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국제학술지

공지 (2025. 10. 28.)

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Reexamination of the influence of ENSO on landfalling tropical cyclones in Korea

Abstract: This study examines the influence of the El Niño-Southern Oscillation (ENSO) on the frequency of landfalling tropical cyclones (TCs) in the Korean Peninsula during the TC season, June through October, of the years 1951–2010. An ENSO year is defined when the seasonal mean of the NINO3.4 sea surface temperature (SST) anomalies is greater/less than the typical seasonal mean by 0.5°C. The overall results of this study support that ENSO does not affect the landfalling TCs in Korea; the mean frequencies of the TC landfalls (influences) during El Niño and La Niña calculated over the entire analysis period are 1.1 (3.3) and 1.2 (3.0), respectively. The variations in the basin-wide distribution of TCs show that the influence of ENSO on TC distribution is extended over southeastern Japan with no significant signals coming from over the Korean Peninsula and the East China Sea. The change in the intensity of the landfalling TCs in the Korean Peninsula due to ENSO leads to the same conclusion as that in the frequency of the landfalling TCs. In addition, the same conclusion is obtained when the TC season duration is expanded to include the entire year and when different definitions of the ENSO years (e.g., based on the preceding or following winter NINO3.4 SST anomalies) are selected for analysis.
- 작성자Ho and Kim
- 작성일2024.07.09
- 조회수91
- 2011
Relationship between Arctic Oscillation and cold surges over East Asia

Abstract: The present study reveals the changes in the characteristics of cold surges over East Asia associated with the Arctic Oscillation (AO). Based on circulation features, cold surges are grouped into two general types: wave train and blocking types. The blocking type of cold surge tends to occur during negative AO periods, that is, the AO-related polarity of the blocking type. However, the wave train type is observed during both positive and negative AO periods, although the wave train features associated with negative AO are relatively weaker. The cold surges during negative AO are stronger than those during positive AO in terms of both amplitude and duration. The cold surges during positive AO in which the extent of effect is confined to inland China passes through East Asia quickly because of weaker Siberian high and Aleutian low, leading to short duration of these cold surges. In contrast, the cold surge during negative AO, characterized by a well-organized anticyclone–cyclone couplet with high pressure over continental East Asia and low pressure over Japan, brings continuous cold air into the entire East Asian region for more than one week with long-lasting cold advection. It is also found that the tracks of the cold surges during negative AO tend to occur more frequently over Korea and Japan and less frequently over China, compared with those during positive AO. The tracks are related to a west–east dipole structure of the ratio of rain conversion to snow according to AO phase, resulting in freezing precipitation or snowfall events over inland China (Korea and Japan) are likely to occur more frequently during the positive (negative) AO periods.
- 작성자Park et al.
- 작성일2024.07.09
- 조회수134
- 2011
Strong landfall typhoons in Korea and Japan in a recent decade

Abstract: Long-term changes in tropical cyclones (TCs) that made landfall in Korea and Japan during the TC seasons (June–October) are examined for the period 1977–2008. The TC activity is characterized by four parameters: power dissipation index (PDI), TC-induced rainfall, number of landfall TCs, and TC duration. The analysis period is divided into 2 decades (1977–1988 and 1997–2008). The PDI and TC-induced rainfall increase significantly in the later decade. This enhancement in the TC activity is because of the increase in the number of landfall TCs and the longer duration of the TCs over the two countries. The increase in the number of landfall TCs is associated with the enhanced northward steering flows over the East China Sea. The longer TC duration is mainly due to the high intensity of the approaching TCs prior to landfall. The other factors (i.e., tracks, translational speeds, mean drift lengths, and weakening rates of TCs) could also affect the TC duration, but they are found to be not significant. The results of our study reveal that the recent intensification of TCs is attributable to the changes observed in the later decade in the large-scale environments in the vicinity of the two countries. These changes include warmer sea surface temperature, highly humid midtroposphere, and weaker vertical wind shear over the region. In addition, another responsible factor is the anomalous upward motion driven by the relocation of secondary circulation near the jet entrance, which is highly related with weaker upper tropospheric jet stream in the recent decade.
- 작성자Park et al.
- 작성일2024.07.09
- 조회수96
- 2011
Observational diagnosis of cloud phase in the winter Antarctic atmosphere for parameterizations in climate models

Abstract: The cloud phase composition of cold clouds in the Antarctic atmosphere is explored using data from the Moderate Resolution Imaging Spectroradiometer (MODIS) and Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) instruments for the period 2000–2006. We used the averaged fraction of liquid-phase clouds out of the total cloud amount at the cloud tops since the value is comparable in the two measurements. MODIS data for the winter months (June, July, and August) reveal liquid cloud fraction out of the total cloud amount significantly decreases with decreasing cloud-top temperature below 0°C. In addition, the CALIOP vertical profiles show that below the ice clouds, low-lying liquid clouds are distributed over ∼20% of the area. With increasing latitude, the liquid cloud fraction decreases as a function of the local temperature. The MODIS-observed relation between the cloud-top liquid fraction and cloud-top temperature is then applied to evaluate the cloud phase parameterization in climate models, in which condensed cloud water is repartitioned between liquid water and ice on the basis of the grid point temperature. It is found that models assuming overly high cut-offs (≫ −40°C) for the separation of ice clouds from mixed-phase clouds may significantly underestimate the liquid cloud fraction in the winter Antarctic atmosphere. Correction of the bias in the liquid cloud fraction would serve to reduce the large uncertainty in cloud radiative effects.
- 작성자Choi et al.
- 작성일2024.06.19
- 조회수70
- 2010
Bayesian forecasting of seasonal typhoon activity: A track-pattern-oriented categorization approach

