• Proceedings of the Korea Air Pollution Research Association Conference
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• 2002.04a
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• pp.73-74
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• 2002

Active upwelling air motion in every summer over the Tibetan plateau is an essential process controlling activities of asian summer monsoon which affects water cycle and precipitation in eastern Asia. Large heating rate of surface air on the high plateau with average height of 4000m is considered to cause such large scale upwelling over the plateau. (omitted)

• Atmosphere
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• v.18 no.1
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• pp.55-70
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• 2008

The global time slice approach is a transient experiment using high resolution atmosphere-only model with boundary condition from the low resolution globally coupled ocean-atmosphere model. The present study employs this "time slice concept" using ECHAM4 atmosphere-only model at a horizontal resolution of T106 with the lower boundary forcing obtained from a lower-resolution (T42) greenhouse gas + aerosol forcing experiment performed using the ECHO-G/S (ECHAM4/HOPE-G) coupled model. In order to assess the impact of horizontal resolution on simulated East Asian summer monsoon climate, the differences in climate response between the time slice experiments of the present and that of IPCC SRES AR4 participating 21 models including coarser (T30) coupled model are compared. The higher resolution model from time slice experiment in the present climate show successful performance in simulating the northward migration and the location of the maximum rainfall during the rainy season over East Asia, although its rainfall amount was somewhat weak compared to the observation. Based on the present climate simulation, the possible change of East Asian summer monsoon rainfall in the future climate by the IPCC SRES A1B scenario, tends to be increased especially over the eastern part of Japan during July and September. The increase of the precipitation over this region seems to be related with the weakening of northwestern part of North Pacific High and the formation of anticyclonic flow over the south of Yangtze River in the future climate.

• 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.

• Korean Journal of Agricultural and Forest Meteorology
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• v.7 no.4
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• pp.240-249
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• 2005

The normal Indian Ocean is characterized by warmer waters over the eastern region and cooler waters over the western region. Changes in sea surface temperature (SST) over the western and eastern Indian Ocean give birth to a phenomenon now referred to as the Indian Ocean Dipole Mode (IODM). The positive phase of this mode is characterized by positive SST anomalies over the western Indian Ocean and negative anomalies over the southeastern Indian Ocean, while the negative phase is characterized by a reversed SST anomaly pattern. On the other hand, the normal Pacific Ocean has warm (cool) waters over the western (eastern) parts. Positive (negative) SST anomalies over the central/eastern (western) Pacific Ocean characterize the E1 Nino phenomenon. The reverse situation leads to the La Nina phenomenon. The coupled ocean-atmosphere phenomenon over the Pacific is referred to as the E1 Nino Southern Oscillation (ENSO) phenomenon. In this study the impact of IODM and ENSO on the East Asian monsoon variability has been studied using observational data and using the Community Atmospheric Model (CAM) of the National Center for Atmospheric Research (NCAR). Five sets of model experiments were performed with anomalous SST patterns associated with IODM/ENSO superimposed on the climatological SSTs. The empirical and dynamic approaches reveal that it takes about 3-4 seasons fur the peak IODM mode to influence the summer monsoon activity over East Asia. On the other hand, the impact of ENSO on the East Asian monsoon could occur simultaneously. Further, the negative (positive) phase of IODM and E1 Nino (La Nina) over the Pacific enhances (suppresses) monsoon activity over the Korea-Japan Sector. Alternatively, IODM appears to have no significant impact on monsoon variability over China. However, El Nino (La Nina) suppresses (enhances) monsoon activity over China. While the IODM appears to influence the North Pacific subtropical high, ENSO appears to influence the Aleutian low over the northwest Pacific. Thus, the moisture supply towards East Asia from the Pacific is determined by the strengthening/weakening of the subtropical high and the Aleutian low.

• Atmosphere
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• v.17 no.1
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• pp.55-68
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• 2007

Future climate changes over East Asia are projected by anthropogenic forcing of greenhouse gases and aerosols using ECHO-G/S (ECHAM4/HOPE-G). Climate simulation in the 21st century is conducted with three standard SRES scenarios (A1B, B1, and A2) and the model performance is assessed by the 20th Century (20C3M) experiment. From the present climate simulation (20C3M), the model reproduced reliable climate state in the most fields, however, cold bias in temperature and dry bias of summer in precipitation occurred. The intercomparison among models using Taylor diagram indicates that ECHO-G/S exhibits smaller mean bias and higher pattern correlation than other nine AOGCMs. Based on SRES scenarios, East Asia will experience warmer and wetter climate in the coming 21st century. Changes of geographical patterns from the present to the future are considerably similar through all the scenarios except for the magnitude difference. The temperature in winter and precipitation in summer show remarkable increase. In spite of the large uncertainty in simulating precipitation by regional scale, we found that the summer (winter) precipitation at eastern coast (north of $40^{\circ}N$) of East Asia has significantly increased. In the 21st century, the warming over the continents of East Asia showed much more increase than that over the ocean. Hence, more enhanced (weakened) land-sea thermal contrast over East Asia in summer (winter) will cause strong (weak) monsoon. In summer, the low pressure located in East Asia becomes deeper and the moisture from the south or southeast is transported more into the land. These result in increasing precipitation amount over East Asia, especially at the coastal region. In winter, the increase (decrease) of precipitation is accompanied by strengthening (weakening) of baroclinicity over the land (sea) of East Asia.

