• Proceedings of the KSRS Conference
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• 2008.10a
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• pp.224-227
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• 2008

Land cover and its changes, affecting multiple aspects of the environmental system such as energy balance, biogeochemical cycles, hydrological cycles and the climate system, are regarded as critical elements in global change studies. Especially in arid and semiarid regions, the observation of ecosystem that is sensitive to climate change can improve an understanding of the relationships between climate and ecosystem dynamics. The purpose of this research is analyzing the ecosystem surrounding the Gobi desert in North Asia quantitatively as well as qualitatively more concretely. We used Normalized Difference Vegetation Index (NDVI) derived from SPOT-VEGETATION (VGT) sensor during 1999${\sim}$2007. Ecosystem monitoring of this area is necessary because it is a hot spot in global environment change. This study will allow predicting areas, which are prone to the rapid environmental change. Eight classes were classified and compare with MODerate resolution Imaging Spectrometer (MODIS) global land cover. The time-series analysis was carried out for these 8 classes. Class-1 and -2 have least amplitude variation with low NDVI as barren areas, while other vegetated classes increase in May and decrease in October (maximum value occurs in July and August). Although the several classes have the similar features of NDVI time-series, we detected a slight difference of inter-annual variation among these classes.

• Ocean and Polar Research
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• v.30 no.1
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• pp.21-31
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• 2008

Analyzing the results of East Sea Regional Ocean Model using a 3-dimensional variational data assimilation scheme, we investigated spatial and temporal variability of the North Korean Cold Current (NKCC) in the East Sea. The climatological monthly mean transport of the NKCC clearly shows seasonal variation of the NKCC within the range of about 0.35 Sv ($=0^6m^3/s$), which increases from its minimum (about 0.45 Sv) through December-January to March, decreases during March and May, and then increases again to the maximum (about 0.8 Sv) in August-September. The volume transport of the NKCC shows interannual variation of the NKCC with the range of about 1.0 Sv that is larger than seasonal variation. The southward current of the NKCC appears often not only in summer but in winter as well. The width of the NKCC is about 35 km near the Korean coast and its core is located under the East Korea Warm Current. The North Korean Cold Water (NKCW), characterized by low salinity and low temperature, is located both under the Tsushima Warm Water and in the western side of the maximum southward current of the NKCC that means the NKCC advects the NKCW southward along the Korean coast. It is revealed that the intermediate low salinity water, formed off the Vladivostok in winter, flows southward to the south of $37^{\circ}N$ through $2{\sim}3$ paths; one path along the Korean coast, another one along $132^{\circ}E$, and the middle path along $130^{\circ}E$. The path of the intermediate low salinity varies with years. The reanalysis fields suggest that the NKCW is advected through the paths along the Korean coast and along $130^{\circ}E$.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.8 no.2
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• pp.94-110
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• 2003

This study utilizes the dataset of Topex/Poseidon(T/P) altimeter sea surface height (1992-2000 yr., 286 cycles)to investigate the tempore-spatial variability in the East (Japan) Sea. Optimal interpolation (Ol) technique was applied to the pre-processed T/P dataset (level 2) to produce sea surface height anomaly (SSHA) map on regular grids. Spectral analyses of the timeseries of the SSHA at chosen stations and empirical orthogonal function (EOF) analysis of the SSHA in the entire East Sea were made. Distribution of the SSHA can be divided by the southern and northern regions sharply by the polar front situated in the middle of the East Sea. The southern region under the direct influence of the Tsushima Current exhibits higher amplitude of the SSHA fluctuation, while the northern region does relatively smaller one. The spatio-temporal variability of the SSHA in the East Sea can be characterized by the five modes of the EOFs accounting for more than 85% of the total variance. The first mode dominates the SSHA variation in the entire domain with strong seasonal and inter-annual periods accounting for the 72.3% of the total variance. The other modes (up to 5th account for 14%) are responsible for the SSHA variation associated with the local current system, meandering of the polar frontal axis, and mesoscale eddies. Spectral peaks with significant confluence level show semi-annual, annual and interannual (2, 3-4 years) periods.

