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  • 1
    Online Resource
    Online Resource
    Robust opposite‐changing tendency between the thermal advection damping by mean current and thermo‐dynamical damping of ENSO Feedback in a changing climate
    Wiley ; 2019
    In:  International Journal of Climatology Vol. 39, No. 15 ( 2019-12), p. 5822-5829
    Details
    In: International Journal of Climatology, Wiley, Vol. 39, No. 15 ( 2019-12), p. 5822-5829
    Abstract: The tropical Pacific climate state response to both the 21st‐century greenhouse gas forcing and orbital forcing on a glacial–interglacial timescale tends to resemble either an El Niño‐ or La Niña‐like pattern. This study reveals that so long as an El Niño‐ or La Niña‐like change in the tropical climate state occurs, changes in two important negative feedback components of the El Niño‐Southern Oscillation (ENSO) system, dynamical damping by mean thermal advection (MA) and thermo‐dynamical damping (TD), largely offset each other. For example, under the El Niño‐like condition, weaker trade winds due to a relaxed zonal sea surface temperature (SST) gradient reduce the mean zonal and meridional currents in the equatorial Pacific oceanic mixed layer, causing a reduction in MA, while wider expansion and enhanced activity of climatological convective clouds due to a warmer ocean surface intensifies negative SST‐cloud‐shortwave feedback. As a result, a change in ENSO activity in changing climate is mainly ruled out not by the change in negative feedback effect, but by the change in positive feedback effect.
    Type of Medium: Online Resource
    ISSN: 0899-8418 , 1097-0088
    URL: Issue
    URL: Article
    DOI: 10.1002/joc.v39.15
    DOI: 10.1002/joc.6176
    RVK:
    RA 1000
    Language: English
    Publisher: Wiley
    Publication Date: 2019
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  • 2
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    Online Resource
    Regime shift increase in East Asia's summer extreme hot day frequency across the late 1990s
    Wiley ; 2023
    In:  International Journal of Climatology Vol. 43, No. 5 ( 2023-04), p. 2305-2317
    Details
    In: International Journal of Climatology, Wiley, Vol. 43, No. 5 ( 2023-04), p. 2305-2317
    Abstract: Here we analysed the long‐term change in extreme hot days (EHDs) in East Asia during boreal summer (June–July–August) since 1979, where EHDs was defined as days exceeding or equalling the 90th percentile threshold of the climatological (1991–2020) daily and . EHDs frequency occurrence in East Asia during summer showed not only an increasing trend but also a distinct regime shift increase since the late 1990s. Based on this regime shift, we divided these years into two periods, P1 (1979–1998) and P2 (1999–2021), and found that different physical processes operated for each period's EHDs variability. P2's EHDs was related to the stationary wave originating from both the North Atlantic Ocean and the Indo‐Pacific warm pool, but these influences did not appear in P1. To investigate whether the observed regime shift increase was caused by natural variability or greenhouse gas concentration increases, we conducted a CO 2 quadrupling experiment as well as a present‐day experiment with a fixed CO 2 concentration using the Community Earth System Model with 28 ensemble members. We demonstrated that the regime shift increase of East Asian EHDs occurrences was due to increasing greenhouse gas concentrations. We further discussed the influence of Arctic sea ice reduction due to global warming on EHDs occurrences in East Asia.
    Type of Medium: Online Resource
    ISSN: 0899-8418 , 1097-0088
    URL: Issue
    URL: Article
    DOI: 10.1002/joc.v43.5
    DOI: 10.1002/joc.7976
    RVK:
    RA 1000
    Language: English
    Publisher: Wiley
    Publication Date: 2023
    detail.hit.zdb_id: 1491204-1
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  • 3
    Online Resource
    Online Resource
    Timescale‐dependent AMOC–AMO relationship in an earth system model of intermediate complexity
    Wiley ; 2021
    In:  International Journal of Climatology Vol. 41, No. S1 ( 2021-01)
    Details
    In: International Journal of Climatology, Wiley, Vol. 41, No. S1 ( 2021-01)
    Abstract: The relationship between Atlantic multi‐decadal oscillation (AMO) and Atlantic meridional overturning circulation (AMOC) is examined with respect to two (inter‐ and multi‐decadal) different timescales using a long‐term unforced simulation of an earth system model of intermediate complexity. In the inter‐decadal timescale, the AMO and the AMOC establish a self‐sustaining oscillatory mode; the AMOC induces the positive AMO through meridional heat transport (MHT), but with the time delay of approximately 7 years as the AMOC anomalies propagate southward over time within the Atlantic basin. After then, the AMO reduces the density in the main sinking region and brings the negative phase of the AMOC, which results in the rest half of the cycle. On the other hand, in the multi‐decadal timescale, the AMO and the AMOC are almost in phase because the AMOC is spatially stationary, resulting in a pan‐Atlantic surface warming. In addition, the Arctic‐originated density fluctuations are required for the multi‐decadal AMOC to switch its phase. The results obtained in this study suggest that timescale dependency should be considered when investigating the AMOC–AMO relationship.