• Atmosphere
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• v.15 no.2
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• pp.75-90
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• 2005

This study examines the impacts of land cover changes on the East Asia summer monsoon with the National Center for Atmospheric Research Regional Climate Model (NCAR RegCM2), coupled with Biosphere Atmosphere Transfer Scheme (BATS). To assess the goals, two types of land cover maps were used in the simulation of summer climate. One type was NCAR land cover map (CTL) and the other was current land cover map derived from satellite data (land cover: LCV). Warm and cold surface temperature biases of $1-3^{\circ}C$ occurred over central China and Mongolia in CTL. The model produced excessive precipitation over northern land area but less over southern ocean of the model domain. Changes of biophysical parameters, such as albedo, minimum stomatal resistance and roughness length, due to the land cover changes resulted in the alteration of land-atmosphere interactions. Latent heat flux and wind speed in LCV increased noticeably over central China where deciduous broad leaf trees have been replaced by mixed farm and irrigated crop. As a result, the systematic warm biases over central China were greatly reduced in LCV. Strong cooling of central China decreased pressure gradient between East Asian continent and Pacific Ocean. The decreased pressure gradient suppressed the northward transport of moisture from south China and South China Sea. These changes reduced not only the excessive precipitation over north China and Mongolia but also less precipitation over south China. However, the land cover changes increased the precipitation over the Korean Peninsula and the Japan Islands, especially in July and August.

• Asia-Pacific Journal of Atmospheric Sciences
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• v.54 no.4
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• pp.545-561
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• 2018

Over the North East Asia, extreme anomalous precipitation were observed in 2013 and 2014. During 2013 summer the precipitation was found to be higher (two standard deviation) than the climatological mean of the region; whereas during 2014, which was a borderline El Ni?o year, precipitation was found to be lower (one standard deviation). To understand the differences of these two anomalous years the Global/Regional Integrated Model system (GRIMs) has been used. The study found that low landsurface temperature and high sea-surface temperature over ocean caused a smaller land-sea contrast of surface temperature between East Asia and North West Pacific Ocean in 2014, which could have caused an eastward shift of mean monsoon circulation in that year compared to the circulation in 2013. Due to a change in the lower level circulation and wind field over East Asia the evaporation and moisture transport patterns became very different in those two years. In 2013, this study found high latent heat flux over Eastern China, which implies an increased surface evaporation over that region, and the moisture transported to the north by the mean monsoon circulation; whereas, there was no correlated transport of moisture to the North East Asia during 2014. The precipitable water over North East Asia has a stronger correlation with the latent heat flux over southern land region than that from Ocean region in the eastern side in both the years. A new approach is proposed to estimate the sub-grid scale hydrometeors from GRIMs, overestimated in the existing model.

• Atmosphere
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• v.30 no.3
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• pp.311-318
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• 2020

Impacts on the atmospheric circulation and ocean system over the Mediterranean during boreal summer are investigated using Coupled Model Intercomparison Project Phase 5 (CMIP5) historical simulations (from 1911 to 2005). As the climate warms, global and remote effects lead to a strengthening in descending motion, an increase in sea surface temperature (SST) and surface dryness, but a decrease in marine primary production over the Western Mediterranean. The global effect is estimated from interannual variability over the global mean SST and the remote effect is driven by diabatic forcing generated from the South and East Asian summer monsoons. On the other hand, a local contribution leads to the strengthened descending motion and increased surface dryness over the Eastern Mediterranean, whereas the marine primary production over this region tends to increase due to possibly the urban wastewater and sewage. Our result suggests that particular attention needs to be paid to conserve the marine ecosystem over the Mediterranean.

• 한국해양학회지
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• v.20 no.1
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• pp.22-30
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• 1985

The mean sea level(MSL) along the coast of Korea is high in summer and low in winter, mainly due to the inverse barometric effect and the steric departure. The MSL associated with the inverse barometric effect is spatially uniform and has an amplitude of 8.5$\pm$0.8cm. The thermal departure, with amplitude of 4~8cm, is most dominant in the Yellow Sea. The MSL in the South Sea of Korea is strongly affected by the haline departure, which has an amplitude up to 5cm. The annual range of MSL along the western and eastern coasts of Korea are about 40 and 20cm, respectively. The spatial inhomogeneity of the annual range of MSL arises mainly due to the influence of the Asian monsoon, which amplifies (weakens) the annual MSL along the western (eastern) coast of Korea.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.5
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• pp.581-588
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• 2019

A long-term trend analysis of cold water masses along eastern coast of South Korea was performed during summer, based on wind speed, wind direction, and sea surface temperature (SST) data. Wind data collected over a 22-year period (1997-2011) were compared with another set of data collected over the successive 7-year (2012-2018), highlighting a general decrease in the frequency and speed of south winds. However, both the frequency and speed of these winds have been higher in June between 2012-2018, rather than between 1997-2011. The cold water season between July and August was faster during the 7-year period; moreover, the SSTs registered around Gangneung (EN) rose by $0.5^{\circ}C- 1.8^{\circ}C$, while those around Yeongdeok (EC) and Gijang (ES) increased by only $0.1^{\circ}C-0.3^{\circ}C$. The number of cold water days during the 7-year period, compared to those recorded during previous years (1990-2011, satellite SST data by NOAA/AVHRR), decreased in the proximity of Yeongdeok and Gijang, but increased in the proximity of Kangneung. Additionally, the number of cold water days around Kangneung, Yeongdeok, and Gijang increased in June highlighting a geographical and temporal change in the occurrence of cold waters. These observation can be explained by variations in the pressure distribution that should have weakened the East Asian monsoon, affecting the direction and speed of winds that regulate the flow of cold waters.