• Atmosphere
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• v.16 no.2
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• pp.85-96
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• 2006

The six-year (2000~2005) record of aerosol optical thickness (AOT or $\tau$) data from the Moderate Resolution Imaging Spectroradiometer (MODIS) was analyzed over the Northeast Asia. The MODIS AOT standard products (MOD04_L2) over both ocean and land were collected to evaluate the spatial and temporal variability of the atmospheric aerosols over the study region ($32^{\circ}N{\sim}42^{\circ}N$ and $115^{\circ}E{\sim}133^{\circ}E$). The monthly averaged AOT result revealed slight changes(${\pm}0.002{\tau}/month$), which was almost unchangeable, over Korea. In contrast, the large AOT values (> 0.6) and a significant AOT increase (> 0.004 ${\tau}/month$) over East China were observed. For the analysis of spatio-temporal variability of AOT values, study area was divided by six sectors (I: North-East China, II: East China, III: Yellow Sea, IV: Korea Peninsular, V: East Sea, and VI: South Sea and Western part of Japan). The considerable result showed that particularly high AOT contribution was observed over sector I (32.5%) and II (25.5%) where some major urban and industrialized areas and agricultural fields are located and other cases were observed 13.2%, 14.6%, 7.1%, 7.0% over sector III, IV, V, and VI, respectively. In addition, yearly AOT changes based on seasons are observed differently at each sector but increasing trends reveal in summer and fall over all sectors.

• The Journal of Internal Korean Medicine
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• v.36 no.3
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• pp.348-360
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• 2015

Objectives From observing the tongue of a patient, one can assess the health status; this method has been frequently used in traditional Korean Medicine (KM) clinics. In particular, KM posits that the color of the tongue is highly related to digestive functions. In this study, the color of tongue and heart rate variability (HRV) were compared between chronic dyspepsia (CD) patients and healthy subjects. Methods Healthy subjects and CD patients with functional dyspepsia (FD), gastroesophageal reflux disease (GERD), or chronic gastritis (CG) were enrolled for the study. Profile view images of the tongue were acquired by using a computerized tongue image acquisition system (CTIS). The color of the tongue body was extracted from the non-coated region on the tongue images. Results Color differences in CIE L*a*b* color space between the three sub-types of CD patients and healthy subjects were analyzed by using multiple linear regression analysis with age and sex as the factors. The variable b* was significantly lower in GERD patients than in the controls (p=0.017). Variable a* was significantly lower in CG than in the controls (p=0.03). No significant difference was seen between FD and controls. In GERD, the tongue body seems to be intense red in color; in CG, pale red. Frequency domain analysis showed that HF was significantly lower in GERD patients than in the controls (p=0.041). Conclusions The color of the tongue body and HF of HRV can be used for diagnosing digestive functions in health care.

• Journal of the Korean earth science society
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• v.35 no.1
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• pp.88-94
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• 2014

The seasonal predictability of the intensity of the Northeast Asian summer monsoon is low while that of the western North subtropical high variability is, when state-of-the-art general circulation models are used, relatively high. The western North Pacific subtropical high dominates the climate anomalies in the western North Pacific-East Asian region. This study discusses the predictability of the western North Pacific subtropical High variability in the National Centers for Environmental Prediction Climate Forecast System (NCEP CFS). The interannual variability of the Northeast Asian summer monsoon is highly correlated with one of the western North Pacific subtropical Highs. Based on this relationship, we suggest a seasonal prediction model using NCEP CFS and canonical correlation analysis for Northeast Asian summer precipitation anomalies and assess the predictability of the prediction model. This methodology provides significant skill in the seasonal prediction of the Northeast Asian summer rainfall anomalies.

