• Atmosphere
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• v.26 no.1
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• pp.159-183
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• 2016

On 31 July 2014, there was a localized torrential rainfall ($58.5mm\;hr^{-1}$) caused by a strong convective cell with thunder showers over Daegwallyeong. In the surface synoptic chart, a typhoon was positioned in the East China Sea and the subtropical high was expanded to the Korean peninsula. A WRF (Weather Research and Forecasting) numerical simulation with a resolution of 1 km was performed for a detailed analysis. The simulation result showed a similar pattern in a reflectivity distribution particularly over the Gangwon-do region, compared with the radar reflectivity. According to the results of the WRF simulation, the process and mechanism of the localized heavy rainfall over Daegwallyeong are as follows: (1) a convective instability over the middle part of the Korean peninsula was enhanced due to the low level advection of warm and humid air from the North Pacific high. (2) There was easterly flow from the coast to the mountainous regions around Daegwallyeong, which was generated by the differential heating of the insolation among Daegwallyeong and the Yeongdong coastal plain, and nearby coastal waters. (3) In addition, westerly flow from the western part of Daegwallyeong caused a strong convergence in this region, generating a strong upward motion combined by an orographic effect. (4) This brought about a new convective cell over Daegwallyeong. And this cell was more developed by the outflow from another thunderstorm cell to the south, and finally these two cells were merged to develop as a strong convective cell with thunder showers, leading to the record breaking maximum rainfall per hour ($58.5mm\;hr^{-1}$) in July.

• Journal of Environmental Science International
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• v.23 no.10
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• pp.1719-1729
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• 2014

This study is carried out in order to bridge the gap to understand the relationships between South Asian and East Asian monsoon systems by comparing the summer (June-September) precipitation of Nepal and South Korea. Summer monsoon precipitation data from Nepal and South Korea during 30 years (1981-2010) are used in this research to investigate the association. NCEP/NCAR reanalysis data are also used to see the nature of large scale phenomena. Statistical applications are used to analyze these data. The analyzed results show that summer monsoon precipitation is higher over Nepal ($1513.98{\pm}159.29mm\;y^{-1}$) than that of South Korea ($907.80{\pm}204.71mm\;y^{-1}$) and the wettest period in both the countries is July. However, the coefficient of variation shows that amplitude of interannual variation of summer monsoon over South Korea (22.55%) is larger in comparison to that of Nepal (10.52%). Summer monsoon precipitation of Nepal is found to be significantly correlated to that of South Korea with a correlation coefficient of 0.52 (99% confidence level). Large-scale circulations are studied to further investigate the relationship between the two countries. wind and specific humidity at 850 hPa show a strong westerly from Arabian Sea to BOB and from BOB, wind moves towards Nepal in a northwestward direction during the positive rainfall years. In case of East Asia, strong northward displacement of wind can be observed from Pacific to South Korea and strong anticyclone over the northwestern Pacific Ocean. However, during the negative rainfall years, in the South Asian region we can find weak westerly from the Arabian Sea to BOB, wind is blowing in a southerly direction from Nepal and Bangladesh to BOB.

• Journal of Environmental Science International
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• v.24 no.7
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• pp.851-864
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• 2015

This study analyzed the climate regime shift using statistical change-point analysis on the time-series tropical cyclone (TC) frequency that affected Japan in July to September. The result showed that there was a significant change in 1995 and since then, it showed a trend of rapidly decreasing frequency. To determine the reason for this, differences between 1995 to 2012 (9512) period and 1978 to 1994 (7894) period were analayzed. First, regarding TC genesis, TCs during the 9512 period showed a characteristic of genesis from the southeast quadrant of the tropical and subtropical western North Pacific and TCs during the 7894 period showed their genesis from the northwest quadrant. Regarding a TC track, TCs in the 7894 period had a strong trend of moving from the far east sea of the Philippines via the East China Sea to the mid-latitude region in East Asia while TCs in the 9512 period showed a trend of moving from the Philippines toward the southern part of China westward. Thus, TC intensity in the 7894 period, which can absorb sufficient energy from the sea as they moved a long distance over the sea, was stronger than that of 9512. Large-scale environments were analyzed to determine the cause of such difference in TC activity occurred between two periods. During the 9512 period, anomalous cold and dry anticyclones were developed strongly in the East Asia continent. As a result, Korea and Japan were affected by the anomalous northerlies thereby preventing TCs in this period from moving toward the mid-latitude region in East Asia. Instead, anomalous easterlies (anomalous trade wind) were developed in the tropical western Pacific so that a high passage frequency from the Philippine to the south China region along the anomalous steering flows was revealed. The characteristics of the anomalous cold and dry anticyclone developed in the East Asia continent were also confirmed by the analysis of air temperature, relative humidity and sensible heat net flux showing that most regions in East Asia had negative values.

