Jong‐Seong Kug

Abstract In this study, two types of El Niño events are classified based on spatial patterns of the sea surface temperature (SST) anomaly. One is the cold tongue (CT) El Niño, which can be regarded as the conventional El Niño, and the other the warm pool (WP) El Niño. The CT El Niño is characterized by relatively large SST anomalies in the Niño-3 region (5°S–5°N, 150°–90°W), while the WP El Niño is associated with SST anomalies mostly confined to the Niño-4 region (5°S–5°N, 160°E–150°W). In addi

Abstract A feedback process of the Indian Ocean SST on ENSO is investigated by using observed data and atmospheric GCM. It is suggested that warming in the Indian Ocean produces an easterly wind stress anomaly over Indonesia and the western edge of the Pacific during the mature phase of El Niño. The anomalous easterly wind in the western Pacific during El Niño helps a rapid termination of El Niño and a fast transition to La Niña by generating upwelling Kelvin waves. Thus, warming in the Indian O

Abstract Recent studies report that two types of El Niño events have been observed. One is the cold tongue (CT) El Niño, which is characterized by relatively large sea surface temperature (SST) anomalies in the eastern Pacific, and the other is the warm pool (WP) El Niño, in which SST anomalies are confined to the central Pacific. Here, both types of El Niño events are analyzed in a long-term coupled GCM simulation. The present model simulates the major observed features of both types of El Niño

[1] In this study, the existence of two types of La Nina events is examined using observations and model output. We find that cold events in the central and eastern Pacific SST, are highly correlated unlike the corresponding warm events. When two types of La Nina are defined based on the same criteria for the types of warm events, the SST and precipitation patterns between the two types of La Nina are much less distinctive or less independent. In other words, there is a strong asymmetric charact

Carbon release through boreal fires could considerably accelerate Arctic warming; however, boreal fire occurrence mechanisms and dynamics remain largely unknown. Here, we analyze fire activity and relevant large-scale atmospheric conditions over southeastern Siberia, which has the largest burned area fraction in the circumboreal and high-level carbon emissions due to high-density peatlands. It is found that the annual burned area increased when a positive Arctic Oscillation (AO) takes place in e

The effect of the Indian Ocean on El Niño/La Niña life cycles has been studied using 200‐yrs simulation data of a coupled GCM. The results show that the interactive feedback between the ENSO and the Indian Ocean holds the key to the rapid transition to an opposite phase. This remote impact of the Indian Ocean SST anomaly is linked to the change of zonal wind stress in the western Pacific, which leads to a rapid demise of El Nino/La Nina. Without the involvement of the Indian Ocean, the phase tra

In this study, scale interaction between synoptic eddies and low‐frequency flow is investigated. The synoptic eddy feedback is a key process in sustaining the low‐frequency flow. We show clear evidence using NCEP reanalysis data that there is a general underlying rule—the “left‐hand rule”, governing the synoptic eddy feedback onto low‐frequency flow. This rule states that eddy‐vorticity fluxes are directed preferentially about 90 degrees toward their left‐hand side, so that they converge into cy

Using the coupled general circulation models (CGCMs) participating in phases 3 and 5 of the Coupled Model Intercomparison Project (CMIP3 and CMIP5), simulations of the two types of El Niño event are evaluated. Previous studies using CMIP3 models pointed out that most of the models tend to simulate a single type of El Niño, and have serious problems in simulating the two types of El Niño independently. On the average, the CGCMs in CMIP5 have slightly better performance in simulating the two types

In this study, a statistical prediction model has been developed to forecast monthly Sea Surface Temperature (SST) in the Indian Ocean. It is a linear regression model based on a lagged relationship between the Indian Ocean SST and the NINO3 SST. A new approach to the statistical modeling has been tried out, in which the model predictors are obtained from not only observed NINO3 SST but also predicted results produced by a dynamical El Niño model. The forecast skill of the present model is bette

El Niño/La Niña onset is a challenging problem of ENSO prediction. In this study, we introduce two precursors of El Niño and La Niña onsets. One is the equatorial heat content, and the other is the Western Pacific (WP) wind. When the two precursors are considered together, both the El Niño and La Niña onsets can be highly predictable. In particular, the persistence of the WP wind is more important for the onset than sporadic wind events. The persistent WP westerly (easterly) wind tends to be con

Abstract Marine heatwaves (MHWs), prolonged ocean temperature extremes, have been enhanced by global warming in recent decades. More intense and longer MHWs have increasingly negative impacts on marine organisms that threaten their resilience of marine ecosystems. In this study, we investigated global marine phytoplankton biomass (chlorophyll) estimated by satellite ocean color and its response to MHWs on global and regional scales. We find that MHWs typically decreases chlorophyll concentration

Abstract An interactive feedback between ENSO and the Indian Ocean is investigated using a Center for Ocean–Land–Atmosphere Studies (COLA) interactive ensemble coupled model. From a long-term simulation of the coupled GCM, it is shown that El Niño events terminate relatively rapidly when the Indian Ocean SST is anomalously warm. The anomalous Indian Ocean warming induces the anomalous easterlies over the western Pacific by modulating the Walker circulation. In turn, the anomalous easterlies gene