• Journal of Environmental Impact Assessment
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• v.19 no.2
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• pp.169-177
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• 2010

One of the most obvious climatic manifestations of urbanization in Korea is a trend towards higher air temperature. The trends of long-term annual temperature generally well describe the warming of urban areas. The increase of air temperature in urban area has been observed to the present since the meteorological observations in Korea began. The objective of this study is to explore the actual increase and the regional long-term trends of air temperature attributed to urbanization in the Korean Peninsula. Therefore, temperatures of the selected urban areas were compared with that of the surrounding rural areas, with the results varying by the application of the estimates of each region. The second objective is to separate the long-term trend of surface air temperature of global warming from urbanization and to find the actual temperature increase from urbanization in Korean peninsula. For the data analysis, daily air temperatures observed by the Korea Meteorological Administration (KMA) during between from 1961 and 2005 were used at five rural sites and cities. The re-analyzed surface air temperatures by the National Centers for Environmental Prediction (NCEP) was also carried out to compare the result from the observed air temperature in the Korean climate domain. In this study, the urban areas in Korea showed high increase rate of air temperature with $0.4^{\circ}C$ per decade during past 50 year period, while rural sites as Chupungryung with the $0.2^{\circ}C$ decadal increase rate. The analyses reflect that the urban area shows the high rate of temperature increase with $1.39^{\circ}C$ of regression value at the urban area, Seoul, and $0.43^{\circ}C$ at the rural site, Chupungnyeong during the period of 30 years. The temperature increas due to the urbanization only showed the increase range between $0.44^{\circ}C$ and $0.86^{\circ}C$, and the observed decrease in diurnal temperature range at five urban areas during the 30 years period.

• Korean Journal of Remote Sensing
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• v.24 no.6
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• pp.535-549
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• 2008

Vicarious calibration for the satellite sensor relies on simulated TOA (Top-of-Atmosphere) radiances over various targets. In this study, TOA visible radiance was calculated over ocean targets which are located in five different regions over the Indian and Pacific ocean, and its possible use for the satellite sensor calibration was examined. TOA radiances are simulated with the 6S radiative transfer model for the comparison with MODIS/Terra and SeaWiFS measurements. Geometric angles and sensor characteristics of the reference satellites were taken into account for the simulation. AOT (Aerosol Optical Thickness) from MODIS/Terra, pigment concentrations from Sea WiFS, and ozone amount from OMI measurements were used as inputs to the model. Other atmospheric input parameters such as surface wind and total column water vapor were taken from NCEP/NCAR reanalysis data. The 5-day averaged radiances over all targets show that the percent differences between simulated and observed radiances are within about ${\pm}5%$ in year 2005, indicating that the calculated radiances are in good agreement with satellite measurements. It has also been shown that the algorithm can produce the SeaWiFS radiances within about ${\pm}5%$ uncertainty range. It has been suggested that the algorithm can be used as a tool for calibrating the VIS bands within about 5% uncertainty range.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.24 no.1
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• pp.79-91
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• 2019

Long-term trends and recent variations of upwelling index (UI), which affects significantly ecosystem in southwestern part of the East Sea, were investigated. The UI was calculated with the NCEP/NCAR reanalysis data from January 1948 to September 2018. The mean UI has positive value that causes upwelling in April to August with a peak in July. The long-term reducing trend of UI was in statistically significant in June and July, and the sum of UI in May, June and July also showed same result. Through the atmospheric pressure analysis around the Korean peninsula, it was found that the trend of the UI was the influence of the pressure change trend in the northwestern region ($35-50^{\circ}N$, $114-129^{\circ}E$) of the southwestern part of the East Sea. Investigating UI in recent 7 years from 2012 to 2018, it was revealed that the UI was bigger than 3 times of standard deviation in July 2013. This was result from the sea level pressure difference became larger in the southwestern part of the East Sea than normal year due to the lowered air pressure in the northeastern region of China and the strengthened high air pressure of western peripheral of the North Pacific High. On the other hand, the UI in July 2018 was negative when the impact of the North Pacific High and the low air pressure in the northeastern China was weak. Due to the decreasing trend of UI and its large year-to-year variation in southwestern part of the East Sea, continuous monitoring is necessary to know the influence of coastal upwelling on the ecosystem.

