scholarly journals Improvement of ENSO Simulation Based on Intermodel Diversity

2015 ◽  
Vol 28 (3) ◽  
pp. 998-1015 ◽  
Author(s):  
Yoo-Geun Ham ◽  
Jong-Seong Kug
Keyword(s):  
Interannual Variability ◽  
El Niño ◽  
Climate Models ◽  
El Nino ◽  
Southern Oscillation ◽  
Global Climate ◽  
Coupled Model ◽  
Global Climate Models ◽  
Climate Simulation ◽  
Central Pacific

Abstract In this study, a new methodology is developed to improve the climate simulation of state-of-the-art coupled global climate models (GCMs), by a postprocessing based on the intermodel diversity. Based on the close connection between the interannual variability and climatological states, the distinctive relation between the intermodel diversity of the interannual variability and that of the basic state is found. Based on this relation, the simulated interannual variabilities can be improved, by correcting their climatological bias. To test this methodology, the dominant intermodel difference in precipitation responses during El Niño–Southern Oscillation (ENSO) is investigated, and its relationship with climatological state. It is found that the dominant intermodel diversity of the ENSO precipitation in phase 5 of the Coupled Model Intercomparison Project (CMIP5) is associated with the zonal shift of the positive precipitation center during El Niño. This dominant intermodel difference is significantly correlated with the basic states. The models with wetter (dryer) climatology than the climatology of the multimodel ensemble (MME) over the central Pacific tend to shift positive ENSO precipitation anomalies to the east (west). Based on the model’s systematic errors in atmospheric ENSO response and bias, the models with better climatological state tend to simulate more realistic atmospheric ENSO responses. Therefore, the statistical method to correct the ENSO response mostly improves the ENSO response. After the statistical correction, simulating quality of the MME ENSO precipitation is distinctively improved. These results provide a possibility that the present methodology can be also applied to improving climate projection and seasonal climate prediction.

scholarly journals Possible Increased Frequency of ENSO-Related Dry and Wet Conditions over Some Major Watersheds in a Warming Climate

2020 ◽  
Vol 101 (4) ◽  
pp. E409-E426 ◽  
Author(s):  
Qiaohong Sun ◽  
Chiyuan Miao ◽  
Amir AghaKouchak ◽  
Iman Mallakpour ◽  
Duoying Ji ◽  
...  
Keyword(s):  
El Niño ◽  
Climate Models ◽  
El Nino ◽  
Southern Oscillation ◽  
Global Climate ◽  
River Basins ◽  
Global Climate Models ◽  
La Niña ◽  
Precipitation Pattern ◽  
La Nina

Abstract Predicting the changes in teleconnection patterns and related hydroclimate extremes can provide vital information necessary to adapt to the effects of the El Niño–Southern Oscillation (ENSO). This study uses the outputs of global climate models to assess the changes in ENSO-related dry/wet patterns and the frequency of severe dry/wet events. The results show anomalous precipitation responding asymmetrically to La Niña and El Niño, indicating the teleconnections may not simply be strengthened. A “dry to drier, wet to wetter” annual anomalous precipitation pattern was projected during La Niña phases in some regions, with drier conditions over southern North America, southern South America, and southern central Asia, and wetter conditions in Southeast Asia and Australia. These results are robust, with agreement from the 26 models and from a subset of 8 models selected for their good performance in capturing observed patterns. However, we did not observe a similar strengthening of anomalous precipitation during future El Niño phases, for which the uncertainties in the projected influences are large. Under the RCP4.5 emissions scenario, 45 river basins under El Niño conditions and 39 river basins under La Niña conditions were predicted to experience an increase in the frequency of severe dry events; similarly, 59 river basins under El Niño conditions and 61 river basins under La Niña conditions were predicted to have an increase in the frequency of severe wet events, suggesting a likely increase in the risk of floods. Our results highlight the implications of changes in ENSO patterns for natural hazards, disaster management, and engineering infrastructure.

scholarly journals Effects of Tropical Cyclones on ENSO

2019 ◽  
Vol 32 (19) ◽  
pp. 6423-6443 ◽  
Author(s):  
Tao Lian ◽  
Jun Ying ◽  
Hong-Li Ren ◽  
Chan Zhang ◽  
Ting Liu ◽  
...  
Keyword(s):  
Tropical Cyclones ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Heat Content ◽  
Coupled Model ◽  
Enso Event ◽  
Central Pacific ◽  
Final State ◽  
Enso Dynamics