Abstract: A new approach to forecasting regional and seasonal tropical cyclone (TC) frequency in the western North Pacific using the antecedent large-scale environmental conditions is proposed. This approach, based on TC track types, yields probabilistic forecasts and its utility to a smaller region in the western Pacific is demonstrated. Environmental variables used include the monthly mean of sea surface temperatures, sea level pressures, low-level relative vorticity, vertical wind shear, and precipitable water of the preceding May. The region considered is the vicinity of Taiwan, and typhoon season runs from June through October. Specifically, historical TC tracks are categorized through a fuzzy clustering method into seven distinct types. For each cluster, a Poisson or probit regression model cast in the Bayesian framework is applied individually to forecast the seasonal TC activity. With a noninformative prior assumption for the model parameters, and following Chu and Zhao for the Poisson regression model, a Bayesian inference for the probit regression model is derived. A Gibbs sampler based on the Markov chain Monte Carlo method is designed to integrate the posterior predictive distribution. Because cluster 5 is the most dominant type affecting Taiwan, a leave-one-out cross-validation procedure is applied to predict seasonal TC frequency for this type for the period of 1979–2006, and the correlation skill is found to be 0.76.
- 작성자Chu et al.
- 작성일2024.06.19
- 조회수88
- 2010
Dipolar redistribution of summertime TCG between the Philippine Sea and the northern SCS and its possible mechanisms

Abstract: Recent observational records show that the dipole oscillation between the Philippine Sea (PS) and the northern South China Sea (nSCS) is a leading empirical orthogonal function (EOF) of summertime tropical cyclone (TC) genesis in the western North Pacific (WNP). This PS-nSCS oscillation is characterized by a distinguished decadal variability in addition to an interannual variability. Meanwhile, the typical El Niño–Southern Oscillation (ENSO)-related mode is found in the second EOF mode, which is predominantly interannual. With regard to the PS-nSCS oscillation, its interannual component appears to be linked with the previous wintertime ENSO event, but the linkage is not so robust in the sense that about half of its significant events are classified as the ENSO-related case, whereas its decadal component is coupled to a sea surface temperature anomaly (SSTA) in the central Pacific with its equatorial core near the Niño-4 region, which is flanked by an opposite SSTA on both sides along the latitudinal belt. Interestingly, this SSTA pattern resembles that related to the ENSO Modoki, and equivalently, the transitional phase of ENSO. The ENSO Modoki is regionally manifested by the anomalous zonal SST gradient between the equatorial western and central Pacific; thus the decadal modulation of this anomalous zonal SST gradient can be regarded as an actual forcing that forms and modulates the decadal PS-nSCS oscillation. In addition, the decadal PS-nSCS oscillation is compared with the decadal basin-wide TC genesis variation in terms of the Pacific SSTA pattern and the associated anomalous large-scale environments. Full title: Dipolar redistribution of summertime tropical cyclone genesis between the Philippine Sea and the northern South China Sea and its possible mechanisms
- 작성자Kim et al.
- 작성일2024.06.19
- 조회수69
- 2010
Influence of tropical cyclone landfalls on spatiotemporal variations in typhoon season rainfall over South China

Abstract: This study examined the impact of tropical cyclone (TC) landfalls on the spatiotemporal variations in the rainfall over South China for the period 1957–2005. The target region was selected to show the noteworthy contribution of TC landfalls to the total rainfall during the typhoon season (July–October). Two prevailing spatial variations in the rainfall were obtained from an EOF analysis. The first EOF mode displays single-sign variability over South China with an explained variance of 23.4%. The associated time series of this mode fluctuates on a decadal timescale and was found to be correlated with TC genesis in the South China Sea. The second EOF mode shows a seesaw pattern between Hainan Island/Guangdong Province and the remaining regions with an explained variance of 11.4%. This seesaw pattern results from an anti-correlation in seasonal TC landfalls between the two regions, which was found in previous studies. This is related to the strengthening (weakening) of the upper tropospheric jets and the corresponding development of a massive anticyclonic (cyclonic) circulation over East Asia. The EOF analysis was also conducted using just the data for rainfall caused by landfalling TCs. This revealed that the first EOF mode using just the TC-induced rainfall is nearly identical to the second mode from the total rainfall. The obvious seesaw pattern of the first mode when employing just the TC-induced rainfall in the EOF analysis implies that this pattern has larger temporal variability than the single-signed pattern (i.e., the first EOF mode using the total rainfall) in terms of TC landfalls. This study suggests that TC landfalls over South China and the accompanying rainfall significantly modulate the spatial variation of the typhoon season rainfall there.
- 작성자Lee et al.
- 작성일2024.06.19
- 조회수77
- 2010
Influences of AO and MJO on cold surges and heavy snowfalls over Korea: A case study for the winter of 2009–2010

