• Ocean and Polar Research
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• v.30 no.3
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• pp.351-359
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• 2008

In an effort to develop high-resolution sea surface temperature (SST) proxies for mid-latitude regions, two massive reef-building coral species, Alveopora and Favia, were collected from Jeju and Tsushima Islands, respectively. Their skeletons were subsequently analyzed for annual growth banding, Sr/Ca and Mg/Ca ratios. Hermatypic corals are thinly distributed in the waters of Jeju Island, where Alveopora japonica was the only dominant coral species. A higher diversity of hermatypic corals were observed in the waters of Tsushima Island, where Favia sp. was the most common coral species and even forming an about 6-m-high reef structure. Both Alveopora and Favia showed annual growth layers consisting of couplets of high- and low-density bands. Sr/Ca ratio of both species and Mg/Ca ratio of Alveopora also showed seasonal variation, likely reflecting SST variation. These results suggest the possibility that Alveopora and Favia species can be used as potential SST proxies. However, this study also highlights the potential growth disturbance of middle latitude corals due to high rainfall during monsoon and low SST during winter. This possibility should be taken into account in the investigation of Sr/Ca(Mg/Ca)-SST relationships.

• Bulletin of the Korean Space Science Society
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• 2010.04a
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• pp.30.3-31
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• 2010

We performed a comprehensive comparison between GPS Global Ionosphere Map (GIM) and TOPEX/Jason (T-J) TEC data for the periods of 1998~2009 in order to assess the performance of GIM over the global ocean where the GPS ground stations are very sparse. Using the GIM model constructed by CODE at University of Bern, the GIM TEC values were obtained along the T-J satellite orbit at the locations and times of the measurements and then binned into various geophysical conditions for direct comparison with the T-J TECs. On the whole, the GIM model was able to reproduce the spatial and temporal variations of the global ionosphere as well as the seasonal variations. However, the GIM model was not accurate enough to represent the well-known ionospheric structures such as the equatorial anomaly, the Weddell Sea Anomaly, and the longitudinal wave structure. Furthermore, there seems to be a fundamental limitation of the model showing the unexpected negative differences (i.e., GPS < T-J) in the northern high latitude and the southern middle and high latitude regions. The positive relative differences (i.e., GIM > T-J) at night represent the plasmaspheric contribution to GPS TEC, which is maximized, reaching up to 100% of the corresponding T-J TEC values in the early morning sector. In particular, the relative differences decreased with increasing solar activity and this may indicate that the plasmaspheric contribution to the maintenance of the nighttime ionosphere does not increase with solar activity, which is different from what we normally anticipate. Among these results, the plasmaspheric contribution to the ionospheric GPS TEC will be presented in this talk and the rest of it will presented in the companion paper (poster presentation).

• Journal of Space Technology and Applications
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• v.3 no.3
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• pp.239-256
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• 2023

The Earth's ionosphere is an area where part of the upper atmosphere is ionized and exists in a plasma state that affects radio waves. It is a field that has been studied for a long time as it directly affects real life in relation to communications. Depending on the altitude, it is divided into D, E, and F layers depending on the main ions that make up the electron density. The density of the neutral atmosphere is very large compared to the electron density, so it should be described as plasma taking that effect into account. It is an area where influences from outside the ionosphere are directly reflected, starting from the sun and extending to the earth's surface, and is a field that involves complex and diverse areas of research. In this paper, we explain the process by which the Earth's upper atmosphere is ionized to form the ionosphere and introduce the characteristics of the ionosphere at low and mid-latitudes. In addition, we introduce the research that domestic researchers have participated in related to the ionosphere to date and hope that it will be used to promote exchange in the field of ionospheric research in the future.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.49 no.6
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• pp.849-855
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• 2016

The community composition and distribution of fish species in the middle of the Yellow Sea were investigated in summer from 2008 to 2014. A total of 72 demersal fish species from 46 families and 17 orders were collected. The most common species were Larimichthys polyactis, Engraulis japonicus, and Chaeturichthys hexane, which accounted for 72.0% of the total number of individuals while Liparis tanakai, Larimichthys polyactis, and Lophius litulon accounted for 67.8% of the total biomass. A cluster analysis based on the Bray-Curtis similarity revealed that the fish community fell into three groups, according to latitude. Principal Component Analysis (PCA) and correlation analysis showed that variation in bottom water temperature could act as an indicator of variation in community structure and abundance of the dominant species. Characteristics of fish communities, such as the number of species, the total number of individuals ($/km^2$), and biomass ($/km^2$), were highly correlated with bottom water temperature and depth.

• Korean Journal of Environment and Ecology
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• v.22 no.5
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• pp.564-594
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• 2008

For this study, which was conducted in summer from $2006{\sim}2007$, 25 places of stream area in Korea, which were not affected by human, were selected by considering variable environmental factors. Plant surveys were performed in five qaudrats per each place of stream area(stream length=about 1km) on the basis of Braun-Blanquet(1964) and in four belt(length=20m) per each place of stream area by using belt-transect method in order to study the vegetation of the present-day potential natural state of water. In the results of the plant survey, the common plant communities in the mid-northern district(latitude$37^{\circ}37.9^{\circ}N$) were Quercus mongolica community and Fraxinus rhynchophylla community(with Quercus mongolica and Quercus aliena), and the common plant communities in the southern district(latitude$35^{\circ}35.9^{\circ}N$) were Quercus serrata community, Styrax japonica community and Quercus variabilis community. The common plant communities in the central district(latitude$36^{\circ}36.9^{\circ}N$) were Quercus serrata community, Fraxinus rhynchophylla community and Quercus aliena community, which have the middle characteristic between mid-northern and southern district. Also, in the results of correlation analysis between environmental factors and appearance of plant species in the survey places of stream area, Eco region showed the most significant correlation, but for the plan to restore flood plain, it is necessary to clarify the vegetation of potential natural stream by increasing the number of study cases considering variable environmental factors, in the future.