AbstractNumerous studies have investigated the role of El Niño–Southern Oscillation (ENSO) in modulating the activity of tropical cyclones (TCs) in the western Pacific on interannual time scales, but the effects of TCs on ENSO are less discussed. Some studies have found that TCs sharply increase surface westerly anomalies over the equatorial western–central Pacific and maintain them there for a few days. Given the strong influence of equatorial surface westerly wind bursts on ENSO, as confirmed by much recent literature, the effects of TCs on ENSO may be much greater than previously expected. Using recently released observations and reanalysis datasets, it is found that the majority of near-equatorial TCs (simply TCs hereafter) are associated with strong westerly anomalies at the equator, and the number and longitude of TCs are significantly correlated with ENSO strength. When TC-related wind stresses are added into an intermediate coupled model, the simulated ENSO becomes more irregular, and both ENSO magnitude and skewness approach those of observations, as compared with simulations without TCs. Adding TCs into the model system does not break the linkage between the heat content anomaly and subsequent ENSO event in the model, which manifest the classic recharge–discharge ENSO dynamics. However, the influence of TCs on ENSO is so strong that ENSO magnitude and sometimes its final state—that is, either El Niño or La Niña—largely depend on the number and timing of TCs during the event year. Our findings suggest that TCs play a prominent role in ENSO dynamics, and their effects must be considered in ENSO forecast models.

scholarly journals Intensification of the Western North Pacific Anticyclone Response to the Short Decaying El Niño Event due to Greenhouse Warming

2016 ◽  
Vol 29 (10) ◽  
pp. 3607-3627 ◽  
Author(s):  
Wei Chen ◽  
June-Yi Lee ◽  
Kyung-Ja Ha ◽  
Kyung-Sook Yun ◽  
Riyu Lu
Keyword(s):  
Global Warming ◽  
El Niño ◽  
North Pacific ◽  
Western North Pacific ◽  
Climate Models ◽  
El Nino ◽  
Coupled Model ◽  
Precipitation Anomaly ◽  
Historical Period ◽  
Central Pacific

Abstract Two types of El Niño evolution have been identified in terms of the lengths of their decaying phases: the first type is a short decaying El Niño that terminates in the following summer after the mature phase, and the second type is a long decaying one that persists until the subsequent winter. The responses of the western North Pacific anticyclone (WNPAC) anomaly to the two types of evolution are remarkably different. Using experiments from phase 5 of the Coupled Model Intercomparison Project (CMIP5), this study investigates how well climate models reproduce the two types of El Niño evolution and their impacts on the WNPAC in the historical period (1950–2005) and how they will change in the future under anthropogenic global warming. To reduce uncertainty in future projection, the nine best models are selected based on their performance in simulating El Niño evolution. In the historical run, the nine best models’ multimodel ensemble (B9MME) well reproduces the enhanced (weakened) WNPAC that is associated with the short (long) decaying El Niño. The comparison between results of the historical run for 1950–2005 and the representative concentration pathway 4.5 run for 2050–99 reveals that individual models and the B9MME tend to project no significant changes in the two types of El Niño evolution for the latter half of the twenty-first century. However, the WNPAC response to the short decaying El Niño is considerably intensified, being associated with the enhanced negative precipitation anomaly response over the equatorial central Pacific. This enhancement is attributable to the robust increase in mean and interannual variability of precipitation over the equatorial central Pacific under global warming.

scholarly journals Impact of westerly wind burst on El Niño-sourthern oscillation

2020 ◽  
Author(s):  
◽  
Mohammad Alam
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Coupled Model ◽  
Vital Role ◽  
Tropical Pacific ◽  
Westerly Wind ◽  
Central Pacific ◽  
Enso Events ◽  
The Tropical Pacific

