• Solar Energy
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• v.13 no.1
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• pp.67-74
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• 1993

Solar radiation intensity in Cheju-Do has been measured and analyzed to study the its characteristic and the possibility of the alternative energy, This work will also support the on-going project "Clean Enertopia in Cheju" which is strongly driven by government recently. The results of this project indicate that 1) Insolation in Cheju-Do is 10% lower than Southern coastal area. 2) A significant difference of insolation is observed between western and eastern part of Cheju-Do.

• Journal of Ecology and Environment
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• v.29 no.4
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• pp.365-379
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• 2006

Collection of moths in four Gotjawal terrains of Jeju Island was conducted using black light trap, beginning July through September 2005. The insects investigated were classified into 146 species, 15 families and 7 superfamilies, and Noctuoidea appeared to have accounted for 41.1%, or 60 species, which was the largest number among them, followed by Geometroidea. Ercheia niveostrigata was found to have been the dominant species over the entire area. The diversity index showed the highest at Aewol Gotjawal and the lowest at Hangyeong-Andeog Gotjawal. Aewol Gotjawal formed a cluster with Gujwa- Sungsan Gotjawal at the lowest chord distance (0.75). At the higher chord distance of 0.82, Jocheon- Hamdeog Gotjawal fused the cluster of Aewol Gotjawal and Gujwa-Sungsan Gotjawal. Hangyeong-Andeog Gotjawal fused with the rest three terrains, forming a single cluster at the highest chord distance of 0.89.

• Journal of the Korean Society of Groundwater Environment
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• v.1 no.1
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• pp.33-50
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• 1994

The Hydrogeologic data of 455 water wells comprising geologic log and aquifer test were analyzed to determine hydrogeologic characteristics of the Cheju island. The groundwater. of the Cheju island is occurred in unconsolidated pyroclastic deposits and crinker interbedded in highly jointed basaltic and andesic rocks as high level, basal and parabasal types under unconfined condition. The average transmissivity and specific yield of the aquifer are at about 29,300㎡/day and 0.12 respectively, The total storage of groundwater is estimated about 44 billion cubic meters. Average annual precipitation is about 3,390 million ㎥ among which average recharge is estimated for 1,494 million ㎥ being equivalent 44.1% of total annual precipitation with 638 million ㎥ of runoff and 1,256 million ㎥ of evapotranspiration. Based on groundwater budget analysis, the sustainable yield is about 620 million ㎥(41% of annual recharge)and rest is discharging into the sea. The geologic logs of recently drilled thermal water wells indicate that very low-permeable marine sediments(Sehwa-ri formation) composed of loosely cemented sandy silt derived from mainly volcanic ashes at the 1st stage volcanic activity of the area is situated at the 120${\pm}$68m below sea level. Another low-permeable sedimentary rock called Seogipo-formation which is deemed younger than the former marine sediment is occured at the area covering north-west and western part of the Cheju island at the ${\pm}$70m below sea level. If these impermeable beds art distributed as a basal formation of fresh water zone of the Cheju island, the most of groundwater in the Cheju island will be para-basal type. These formations will be one of the most important hydrogeologic boundary and groundwater occurences in the area.

• Korean Journal of Ichthyology
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• v.18 no.3
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• pp.184-192
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• 2006

To investigate reproductive cycle of Tridentiger obscurus in Jeju, total 408 fish were collected in brackish area (May 2004 to August 2005) and total 271 fish were collected in tidal pool (July 2004 to August 2005), respectively. Water temperature ranged $11.0{\sim}21.6^{\circ}C$ in brackish area. Water temperature of tidal pool ($11.1{\sim}24.5^{\circ}C$) in 2005 was similar to that of brackish area although it were highest $30.1{\sim}29.2^{\circ}C$ from July to August in 2004. In brackish area, female gonadosomatic index (GSI) increased in April and maintained high values from May to August. The reproductive cycle can be grouped into the following successive stages in the ovary: immature (November to May), maturing (March to September), ripe and spawning (May to September), and degenerating (July to December). In the tidal pool, female GSI rapidly increased in April and maintained high values until July in 2005. However, it has been low in July 2004 when water temperature was highest. The reproductive cycle can be grouped into the following successive stages in the ovary: immature (August to April), maturing (March to August), ripe and spawning (March to July), and degenerating (July to August 2004 and August 2005). Fecundity of mature female ranged from 1,214 to 12,109 in brackish and ranged from 2,427 to 13,892 in tidal pool area. The fecundity of fish in the tidal pool was significantly higher than that of fish in brackish area. Fecundity was correlated positively with total length and body weigh. Although the large group (> 111 mm total length) in brackish area observed only in spawning season, one in the tidal pool observed from October 2004 until next spawning season. Frequency of the large group was 0 to 12% and 11.4 to 57.9% in brackish area and tidal pool, respectively. These results were indicated that gonadal development of T. obscurus was affected to water temperature and day length.

