• 한국지구과학회지
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• 제30권1호
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• pp.58-68
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• 2009

몬순 기간에 구름의 복사 강제력의 영향을 파악하기 위하여 1998년 4월부터 9월까지 International Satellite Cloud Climatology Project (ISCCP) 구름자료와 GEWEX Asian Monsoon Experiment (GAME) 재분석 자료를 입력 자료로 복사 모델을 수행하여 3차원의 장파 복사 플럭스를 구하였다. 구름에 의한 대기 복사 가열은 구름을 포함한 평균 대기와 맑은 대기에서의 복사 가열율의 차이를 이용하여 계산하였다 구름에 의한 복사 가열율이 아시아 몬순에 미치는 영향을 중점적으로 살펴보았다. 구름에 의한 복사 가열은 인도양에서 최대를 티벳 고원에서 최소를 나타내어, 남북으로 차등 가열의 경도를 나타내었다. 이러한 차등 가열이 대기 순환의 최대 원인임을 고려해볼 때, 인도양과 티벳 고원에서의 구름에 의한 차등 가열의 경도는 해들리 타입의 남북 몬순 순환을 강화시키고 있다. 또한 운정에서의 가열, 운저에서의 냉각의 형태로 나타나는 구름의 복사 가열 분포는, 대기의 불안정성을 높여서 몬순 순환을 증대시킬 수 있는 역할을 하고 있다.

• 대기
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• 제28권4호
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• pp.415-425
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• 2018

The roles of atmospheric heating formation and distribution on the global circulation are of utmost importance, and those are directly related to not only spatial but also temporal characteristics of monsoon system. In this study, before we clarify the characteristics of apparent heat source <$Q_1$> and moisture sink <$Q_2$>, comparisons of three reanalysis datasets (NCEP2, ERA-Interim, and JRA-55) in its global or regional patterns are performed to clearly evaluate differences among datasets. Considering inter-hemispheric difference of global monsoon regions, seasonal means of June-July-August and December-January-February, which is summer (winter) and winter (summer) in the Northern (Southern) Hemisphere are employed respectively. Here we show the characteristics of eight different regional monsoon regions and find contributions of <$Q_2$> to <$Q_1$> for the regional monsoon regions. Each term in apparent heat source and moisture sink is shown to come from the ERA-Interim dataset, since the ERA-Interim could be representative of three datasets. The NCEP2 data has a different characteristic in the ratio of <$Q_2$> and <$Q_1$> because it overestimates <$Q_1$> compared to the other two different datasets. The Australia monsoon has been performing better over time, while some regional monsoons (South America, North America, and North Africa) have been showing increasing data inconsistency. In addition, the three reanalysis datasets are getting different marching with time, in particular since the early 2000s over South America, North America, and North Africa monsoon regions. The recent inconsistency among the three datasets that may be associated with the global warming hiatus remains unexplored.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 1999년도 Proceedings of International Symposium on Remote Sensing
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• pp.325-329
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• 1999

The characteristic of East Asian summer monsoon is investigated using 8-year (March 1987-February 1995) - averaged monthly and 5-day mean 1 degree latitude-longitude gridded GMS high-cloud-amount data (HCA). An analysis of these data shows the convective zone (ITCZ) clouds which defined as the percentage of the total grid area covered by clouds with a cloud-top temperature below the 400 hPa-level climatological temperature. The HCA increased clearly over equatorial zone during December and January and 30-40 $^{\circ}$N during May and June. These HCA patterns are coincided with seasonal cycles of summer monsoon which is introduced in historical references. The relationship with the summer monsoon winds as climatological changing of wind direction is analyzed by ECMWF re-analysis 2.5-degree latitude-longitude grid surface data which is calculated with 8-year averaged from January 1987 to January 1995. In addition, the monsoon winds are showed by separated U, V-wind components far manifestation a tendency of onset and retreat data of seasonal monsoon.

• 한국제4기학회지
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• 제24권1호
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• pp.1-10
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• 2010

The Indian summer monsoon behaved an abnormal way in 2002 and as a result there was a large deficiency in precipitation (especially in July) over a large part of the Indian subcontinent. For the study of deficient monsoon of 2002, a recent version of the NCAR regional climate model (RegCM3) has been used to examine the important features of summer monsoon circulations and precipitation during 2002. The main characteristics of wind fields at lower level (850 hPa) and upper level (200 hPa) and precipitation simulated with the RegCM3 over the Indian subcontinent are studied using different cumulus parameterization schemes namely, mass flux schemes, a simplified Kuo-type scheme and Emanuel (EMU) scheme. The monsoon circulation features simulated by RegCM3 are compared with the NCEP/NCAR reanalysis and simulated precipitation is validated against observation from the Global Precipitation Climatology Centre (GPCC). Validation of the wind fields at lower and upper levels show that the use of Arakawa and Schubert (AS) closure in Grell convection scheme, a Kuo type and Emanuel schemes produces results close to the NCEP/NCAR reanalysis. Similarly, precipitation simulated with RegCM3 over different homogeneous zones of India with the AS closure in Grell is more close to the corresponding observed monthly and seasonal values. RegcM3 simulation also captured the spatial distribution of deficient rainfall in 2002.