• Atmosphere
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• v.34 no.4
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• pp.359-369
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• 2024

This study evaluates the performance of various soil moisture reanalysis datasets over the East Asian region to identify the most suitable product for climate and hydrological studies. The analysis includes land reanalysis products generated by the Noah, VIC, and Catchment land surface models (LSMs), driven by GLDAS2.0 near-surface atmospheric forcing, alongside MERRA2 and ERA5-land datasets. The 62 in-situ soil moisture measurements observed from 1980 to 2014 are used to validate the modeled data across the entire study period, while 58 of these measurements are used for the May to September (MJJAS) period. Results indicate that, when driven by the same atmospheric forcing, the Noah and Catchment models outperform VIC, and MERRA2 shows lower errors compared to ERA5-land. Seasonal soil moisture variability, primarily driven by the East Asian monsoon, peaks in September, with MERRA2 providing the most realistic simulation of seasonal phase and amplitude. Daily soil moisture variations are better captured by MERRA2 and ERA5-land than by GLDAS2.0-based products. Overall, MERRA2 emerges as the most reliable reanalysis dataset for evaluating both the climatological mean and variability of soil moisture in East Asia. Additionally, multi-model mean analysis reveals a long-term trend of drying soil moisture and enhanced land-atmosphere coupling in northern East Asia.

• Journal of the Korean Geophysical Society
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• v.9 no.4
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• pp.397-408
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• 2006

Due to the temporal and spatial variability of the warming at and near the Antarctic Peninsular, it is required to better understand local climate at the issued region. The purpose of the study are to characterize surface radiation, air temperature and wind direction and investigate their relations at the King Sejong Station near the Antarctic Peninsular during last three and half years. While the study site was a weak radiative energy sink (positive net radiation) with annual mean of 15-20 Wm-2, it played a role as a strong sink in summer (December to January) with mean of 85 Wm-2, a magnitude that was significantly larger than those at other surface covered with snow or ice in Antarctica. Monthly averaged air temperature ranged from -7.7-2.8oC and the variations of monthly averaged air temperature showed the distinct differences with year. Northwesterly, westerly and easterly were dominant and the variability of air temperature could be explained by the variability of the frequency of wind direction with cold easterly and warm northwesterly/northerly to some degree, which in turn influenced radiation budget through albedo in summer.

• Communications of the Korean Mathematical Society
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• v.25 no.4
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• pp.557-569
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• 2010

Suppose that n is a positive integer. For any real number $\alpha$($\beta$ resp.) with $\alpha$ < 1 ($\beta$ > 1 resp.), let $K^{(n)}(\alpha)$ ($K^{(n)}(\beta)$ resp.) be the class of analytic functions in the unit disk $\mathbb{D}$ with f(0) = f'(0) = $\cdots$ = $f^{(n-1)}(0)$ = $f^{(n)}(0)-1\;=\;0$, Re($\frac{zf^{n+1}(z)}{f^{(n)}(z)}+1$) > $\alpha$ (Re($\frac{zf^{n+1}(z)}{f^{(n)}(z)}+1$) < $\beta$ resp.) in $\mathbb{D}$, and for any ${\lambda}\;{\in}\;\bar{\mathbb{D}}$, let $K^{(n)}({\alpha},\;{\lambda})$ $K^{(n)}({\beta},\;{\lambda})$ resp.) denote a subclass of $K^{(n)}(\alpha)$ ($K^{(n)}(\beta)$ resp.) whose elements satisfy some condition about derivatives. For any fixed $z_0\;{\in}\;\mathbb{D}$, we shall determine the two regions of variability $V^{(n)}(z_0,\;{\alpha})$, ($V^{(n)}(z_0,\;{\beta})$ resp.) and $V^{(n)}(z_0,\;{\alpha},\;{\lambda})$ ($V^{(n)}(z_0,\;{\beta},\;{\lambda})$ resp.). Also we shall determine the extreme points of the families of analytic functions which satisfy $f(\mathbb{D})\;{\subset}\;V^{(n)}(z_0,\;{\alpha})$ ($f(\mathbb{D})\;{\subset}\;V^{(n)}(z_0,\;{\beta})$ resp.) when f ranges over the classes $K^{(n)}(\alpha)$ ($K^{(n)(\beta)$ resp.) and $K^{(n)}({\alpha},\;{\lambda})$ ($K^{(n)}({\beta},\;{\lambda})$ resp.), respectively.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.87-87
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• 2023