• Journal of Korean Society of Water and Wastewater
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• v.13 no.3
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• pp.83-90
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• 1999

This study was carried out to investigate the characteristics of trihalomethane (THM) formation from chlorination of groundwater in the northeastern area of Cheju Island. Effects of total organic carbon (TOC) and bromide in groundwater on the THM formation were studied. Samples were taken from two regions withe altitude. The concentrations of TOC and bromide in groundwater were higher at the regions of lower altitude, especially at the altitude below 50m. Generally the THM formation in GA region containing a high TOC was higher than that in GB region containing a relatively high bromide. At the altitude below 100m, the formation of total and brominated THM was highest at GB region. The most part of THM formation was brominated THM at GB region. The formation ratio of chloroform and brominated THM was similar to the others. Among the brominated THM, dibromochloromethane and bromoform in GB region were containing high bromide. Bromodichloromethane and dibromochloromethane in GA region were containing low bromide. At the altitude above 200m, chloroform was formed mainly. Comparing the ratio of brominated THM of total THM in Cheju Island with that in other areas, Seoul and Pusan, it can be konwn that the former showing 51.3% was much higher than the latter showing 6.7% and 28.8%, respectively.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.27 no.5
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• pp.515-528
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• 1994

China Coastal Water(CCW) appeared in the neighbouring seas of Cheju Island has been analyzed and the results are as follows: The water with salinity below $32.20\%0$ in the neighbouring seas of Cheju Island in summer is thought CCW. During the period from April 1985 to August 1986, salinity of more than $34.00\%0$ was appeared in the Cheju Strait during January to mid May, but it decreased gradually from late May. CCW with salinity below $32.20\%0$ appeared in the Cheju Strait in early July and disappeared in October. The mean thickness of CCW in the Cheju Strait was about 25m and CCW had an influence of up to about 50m depth. And stratification structure of the Cheju Strait in summer was halocline between the surface and 50m depth and homogeneous salinity layer below 50m depth. It seems that although CCW appears in the wide area of neighbouring seas surface of Cheju Island in summer, the core of this CCW which has the lowest salinity flows into the Cheju Strait from the western seas of Cheju Island. This CCW flows out the east through the central part of the Cheju Strait and then seems to be transported further in the form of eddy.

• Applied Biological Chemistry
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• v.41 no.2
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• pp.141-146
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• 1998

In order to determine the optimmum harvest time of Citrus unshiu Marc. var. miyagawa and C. unshiu Marc. var. okitsu produced in Cheju, citrus fruits sampled at packing houses or harvested directly on citrus tree in south and north area of Cheju were analyzed. The fruits were grown in size till middle of October, and soluble solids were increased continuously after that. The fruits size were different by positional directions on the tree, the quality of citrus fruits in central southern positions on the tree was good for fresh fruit consumptions. Compared with only the quality of citrus fruits as a factor of soluble solids, total sugar, pH, and color index, the optimum harvest time were supposed to be reasonable at late of November for C. unshiu Marc. var. okitsu, and at early of December for C. unshiu Marc. var. miyagawa. The results obtained from citrus fruits sampled at packing houses were supposed to be not suitable for determing the optimum harvest time, because of storage after harvest at ordinary harvesting time.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.43 no.1
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• pp.44-48
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• 1998

