode dynamics and improving predictions of its climate impacts.

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