• 한국제4기학회지
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• 제22권1호
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• pp.13-22
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• 2008

The Indian summer monsoon behaved in an abnormal way in 2002 and as a result there was a large deficiency in precipitation (especially in July) over a large part of the Indian subcontinent. For the study of deficient monsoon of 2002, a recent version of the NCAR regional climate model (RegCM3) has been used to examine the important features of summer monsoon circulations and precipitation during 2002. The main characteristics of wind fields at lower level (850 hPa) and upper level (200 hPa) and precipitation simulated with the RegCM3 over the Indian subcontinent are studied using different cumulus parameterization schemes namely, mass flux schemes, a simplified Kuo-type scheme and Emanuel (EMU) scheme. The monsoon circulation features simulated by RegCM3 are compared with the NCEP/NCAR reanalysis and simulated precipitation is validated against observation from the Global Precipitation Climatology Centre (GPCC). Validation of the wind fields at lower and upper levels shows that the use of Arakawa and Schubert (AS) closure in Grell convection scheme, a Kuo type and Emanuel schemes produces results close to the NCEP/NCAR reanalysis. Similarly, precipitation simulated with RegCM3 over different homogeneous zones of India with the AS closure in Grell is more close to the corresponding observed monthly and seasonal values. RegcM3 simulation also captured the spatial distribution of deficient rainfall in 2002.

• 생태와환경
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• 제41권spc호
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• pp.27-34
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• 2008

본 연구는 부영양상태의 신구저수지에서 강우기 전 후의 수질 변화와 강우기 유입수의 영향을 평가하기 위해 이루어졌다. 강우기 전에는 수심에 따른 수온차가 $1^{\circ}C$이하였지만 강우기 후에는 $4^{\circ}C$차 이상까지 벌어져 수온 약층이 뚜렷하게 형성되었다. 탁도는 강우기 전보다 강우기 후에 표층에서 12NTU, 저층 120NTU로 크게 증가하였다. POC의 농도는 강우기 전의 조사에서 수심에 따라서 $4.96{\sim}6.68mg\;L^{-1}$의 범위를 나타내고 강우기 후의 조사에서는 $1.73{\sim}5.32mg\;L^{-1}$의 범위를 나타내고 있어 전체적으로 강우기 전보다 강우기 후의 POC의 농도가 낮았으나 수심에 따라서 크게 증가하는 경향을 보이고 있다. 또한, DOC의 농도는 강우기 전의 조사에서 $3.82{\sim}3.96mg\;L^{-1}$의 범위를 나타내고 있고, 강우기 후의 조사에서 $2.18{\sim}2.57mg\;L^{-1}$의 범위를 나타내고 있어 전체적으로 강우기 전보다 강우기 후의 DOC농도는 감소하고 있다. 또한 강우기 후 저층의 높은 탁도층에서 강우기 전보다 입자성유기물의 C/N비가 크게 증가하였고 입자성 유기물의 ${\delta}^{13}C$와 ${\delta}^{15}C$값이 뚜렷하게 가벼운 값을 보이는 것으로 볼 때 저수지 주변 유역에서 유입된 유기물의 영향을 크게 받았다는 것을 알 수 있다. 본 연구 결과로 볼 때 농업용 저수지인 신구저수지는 하계 강우기시 유입하천을 통해 외부로부터 유입된 육상식물 유기물이 저층에 부유된 상태로 존재하며 이는 저수지 내 저층 수생태계의 에너지 흐름에 영향을 줄 수 있는 것으로 사료된다.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2023년도 학술발표회
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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.

• 한국제4기학회:학술대회논문집
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• 한국제4기학회 2004년도 하계학술대회
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• pp.24-25
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• 2004

