• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.276-276
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• 2023

미국의 열대저기압(tropical cyclone)은 강풍, 폭우, 해일 등의 위험을 동반하는 기후와 관련된 자연재해다. 여러 연구에 따르면 열대저기압이 동반하는 강우는 해안과 내륙지역에서의 홍수로 이어지며 인명피해 및 경제적 손실의 주원인인 것으로 조사되었다. 최근 열대저기압이 동반하는 강우와 해안지역에서 열대저기압의 이동 특성과 관련하여 다양한 연구가 진행되고 있다. 또한, 열대폭풍(tropical storm)은 열대저기압에 비해 바람세기의 등급은 낮지만 비교적 많은 양의 강우를 동반하는 경우가 많았다. 따라서, 본 연구에서는 미국 남동부에서 1979년부터 2021년 사이에 발생한 열대폭풍이 동반한 극한강우와 열대폭풍의 이동 특성을 관련지어 분석하였다. 열대폭풍 보다 높은 등급의 사상에 대한 이동 경로, 거리, 속도 등의 자료를 얻기 위해 HURDAT2를 이용하고, 열대폭풍의 이동과 중심반경에 따른 강우자료를 얻기 위해 NLDAS-2와 시공간분석을 수행하였다. 분석결과, 2000년도를 기준으로 과거기간(1979-2000년)과 현재기간(2000-2021년)에 대하여 열대폭풍의 해안과 내륙지역 이동에 따른 극한강우의 경향성과 변동추세 및 강우 특성을 확인할 수 있었다. 본 연구는 열대폭풍의 이동에 따른 극한강우의 특성을 이해하는데 유용한 정보로 활용될 것으로 예상된다.

• Korean Journal of Remote Sensing
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• v.34 no.6_2
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• pp.1299-1310
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• 2018

In this study, we analyzed distribution and movement trends using in-situ observations and particle tracking methods to understand the movement of the drift ice in the Arctic Ocean. The in-situ movement data of the drift ice in the Arctic Ocean used ITP (Ice-Tethered Profiler) provided by NOAA (National Oceanic and Atmospheric Administration) from 2009 to 2018, which was analyzed with the location and speed for each year. Particle tracking simulates the movement of the drift ice using daily current and wind data provided by HYCOM (Hybrid Coordinate Ocean Model) and ECMWF (European Centre for Medium-Range Weather Forecasts, 2009-2017). In order to simulate the movement of the drift ice throughout the Arctic Ocean, ITP data, a field observation data, were used as input to calculate the relationship between the current and wind and follow up the Lagrangian particle tracking. Particle tracking simulations were conducted with two experiments taking into account the effects of current and the combined effects of current and wind, most of which were reproduced in the same way as in-situ observations, given the effects of currents and winds. The movement of the drift ice in the Arctic Ocean was reproduced using a wind-imposed equation, which analyzed the movement of the drift ice in a particular year. In 2010, the Arctic Ocean Index (AOI) was a negative year, with particles clearly moving along the Beaufort Gyre, resulting in relatively large movements in Beaufort Sea. On the other hand, in 2017 AOI was a positive year, with most particles not affected by Gyre, resulting in relatively low speed and distance. Around the pole, the speed of the drift ice is lower in 2017 than 2010. From seasonal characteristics in 2010 and 2017, the movement of the drift ice increase in winter 2010 (0.22 m/s) and decrease to spring 2010 (0.16 m/s). In the case of 2017, the movement is increased in summer (0.22 m/s) and decreased to spring time (0.13 m/s). As a result, the particle tracking method will be appropriate to understand long-term drift ice movement trends by linking them with satellite data in place of limited field observations.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.15 no.5
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• pp.12-19
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• 2016

