• Korean Journal of Remote Sensing
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• v.11 no.3
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• pp.1-21
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• 1995

The characteristics of the Asian summer monsoon have been investigated for the periods of 1993/1994, the contrasting years in a view of the summer monsoon precipitation. In order to investigate the monsoon features over the eastern Asian monsoon region, the cloudiness(using the extensive data derived by the geostationary meteorological satellite), the condition of underlying surface including sea-surface temperature, and the summer rainfall are analyzed and some comparisons with 1993 and 1994 are also made and the characteristic differences are discussed. An analysis of the 2-degree latitude-longitude gridded 5-day mean high cloud amount data shows the detailed movement and persistence of the convective activities. In order to describe the spatial and temporal structures of the intraseasonal oscillation for the movement and evolution of the monsoon cloud, the extended empirical orthogonal fnction analysis with the twenty-day window size is used for the each year. Also, in order to find out the periodicity of the equatorial convective cluster, Fourier harmonic analysis is applied to the each year. The most prevailing intraseasonal oscillations of high cloud amount are 61 day mode and 15day mode in the equatorial and the subtropical oceans. However it was found that the most prevailing modes over the equatorial western Pacific and Indian Ocean were different for each year, hence raising the possibillity that the contrasting monsoon presipitation may be more fundamentally related to the interaction of intraseasonal oscillations and seasonal variation of convective activities over the lower latitude ocean.

• Journal of the Korean earth science society
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• v.36 no.7
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• pp.611-616
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• 2015

El Nino and Southern Oscillation (ENSO) presents a broad band (2-8 year) variability and slowly changing amplitude and period, which are respectively referred to as ENSO irregularity and ENSO modulation. In this study, we developed a nonlinear low-order climate model by combining the Lorenz-63 model of nonlinear atmospheric variability and a simple ENSO model with recharge oscillator characteristics. The model successfully reproduced the ENSO-like variations in the sea surface temperature of eastern Pacific, such as the peak period, wide periodicity, and decadal modulations. The results show that the chaotic atmospheric forcing can lead to ENSO irregularity and ENSO modulation. It is also suggested the high probability of La Nina development could be associated with strong convection of the western warm pool. Although it is simple, this model is expected to be used in research on long-term climate change because it well captures the nonlinear air-sea interactions in the equatorial Pacific.

• Atmosphere
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• v.28 no.1
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• pp.37-51
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• 2018

In this study, we investigate the performance of Global Seasonal Forecasting System version 5 (GloSea5) in Korea Meteorological Administration on the relationship between El $Ni{\tilde{n}}o$ and East Asian climate for the period of 1991~2010. It is found that the GloSea5 has a great prediction skill of El $Ni{\tilde{n}}o$ whose anomaly correlation coefficients of $Ni{\tilde{n}}o$ indices are over 0.96 during winter. The eastern Pacific (EP) El $Ni{\tilde{n}}o$ and the central Pacific (CP) El $Ni{\tilde{n}}o$ are considered and we analyze for EP El $Ni{\tilde{n}}o$, which is well simulated in GloSea5. The analysis period is divided into the developing phase of El $Ni{\tilde{n}}o$ summer (JJA(0)), mature phase of El $Ni{\tilde{n}}o$ winter (D(0)JF(1)), and decaying phase of El $Ni{\tilde{n}}o$ summer (JJA(1)). The GloSea5 simulates the relationship between precipitation and temperature in East Asia and the prediction skill for the East Asian precipitation and temperature varies depending on the El $Ni{\tilde{n}}o$ phase. While the precipitation and temperature are simulated well over the equatorial western Pacific region, there are biases in mid-latitude region during the JJA(0) and JJA(1). Because the low level pressure, wind, and vertical stream function are simulated weakly toward mid-latitude region, though they are similar with observation in low-latitude region. During the D(0)JF(1), the precipitation and temperature patterns analogize with observation in most regions, but there is temperature bias in inland over East Asia. The reason is that the GloSea5 poorly predicts the weakening of Siberian high, even though the shift of Aleutian low is predicted. Overall, the predictability of precipitation and temperature related to El $Ni{\tilde{n}}o$ in the GloSea5 is considered to be better in D(0)JF(1) than JJA(0) and JJA(1) and better in ocean than in inland region.