Westerly wind bursts (WWBs), usually occurring in the tropical Pacific region, play a vital role in El Niño–Southern Oscillation (ENSO). In this study, we use a hybrid coupled model (HCM) for the tropical Pacific Ocean-atmosphere system to investigate WWBs impact on ENSO. To achieve this goal, two experiments are performed: (a) first, the standard version of the HCM is integrated for years without prescribed WWBs events; and (b) second, the WWBs are added into the HCM (HCM-WWBs). Results show that HCM-WWBs can generate not only more realistic climatology of sea surface temperature (SST) in both spatial structure and temporal amplitudes, but also better ENSO features, than the HCM. In particular, the HCM-WWBs can capture the central Pacific (CP) ENSO events, which is absent in original HCM. Furthermore, the possible physical mechanisms responsible for these improvements by WWBs are discussed.

scholarly journals An Assessment of Multimodel Simulations for the Variability of Western North Pacific Tropical Cyclones and Its Association with ENSO

2016 ◽  
Vol 29 (18) ◽  
pp. 6401-6423 ◽  
Author(s):  
Rongqing Han ◽  
Hui Wang ◽  
Zeng-Zhen Hu ◽  
Arun Kumar ◽  
Weijing Li ◽  
...  
Keyword(s):  
Interannual Variability ◽  
Tropical Cyclones ◽  
El Niño ◽  
North Pacific ◽  
Western North Pacific ◽  
El Nino ◽  
Southern Oscillation ◽  
Annual Number ◽  
Central Pacific ◽  
Cp El Niño

Abstract An assessment of simulations of the interannual variability of tropical cyclones (TCs) over the western North Pacific (WNP) and its association with El Niño–Southern Oscillation (ENSO), as well as a subsequent diagnosis for possible causes of model biases generated from simulated large-scale climate conditions, are documented in the paper. The model experiments are carried out by the Hurricane Work Group under the U.S. Climate Variability and Predictability Research Program (CLIVAR) using five global climate models (GCMs) with a total of 16 ensemble members forced by the observed sea surface temperature and spanning the 28-yr period from 1982 to 2009. The results show GISS and GFDL model ensemble means best simulate the interannual variability of TCs, and the multimodel ensemble mean (MME) follows. Also, the MME has the closest climate mean annual number of WNP TCs and the smallest root-mean-square error to the observation. Most GCMs can simulate the interannual variability of WNP TCs well, with stronger TC activities during two types of El Niño—namely, eastern Pacific (EP) and central Pacific (CP) El Niño—and weaker activity during La Niña. However, none of the models capture the differences in TC activity between EP and CP El Niño as are shown in observations. The inability of models to distinguish the differences in TC activities between the two types of El Niño events may be due to the bias of the models in response to the shift of tropical heating associated with CP El Niño.

scholarly journals The seasonal relationship between intraseasonal tropical variability and ENSO in CMIP5

2018 ◽  
Vol 11 (6) ◽  
pp. 2373-2392 ◽  
Author(s):  
Tatiana Matveeva ◽  
Daria Gushchina ◽  
Boris Dewitte
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Coupled Model ◽  
Ocean Dynamics ◽  
Central Pacific ◽  
Tropical Variability ◽  
Large Dispersion ◽  
Enso Diversity ◽  
Intraseasonal Tropical Variability

Abstract. The El Niño–Southern Oscillation (ENSO) is tightly linked to the intraseasonal tropical variability (ITV) that contributes to energise the deterministic ocean dynamics during the development of El Niño. Here, the relationship between ITV and ENSO is assessed based on models from the Coupled Model Intercomparison Project (CMIP) phase 5 (CMIP5) taking into account the so-called diversity of ENSO, that is, the existence of two types of events (central Pacific versus eastern Pacific El Niño). As a first step, the models' skill in simulating ENSO diversity is assessed. The characteristics of the ITV are then documented revealing a large dispersion within an ensemble of 16 models. A total of 11 models exhibit some skill in simulating the key aspects of the ITV for ENSO: the total variance along the Equator, the seasonal cycle and the characteristics of the propagation along the Equator of the Madden–Julian oscillation (MJO) and the convectively coupled equatorial Rossby (ER) waves. Five models that account realistically for both the two types of El Niño events and ITV characteristics are used for the further analysis of seasonal ITV ∕ ENSO relationship. The results indicate a large dispersion among the models and an overall limited skill in accounting for the observed seasonal ITV ∕ ENSO relationship. Implications of our results are discussed in light of recent studies on the forcing mechanism of ENSO diversity.