• Korean journal of applied entomology
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• v.62 no.4
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• pp.227-243
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• 2023

The Asiatic pink stem borer, Sesamia inferens (Walker, 1856) (Lepidoptera: Noctuidae) is a pest that attacks rice stems. In this study, we estimated the annual generation of insect in several regions of the Republic of Korea. Adult trapping using a sex pheromone trap detected the occurrence of S. inferens adults in the three northernmost areas around 38° latitude and showed that the insect inhabits all of Korea. In most areas investigated, the seasons of the adult generations estimated using the single-sine degree-day model did not deviate from the corresponding observed seasons of adult occurrence. We estimated that the overwintering larvae hypothetically-estimated using the model could be originated from the last generation of adults. When larvae collected in paddy fields during the autumn season in a few middle and southern areas were reared at 25℃, ca. 70% of pupae did not show additional larval molting before their pupation. All larvae collected in early March in a southern area (Goseong, Gyeongsangnam-do) pupated without additional larval molting when reared at 25℃. Based on these results, we presumed that S. inferens could overwinter as mainly the last instar larval stage in the area. Taken together, we conclude that S. inferens primarily has two generations per year in areas around 38° latitude, and three generations in the areas between 35.3° and 37.3° latitude. In addition, approximately 35% of insects captured by the sex pheromone trap were species other than S. inferens, as determined by analyzing the nucleotide sequences of the cytochrome c oxidase 1 gene. These species were not morphologically misidentified as S. inferens.

• 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.

• Korean Journal of Remote Sensing
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• v.37 no.6_1
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• pp.1631-1645
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• 2021

This research aims to provide the characteristics of the world's first active lidar sensor Atmospheric Laser Doppler Instrument (ALADIN) wind data and Geostationary Korea Multi Purpose Satellite 2A (GK2A) Atmospheric Motion Vector (AMV) data by comparing two wind data. As a result of comparing the data from September 2019 to August 1, 2020, The total number of collocated data for the AMV (using IR channel) and Mie channel ALADIN data is 177,681 which gives the Root Mean Square Error (RMSE) of 3.73 m/s and the correlation coefficient is 0.98. For a more detailed analysis, Comparison result considering altitude and latitude, the Normalized Root Mean Squared Error (NRMSE) is 0.2-0.3 at most latitude bands. However, the upper and middle layers in the lower latitudes and the lower layer in the southern hemispheric are larger than 0.4 at specific latitudes. These results are the same for the water vapor channel and the visible channel regardless of the season, and the channel-specific and seasonal characteristics do not appear prominently. Furthermore, as a result of analyzing the distribution of clouds in the latitude band with a large difference between the two wind data, Cirrus or cumulus clouds, which can lower the accuracy of height assignment of AMV, are distributed more than at other latitude bands. Accordingly, it is suggested that ALADIN wind data in the southern hemisphere and low latitude band, where the error of the AMV is large, can have a positive effect on the numerical forecast model.

• Journal of the Korea Institute of Military Science and Technology
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• v.19 no.4
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• pp.551-558
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• 2016

We analyzed wind speed over South Korea for HALE UAV(High Altitude Long Endurance Unmaned Aerial Vehicle) flight safety. Annual variation of wind speed at 200 hPa showed that winter season was stronger than summer. According to latitude, wind speeds in January and August were found to be $52{\sim}74m\;s^{-1}$ and $15{\sim}26m\;s^{-1}$, respectively. Wind speed was stronger(weaker) at lower latitudes than higher latitudes in winter(summer). Frequency(%) of wind speed less than threshold value($18m\;s^{-1}$) for the operation date was investigated. The days showing the frequency greater than 60 % in all altitudes of surface ~ 50 hPa showed the range of 1 ~ 33 days at 7 stations. Operation date was the longest period at Gosan. The appropriate date of HALE UAV operation at Gosan and Osan is considered as the middle of July ~ middle of August and end of July ~ early August, respectively. These results can be used to determine the operation date of HALE UAV.

• The Korean Journal of Quaternary Research
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• v.17 no.2
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• pp.33-38
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• 2003

This study is conducted to examine the data of climate or environmental change in the northeastern Asia during the last glacial maximum. A remarkable feature of the 18,000 BP biome reconstructions for China is the mid-latitude extention of steppe and desert biomes to the modem eastern coast. Terrestrial deposits of glacial maximum age from the northern part of Yellow Sea suggest that this region of the continental shelf was occupied by desert and steppe vegetation. And the shift from temperate forest to steppe and desert implies conditions very much drier than present in eastern Asia. Dry conditions might be explained by a strong winter monsoon and/or a weak summer monsoon. A very strong depression of winter temperatures at LGM. has in the center of continent has influenced in northeast Asia similarly. The vegetation of Hokkaido at LGM was subarctic thin forest distributed on the northern area of middle Honshu and cool and temperate mixed forest at southern area of middle Honshu in Japan. The vegetation landscape of mountain- and East coast region of Korea was composed of herbaceous plants with sparse arctic or subarctic trees. The climate of yellow sea surface and west region of Korea was much drier and temperate steppe landscape was extended broadly. It is supposed that a temperate desert appeared on the west coast area of Pyeongan-Do and Cheolla-Do of Korea. The reconstruction of year-round conditions much colder than today right across China, Korea and Japan is consistent with biome reconstruction at the LGM.