• Ocean and Polar Research
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• v.29 no.4
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• pp.283-295
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• 2007

We investigated the longitudinal variations in zooplankton abundances and their related physicochemical properties at nine stations located between $136^{\circ}W$ and $128^{\circ}W$ at $10.5^{\circ}N$ in the northeastern Pacific in summer 2004. Temperature, salinity, inorganic nutrients, chlorophyll-a (hereafter chl-a) and zooplankton ($>200\;{\mu}m$) were sampled within the depth from the surface to 200 m depth at $1^{\circ}$ longitude intervals. Zooplankton($>200\;{\mu}m$) samples were vertically collected at two depth intervals from surface to 200 m, consisting of surface mixed and lower layers (thermocline$\sim$200 m). Longitudinal distributional pattern of hydrological parameters (especially salinity) was physically influenced by the intensity of westward geostrophic current passage relating to the NEC (North Equatorial Current). Data from the longitudinal survey showed clear zonal distributions in the hydrological parameters(temperature, salinity and nutrients). However, spatial patterns of the chl-a concentrations and zooplankton abundances were mostly independent of the zonal distributions of hydrological parameters. The two peaks of zooplankton abundance in the surface mixed layer were characterized by different controlling factors such as bottom-up control from nutrients to zooplankton ($129^{\circ}W$) and accumulation by increment of friction force and taxonomic interrelationship ($133^{\circ}$ and $134^{\circ}W$). Divergence-related upwelling caused introduction of nutrients into surface waters leading to the increment of chl-a concentration and zooplankton abundances ($129^{\circ}W$). Increased friction force in relation to reduced flow rates of geostrophic currents caused accumulation of zooplankton drifting from eastern stations of study area($133^{\circ}$ and $134^{\circ}W$). Besides, high correlation between immature copepods and carnivorous groups such as chaetognaths and cyclopoids also possibly contributed to the enhanced total abundance of zooplankton in the surface mixed layer (p<0.05). Zooplankton community was divided into three groups (A, B, C) which consecutively included the eastern peak of zooplankton($129^{\circ}W$), the western peak($133^{\circ}$ and $134^{\circ}W$) and high nutrient but low chl-a concentration and zooplankton abundance ($136^{\circ}W$). Moreover, Group B corresponded to the westward movement of low saline waters(<33.6 psu) from 128 to $132^{\circ}W$. In summary, longitudinal distributions of zooplankton community was characterized by three different controlling factors: bottom-up control ($129^{\circ}W$), accumulation by increased friction force and relationships among zooplankton groups ($133^{\circ}$ and $134^{\circ}W$), and mismatch between hydrological parameters and zooplankton in the high nutrient low chlorophyll area ($136^{\circ}W$) during the study period.

• Journal of the Korean earth science society
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• v.34 no.2
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• pp.136-147
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• 2013

This study examined the effect of the Antarctic Oscillation (AAO) in June on the June rainfall in Korea by using a correlational statistical analysis. Results showed that there is a highly positive correlation between the two variables. In other words, the June rainfall in Korea is influenced by the Mascarene High and Australian High that are strengthened in the Southern Hemisphere, which is a typical positive AAO pattern. When these two anomalous pressure systems strengthen, the cold cross-equatorial flows in the direction from the region around Australia to the equator are intensified, which in turn, force a western North Pacific subtropical high (WNPSH) to develop northward. This pressure development eventually drives the rain belt to head north. As a result, the Changma begins early in the positive AAO phase and the June rainfall increases in Korea. In addition, a WNPSH that develops more northward increases the landfall (or affecting) frequency of tropical cyclones in Korea, which plays an important role in increasing the June rainfall.

• 한국해양학회지
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• v.21 no.2
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• pp.92-100
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• 1986

Laboratory investigations of physical (density and porosity), acoustic (velocity and velocity anisotropy), and electrical (resistivity and resistivity anisotropy) properties in deep-sea carbonate sequences at DSDPsites 288 and 289 in the western equatorial Pacific were made and correlated as a function of diagenesis. Profile of resistivity shows almost a mirror image of velocity indicating that electrical resistivity can be a useful variable to determine the diagenetic stage. Some fluctuations in acoustic and electrical properties near the zones of cherty and siliceous limestones for both sites imply significant changes in pore geometry due to interbedded silica. The significantly reduced pore throat size by the presence of silica which provides excess calcium carbonate to adjacent pore spaces is partly responsible for several jumps in acoustic and electrical properties of the zones. These observed geophysical data are interpreted as the result of silica diagenesis influencing carbonate diagenesis.