• Korean Journal of Remote Sensing
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• v.29 no.2
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• pp.219-233
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• 2013

In this study, spatio-temporal variations of Land Surface Emissivity (LSE) of the three LSE data sets in the Asian-Oceanian regions were addressed. The MODerate Resolution Imaging Spectroradiometer (MODIS) LSE, Cooperative Institute for Meteorological Satellite Studies (CIMSS) LSE, and Kongju National Univ. (KNU) LSE data sets were used. The three data sets showed very similar emissivity in the Tibetan Plateau, desert in the Middle East and Australia, and low latitude regions irrespective of season. The emissivity of $12{\mu}m$ was systematically greater than that of $11{\mu}m$, in particular, in the Tibetan Plateau, desert over Middle East and Australia. In general, they showed a weak seasonal variation in the low latitude regions although the emissivity was different among them. However, the three data sets showed quite different spatial and temporal variations in the other regions of Asian-Oceanian regions. The KNU LSE showed a systematic seasonal variation with a high emissivity during summer and low emissivity during winter but the other two LSE data sets showed irregular seasonal variations without regard to the regions. And the annual mean correlations of $11{\mu}m$ and $12{\mu}m$ between KNU LSE and MODIS LSE (KNU LSE and CIMSS LSE; MODIS LSE and CIMSS LSE) were 0.423 and 0.399 (0.330, 0.101; 0.541, 0.154), respectively. The relatively low correlations and strong inter-month variations, in particular, in $12{\mu}m$, indicated that consistency in spatial variation was very low. The comparison results showed that caution should be given before operational use of the LSE data sets in these regions.

• Ocean and Polar Research
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• v.33 no.spc3
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• pp.325-336
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• 2011

Seasonal to inter-annual variations of water properties in the western channel of the Korea Strait are investigated using quasi-monthly hydrographic observations collected during 2006-2010. Weak vertical temperature and salinity gradients are observed during the winter months and these remain until May. At the upper layer, temperature increases from March and reaches a maximum in August, while salinity decreases during the same period. Near-bottom water shows low temperatures during late winter and fall with a minimum peak in September. Korea Strait Bottom Cold Water produces thick layers (>20 m) in 2006 and 2010, while it is observed very near the bottom with relatively high temperature in 2008 and 2009.

• Journal of Astronomy and Space Sciences
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• v.14 no.1
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• pp.109-116
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• 1997

The Mesopause (85km) is the boundary between the Mesosphere and the Thermosphere and is very interesting region because there are active fluid dynamic motions and airglow phenomena due to various chemical reactions. But there have been not many studies due to the difficulties of insitu measurement. However in this study we have obtained the Doppler temperatures and winds through the observing Hydroxyl(OH) emission at 843nm using a ground-based Fabry-Perot interferometer. Due to the 2 years of long term observation, we can confirm the seasonal Mesopause temperature variation, which is the opposite trend against the temperature at the ground level, and reveal annual and biannual variations for meridional and zonal wind respectively. These seasonal variations might be the result of the inter-hemispheric circulation.

• Horticultural Science & Technology
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• v.31 no.1
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• pp.103-109
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• 2013

Estimating the high tuber solids needs a simulation system on potato growth, and its development should be obtained by using agricultural elements which analyze the relationship between crop growth and agricultural factors. An accurate simulation to predict solids level against climatic change employs a calculation of in vivo energy consumption and bias for growth and induction shape in a slight environmental adaptation. So, to calculate in vivo energy consumption, this study took a concept of estimate of the amount of basal metabolism in each tuber. In the validation experiments, the results of measuring solid accumulation of potatoes harvested at dates suggested by simulation agreed with the actual measured values in each regional field during the growth period of years from 2006 till 2010. The mean values of tuber solids level and inter-annual level variation in validation experiments were predicted well by the simulation model. And also, the results of validation experiments represent that concentration of tuber solids were due mainly to the duration of sunshine, above 190 hours per a month, and the cumulative amount of radiation, above 2,200 $MJ{\cdot}m^{-2}$, of the effective growth period.