scholarly journals Two Leading ENSO Modes and El Niño Types in the Zebiak–Cane Model

2018 ◽  
Vol 31 (5) ◽  
pp. 1943-1962 ◽  
Author(s):  
Ruihuang Xie ◽  
Fei-Fei Jin
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Heat Budget ◽  
Coupled Model ◽  
Warm Pool ◽  
Central Pacific ◽  
El Niño Events ◽  
Instrumental Records ◽  
El Nino Events

Modern instrumental records reveal that El Niño events differ in their spatial patterns and temporal evolutions. Attempts have been made to categorize them roughly into two main types: eastern Pacific (EP; or cold tongue) and central Pacific (CP; or warm pool) El Niño events. In this study, a modified version of the Zebiak–Cane (MZC) coupled model is used to examine the dynamics of these two types of El Niño events. Linear eigenanalysis of the model is conducted to show that there are two leading El Niño–Southern Oscillation (ENSO) modes with their SST patterns resembling those of two types of El Niño. Thus, they are referred to as the EP and CP ENSO modes. These two modes are sensitive to changes in the mean states. The heat budget analyses demonstrate that the EP (CP) mode is dominated by thermocline (zonal advective) feedback. Therefore, the weak (strong) mean wind stress and deep (shallow) mean thermocline prefer the EP (CP) ENSO mode because of the relative dominance of thermocline (zonal advective) feedback under such a mean state. Consistent with the linear stability analysis, the occurrence ratio of CP/EP El Niño events in the nonlinear simulations generally increases toward the regime where the linear CP ENSO mode has relatively higher growth rate. These analyses suggest that the coexistence of two leading ENSO modes is responsible for two types of El Niño simulated in the MZC model. This model result may provide a plausible scenario for the observed ENSO diversity.

scholarly journals How Well Do Global Climate Models Simulate the Variability of Atlantic Tropical Cyclones Associated with ENSO?

2014 ◽  
Vol 27 (15) ◽  
pp. 5673-5692 ◽  
Author(s):  
Hui Wang ◽  
Lindsey Long ◽  
Arun Kumar ◽  
Wanqiu Wang ◽  
Jae-Kyung E. Schemm ◽  
...  
Keyword(s):  
Tropical Cyclones ◽  
El Niño ◽  
Climate Models ◽  
El Nino ◽  
Global Climate ◽  
Global Climate Models ◽  
Track Density ◽  
Cp El Niño ◽  
Ep El Niño ◽  
The U.S

Abstract The variability of Atlantic tropical cyclones (TCs) associated with El Niño–Southern Oscillation (ENSO) in model simulations is assessed and compared with observations. The model experiments are 28-yr simulations forced with the observed sea surface temperature from 1982 to 2009. The simulations were coordinated by the U.S. Climate Variability and Predictability Research Program (CLIVAR) Hurricane Working Group and conducted with five global climate models (GCMs) with a total of 16 ensemble members. The model performance is evaluated based on both individual model ensemble means and multimodel ensemble mean. The latter has the highest anomaly correlation (0.86) for the interannual variability of TCs. Previous observational studies show a strong association between ENSO and Atlantic TC activity, as well as distinctions during eastern Pacific (EP) and central Pacific (CP) El Niño events. The analysis of track density and TC origin indicates that each model has different mean biases. Overall, the GCMs simulate the variability of Atlantic TCs well with weaker activity during EP El Niño and stronger activity during La Niña. For CP El Niño, there is a slight increase in the number of TCs as compared with EP El Niño. However, the spatial distribution of track density and TC origin is less consistent among the models. Particularly, there is no indication of increasing TC activity over the U.S. southeast coastal region during CP El Niño as in observations. The difference between the models and observations is likely due to the bias of the models in response to the shift of tropical heating associated with CP El Niño, as well as the model bias in the mean circulation.

scholarly journals How Robust is the Asian Precipitation–ENSO Relationship during the Industrial Warming Period (1901–2017)?

