Investigation was carried out to observe the dominant bacteria and the effect of metals(Cd & Zn) and its nitrate compound on growth of bacteria isolated from the three tributaries and lower reach of the Nakdong River. Mean CFU(log10) level was highest in Kumho River(8.30 CFU), Nam River, Hwang River, and Mulgum followed. Staphylococcus xylosus, Staph. lentus, Pasteurella pneumotropica, Aeromonas hydrophilla were dominant species in each study site. Cadmium powder and Zinc powder showed strong effect to inhibit the growth of Micrococcus spp., Pasteurella pneumotropica, Aeromonas hydrophilla. But, nitrate compounds of Cd and Zn(Cd(NO3)24H2O, Zn(NO3)26H2O) did not clearly show the strong effect to inhibit the growth of dominants.

Investigations were carried out to observe the seasonal succession of phytoplankton, and viable counts of bacteria from the mid to lower reaches of Nakdong River. An intensive monitoring was conducted from May to December 1999 biweekly at 6 sites in a main channel and 3 tributaries. Although there are several sites with high nutrient loading from the basin, all of study sites showed mesotrophic states owing to high discharge(June∼September). Relatively low algal biomass and CFUs(mean of chl. a, 12.3±11.5 ㎍/ℓ, CFUs : 1.8×10 7) were observed during the rainy season. The diatom population was dominant(over 85% of total community) year-long with peaks (Stephanodiscus hantzschii) in the fall and winter. Dominance of blue-green algal groups during the summer was not observed in the summer. Microorganisms peaked in the summer and fall (June∼September), affected mainly by the inputs of phytoplankton and nutrients. Biomass of phytoplankton and CFU counts were higher in the Kumho River than the other tributaries and main channel.

During the spring and fall of 1994 and winter of 1995, the exposure time of periphyton biomass on the artificial substrata at 10 headwater streams in the southeastern Korea was evaluated in 7-14 day interval. In the streams with low periphyton biomass (chl a: 2-4 ㎎/㎡) in natural rocks, biomass of artificial substrata (unglazed the: 3.7 × 9.5 × 2 ㎝) exceeded that of the natural rocks after 28 days, while sites with high biomass (chl. a: 20-60 ㎎/㎡) in natural rocks showed slower biomass accumulation after 40 days. Due to the high light input and temperature in a partially shaded mountain stream, development of periphyton biomass in spring occurred faster than that of winter. In general, development of periphyton biomass placed on artificial substrata took 4-5 weeks in spring and at least 6 weeks in winter to reach the natural level.

The present study intends to investigate the transient response of an atmosphere/ocean general circulation model to a gradual increase of atmospheric carbon dioxide. To detect the climatic change of the surface air temperature due to gradual increasing carbon dioxide for 100 years, two runs of GFDL CGCM for 1 % CO_2 run with increasing CO_2 and the control run with fixed CO_2 are compared. From results it is noted that the transient response of surface air temperature is more increased over the Northern Hemisphere than the Southern Hemisphere. However, in Northern Hemisphere the transient response of the surface air temperature due to the gradual increase of atmospheric carbon dioxide is slowly increased with latitudes and is clearly larger over continents than oceans. The annual global mean temperature is continuously increased with 0.03552 per one year with strong S/N ratio and distinguished from the natural variability. The time dependent response of the gradual increasing CO_2 has the strong seasonal variability with small change in summer and large change in winter, and the strong regionality in the Asian and the American continents. It has been suggested that the direct and the feedback processes in the climate systems should be investigated by the detailed sensitivity runs to get the meaningful estimate of the CO_2 forced variability.

The aim of the present study is to investigate the interannual variabilities of the East Asia monsoon rainfall associated with the global sea surface temperature anomaly(SSTA). For this study, the summer rainfall(from June to August) over the twenty-eight period of 1961-1988 were analyzed with being divided by nine-subregions over East Asia including Korea, China and Japan. From the analysis of the principal modes explaining the interannual variation, the interannual variabilities of summer rainfalls in South Japan and Korea are larger than those of the other subregions of the East Asia. There is a strong negative correlation between the summer rainfalls of south China and Korea. In this study, the relationship between the summer monsoon of each subregion and SSTs of the tropical NINO regions, of western Pacific warm pool, and of the subtropical ocean were investigated. The longitudinal sections of the lagged cross correlations of the summer rainfall anomaly in (a) Korea and (b) south China, and the monthly SSTA in the equatorial (averaged from 6S to 6N) Pacific were analyzed. The negative maximum correlation pattern of Korea`s summer rainfall and SSTs over the eastern Pacific is transfered to positive maximum correlation over central Pacific region with a biennial periodicity. In South China, the significant positive correlations are found at -12 month lag over the eastern Pacific and maximum negative correlation at +6 month lag over the central Pacific with the quasi-biennial oscillation. But the correlation coefficient reverses completely to that in Korea. In order to investigate the most prevailing interannual variability of rainfall related to the favored SSTA region, the lagged cross correlations between East Asia rainfall and SSTs over the NINO regions(NINO 1+2(0-10S, 90W-80W), NINO 3(5N-5S, 150W-90W), NINO 4(5N-5S, 160E-150W) and the western Pacific warm pool (5N-5S, 120E-160E) were analyzed. Among the lagged cross-correlation cycles in NINO regions, the maximum correlations for the negative lagged months prevail in NINO 1+2 and NINO 3, and the cross correlations for the positive lagged months NINO 4. It is noteworthy that correlation between the western Pacific warm pool SSTA and the monsoon rainfall in Korea and South China have the maximum value at negative 4 month lag. The evolution of the correlation between the East Asia monsoon rainfall and SSTA is linked to the equatorial convective cluster and related to northward propagating situation, and raising the possibility that the East Asia monsoon precipitation may be more fundamentally related to the interaction of intraseasonal oscillations and the sub-regional characteristics including the surface boundary conditions and the behavior of climatological air mass.