• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.224-224
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• 2015

The East Asia monsoon is one of the most complex atmospheric phenomena caused by Land-Sea thermal contrast. It plays essential role in fulfilling the water needs of the region but also poses stern consequences in terms of flooding and droughts. This study analyzed the influence of Global Sea Surface Temperature Anomalies (SSTA) on occurrence of droughts in the East Asia monsoon region ($20^{\circ}N-50^{\circ}N$, $103^{\circ}E-149^{\circ}E$). Standardized Precipitation Index (SPI) was employed to characterize the droughts over the region using 30-year (1978-2007) gridded rainfall dataset at $0.5^{\circ}$ grid resolution. Due to high variability in intensity and spatial extent of monsoon rainfall the East Asia monsoon region was divided into the homogeneous rainfall zones using cluster analysis method. Seven zones were delineated that showed unique rainfall regimes over the region. The influence of SSTA was assessed by using lagged-correlation between global gridded SSTA ($0.2^{\circ}$ grid resolution) and SPI of each zone. Sea regions with potential influence on droughts in different zones were identified based on significant positive and negative correlation between SSTA and SPI with a lag period of 3-month. The results showed that SSTA have the potential to be used as predictor variables for prediction of droughts with a reasonable lead time. The findings of this study will assist to improve the drought prediction over the region.

• Journal of Korean Society on Water Environment
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• v.31 no.3
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• pp.313-318
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• 2015

To study the influence of changes in river discharge on water quality of the main stem of the Geum River, we investigated variation of inflow load from tributaries with river discharge. We also studied the mixing behavior of pollutants during mixing of waters of the main stem and Gap Stream. For this study, we collected water quality data such as suspended solids (SS), biochemical oxygen demand (BOD), chemical oxygen demand (COD), total organic carbon (TOC), total nitrogen (TN) and total phosphorus (TP) representing pre-monsoon, monsoon, and post-monsoon events of 2013 from a website of Water Information System. Based on inflow load, the Gap and Miho streams may be ones of tributaries which may largely influence water quality of main stem in upper river region. The Suksung and Nonsan Streams seemed to further affect water quality downstream. Results of modified EMMA indicated SS and TP may have another source(besides Gap Stream) at pre-monsoon, monsoon, and post-monsoon period. In contrast, TN and organic matter (BOD, COD, TOC) were conservative at pre-monsoon and post-monsoon. However, when river discharge increased, these pollutants may also came from unspecified non-point sources. Therefore, we need to attempt to find non-point sources for the pollutants in the main channel of upper Geum River region.

• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.1298-1300
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• 2003

Based on the Leaf Area Index (LAI) data derived from remote sensing information and eco-climate data, the responses of regional ecosystem variations in seasonal and interannual scales to the East Asian monsoon are studied in this paper. It is found that the vegetation ecosystems of eastern China are remarkably correlated with the East Asian monsoon in seasonal and interannual scales. In the seasonal timescale, the obvious variations of the vegetation ecosystems occur with the development of the East Asian monsoon from the south in the spring to the north in the autumn. In the interannual scale, high LAI appears in the strong East Asian monsoon year, whereas low LAI is related to the weak East Asian monsoon year. These further lead to the characteristic of 'onsoon-driven ecosystem' in the eastern China monsoon region, which can be revealed by LAI.

• The Korean Journal of Quaternary Research
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• v.17 no.2
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• pp.63-69
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• 2003

Three tree-ring monsoon rainfall reconstructions from China and Korea have been used in this paper to investigate the variation of the East Asian summer monsoon over the past 160 years. Statistically, there is no linear correlation on a year-by-year basis between Chinese and Korean monsoon rainfall, but region-wide synchronous variation on decadal-scale was observed. Strong monsoon intervals (more rainfall) were 1860-1890, 1910-1925,1940-1960, and weak monsoon periods (dry or even drought) were 1890-1910, 1925-1940, 1960- present. Reconstructions also display that the East Asian summer monsoon suddenly changed from strong into weak around mid-1920, and the East Asian summer monsoon keeps going weak after 1960.

• The Korean Journal of Quaternary Research
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• v.21 no.1
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• pp.15-26
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• 2007

A wide tree-ring data network from Western Himalayan region as well as from Central and Peninsular India have been established by the Indian Institute of Tropical Meteorology (IITM), Pune, India. This includes several ring width and density chronologies of Himalayan conifers (Pinus, Picea, Cedrus, Abies)covering entire area of Western Himalaya and teak (Tectona grandis L.F.) from central and peninsular India. Many of these chronologies go back to $15^{th}$ century. Tree-ring based reconstructed pre-monsoon (March-April-May) summer climate of Western Himalaya do not show any significant increasing or decreasing trend since past several centuries. High altitude tree-ring chronologies near tree line-glacier boundary are sensitive to the winter temperature. Unprecedented higher growth in recent decades is closely associated with the warming trend over the Himalayan region. Dendroclimatic analysis of teak (Tectona grandis) from Central and Peninsular India show significant relationship with pre-monsoon and monsoon climate. Moisture index over the region indicates strong association with tree-ring variations rather than the direct influence of rainfall. It is evident that, two to three consecutive good monsoon years are capable of maintaining normal or above normal tree growth, even though the following year is low precipitation year.