2020 ◽  
Vol 33 (7) ◽  
pp. 2779-2792 ◽  
Author(s):  
Bin Wang ◽  
Xiao Luo ◽  
Jian Liu
Keyword(s):  
El Niño ◽  
Climate Models ◽  
El Nino ◽  
Southern Oscillation ◽  
The Philippines ◽  
Secular Change ◽  
Large Area ◽  
Central Pacific ◽  
Tropical Asia ◽  
Enso Events

AbstractInstrumental observations (1901–2017) are used to uncover the seasonality, regionality, spatial–temporal coherency, and secular change of the relationship between El Niño–Southern Oscillation (ENSO) and Asian precipitation (AP). We find an abrupt seasonal reversal of the AP–ENSO relationship occurring from October to November in a large area of Asia north of 20°N due to a rapid northward shift of the ENSO-induced subsidence from Indonesia to the Philippines. We identified six subregions that have significant correlations with ENSO over the past 116 years with |r| > 0.5 (p < 0.001). Regardless of the prominent subregional differences, the total amount of AP during a monsoon year (from May to the next April) shows a robust response to ENSO with r = −0.86 (1901–2017), implying a 4.5% decrease in the total Asian precipitation for 1° of SST increase in the equatorial central Pacific. Rainfall in tropical Asia (Maritime Continent, Southeast Asia, and India) shows a stable relationship with ENSO with significant 31-yr running correlation coefficients (CCs). However, precipitation in North China, the East Asian winter monsoon front zone, and arid central Asia exhibit unstable relationships with ENSO. Since the 1950s, the AP–ENSO relationships have been enhanced in all subregions except over India. A major factor that determines the increasing trends of the AP–ENSO relationship is the increasing ENSO amplitude. Notably, the AP response is asymmetric with respect to El Niño and La Niña and markedly different between the major and minor ENSO events. The results provide guidance for seasonal prediction and a metric for assessment of climate models’ capability to reproduce the Asian hydroclimate response to ENSO and projected future change.

scholarly journals Global Monsoon, El Niño, and Their Interannual Linkage Simulated by MIROC5 and the CMIP3 CGCMs

2011 ◽  
Vol 24 (21) ◽  
pp. 5604-5618 ◽  
Author(s):  
Hyung-Jin Kim ◽  
Kumiko Takata ◽  
Bin Wang ◽  
Masahiro Watanabe ◽  
Masahide Kimoto ◽  
...  
Keyword(s):  
El Niño ◽  
Climate Models ◽  
El Nino ◽  
Rainfall Variability ◽  
Forced Response ◽  
Global Climate Models ◽  
Monsoon Precipitation ◽  
Bjerknes Feedback ◽  
Central Pacific ◽  
Global Monsoon

Abstract This study evaluates the capability of coupled global climate models (CGCMs) in simulating the prime examples of the forced response (global monsoon) and internal feedback process (El Niño). Emphases are also placed on the fidelity of the year-to-year variability of global monsoon precipitation that is coordinated by the interannual sea surface temperature (SST) fluctuation over the tropics. The latest version of the Model for Interdisciplinary Research on Climate 5 (MIROC5) with advanced physical schemes is compared with the two previous versions (MIROC3.2, high- and medium-resolution versions) and with the 20 CGCMs participating in the third phase of the Coupled Model Intercomparison Project (CMIP3). The climatological annual mean and cycles of precipitation and 850-hPa winds, the key components to demarcate the global monsoon domain, are reproduced better in MIROC5 than in MIROC3 versions. As a consequence, the former considerably outperforms the latter and is generally superior to the CMIP3 CGCMs in replicating the intensity and domain of global monsoon precipitation and circulations. These results highlight the importance of the improved physical parameterization in a model. Analyses of the monthly Niño-3 index suggest that the amplitude and periodicity of El Niño are simulated better in MIROC5 than in the MIROC3 versions. Yet the reality of nonlinear ENSO dynamics measured indirectly by the SST asymmetricity over the equatorial Pacific is unsatisfactory in the MIROC family as well as in the majority of the CMIP3 models. The maximum covariance analysis shows that a significant fraction of the interannual global monsoon rainfall variability is in concert with El Niño. The multimodel results reveal that such coupling is robust across the current CGCMs. More importantly, the fidelity of the global monsoon precipitation significantly relies on the realism of tropical SST. Comparison among the MIROC models suggests that improved El Niño is likely attributable to the more realistic Bjerknes feedback loop, which results from the intensified convective activity over the equatorial central Pacific Ocean.

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