Abstract: In the winter of 2009–2010, frequent and long-lasting cold weather affected Korea. Four major cold surges and several heavy snowfall events were observed, including a record-breaking event on 4 January 2010. These four cold surges had distinct properties with regard to their relationships to the phases of the Arctic Oscillation (AO) and the Madden-Julian Oscillation (MJO), suggesting the possible influences of the AO and MJO on the cold surges and heavy snowfalls. The four cold surges were of two distinct types: the wave train type and the blocking type, which were differentiated by their mechanisms. With regard to the relationships of the cold surges to the AO, three cold surges occurred during a strongly negative AO period, which lasted for more than 1 month. The Siberian High expanded from the Arctic high-pressure region to East Asia during the negative AO period. A cold surge occurred during a positive AO, with the expansion of the Siberian High across the Eurasian continent. An MJO-induced circulation, corresponding to strong tropical convection over the tropical Indian Ocean, seems to have reinforced the cold surges over East Asia. In addition, the active local Hadley circulation modulated by a convection center over the Indian Ocean tends to enhance midlatitude synoptic disturbances across East Asia and provides favorable conditions for upward motion over the region. In short, the effects of the AO and MJO, along with the existing low-level moisture supply, contributed to heavy snowfalls associated with strong cold surges over Korea during the winter of 2009–2010. Full title: Influences of Arctic Oscillation and Madden-Julian Oscillation on cold surges and heavy snowfalls over Korea: A case study for the winter of 2009–2010
- 작성자Park et al.
- 작성일2024.06.19
- 조회수122
- 2010
On the relationship between Indian Ocean sea surface temperature and the transition from El Niño to La Niña

Abstract: The relationship between Indian Ocean sea surface temperature and the transition of El Niño events into either La Niña or El Niño–Southern Oscillation neutral conditions is examined in both observations and the retrospective ensemble hindcasts of the National Center for Environmental Prediction Climate Forecast System. The southern Indian Ocean is shown to demonstrate a particularly robust and consistent relationship with the evolution of these transitions. These associations are described, and a physical mechanism involving air-sea interaction in the Indian and western Pacific Oceans is proposed. Observations suggest that easterly surface wind anomalies in the western Pacific Ocean are associated with the emergence of La Niña during boreal summer and fall. Here it is shown that these winds are significantly correlated to southern Indian Ocean sea surface temperature in the preceding spring that is characterized by a large-scale zonal dipole of cool and warm anomalies in the southwestern and southeastern Indian Oceans, respectively. These associations are particularly pronounced for strong El Niño conditions, during the dissipation of which a pronounced wavetrain-like atmospheric pattern accompanies sea surface temperature anomalies in the southern Indian Ocean. Together, the circulation and sea surface temperature anomalies increase the meridional cross-equatorial temperature gradient in the western Indian Ocean and mute intraseasonal variability while strengthening surface equatorial easterly winds in the Indo-Pacific warm pool. Collectively, these anomalies favor subsequent La Niña development. On the basis of these observed associations, a predictive model that demonstrates skill in anticipating the nature of El Niño transitions, involving the southern Indian Ocean, Asian monsoon, and El Niño–Southern Oscillation, is proposed. In the National Center for Environmental Prediction Climate Forecast System, the relationships described above are simulated both consistently and realistically, despite model weaknesses, further bolstering a key role of southern Indian Ocean and predictive relationship. Comparison of fully coupled and sea surface temperature–forced simulations suggests a key role for air-sea interaction in the observed associations. Moreover, it is demonstrated that coupled simulations of El Niño–Southern Oscillation may benefit substantially from improved representation of Indian Ocean variability and Indo-Pacific interaction.
- 작성자Yoo et al.
- 작성일2024.06.19
- 조회수86
- 2010
Potential impact of vegetation feedback on European heat waves in a 2 x CO 2 climate

Abstract: Inclusion of the effects of vegetation feedback in a global climate change simulation suggests that the vegetation–climate feedback works to alleviate partially the summer surface warming and the associated heat waves over Europe induced by the increase in atmospheric CO2 concentrations. The projected warming of 4°C over most of Europe with static vegetation has been reduced by 1°C as the dynamic vegetation feedback effects are included. Examination of the simulated surface energy fluxes suggests that additional greening in the presence of vegetation feedback effects enhances evapotranspiration and precipitation, thereby limiting the warming, particularly in the daily maximum temperature. The greening also tends to reduce the frequency and duration of heat waves. Results in this study strongly suggest that the inclusion of vegetation feedback within climate models is a crucial factor for improving the projection of warm season temperatures and heat waves over Europe.
- 작성자Jeong et al.
- 작성일2024.06.19
- 조회수92
- 2010