• Atmosphere
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• v.22 no.4
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• pp.483-488
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• 2012

The monsoon front lies on East Asian region, but it gradually propagates to the north during the boreal summer. The equivalent potential temperature (EPT) reveals the thermodynamical features of air masses and monsoon front. Therefore, this study considered the thermodynamical EPT and dynamical wind fields to clarify the peculiarity of East Asian summer monsoon (EASM) variations in June and July, respectively. Western North Pacific subtropical high (WNPSH) and Okhotsk sea high (OSH) both play the crucial role to interannual variations of EASM frontal activity and amount of rainfall. The OSH is important in June, but the WNPSH is key factor in July. Furthermore, the OSH (June) is affected by North Atlantic tripolar sea surface temperature (SST) pattern and WNPSH (July) is influenced by North Indian Ocean SST warming.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.174-174
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• 2023

The impact of global warming on the south Asian summer monsoon is of critical importance for the large population of this region. This study aims to investigate the future changes of the precipitation extremes during pre-monsoon and monsoon, across this region in a more organized regional structure. The study area is divided into six major divisions based on the Köppen-Geiger's climate structure and 10 sub-divisions considering the geographical locations. The future changes of extreme precipitation indices are analyzed for each zone separately using five indices from ETCCDI (Expert Team on Climate Change Detection and Indices); R10mm, Rx1day, Rx5day, R95pTOT and PRCPTOT. 10 global climate model (GCM) outputs from the latest CMIP6 under four combinations of SSP-RCP scenarios (SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5) are used. The GCMs are bias corrected using nonparametric quantile transformation based on the smoothing spline method. The future period is divided into near future (2031-2065) and far future (2066-2100) and then the changes are compared based on the historical period (1980-2014). The analysis is carried out separately for pre-monsoon (March, April, May) and monsoon (June, July, August, September). The methodology used to compare the changes is probability distribution functions (PDF). Kernel density estimation is used to plot the PDFs. For this study we did not use a multi-model ensemble output and the changes in each extreme precipitation index are analyzed GCM wise. From the results it can be observed that the performance of the GCMs vary depending on the sub-zone as well as on the precipitation index. Final conclusions are made by removing the poor performing GCMs and by analyzing the overall changes in the PDFs of the remaining GCMs.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.04a
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• pp.163-167
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• 2003

Based on the transient finite difference solution of Richards' equation, an infiltration model is developed to analyze temporal variation of precipitation recharge in the region of monsoon climates. Simulation results obtained by using time series data of 20-year daily precipitation and pan evaporation indicate that a linear relationship between the annual precipitation and the annual recharge holds for the soils under the monsoon climates with varying degrees of the correlation coefficient depending on the soil types. A sensitivity analysis reveals that the water table depth has little effects on the recharge for the sandy soil, whereas, for the loamy and silty soils, rise of the water table at shallow depths causes increase of evaporation by approximately 100㎜/yr and a corresponding decrease in recharge. A series of simulations for two-layered soils illustrate that the amount of recharge is dominantly determined by the soil properties of the upper layer, although the temporal variation of recharge is affected by both layers.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.05a
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• pp.334-337
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• 2003

The results of this numerical model is usable to analysis for the phenomena of precipitation during the periods of a rainy season in the Northeastern Asia. Case l(start of rainy season) dominates over precipitation by the processing of convection from the equator region through the East China region, and then the most of water vapor is transported by the processing of advection from the India-monsoon region to this study region. Case 2(heavy rainy season) faints precipitation by the processing of convection in the Korean peninsula, but dominates precipitation by the processing of microphysics. the water vapor originates from the India-monsoon region.

• Korean Journal of Ecology and Environment
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• v.52 no.1
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• pp.40-49
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• 2019

Seasonal succession of zooplankton community and species composition was studied from 2003 to 2014 in a deep reservoir, Lake Soyang, in monsoon climate region, Korea. Annual precipitation was concentrated more than 70% between June and September and it showed remarkably that seasonal variation in water quality. Seasonal variation of water quality in Lake Soyang appeared to be more significant than annual variations, and the inflow of turbid water during the summer rainfall was the most important environmental factor. Zooplankton sepecies composition in Lake Soyang showed obvious tendency through two periods (May to June and August to October) every year. Small zooplankton (rotifer; Keratella cochlearis, Polyarthra vulgaris) dominated in spring and mesozooplankton such as copepods and crustaceans were dominant in summer and fall. Zooplankton biomass showed the maximum in September after monsoon rainfall, and chlorophyll showed a similar seasonal variation and it showed a high correlation (r=0.45). The increase of zooplankton biomass is considered to be a bottom-up effect due to the increase of primary producers and inflow of nutrients and organic matter from rainfall. In this study, we found that the variation of zooplankton community was affected by rainfall in monsoon climate region and inflow of turbid water was an important environmental factor, which influenced the water quality, zooplankton seasonal succession in Lake Soyang. It was also considered to be influenced by hydrological characteristics of lake and environment of watershed. In conclusion, seasonal succession of zooplankton species composition was the same as the PEG model. But seasonal succession of zooplankton biomass differed not only in the temperate lake but also in the monsoon region.