• Korean Journal of Agricultural and Forest Meteorology
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• v.6 no.1
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• pp.61-69
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• 2004

A long-term growth simulation was performed at 99 land units in Yeoncheon county to test the potential adaptability of each land unit for growing soybean cultivars. The land units for soybean cultivation(CZU), each represented by a geographically referenced land patch, were selected based on land use, soil characteristics, and minimum arable land area. Monthly climatic normals for daily maximum and minimum temperature, precipitation, number of rain days and solar radiation were extracted for each CZU from digital climate models(DCM). The DCM grid cells falling within a same CZU were aggregated to make spatially explicit climatic normals relevant to the CZU. A daily weather dataset for 30 years was randomly generated from the monthly climatic normals of each CZU. Growth and development parameters of CROPGRO-soybean model suitable for 2 domestic soybean cultivars were derived from long-term field observations. Three foreign cultivars with well established parameters were also added to this study, representing maturity groups 3, 4, and 5. Each treatment was simulated with the randomly generated 30 years' daily weather data(from planting to physiological maturity) for 99 land units in Yeoncheon to simulate the growth and yield responses to the inter-annual climate variation. The same model was run with input data from the Crop Experiment Station in Suwon to obtain a 30 year normal performance of each cultivar, which was used as a "reference" for evaluation. Results were analyzed with respect to spatial and temporal variation in yield and maturity, and used to evaluate the suitability of each land unit for growing a specific cultivar. A computer program(MAPSOY) was written to help utilize the results in a decision-making procedure for agrotechnology transfer. transfer.

• Korean Journal of Agricultural and Forest Meteorology
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• v.14 no.1
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• pp.11-18
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• 2012

Daily temperature data produced by harmonic analysis of monthly climate summary have been used as an input to plant phenology model. This study was carried out to evaluate the performance of the harmonic based daily temperature data in prediction of major phenological developments and to apply the results in improving decision support for agricultural production in relation to the climate change scenarios. Daily maximum and minimum temperature data for a climatological normal year (Jan. 1 to Dec. 31, 1971-2000) were produced by harmonic analysis of the monthly climate means for Seoul weather station. The data were used as inputs to a thermal time - based phenology model to predict dormancy, budburst, and flowering of Japanese cherry in Seoul. Daily temperature measurements at Seoul station from 1971 to 2000 were used to run the same model and the results were compared with the harmonic data case. Leaving no information on annual variation aside, the harmonic based simulation showed 25 days earlier release from endodormancy, 57 days longer period for maximum cold tolerance, delayed budburst and flowering by 14 and 13 days, respectively, compared with the simulation based on the observed data. As an alternative to the harmonic data, 30 years daily temperature data were generated by a stochastic process (SIMMETEO + WGEN) using climatic summary of Seoul station for 1971-2000. When these data were used to simulate major phenology of Japanese cherry for 30 years, deviations from the results using observed data were much less than the harmonic data case: 6 days earlier dormancy release, 10 days reduction in maximum cold tolerance period, only 3 and 2 days delay in budburst and flowering, respectively. Inter-annual variation in phenological developments was also in accordance with the observed data. If stochastically generated temperature data could be used in agroclimatic mapping and zoning, more reliable and practical aids will be available to climate change adaptation policy or decision makers.

• Korean Journal of Agricultural and Forest Meteorology
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• v.18 no.4
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• pp.366-377
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• 2016

Water use efficiency (WUE) is considered as an important ecological indicator which may provide information on the process-structure relationships associated with energy-matter-information flows in ecosystem. The WUE at ecosystem-level can be defined as the ratio of gross primary productivity (GPP) to evapotranspiration (ET). In this study, KoFlux's long-term (2007-2015) eddy covariance measurements of $CO_2$ and water vapor fluxes were used to examine the WUE of needle fir plantation in Korea National Arboretum. Our objective is to ascertain the seasonality and inter-annual variability in WUE of this needle fir plantation so that the results may be assimilated into the development of a holistic ecological indicator for resilience assessment. Our results show that the WUE of needle fir plantation is characterized by a concave seasonal pattern with a minimum ($1.8-3.3g\;C{\cdot}(kg\;H_2O)^{-1}$) in August and a maximum ($5.1-11.4g\;C{\cdot}(kg\;H_2O)^{-1}$) in February. During the growing season (April to October), WUE was on average $3.5{\pm}0.3g\;C\;(kg\;H_2O)^{-1}$. During the dormant seasons (November to March), WUE showed more variations with a mean of $7.4{\pm}1.0g\;C{\cdot}(kg\;H_2O)^{-1}$. These values are in the upper ranges of WUE reported in the literature for coniferous forests in temperate zone. Although the growing season was defined as the period from April to October, the actual length of the growing season (GSL) varied each year and its variation explained 62% of the inter-annual variability of the growing season WUE. This is the first study to quantify long-term changes in ecosystem-level WUE in Korea and the results can be used to test models, remote-sensing algorithms and resilience of forest ecosystem.