• Journal of applied mathematics & informatics
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• v.35 no.3_4
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• pp.217-230
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• 2017

In this paper we deal with the difference equation $$y_{n+1}=\frac{ay_{n-1}}{by_ny_{n-1}+cy_{n-1}y_{n-2}+d}$$, $$n{\in}\mathbb{N}_0$$, where the coefficients a, b, c, d are positive real numbers and the initial conditions $y_{-2}$, $y_{-1}$, $y_0$ are nonnegative real numbers. Here, we investigate global asymptotic stability, periodicity, boundedness and oscillation of positive solutions of the above equation.

• Proceedings of the Korea Water Resources Association Conference
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• 2004.05b
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• pp.124-133
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• 2004

Global climate variations are expected to affect local hydro-meteorological variables like precipitation and temperature. The Southern Oscillation (SO) is one of the major driving forces that give impact on regional and local climatic variation. The relationships between SO and local climate variation are, however, characterized by strong nonlinear variation patterns. In this paper, the nonlinear dynamic relationship between the Southern Oscillation Index (SOI), precipitation, and temperature in Fukuoka, Japan, is investigated using by a nonlinear multivariable approach. This approach is based on the joint variation of these variables in the phase space. The joint phase-space variation of SOI, precipitation, and temperature is studied with the primary objective to obtain a better understanding of the dynamical evolution of local hydro-meteorological variables affected by global atmospheric-oceanic phenomena.

• Journal of the Korean Mathematical Society
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• v.51 no.6
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• pp.1209-1220
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• 2014

We prove global gradient estimates in weighted Orlicz spaces for weak solutions of nonlinear elliptic equations in divergence form over a bounded non-smooth domain as a generalization of Calder$\acute{o}$n-Zygmund theory. For each point and each small scale, the main assumptions are that nonlinearity is assumed to have a uniformly small mean oscillation and that the boundary of the domain is sufficiently flat.

• Atmosphere
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• v.29 no.5
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• pp.627-637
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• 2019

Severe and long-lasting heat waves over Korea and many regions in the Northern Hemisphere (NH) during the 2016 summer, have been attributed to global warming and atmospheric teleconnection coupled with tropical convective activities. Yet, what controls subseasonsal time scale of heat wave has not been well addressed. Here we show a critical role of two dominant boreal summer intraseasonal oscillation (BSISO) modes, denominated as BSISO1 and BSISO2, on modulating temporal structure of heat waves in the midst of similar climate background. The 2016 summer was characterized by La Nina development following decay of strong 2015/2016 El Nino. The NH circumglobal teleconnection pattern (CGT) and associated high temperature anomalies and heat waves were largely driven by convective activity over northwest India and Pakistan during summer associated with La Nina development. However, the heat wave event in Korea from late July to late August was accompanied by the phase 7~8 of 30~60-day BSISO1 characterized by convective activity over the South China Sea and Western North Pacific and anticyclonic circulation (AC) anomaly over East Asia. Although the 2010 summer had very similar climate anomalies as the 2016 summer with La Nina development and CGT, short-lasting but frequent heat waves were occurred during August associated with the phase 1~2 of 10~30-day BSISO2 characterized by convective activity over the Philippine and South China Sea and AC anomaly over East Asia. This study has an implication on importance of BSISO for better understanding mechanism and temporal structure of heat waves in Korea.

• Atmosphere
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• v.33 no.2
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• pp.125-154
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• 2023

Since the Korean Meteorological Society was organized in 1963, the climate dynamics fields have been made remarkable progress. Here, we documented the academic developments in the area of climate dynamics performed by members of Korean Meteorological Society, based on studies that have been published mainly in the Journal of Korean Meteorological Society, Atmosphere, and Asia-Pacific Journal of Atmospheric Sciences. In these journals, the fundamental principles of typical ocean-atmosphere climatic phenomena such as El Niño, Madden-Julian Oscillation, Pacific Decadal Oscillation, and Atlantic Multi-decadal Oscillation, their modeling, prediction, and its impact, are being conducted by members of Korean Meteorological Society. Recently, research has been expanded to almost all climatic factors including cryosphere and biosphere, as well as areas from a global perspective, not limited to one region. In addition, research using an artificial intelligence (AI), which can be called a cutting-edge field, has been actively conducted. In this paper, topics including intra-seasonal and Madden-Julian Oscillations, East Asian summer monsoon, El Niño-Southern Oscillation, mid-latitude and polar climate variations and some paleo climate and ecosystem studies, of which driving mechanism, modeling, prediction, and global impact, are particularly documented.