• 한국해양학회지
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• v.26 no.3
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• pp.193-203
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• 1991

KODOS (Korea Deep ocean Study)-89 sediments, recovered from western part of Clarion-Clipperton fracture zone in north Pacific, show two distinctly colored layer zones: surface yellow brown layer (unit A) and subsurface dark brown layer (unit B), and roughly recognized as Quaternary and Tertiary in age, respectively. Geochemical characteristics are also different in those two units. Smectite, water, micronodule, and heavy metal contents are higher in unit B, while POC content is higher in unit A. High smectite and low POC contents in unit B are due to the longer formation period of smectite, almost decomposition of labile organic matter in unit B relative to unit A. High water content in unit B is caused by coarse fabric which results from higher content of spicules and spines. Additionally, stronger electrostatic repulsion force caused by high smectite content also supports high water content in unit B relative to unit A. Variations in heavy metal contents are closely related to the amount of micronodule, which has higher metal contents than that of sediment. Therefore, we conclude that the differences of geochemical characteristics in unit A and unit B are resulted from the different diagenetic durations of unit A and unit B.

• Ocean Science Journal
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• v.43 no.4
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• pp.195-208
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• 2008

This paper evaluates whether a thermodynamic ocean-carbon model can be used to predict the monthly mean global fields of the surface-water partial pressure of $CO_2$ ($pCO_{2SEA}$) from sea surface salinity (SSS), temperature (SST), and/or nitrate ($NO_3$) concentration using previously published regional total inorganic carbon ($C_T$) and total alkalinity ($A_T$) algorithms. The obtained $pCO_{2SEA}$ values and their amplitudes of seasonal variability are in good agreement with multi-year observations undertaken at the sites of the Bermuda Atlantic Timeseries Study (BATS) ($31^{\circ}50'N$, $60^{\circ}10'W$) and the Hawaiian Ocean Time-series (HOT) ($22^{\circ}45'N$, $158^{\circ}00'W$). By contrast, the empirical models predicted $C_T$ less accurately at the Kyodo western North Pacific Ocean Time-series (KNOT) site ($44^{\circ}N$, $155^{\circ}E$) than at the BATS and HOT sites, resulting in greater uncertainties in $pCO_{2SEA}$ predictions. Our analysis indicates that the previously published empirical $C_T$ and $A_T$ models provide reasonable predictions of seasonal variations in surface-water $pCO_{2SEA}$ within the (sub) tropical oceans based on changes in SSS and SST; however, in high-latitude oceans where ocean biology affects $C_T$ to a significant degree, improved $C_T$ algorithms are required to capture the full biological effect on $C_T$ with greater accuracy and in turn improve the accuracy of predictions of $pCO_{2SEA}$.

• Strategy21
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• s.41
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• pp.30-51
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• 2017

Neighboring powers in the Korean Peninsula have started to develop and operate aircraft carriers or equivalent forces to cope with rising North Korean nuclear and missile threats and also to show its national might. For example, the United States has added a aircraft carrier from the 3rd fleet to western pacific theater of operation, while Peoples Republic of China is undergoing operational test of Liaoning as well as preparing for christening of its 2nd aircraft carrier. Japan is flexing its muscle as well by deploying Izumo capable of operating F-35B to Southeast Asia to participate in multilateral exercises starting this year. It is a high time to know more about aircraft carriers or similar types in terms of maritime strategy and history. The U.S. has had by far the vast amount of experiences in utilizing aircraft carrier that it would be beneficial for us to examine U.S. perspectives and its application in the Korean Peninsula. It will provide us with insights to understand and predict what it would be like in times of crisis in the Korean Peninsula in the perspective of aircraft carrier's involvement. This paper intends to show some aspects of future conflicts in the Korean Peninsula and how the ROK Navy can best be ready for such situation. For research purpose, U.S. maritime strategy has been developed in stages ; establishment phase, WWI phase, WWII phase, Cold war phase, post Cold war phase. Each phase includes such factors as threats, strategic concept, applications, and ways to improve maritime strategy. Finally, the role of aircraft carrier based on past history as well as future conflict shines the importance to have power projection capabilities for the ROK Navy. The intrinsic nature of the navy in the world is to project power ashore just as history proved it.