An average of 20 million individual transit unit activities per day on the Seoul-Gyeonggi-Incheon public transportation network are provided as transportation card analysis data by the metropolitan district (99.02% by 2014 standard, Humanlive, 2015.4). The metropolitan transportation card data can be employed in a comprehensive analysis of public transportation users' current transit patterns and by means of this, an effective use plan can be explored. In enhancing the existing information on the bus and rail integrated network of the metropolis with public transportation card data, the constraints in the existing methodology of metropolitan transit analysis, which functions on a zone unit origin and destination basis, can be overcome. Framework for metropolitan public transportation card data based integrated public transportation analysis, which consists of bus and rail integrated transport modes, is constructed, and through this, a single passenger's transit behavior transit volume can be approximated. This research proposes that in the use of metropolitan public transportation card data, integrated public transportation usage, as a part of individual passenger spatial movements, can be analyzed. Furthermore, metropolitan public transportation card usage data can provide insights into understanding not only movements of populations taking on transit activities, but also, characteristics of metropolitan local space.

• Journal of The Korean Society For Urban Railway
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• v.6 no.4
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• pp.373-381
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• 2018

The floating population that is index to figure out dynamic activities in urban area will be important in urban railway planning, but it is not useful because it is collected by posterior method. This study aims to investigate factors influencing floating population. The floating population data that was collected in Seoul for a month in December 2013 is used as dependent variable, and the negative binomial regression analysis is used in modelling. The number of households, number of employees, number of subway stations, and number of bus lines variables are statistically significant in predicting floating population.

• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.361-361
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• 2018

강우패턴이 유출반응에 미치는 영향을 분석하는 것은 수문연구에서 중요한 주제 중 하나이며 댐유역에 대해 기상 및 유출자료를 사용하여 이를 상세히 분석함으로써 이수기에 필요한 수자원을 예측 및 확보하는 것은 중요하다. 강우패턴이 유출반응에 미치는 영향을 상세히 분석하기 위해서는 댐유역의 상류부터 하류까지 많은 유출관측지점의 자료를 사용해야 하지만 상류의 소유역들은 대부분 미계측유역이라는 문제점이 있다. 본 연구에서는 자료공간확장 방법을 사용하여 미계측유역의 유출자료를 생성하고 이 자료들을 분석함으로써 강우패턴이 유출반응에 미치는 영향을 자세히 분석하였다. 먼저 안동댐유역내 관측유역인 안동댐, 도산, 소천유역을 대상으로 1989년부터 2009년까지의 기간 중 20개의 사상에 대하여 분포형 모형인 GRM 모형의 적용성을 조사하였으며 전반적으로 0.5 Nash-Sutcliffe 계수 이상의 타당한 모형효율성 결과를 얻었다. 그 후 자료공간확장 방법을 사용하여 안동댐 상류에 위치한 47개의 미계측 소유역들의 유출자료를 생성하였으며 세 관측유역을 포함한 총 50개 유역의 유출자료를 연구에 사용하였다. 그리고 총 50개 유역의 평균강우량 시계열 자료를 생성하고 이동평균방법을 사용하여 이 평균강우량 자료를 강우강도-지속시간 곡선으로 변환하였다. 강우패턴과 유출반응간의 관계를 분석하기 위해 합리식의 유출계수와 강우강도비율을 사용하였으며 유출계수와 강우강도비율을 계산하기 위해 유역별 도달시간을 사용하였다. 여기서 강우강도비율은 강우강도지속시간 곡선을 사용하여 첨두강우강도를 도달시간에 해당하는 평균강우강도로 나눠준 값이다. 그리고 이 유출계수와 강우강도비율을 유역면적에 대해 도시함으로써 그 경향을 조사하였다. 그 결과 20개 사상은 유출계수, 강우강도비율과 유역면적을 사용하여 물리적으로 타당한 네 가지의 타입으로 분류될 수 있었다. 이 네 가지 타입은 강우의 이동 및 분포와 상관이 있었는데 첫번째 타입은 안동댐 유역전체에 강우가 거의 등분포하는 경우, 두 번째는 강우가 유역의 상류방향으로 이동하는 경우, 세 번째는 강우가 유역의 하류방향으로 이동하는 경우, 그리고 네 번째는 강우가 유역에 무작위로 분포하는 경우였다. 이것은 어떠한 사상에 대해서도 유출계수와 강우강도비율을 유역면적에 대해 도시함으로써 강우패턴과 유출간의 관계를 분석할 수 있다는 것을 나타낸다. 그리고 이 네 가지 타입에 대한 강우사상들의 비율은 각각 65%, 20%, 10%, 그리고 5% 였다. 이 타입별 강우사상의 비율은 향후 강우-유출관계에 의한 수자원 예측 및 확보에 활용될 수 있다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.4B
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• pp.355-362
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• 2006

