• Journal of the Korean earth science society
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• v.38 no.1
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• pp.35-48
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• 2017

This study analyzed the obvious increasing tendency of summer (June to August) rainfall in the region of Korea- and northern China ($35^{\circ}-40^{\circ}N$, $110^{\circ}-130^{\circ}E$) in the late 1990s. In order to investigate the causes of the increase in summer rainfall since 1998, we analyzed the difference of the rainfall average between 1998-2012 and 1981-1997. The analysis of the 850 hPa stream flows showed that the huge anomalous anticyclonic circulations were developed in North Pacific and eastern Australia. In both hemispheres, the anomalous easterlies (anomalous trade winds) were strengthened from the equatorial central Pacific to the tropical western Pacific by the anomalous circulations, which was an anomalous circulation pattern shown in La $Ni{\tilde{n}}a$ years. As for the 200 hPa stream flows, the huge anomalous cyclonic circulations were also developed in both South Pacific and North Pacific. These two anomalous circulations reinforced the anomalous westerlies in the equatorial central and western Pacific, leading to the increase in summer rainfall in the region of Korea- and northern China since the late 1990s in association with La $Ni{\tilde{n}}a$ pattern, which was resulted in strengthening the Walker circulation. Recently in East Asia, the local Hadley circulation has been strengthened in which upward flows in the equatorial western Pacific and mid-latitude region of East Asia have descended in the subtropical western Pacific.

• Ocean and Polar Research
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• v.33 no.4
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• pp.507-516
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• 2011

Tropical Atmosphere Ocean/Triangle Trans-Ocean Buoy Network (TAO/TRITON) Array is the series of buoys for the international ocean research project, which is mostly supported by National Ocean and Atmosphere Administration (NOAA) and Japan Agency for Marine-Earth Science and Technology (JAMSTEC). We can determine the effect of the equatorial and Pacific Ocean conditions on global climate change from buoy array measurement data. The TAO/TRITON array comprises around 70 measurement buoys from $10^{\circ}$ north to $10^{\circ}$ south in the tropics and between Galpagos and New Guinea. NOAA maintains ATLAS buoys in the central and eastern Pacific between $165^{\circ}E$ and $95^{\circ}W$, and JAMSTEC maintains the 12 buoys in the western Pacific along $137^{\circ}E$, $147^{\circ}E$, and $156^{\circ}E$. The KA-10-03 cruise excursion provided us with a good opportunity to obtain knowledge on oceanic buoy operation and maintenance. Further, we learned advanced techniques and know-how on buoy operation and maintenance. Once we are confident with our buoy management and maintenance techniques, both KORDI and NOAA technicians may be able to help each other when needed and share available resources.

• Journal of the Korean earth science society
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• v.24 no.6
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• pp.558-567
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• 2003

The regional dependency of cloud-radiative forcing at the top of atmosphere is studied using ERBE (Earth Radiation Budget Experiment), ISCCP (International Satellite Cloud Climatology Project) and NCEP/NCAR (National Centers for Environmental Prediction/National Center for Atmospheric Research) reanalysis data for 60 months from January 1985 to December 1989 over tropical ocean. In the interannual time scale, the dependency of cloud-radiative forcing on the sea surface temperature over the equatorial eastern Pacific ocean is about 7.4Wm$^{-2}$K$^{-1}$ for longwave radiation and about -4.4Wm$^{-2}$K$^{-1}$ for shortwave radiation, respectively. This shows that the net cloud-radiative forcing due to the increase of sea surface temperature over the equatorial eastern Pacific ocean heats the atmosphere. But the dependency is reversed over tropical oceans with -3.4Wm$^{-2}$K$^{-1}$ for longwave and 1.9WmWm$^{-2}$K$^{-1}$ for shortwave radiation, indicating that the net cloud-radiative forcing cools the atmosphere over tropical oceans. In raw data including seasonal cycle, the dependency of cloud-radiative forcing over the equatorial eastern Pacific ocean is very similar to that in interannual time scale in both the magnitude and the sign. But the dependency of cloud-radiative forcing on the sea surface temperature over tropical oceans is about 0.2Wm$^{-2}$K$^{-1}$ for longwave and 2.7Wm$^{-2}$K$^{-1}$ for shortwave radiation, respectively. These results represent that the role of seasonal cycle on the cloud radiative forcing is gradually more important than role of interannual time scale as the ocean area is broadening from the tropical central Pacific to the tropical ocean.

• Atmosphere
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• v.24 no.2
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• pp.141-150
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• 2014

This study investigates the characteristics of the Gross Moist Stability (GMS) over the tropics. The GMS summarizes the relationship between large-scale entropy forcing due to radiation and surface fluxes and the response of smaller-scale convection. The GMS is able to explain both to where moist entropy is advected by the atmospheric circulation and how deep the moisture flux convergence is in the tropical region. In the deep convective region, positive GMS appears over the warm pool region due to the strong column-integrated moisture convergence and the ensuing export of moist entropy to the environment. The vertical advection of moist entropy dominates over the horizontal advection in this region. Meanwhile, over the eastern tropical ITCZ region, which is characterized by shallow convective area, import of moist entropy by horizontal winds is dominant compared to the vertical moist entropy advection. Future changes in the GMS are also examined using the 22 CMIP5 model simulations. A decrease in the GMS appears widely across the tropics, but its increase occurs over the western-central equatorial Pacific. It is evident that the increased GMS region corresponds to an increased region of precipitation, implying that strengthened convection in the future due to increased entropy forcing exports the enhanced moist energy to stabilize the environment.

• 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.