    Type of Medium: Online Resource
    ISSN: 0899-8418 , 1097-0088
    URL: Issue
    URL: Article
    DOI: 10.1002/joc.v41.S1
    DOI: 10.1002/joc.6926
    RVK:
    RA 1000
    Language: English
    Publisher: Wiley
    Publication Date: 2021
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  • 4
    Online Resource
    Online Resource
    Influence of retreating Barents–Kara sea ice on the periodicity of El Niño–Southern Oscillation
    Wiley ; 2022
    In:  International Journal of Climatology Vol. 42, No. 9 ( 2022-07), p. 4881-4892
    Details
    In: International Journal of Climatology, Wiley, Vol. 42, No. 9 ( 2022-07), p. 4881-4892
    Abstract: The abrupt decline in sea ice in the Barents–Kara (BK) Sea because of global warming has been argued to influence not only higher latitudes but also the tropics. Using EC‐Earth model simulations, we demonstrated that the El Niño–Southern Oscillation (ENSO) period becomes longer when BK sea ice substantially decreases. As BK sea ice was forcibly reduced through nudging experiments, the mean Walker circulation shifted to the west, and the zonal sea surface temperature contrast in the tropical Pacific was enhanced. Consequently, the western Pacific mean thermocline became deeper, which reduced the sensitivity of oceanic wave response to wind forcing. Therefore, the oceanic Kelvin waves reflected by ENSO‐induced surface winds, a primary delayed negative feedback factor, were significantly weakened. Thus, ENSO phases could be sustained for longer.
    Type of Medium: Online Resource
    ISSN: 0899-8418 , 1097-0088
    URL: Issue
    URL: Article
    DOI: 10.1002/joc.v42.9
    DOI: 10.1002/joc.7509
    RVK:
    RA 1000
    Language: English
    Publisher: Wiley
    Publication Date: 2022
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  • 5
    Online Resource
    Online Resource
    Quantifying the residual effects of ENSO on low‐frequency variability in the tropical Pacific
    Wiley ; 2013
    In:  International Journal of Climatology Vol. 33, No. 4 ( 2013-03-30), p. 1047-1052
    Details
    In: International Journal of Climatology, Wiley, Vol. 33, No. 4 ( 2013-03-30), p. 1047-1052
    Abstract: The asymmetry of El Niño‐La Niña, one of the well‐known characteristics of the El Niño‐Southern Oscillation (ENSO), is suggested to produce a non‐zero residual effect that could rectify the background state, and thereby generates the low‐frequency variability in the tropical Pacific. So far, this rectification effect has been hardly quantified apart from the low‐frequency variability because the low‐frequency variability captured via conventional methods represents the mixture of both the residual effects of ENSO and the no‐ENSO‐related natural decadal variability. Here we separate the residual effects of ENSO from the natural decadal variability that appears in four historical sea surface temperature datasets during the last century by applying a long‐term moving average. A significant correlation between the computed residual effect and the decadal change in the ENSO skewness (i.e. the measure of the El Niño‐La Niña asymmetry) confirmed the applicability of our computational method. Quantitatively, the residual effects of ENSO consistently account for at least 15% of the total low‐frequency variability in four datasets, especially over the eastern and central tropical Pacific. This implies that the asymmetry of ENSO enhances the tropical Pacific decadal variability for the last century. Copyright © 2012 Royal Meteorological Society
    Type of Medium: Online Resource
    ISSN: 0899-8418 , 1097-0088
    URL: Issue
    URL: Article
    DOI: 10.1002/joc.v33.4
    DOI: 10.1002/joc.3470
    RVK:
    RA 1000
    Language: English
    Publisher: Wiley
    Publication Date: 2013
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  • 6
    Online Resource
    Online Resource
    The effects of ENSO under negative AO phase on spring dust activity over northern China: an observational investigation
    Wiley ; 2015
    In:  International Journal of Climatology Vol. 35, No. 6 ( 2015-05), p. 935-947
    Details
    In: International Journal of Climatology, Wiley, Vol. 35, No. 6 ( 2015-05), p. 935-947
    Abstract: The effects of El Niño/Southern Oscillation ( ENSO ) under negative Arctic Oscillation ( AO ) phase on the Asian dust activity are investigated for springs of the period 1961–2002. The spring dust index ( DI ) describing the monthly frequencies of three types of dust events (e.g. dust storm, blowing dust, and floating dust) exhibits a significant increase in the years of negative AO phase (hereafter AO −) and El Niño, compared with that in the years of AO − and La Niña. Averaged over all observation stations, the spring DI (49.7) during the El Niño/ AO − years is higher by 11.4% or 29.8% than that (38.3) during the La Niña/ AO − years. We suggest possible physical mechanism that the anomalous large‐scale environments associated with AO − and El Niño are more effective to provide favourable conditions to enhance Asian dust activity. During the El Niño/ AO − years, meridional gradients of pressure and temperature over the dust source regions are significantly enhanced by decreasing the geopotential height and warming air temperature that originated from the north and south of source regions, respectively, under the influence of AO − and El Niño. These also intensify the zonal wind shear and atmospheric baroclinicity, thereby producing enhanced cyclogenesis and dust occurrences over the major source regions. At the same time, dust transport paths with the stronger westerly winds are developed by the combined constraints of anomalous cyclone over the Siberia and the Mongolia and anomalous anticyclone over the western North Pacific, and thus strengthen dust transport to the downwind regions.