Two determinate soybean cultivars, 'Baegunkong' and 'Namhaekong', were planted on 8 Jone, 23 June, and 8 July 1996 at Cheju at planting densities of 33, 43, 53, 63 plants per $m^2$ to determine the optimum planting density of double crop soybean for recently recommended cultivars in Cheju area at various planting dates. The plant height, and the diameter and node number of main stems decreased as planting was delayed. The plant height increased but the stem diameter and node number decreased with increasing planting density. Pod number per plant was greater for Namhaekong than for Baegunkong and was not affected by planting date. Pod number per plant decreased but pod numbers per $\textrm{m}^2$ increased with increasing planting density. The number of seeds per pod was greater at the two later plantings and fewer at the highest planting density. 100-seed weight decreased with delaying planting. The seed weight was lighter at the highest planting density for Baegunkong but there was no difference for Namhaekong among the planting densities. The seed yield of Baegunkong was greater for 23 June and 8 July plantings (2,280 and 2,420 kg/ha) than for 8 June planting (1,450 kg/ha) while that of Namhaekong was greatest at 23 June planting (2,690 kg/ha) compared with 8 June and 8 July plantings (1,890 and 2,080 kg/ha). Across the planting dates and cultivars, seed yield increased from 1,860 to 2,290kg/ha as the planting density increased from 33 to 53 plants/$\textrm{m}^2$ and then leveled off with a further increase in planting density.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.31 no.2
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• pp.296-301
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• 1998

The physical and chemical characteristics were examined in the southern sea of Korea including the Cheju Strait, and the entrance of the Korea Strait in the period of May 30 to June 8, 1995. The results are as follows. Firstly, the variation ranges of the temperature and salinity at the Cheju Stratit during 24 hours observation were larger in the surface layer than that in the deep layers. Secondly, daily variations of nutrients show that total inorganic nitrogen, phosphate phosphorous, and silicate silicon concentration are higher at night than at day. Thirdly, water temperature and salinity distributions show highest values at the entrance of Korea Strait, which is thought to be influenced directly by Tsushima Warm Current, while they show the lowest values in Cheju Strait. This means that the surface waters in Korea Strait are greatly influenced from the entrance of Korea Strait and bottom waters is greatly influenced from Cheju Strait. Fourthly, nutrients distribution shows highest values in Korea Strait but dissolved oxygen shows lowest values in the area. These seem to be caused by the oxygen consumption used in the inorganization of nutrients to decompose organisms and the liquidation of nutrients.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.34 no.2
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• pp.117-134
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• 1998

The study on the Assembling Mechanism of the Hairtail, Trichiurus lenpturus, at the Fishing Grounds of the Cheju Strait had been investigated by analyzing the relationship of the oceanographic conditions and the fishing ground of the Hairtail in the Cheju Strait. 1. The fishing grounds of the hairtail at the Cheju Strait are formed at the bottom of a high temperature of the tidal front at the coast. area of northern Cheju Island, the tip of the linguiform is high in salinity at the eastern and western entrances of Cheju Island, low salinity eddy on the surface and its surrounding front, various water masses in the Strait and coastal waters of the South Sea in Korea. 2. The fishing grounds of the Hairtail at the Cheju Strait begins with the sea surface temperature higher than $15^{\circ}C$ and the incoming of low salinity water now from the East China Sea. 3. Estimation of optimum temperature and salinity per season based upon analysis for relationship between temperature of water and salinity of the bottom layer and the catch is : 15.2~$16.4^{\circ}C$, 34.20~34.40${\textperthousand}$ in spring(June); 14.4~ $17.0^{\circ}C$, 33.70~34.30${\textperthousand}$ in summer(July~September); and 15.7~ $18.6^{\circ}C$, 33.70~34.50$\textperthousand$ in autumn(October~December). Hairtail are mostly caught at the Yellow Sea Warm Current and Tsushima Current with temperature over $14.5^{\circ}C$ and salinity over 33.70${\textperthousand}$ at the bottom layers of the Cheju Strait. 4. Considering the relationship between the amount of hairtail catch and the water temperature of bottom layer, when the bottom water being above $14.0^{\circ}C$ flowed into Cheju Strait through the western entrance of the strait in summer, the ca-h appears to have been abundant. In contrast, the catch has been poor when the temperature of such water was recorded to be below $13^{\circ}C$ Therefore, distribution patterns of water at the bottom layer can be used as a forecast index whether the catch of a certain year will be good or poor.