The impact of climate change on typhoons is a major concern in East Asia, especially due to the destructive effects of heavy rainfall on society and the economy, as many megacities are located along coastal regions. Although observations suggest significant changes in typhoon heavy rainfall, the extent to which anthropogenic forcing contributes to these changes has yet to be determined. In this study, we demonstrate that anthropogenic global warming has a substantial impact on the observed changes in typhoon heavy rainfall in the western North Pacific region. Observation data indicates that, in general, typhoon heavy rainfall has increased (decreased) in coastal East Asia (tropical western North Pacific) during the latter half of the 20th century and beyond. This spatial distribution is similar to the "anthropogenic fingerprint" observed from a set of large ensemble climate simulations, which represents the difference between Earth systems with and without human-induced greenhouse gas emissions. This provides evidence to support the claim that the significant increase in the frequency of typhoon heavy rainfall along coastal East Asia cannot be solely explained by natural variability. In addition, our results indicate that the signal of the "anthropogenic fingerprint" has been increasing rapidly since the mid-1970s and departed from natural variability in the early 2000s, indicating that the regional summer climate has already crossed the tipping point.

• 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.

• Journal of Environmental Science International
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• v.2 no.1
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• pp.27-42
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• 1993

Based on the Results of Marine Meteorological and Oceanographical Observations during 1966∼1987 and the Ten-day Marine Report during 1970∼1989 by Japan Meteorological Agency, the possible area where the Japan Sea Proper Water (JSPW) can be formed is investigated by analyzing the distribution of water types in the Japan Sea. The Japan Sea can be divided into three subareas of Northern Cold Water(NCW), Polar Front(PF) and Tsushima Warm Current (TWC) by the Polar Front identified by a 6℃ isothermal line at the sea surface in vinter. Mean position of the Polar Front is approximately parallel to the latitude 39∼40。N. The standard deviation of the Polar Front from the mean position of about 130km width is the smallest in the region between 136。E and 138。E where the Polar Front is very stable, because the branches of the Tsushima Current are converging in this region. However, standard deviations are about 180∼250km near the Korean peninsula and the Tsugaru Strait due to greater variability of warm currents. In the NCW area north of 40∼30。N and west of 138。E, the water types of the sea surface to the loom depth are similar to those of the JSPW. This fact indicates that the surface layer of the NCW area is the possible region of the JSPW formation in winter.

• Journal of the Korean earth science society
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• v.27 no.7
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• pp.787-803
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• 2006

The drought index has been developed, based on a $8.6{\mu}m$ surface emissivity in the $8-12{\mu}m$ MODIS channels over the African Sahel region (10-20 N, 13 W-35 W) and the Seoul Metropolitan Area (SMA: 37.2-37.7 N, 126.6-127.2 E). The emissivity indicates the $SiO_2$ strength and can vary interannually by vegetation, water vapor, and soil moisture, as a potential indicator of drought conditions. In a well-vegetated region close to 10 N of the Sahel, the Normalized Difference Vegetation Index (NDVI) showed high sensitivity, while the emissivity did not. On the other hand, the NDVI experienced negligible variability in a poorly vegetated region near 20 N, while the emissivity reflected sensitively the effects of atmospheric water vapor and soil moisture conditions. Seasonal variations of the emissivity (0.94-0.97) have been examined over the SMA during the 2003-2004 period compared to NDVI (or Enhanced Vegetation Index; EVI). Here, the dryness was more severe in urban area with less vegetation than in suburban area; the two areas corresponded to the north and south of the Han river, respectively. The emissivity exhibiting a significant spatial correlation of ${\sim}0.8$ with the two indices can supplement their information.