• Atmosphere
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• v.27 no.2
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• pp.199-211
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• 2017

The cold surges over East Asia can be grouped to two types of the wave-train and the blocking. Recently, the observational study proposed new dynamical index to objectively identify cold surge types. In this study, the dynamical index is applied to the simulations of 10 climate models, which participate in the Coupled Model Intercomparison Project Phase 5 (CMIP5). Focusing on assessment of cold surge simulation, we discuss characteristic of the wave-train and blocking cold surges in the climate models. The wave-train index (WI) and the blocking index (BI) based on potential temperature anomalies at dynamical tropopause over the subarctic region, the northeast China, and the western North Pacific enable us to classify cold surges in the climate models into two types. The climate models well simulate the occurrence mechanism of the wave-train cold surges with vertical structure related to growing baroclinic wave. However, while the wave-train in the observation propagates in west-east direction across the Eurasia Continent, most of the models simulate the southeastward propagation of the wave-train originated from the Kara Sea. For the blocking cold surges, the general features in the climate models well follow those in the observation to show the dipole pattern of a barotropic high-latitude blocking and a baroclinic coastal trough, leading to the Arctic cold surges with the strong northerly wind originated from the Arctic Sea. In both of the observation and climate models, the blocking cold surges tend to be more intense and last longer compared to the wave-train type.

• 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.

• Journal of Integrative Natural Science
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• v.4 no.1
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• pp.44-57
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• 2011

In general, heavy rainfall in Korea is mostly associated with inflow of 850hPa low-level jet. It transports abundant heat and moisture flux to the Changma front. In this study, synoptic characteristics of heavy rainfall in Korea from a case study is examined by classifying heavy rainfall cases with synoptic patterns, in particular distribution of upper- and low-level jets, western North Pacific high, and moisture flux. The surface and upper-level weather charts including auxiliary analysis chart and radar and satellite images obtained from the Korea Meteorological Administration, and 500hPa geopotential heights from NCEP/NCAR are used and then KLAPS is applied to understand the local atmospheric structure associated with heavy rainfall. Results show that maximum frequency in 60 heavy rainfall cases with more than 150mm/day appears in the Changma type of 43 cases (a proportion in relation to a whole is 52%) including the combined Changma types with typhoon and cyclone. As indicated in previous studies, most heavy rainfall cases are related to inflow of low-level jet. In addition, synoptic characteristics based on the analyses of weather charts, radar and satellite images, and KLAPS in heavy rainfall case of 12 July, 2009 reveal that the atmospheric vertical structure in particular equivalent potential temperature favorable for effective inflow of warm and moist southwesterly into the Changma front is linked to large potential instability and the strong convergence accompanied with low-level jet around Suwon contributes to atmospheric upsliding along the Changma front, producing heavy rainfall.

• Journal of Climate Change Research
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• v.7 no.1
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• pp.49-57
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• 2016

In the present study, the time series of the number of days on which temperatures were not higher than $-5^{\circ}C$ in winter in Seoul was analyzed. The results showed a decreasing tendency until recently. Statistical change-point analysis was conducted to examine whether climate regime shifts existed in this time series. According to the results, the number of days on which temperatures were not higher than $-5^{\circ}C$ in winter in Seoul drastically decreased since 1988. Therefore, to find out the reason for the recent decrease in the number of days, differences between the means of large-scale environments in winder during 1988~2010 and those during 1974~1987 were analyzed. In all layers of the troposphere, anomalous anticyclones developed in regions around the Korean Peninsula and thus the Korean Peninsula was affected by westerlies or south-westerlies. This was associated with the recent a little further northward development of western North Pacific subtropical high. Therefore, environments good for warm and humid air to flow into the Korean Peninsula were formed. To examine whether relatively warm and humid air actually flowed into the Korean Peninsula recently, temperatures and specific humidity in all layers in the troposphere were analyzed and according to the results the Korean Peninsula showed warm and humid anomalies. In the analyses of sensible heat net flux and maximum temperatures at a height of 2 m that can be felt by humans, the East Asia Continent including the Korean Peninsula showed positive anomalies.