    Type of Medium: Online Resource
    ISSN: 0899-8418 , 1097-0088
    URL: Issue
    URL: Article
    DOI: 10.1002/joc.2015.35.issue-6
    DOI: 10.1002/joc.4028
    RVK:
    RA 1000
    Language: English
    Publisher: Wiley
    Publication Date: 2015
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  • 7
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    Online Resource
    Decadal phase shift of summertime Arctic dipole pattern and its nonlinear effect on sea ice extent
    Wiley ; 2021
    In:  International Journal of Climatology Vol. 41, No. 9 ( 2021-07), p. 4732-4742
    Details
    In: International Journal of Climatology, Wiley, Vol. 41, No. 9 ( 2021-07), p. 4732-4742
    Abstract: The rapid decline in Arctic sea ice during recent decades has been attributed to the combined influence of global warming and internal climate variability. Herein, we elucidate the process by which the decrease in sea ice is accelerated in association with the decadal phase shift of the Arctic dipole (AD), using observational data and Community Earth System Model (CESM1) simulations. The influence of the AD on Arctic sea ice varied according to its phase; in the negative‐AD decades (1979–1998), atmospheric circulation during summers of positive phase AD acts to reduce the sea ice extent (SIE) in the Pacific sector but increases it in the Atlantic sector. In contrast, in the positive‐AD decades (after 1999), the same atmospheric circulation pattern reduces the SIE in both sectors, resulting in enhanced sea ice melting across the entire Arctic region. A similar nonlinear relationship between the AD phase and SIE change is also observed in CESM1 Pre‐Industrial simulations, which stem from altered background temperature conditions between periods, implying the significant role of internal variability, particularly over the Atlantic sector. However, contrary to the recently observed AD trend, CESM1 Large Ensemble experiments predicted a negative AD trend as global warming proceeded. This suggests that the recent positive AD phase may be naturally driven, but the current state of sea ice decline associated with AD could be altered in the near future because of enhanced global warming.
    Type of Medium: Online Resource
    ISSN: 0899-8418 , 1097-0088
    URL: Issue
    URL: Article
    DOI: 10.1002/joc.v41.9
    DOI: 10.1002/joc.7097
    RVK:
    RA 1000
    Language: English
    Publisher: Wiley
    Publication Date: 2021
    detail.hit.zdb_id: 1491204-1
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  • 8
    Online Resource
    Online Resource
    Origin of early‐spring central Pacific warming as the 1982–1983 El Niño precursor
    Wiley ; 2018
    In:  International Journal of Climatology Vol. 38, No. 6 ( 2018-05), p. 2899-2906
    Details
    In: International Journal of Climatology, Wiley, Vol. 38, No. 6 ( 2018-05), p. 2899-2906
    Abstract: The extreme El Niño events, such as those which occurred in 1982–1983, 1997–1998, and 2015–2016, exerted devastating impacts in many parts of the globe. Hence, it is crucial to understand the precursors of such extreme events. Nevertheless, each El Niño event has its own characteristics even in the initiation. Here, we show that the development of early‐spring equatorial central Pacific warming forced by the increased solar radiation due to a suppressed convection was a crucial factor in developing the 1982–1983 extreme El Niño event. The central Pacific warming anomalies in the spring of 1982 were induced by atmospheric subsidence connected to the northern subtropical Pacific convection, subsequently reinforced by a reduced evaporative cooling via westerly anomalies. On the other hand, springtime warming anomalies over the equatorial central and eastern Pacific regions during other extreme El Niño events were induced mainly by oceanic dynamical processes.