• Atmosphere
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• v.15 no.2
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• pp.91-99
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• 2005

This study compares the summer monsoon circulations during a heavy rainfall period over the Korean peninsular from 11 to 18 July 2004, simulated by three widely used regional models; WRF, MM5, and RSM. An identical model setup is carried out for all the experiments, except for the physical option differences in the RSM. The three models with a nominal resolution of about 50 km over Korea are nested by NCEP-DOE reanalysis data. Another RSM experiment with the same cumulus parameterization scheme as in the WRF and MM5 is designed to investigate the importance of the representation of subgrid-scale parameterized convection in reproducing monsoonal circulations in East Asia. All thee models are found to be capable of reproducing the general distribution of monsoonal precipitation, extending northeastward from south China across the Korean peninsula, to northern Japan. The results from the WRF and MM5 are similar in terms of accumulated precipitation, but a slightly better performance in the WRF than in the MM5. The RSM improves the bias for precipitation as compared to those from the WRF and MM5, but the pattern correlation is degraded due to overestimation of precipitation in northern China. In the comparison of simulated synoptic scale features, the RSM is found to reproduce the large-scale features well compared to the results from the MM5 and WRF. On the other hand, the simulated precipitation from the RSM with the convection scheme used in the MM5 and WRF is closer to that from the WRF and MM5 simulations, indicating the significant dependency of simulated precipitation in East Asia on the cumulus parameterization scheme.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• v.10 no.S_4
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• pp.197-206
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• 2001

The long-range transport mechanisms of Asian dust were analyzed based on the synoptic weather system and numerical simulation by using NCEP/NCAR reanalysis and TOMS data during the periods of 1996-2001. We classified the whole weather types of eastern Asia during spring and created the representative weather types during the yellow sand events using cluster analysis and weather charts for the last 6 years(1996~2001). These long-range transport mechanisms were related to various pressure patterns including high and low, trough and ridge, and upper-level fronts. Case studies of the yellow sand events have performed by the simulation of MM5 with meteorological elements such as the horizontal wind of u and v component, potential temperature, potential vorticity, and vertical circulation during the episodic days(2~8 March 2001). In addition, the origin of the long-range transport was examined with the estimation of backward trajectory using HYSPLIT4 Model. In this paper, we concluded that three weather types at 1000 hPa, 850 hPa, 500 hPa, and 300 hPa levels were classified respectively. The dominant features were the extending continental outflow from China to Korea at 1000 hPa and 850 hPa levels, the deep trough passage and cold advection at 500 hPa and 300 hPa levels during the yellow sand events. And also, we confirmed the existence of pola $r_tropical jets in the upper-level, the behavior of potential vorticity over Korea, the estimation of potential vorticity through vertical cross section, and the transport of yellow sand through backward trajectories.es.

• Atmosphere
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• v.22 no.4
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• pp.401-413
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• 2012

In this study, an investigation has been carried out to understand 1) temporal variation of rainfall amount in summer over south Korea during the 30-year period of 1979-2008 and 2) the relationship between the variation of rainfall amount and the change of large-scale monsoon circulation around 1993/1994 over East Asia. The analysis of rainfall amount is carried out separately for whole summer (June-August), climatological Changma period of 23 June-23 July, and August to consider variations within summer. To relate the variation of rainfall amount with the change of large-scale circulation, we have considered two 15-year periods of 1979-1993 and 1994-2008. This study has used observations at 58 stations in South Korea and NCEP-NCAR $2.5^{\circ}{\times}2.5^{\circ}$ reanalysis data. The major change in synoptic environment for the Changma period is characterized by the intensified anticyclone over Mongolia during 1994-2008, which results in a weak meridional oscillation of Changma front. As a result, rainfall amount for the Changma period and the frequency of extreme events have significantly increased after 1993/1994. A major change of synoptic environment for August is the significant westward extension of the western Pacific subtropical high, which allows not only more moisture transports but also stronger cyclonic circulation over the Korean peninsula. Rainfall amount for August and frequency of extreme events have also increased after 1993/1994. However, variability of rainfall amount is larger for August than that for the Changma period, with some years showing very dry August (monthly rainfall amount less than 150 mm).

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.229-229
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• 2015

Downscaling is a fundamental procedure in the assessment of the future climate change impact at regional and watershed scales. Hence, it is important to investigate the spatial variability of the climate conditions that are constructed by various downscaling methods in order to assess whether each method can model the climate conditions at various spatial scales properly. This study introduces a fundamental research from Jang and Kavvas(2015) that precipitation variability from a popular statistical downscaling method (BCSD) and a dynamical downscaling method (MM5) that is based on the NCAR/NCEP reanalysis data for a historical period and on the CCSM3 GCM A1B emission scenario simulations for a projection period, is investigated by means of some spatial characteristics: a) the normalized standard deviation (NSD), and b) the precipitation change over Northern California region. From the results of this study it is found that the BCSD method has limitations in projecting future precipitation values since the BCSD-projected precipitation, being based on the interpolated change factors from GCM projected precipitation, does not consider the interactions between GCM outputs and local geomorphological characteristics such as orographic effects and land use/cover patterns. As such, it is not clear whether the popular BCSD method is suitable for the assessment of the impact of future climate change at regional, watershed and local scales as the future climate will evolve in time and space as a nonlinear system with land-atmosphere feedbacks. However, it is noted that in this study only the BCSD procedure for the statistical downscaling method has been investigated, and the results by other statistical downscaling methods might be different.