• Journal of the Korean earth science society
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• v.26 no.3
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• pp.199-217
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• 2005

Using monthly total ozone data obtained from a Total Ozone Mapping Spectrometer (TOMS) onboard the Nimbus-7 and Earth Probe satellite, this study examined the trend in the total amount of global ozone during two periods: from 1979-1992 [Early period] and 1997-2002 [Latter period]. The Annual average of total ozone during the Early period was globally reduced by about 10 DU compared to the amount during the Latter, except in some areas between the equator and 20 N. Global trends of total ozone showed a decrease of -6.30 DU/decade during 1979-1992, and an increase of 0.12 DU/decade during 1997-2002. Its enhancement during the Latter period was especially noticeable in tropical areas. The EOF analyses of total ozone from this period indicated signs of temporal/spatial variability, associated with the phenomena of Quasi-Biennial Oscillation (QBO), Quasi-Triennial Oscillation (QTO), El Nino Southern Oscillation (ENSO), and volcanic eruption. Seasonal profiles of tropospheric ozone in the tropics obtained from ozonesondes, showed the spatial pattern of zonal wavenumber one. Overall, this study may be useful in analyzing possible causes in the variations of statospheric and tropospheric ozone.

• Journal of the Korean Society of Combustion
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• v.12 no.2
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• pp.34-41
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• 2007

The dynamic behaviors of counterflow non-premixed flame have been investigated experimentally to study effects of heat losses and Lewis number on edge flame oscillation, which result from the advancing and retreating edge flame motion of outer flame edge at low strain rate flame. For low strain rate flame, lateral conduction heat loss in addition to radiation heat loss could be more remarkable than the others. Oscillatory instabilities appear at fuel Lewis number greater than unity. But excessive lateral conduction heat loss causes edge flame instability even at fuel Lewis number less than unity. The excessive heat loss caused by the smaller burner diameter in which the flame length is an indicator of lateral conduction heat loss extends the region of flame oscillation and accelerates oscillatory instability in comparison to the previous study with the burner diameter of 26mm. Extinction behaviors quite different from the previous study are also addressed.

• Proceedings of the Korea Water Resources Association Conference
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• 2003.05a
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• pp.151-158
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• 2003

Recently, there has been considerable interest in the influence of El Nino/Southern Oscillation (ENSO) on a global scale. ENSO has been measured by a simple index called Southern Oscillation Index (SOI). The statistical characteristics of SOI have been also focused to reveal the influence of ENSO. The SOI trend shows that El Nino events are generally getting stronger and more frequently occurring than La Nina events. However, the variation of SOI has varied significantly in a long-term. The SOI values are computed using the mean value and its standard deviation of the base period from 1951 to 1980. In the present study, the different base periods are applied to compute the SOI values and the influence of the different base periods is investigated in detail to reveal the long-term variation of SOI From the results, we could conclude that the present SOI should be carefully considered as a criterion to judge whether the El Nino and La Nina events are occurring.

• Bulletin of the Korean Mathematical Society
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• v.44 no.3
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• pp.439-445
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• 2007

The aim of this work is to investigate the global stability, periodic nature, oscillation and the boundedness of solutions of the difference equation $$x_{n+1}={\frac{Ax_{n-1}}{B+Cx_{n-2}{\iota}x_{n-2k}$$, n = 0, 1, 2,..., where A, B, C are nonnegative real numbers and $\iota$, k are nonnegative in tegers, $\iota{\leq}k$.

• Journal of Korea Water Resources Association
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• v.38 no.12 s.161
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• pp.985-994
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• 2005

We examined problems of the principal component analysis(PCA), which is able to analyze at the low dimensionality as a methodologv to assess hydrologic time series, and introduced the theory and characteristics of independent component analysis(ICA) that can supplement problems of principal component analysis. We also applied the global sea surface temperature(SST) of the Nino region and assessed the correlation between El $\tilde{n}ino$-Southern Oscillation(ENSO) and SST. The results of examining separation-ability of principal components using mixed signals indicate that the independent component analysis is statistically superior compared to that of the principal component analysis. Finally, we assessed correlation between ENSO and global anomaly SST. The independent component analysis was applied to the $5^{\circ}{\times}5^{\circ}$(latitude and longitude) global anomaly SST in the Nino+3.4 region that is the El $\tilde{n}ino$ observation section. We assessed the correlation with the ENSO years. These results of the analysis show that only one independent component($86\%$) was able to represent the entire behavior and was consistent with the main ENSO years. Finally, we carried out independent component analysis for summer seasonal rainfalls at nine stations and could extract ICs to reflect geographical characteristics. The increasing trend has been shown at IC-1 and IC-2 since 1970s.