    Type of Medium: Online Resource
    ISSN: 0899-8418 , 1097-0088
    URL: Issue
    URL: Article
    DOI: 10.1002/joc.2018.38.issue-6
    DOI: 10.1002/joc.5465
    RVK:
    RA 1000
    Language: English
    Publisher: Wiley
    Publication Date: 2018
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  • 9
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    Online Resource
    Western North Pacific anticyclone change associated with the El Niño–Indian Ocean Dipole coupling
    Wiley ; 2019
    In:  International Journal of Climatology Vol. 39, No. 5 ( 2019-04), p. 2505-2521
    Details
    In: International Journal of Climatology, Wiley, Vol. 39, No. 5 ( 2019-04), p. 2505-2521
    Abstract: It is known that the lower‐tropospheric anomalous anticyclone over the western North Pacific (WNPAC) is strongly influenced by the sea surface temperature (SST) variations in the tropical Pacific and Indian Oceans. In this study, we re‐examine a role of the dominant inter‐annual SST variability in the Indian Ocean basin (represented by the Indian Ocean Dipole [IOD] ) in the formation and development of the WNPAC during El Niño. Regardless of the data sets obtained from observations and long‐term (1,300 years) model simulations, it is found that the WNPAC is strongly developed with larger circulation intensities when El Niño co‐occurs with a positive phase of IOD (i.e., El Niño–IOD coupling), whereas it is weakly developed when El Niño solely occurs (i.e., El Niño–IOD decoupling). Sensitivities computed by ratios of the WNPAC intensities to the El Niño intensities from the three cases of El Niño–IOD coupling strengths further capture the aforementioned changes, supporting the idea that the IOD has an active role in modulating the WNPAC intensity during its development phase in a co‐operation with the known El Niño‐related processes that drive the WNPAC. Additional analyses suggest that the pronounced atmospheric convection anomalies occurring over the western Indian Ocean during the WNPAC development season, which are only manifested in the El Niño–IOD coupled cases, may play an essential role for the WNPAC intensity modulation by concurrently enhancing the subsidence anomalies over the western Pacific including the Maritime Continent through a change in the tropical Walker circulation.
    Type of Medium: Online Resource
    ISSN: 0899-8418 , 1097-0088
    URL: Issue
    URL: Article
    DOI: 10.1002/joc.2019.39.issue-5
    DOI: 10.1002/joc.5967
    RVK:
    RA 1000
    Language: English
    Publisher: Wiley
    Publication Date: 2019
    detail.hit.zdb_id: 1491204-1
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  • 10
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    Mid‐latitude leading double‐dip La Niña
    Wiley ; 2021
    In:  International Journal of Climatology Vol. 41, No. S1 ( 2021-01)
    Details
    In: International Journal of Climatology, Wiley, Vol. 41, No. S1 ( 2021-01)
    Abstract: Understanding the evolution asymmetry between El Niño and La Niña events is challenging. Unlike El Niño, most La Niña events are characterised by a double‐dip cooling (a.k.a. multi‐year La Niña). Herein, we examined how single‐ and multi‐year La Niña events differ by analysing observational and climate‐model data sets. Single‐year La Niña events tend to develop narrowly within the tropics from a central Pacific‐type El Niño (Niño‐4  〉  Niño‐3), whereas multi‐year La Niña events tend to originate from an eastern Pacific‐type El Niño (Niño‐3  〉  Niño‐4) and are well‐connected to mid‐latitudes through the Pacific meridional mode , which leads to a meridionally wider response of the off‐equatorial low‐level atmospheric anti‐cyclonic circulation. As the anti‐cyclonic circulation controls the amount of equatorial upper‐ocean heat recharge through Sverdrup transport, for single‐year La Niña, efficient ocean recharging due to a narrower anti‐cyclonic circulation causes a fast transition to an El Niño or a fast termination of a La Niña. In contrast, for multi‐year La Niña, a weaker recharging causes surface cooling to persist, leading to another La Niña in the following year.
    Type of Medium: Online Resource
    ISSN: 0899-8418 , 1097-0088
    URL: Issue
    URL: Article
    URL: Article
    DOI: 10.1002/joc.v41.S1
    DOI: 10.1002/joc.6772
    DOI: 10.37473/fic/10.1002/joc.6772
    RVK:
    RA 1000
    Language: English
    Publisher: Wiley
    Publication Date: 2021
    detail.hit.zdb_id: 1491204-1
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