• Atmosphere
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• v.23 no.2
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• pp.187-204
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• 2013

This study analyzed the synoptic distribution and vertical structure about four cases of precipitation occurrences using NCEP/NCAR reanalysis data and upper level data of winter intensive observation to be performed by National Institute of Meteorological Research at Bukgangneung, Incheon, Boseong during 63days from 4 JAN to 6 MAR in 2012, and Observing System Experiment (OSE) using 3DVAR-WRF system was conducted to examine the precipitation predictability of upper level data at western and southern coastal regions. The synoptic characteristics of selected precipitation occurrences were investigated as causes for 1) rainfall events with effect of moisture convergence owing to low pressure passing through south sea on 19 JAN, 2) snowfall events due to moisture inflowing from yellow sea with propagation of Siberian high pressure after low pressure passage over middle northern region on 31 JAN, 3) rainfall event with effect of weak pressure trough in west low and east high pressure system on 25 FEB, 4) rainfall event due to moisture inflow according to low pressures over Bohai bay and south eastern sea on 5 MAR. However, it is identified that vertical structure of atmosphere had different characteristics with heavy rainfall system in summer. Firstly, depth of convection was narrow due to absence of moisture convergence and strong ascending air current in middle layer. Secondly, warm air advection by veering wind with height only existed in low layer. Thirdly, unstable layer was limited in the narrow depth due to low surface temperature although it formed, and also values of instability indices were not high. Fourthly, total water vapor amounts containing into atmosphere was small due to low temperature distribution so that precipitable water vapor could be little amounts. As result of OSE conducting with upper level data of Incheon and Boseong station, 12 hours accumulated precipitation distributions of control experiment and experiments with additional upper level data were similar with ones of observation data at 610 stations. Although Equitable Threat Scores (ETS) were different according to cases and thresholds, it was verified positive influence of upper level data for precipitation predictability as resulting with high improvement rates of 33.3% in experiment with upper level data of Incheon (INC_EXP), 85.7% in experiment with upper level data of Boseong (BOS_EXP), and 142.9% in experiment with upper level data of both Incheon and Boseong (INC_BOS_EXP) about accumulated precipitation more than 5 mm / 12 hours on 31 January 2012.

• Journal of the Korean Geographical Society
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• v.51 no.1
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• pp.23-40
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• 2016

In this study, long-term changes in means and extreme events of precipitation during summer rainy period called Changma (late June~early September) are examined based on rainfall data observed by Chukwooki during Joseon Dynasty (1777~1907) and by modern rain-gauge onward (1908~2015) in Seoul, Korea. Also, characterizations of the relevant changes in synoptic climate fields in East Asia are made by the examination of the NCEP-NCAR reanalysis I data. Analyses of 239-year time series of precipitation data demonstrate that the total precipitation as well as their inter-annual variability during the entire Changma period (late June~early September) has increased in the late 20th century and onward. Notably, since the early 1990s the means and extreme events during the summer Changma period (late June~mid-July) and Changma break period (late July~early August) has significantly increased, resulting in less clear demarcations of sub-Changma periods. In this regard, comparisons of synoptic climate fields before and after the early 1990s reveal that in recent decades the subtropical high pressure has expanded in the warmer Pacific as the advection of high-latitude air masses toward East Asia was enhanced due to more active northerly wind vector around the high pressure departure core over Mongolia. Consequently, it is suggested that the enhancement of rising motions due to more active confluence of the two different air masses along the northwestern borders of the Pacific might lead to the increases of the means and extreme events of Changma precipitation in Seoul in recent decades.

• Ocean and Polar Research
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• v.25 no.4
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• pp.503-518
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• 2003

This study examines the relationship among temperature, wind, and sea level pressure to understand recent warming in the vicinity of the Antarctic Peninsula. To do this, the surface air temperature, NCEP/NCAR reanalysis wind data and sea level pressure data for the period of 40 years are analyzed. The 40-year surface air temperature data in the Antarctic Peninsula reveals relatively the larger warming trends for autumn and winter than other seasons. The variability of the surface air temperature in this region is compared with that of the regional atmospheric circulation. The surface air temperature is positively correlated with frequency of northwesterlies and negatively correlated with frequency of southeasterlies. This relation is more evident in the northern tip of the Antarctic Peninsula for autumn and winter. The trend analysis of wind frequency in the study area shows increasing and decreasing trends in the frequency of northwesterlies and southeasterlies, respectively, in the northwestern part of the Weddell Sea for autumn and winter. And also it is found that these winds are closely related with decreasing of sea level pressure in the southeastern region of the Antarctic Peninsula. Furthermore from the seasonal variation of sea level pressure in this area, it may be presumed that decreasing of sea level pressure in the southeastern region of the Antarctic Peninsula is related with warming in the vicinity of the Antarctic Peninsula for autumn and winter. Therefore it can be explained that recent warming in the vicinity of the Antarctic Peninsula is caused by positive feedback mechanism, that is, the process that warming in the vicinity of the Antarctic Peninsula can lead to the decrease of sea level pressure in the southeastern region of the Antarctic Peninsula and these pressure decrease in turn lead to the variation of wind direction in northwestern part of Weddell Sea, again the variation of wind direction enhances the warming in the Antarctic Peninsula.