• Korean Journal of Remote Sensing
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• v.13 no.1
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• pp.1-12
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• 1997

The western equatorial Pacific Ocean, where sea surface temperature is the warmest on the globe, is characterized by numerous convective systems and large annual precipitation. In this region, the cloudiness data with tops higher than 8km level obtained from the GMS-IR data are used to investigate the diurnal variation of cloudiness. The amplitude and phase of diurnal and semi-diurnal cycles are mainly investigated to examine details on the temporal and spatial structure of clouds. Cloudiness variation has typical cycles and each cycle is associated with the air-sea interactive phenomena. Spectral analysis on the cloudiness time series data indicates that 30-60 day, 17-20day, 7-8 day, diurnal and semi diurnal cycle are peaked. During Northern Winter and Southern Summer, the large cloudiness exsists over New Guinea, the adjacent seas of North Australia, and the open oceanic regions east of $160^{\circ}$E. Cloudiness diurnal variability over the lands and their adjacent seas is about 2.0 times larger than that over the open sea regions. That may be due to the difference of specific heat between the land and sea. The maximum and minimum cloudiness appeared at 18:00 and 09:00 hours over the land, and at noon and 21:00 hours over the sea, respectively. The amplitude of diurnal component over the land is 4,7 times larger than that of semi-diurnal component, and 1.5 times over the sea.

• Economic and Environmental Geology
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• v.35 no.1
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• pp.1-12
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• 2002

Manus Basin, located in the equatorial western Pacific, is a back arc basin formed by collision between the IndoAustralian and the Pacific Plates. The basin is host to numerous hydrothermal vent fields and ore deposits. The basement rocks of the Manus Basin consist primarily of dacite and basaltic andesite. Some of the minerals that form the hydrothermal chimneys that were dredged on the Manus basin include pyrite, chalcopyrite, marcasite, sphalerite and galena. The chimneys can be classified into chalcopyrite dominant Cu-rich type and sphalerite dominant Zn-rich type. The concentration of Zn shows good positive correlation with that of Sb, Cd and Ag. The content of Cu, on the other hand, positively correlates with that of Mo, Mn and Co. For samples that were taken from Zn-rich chimney, a strong positive correlation is found between Au and Zn contents. The chimney also shows enrichments of Cd, Mn and Sb. On the other hand, the samples from Cu-rich chimney exhibit strong correlation among Au, Zn and Pb, and are enriched in Mo and Co concentration. Average contents of Au in Cu-rich and Znrich chimneys were 15.9 ppm and 29.0 ppm, respectively. Because of high concentration of Au with Ag and Cu, the ore deposit have high economic potential. Homogenization temperatures and salinities of fluid inclusions in anhydrite and amorphous silica from Zn-rich chimney are estimated to be l74-220$^{\circ}$C and 2.7-3.6 equiv. wt. % NaCI, respectively. These value suggest that ore forming processes were occurred at around 200$^{\circ}$C and that the oxygen fugacity changed from 2: 10$^{-39.5}$bar to -s: 10$^{-40.8}$bar and the sulfur fugacity from -s: 10$^{-14.7}$bar to 10$^{-13.4}$bar during the process. It appears that the temperature at which the ores formed on Cu-rich chimney was higher than that on Zn-rich chimney.

• Journal of the Korean earth science society
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• v.21 no.5
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• pp.503-524
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• 2000

Intercomparisons between four kinds of data have been done to estimate the accuracy of satellite observations and model reanalysis for middle and lower tropospheric thermal state over regional oceans. The data include the Microwave Sounding Units (MSU) Channel 2 (Ch2) brightness temperatures of NOAA satellites and the vertically weighted corresponding temperature of ECMWF GCM (1980-93). The satellite data for midtropospheric temperatures are MSU2 (1980-98) in nadir direction and SC2 (1980-97) in multiple scans, and for lower tropospheric temperature SC2R (1980-97). MSU2 was derived in this study while SC2 and SC2R were described in Spencer and Christy (1992a, 1992b). Temporal correlations between the above data were high (r${\ge}$0.90) in the middle and high latitudes, but low(r${\sim}$0.65) over the low latitude and more convective regions. Their values with SC2R which included the noises due to hydrometeors and surface emission were conspicuously low. The reanalysis shows higher correlation with SC2 than with MSU2 partially because of the hydrometeors screening. SC2R in monthly climatological anomalies was more sensitive to surface thermal condition in northern hemisphere than MSU2 or SC2. The first EOF mode for the monthly mean data of MSU and ECMWF shows annual cycle over most regions except the tropics. The mode in MSU2 over the Pacific suggests the east-west dipole due to the Walker circulation, but this tendency is not clear in other data. In the first and second modes for the Ch2 anomalies over most regions, the MSU and ECMWF data commonly indicate interannual variability due to El Ni${\tilde{n}$o and La Ni${\tilde{n}$a. The substantial disagreement between observations and model reanalysis occurs over the equatorial upwelling region of the western Pacific, suggesting uncertainties in the model parameterization of atmosphere-ocean interaction.