Several techniques of MK test, Spearman's Rho test, Linear Regression test, CUSUM test, Cumulative Deviation, Worsley Likelihood Ratio test, Rank Sum test, and Students' t test were applied to detect the trends of slope and shift which exist in hydrologic and climate time series. The time series of annual rainfall, inflow, tree ring index, and southern oscillation index (SOI) were used and the trends of these series were compared in the study. From the results, it can be found that the data could be classified into two categories such as linear trend and shift. 4 series data of 8 rainfall series which reveal the trend show the shift and 8 series data of 18 tree ring index and March and April series of monthly SOI data show shift. Moreover, ADF test and BDS test were used to test stationarity and non-linearity of the data. In conclusion, through the study, various trend analysis techniques were compared and 6 kinds of characteristics which can exist in hydrologic time series were identified.

• Journal of the Korean Regional Science Association
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• v.39 no.4
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• pp.111-125
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• 2023

China's rapid economic growth and accelerated urbanization have significantly increased labor force mobility. The choice of city residence and long-term residence intentions of migrants will have significant consequences on both economic output and societal dynamics. This paper investigates the impact of air quality on the long-term residence intention of migrants. By matching an individual-level survey on willingness to stay in the long run and the city-level air quality, represented by PM2.5, we find that the willingness to stay in the long run increases with better air quality. This implies that public policy to maintain good air quality is crucial in keeping those who moved to the city.

• Journal of Korean Society of Transportation
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• v.34 no.3
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• pp.222-233
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• 2016

Recently, mobile phone data was applied in travel demand modeling as a new source of dynamic population movement. This study is also aimed to estimate "occupancy population" during a given period of time within a given spatial region using mobile phone data. An occupancy population was defined as the number of people residing or moving within a given time and space. In case of Seoul Metropolitan area, we divided the area into a number of administrative districts as zones for analysis and estimated the occupancy population of each zone by mobile phone data collected by SK telecom Co., a wireless telecommunication provider in Korea. For the expansion of mobile phone data, a new concept of "communication probability" was introduced and applied in the estimation of occupancy population of each zone by the hour. We compared the estimated number with the daytime population and the daytime population index referred by the Statistics Korea. The results showed that a positive correlation existed between the estimated number and the statistical number by nationwide survey. It was concluded that mobile phone data could be more cost-effective sources than a conventional survey method to estimate the pattern of population movement by the hour or by the day.

• The Korean Journal of Applied Statistics
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• v.19 no.2
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• pp.283-290
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• 2006

Generally speaking, power transformations such as Box-Cox transformation(1964) is applied for variance stabilization and symmetry. But, when the distribution of the original data has a large mean with a small variance or the coefficient of variation is very small, they don't work at all. This paper propose a simple method to introduce a shift parameter before applying power transformations and showed the numerical evidence by Monte Carlo simulation and a real data analysis.

• The Korean Journal of Applied Statistics
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• v.19 no.3
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• pp.379-393
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• 2006

In this paper, we propose a method to summarize the monthly traffic amount for analyzing network load in mobile communication system. We used the traffic data obtained from a domestic telecommunication company. Based on the statistical properties of the traffic data, we devise an efficient method to summarize monthly traffic amount.