It is well known that there is an inverse relationship between the strength of Indian summer monsoon Rainfall (ISMR) and extent of Eurasian snow cover/depth in the preceding season. Tibetan snow cover/depth also affects the Asian monsoon rainy season largely. The positive correlation between Tibetan sensible heat flux and southeast Asian rainfall suggest an inverse relationship between Tibetan snow cover and southeast Asian rainfall. Developments in Regional Climate Models suggest that the effect of Tibetan snow on the ISMR can be well studied by Limited Area Models (LAMs). LAMs are used for regional climate studies and operational weather forecast of several hours to 3 days in future. The Eta model developed by the National Center for Environmental Prediction (NCEP), the Fifth-Generation NCAR/Penn State Mesoscale Model (MM5) and Regional Climate Model (RegCM) have been used for weather prediction as well as for the study of present-day climate and variability over different parts of the world. Regional Climate Model (RegCM3) has been widely . used for various mesoscale studies. However, it has not been tested to study the characteristics of circulation features and associated rainfall over India so far. In the present study, Regional Climate Model (RegCM-3) has been integrated from 1 st April to 30th September for the years 1993-1996 and monthly mean monsoon circulation features and rainfall simulated by the model at 55km resolution have been studied for the Indian summer monsoon season. Characteristics of wind at 850hPa and 200hPa, temperature at 500hPa, surface pressure and rainfall simulated by the model have been examined for two convective schemes such as Kuo and Grell with Arakawa-Schubert as the closure scheme, Model simulated monsoon circulation features have been compared with those of NCEP/NCAR reanalyzed fields and the rainfall with those of India Meteorological Department (IMD) observational rainfall datasets, Comparisons of wind and temperature fields show that Grell scheme is closer to the NCEP/NCAR reanalysis, The influence of Tibetan snowdepth in spring season on the summer monsoon circulation features and subsequent rainfall over India have been examined. For such sensitivity experiment, NIMBUS-7 SMMR snowdepth data have been used as a boundary condition in the RegCM3, Model simulation indicates that ISMR is reduced by 30% when 10cm of snow has been introduced over Tibetan region in the month of previous April. The existence of Tibetan snow in RegCM3 also indicates weak lower level monsoon westerlies and upper level easterlies.

• 생태와환경
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• 제40권4호
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• pp.503-510
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• 2007

The purposes of the study were to analyze the seasonal effects on the fish fauna and compositions including trophic guilds and tolerance guilds. For the study, we collected fish samples twice in June as premonsoon period and early September 2007 as monsoon periods in five sampling sites of the Gap Stream, and then biological oxygen demand (BOD), nutrients (TN, TP) and suspended solids (SS) were compared with the guild data along the gradient of upstream-to-downstream. Chemical water quality, based on BOD, TP, and TN degraded gradually from the upstream to downstream reach and there were about 3 fold difference between S1 and S5. Water quality was worse in the premonsoon than the monsoon, and the heavy monsoon resulted in a dilution of the polluted river by rain water, especially, in the downstream reach. Total number of fish species, based on the catch per unit effort (CPUE), showed a distinct difference between the two seasons; 30 species were sampled in premonsoon, but 23 species were sampled in the monsoon, indicating a seasonal difference in the fish fauna. Tolerant species dominated the fish community (48.3%) in the stream, and the proportions prior to physical disturbance by the monsoon rain were evidently greater in the downstream reach than the upstream. This reflected the characteristics of urban stream polluted by nutrient enrichment as shown in the BOD and TP values. Sensitive species in the premonsoon decreased from the gradient of upstream-to-downstream reach. Such seasonal modifications in the trophic and tolerance guilds were evident. In the analysis of trophic guild and habitat guild, during the premonsoon the proportion of insectivore and riffle-benthic species were largely greater in the upstream reach than the downstream, whereas the proportions were opposite along the gradient of the stream in monsoon. Thus, the patterns of chemical water quality along the longitudinal gradients reflected the premonsoon conditions of insectivores and tolerant species, indicating that summer monsoon data of fish may not match with water quality due to large physical disturbance by flow regime. Seasonal monsoon in this region as well as the chemical pollution may act as a key role influencing the fish compositions of trophic and tolerance guilds and fauna. The data collected during the premonsoon rather than the monsoon, thus, may be better predictor for a diagnosis of stream health conditions.

• Ocean and Polar Research
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• 제27권3호
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• pp.289-297
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• 2005

The change in global climate and Asian monsoon patterns during the mid-Holocene, 6000 years before present (6 ka), is simulated by a climate model at spectral truncations of T170 with 18 vertical layers, corresponding to grid-cell sizes of roughly 75km. The present simulation is forced with the observed monthly data of sea surface temperatures, and the specified concentration of atmospheric carbon dioxide, while in the mid-Holocene experiment, orbital parameters such as obliquity, precession, and eccentricity are changed to the 6ka conditions. Under such conditions, the precipitation associated with the summer monsoon is enhanced over a wider zonal band from the Middle East to Southeast Asia, while no significant alteration takes Place in winter. The monsoonal wind also increases over the Arabian Sea, showing the enhanced southwesterly wind during summer and northeasterly wind during winter. Overall, the showing of the Asian monsoon is enhanced during the mid-Holocene, especially in summer, which is consistent with the proxy estimates and other previous model simulations.