• Title/Summary/Keyword: rain gauge

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A Methodology for Rain Gauge Network Evaluation Considering the Altitude of Rain Gauge (강우관측소의 설치고도를 고려한 강우관측망 평가방안)

  • Lee, Ji Ho;Jun, Hwan Don
    • Journal of Wetlands Research
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    • v.16 no.1
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    • pp.113-124
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    • 2014
  • The observed rainfall may be different along with the altitude of rain gauge, resulting in the fact that the characteristics of rainfall events occurred in urban or mountainous areas are different. Due to the mountainous effects, in higher altitude, the uncertainty involved in the rainfall observation gets higher so that the density of rain gauges should be more dense. Basically, a methodology for the rain gauge network evaluation, considering this altitude effect of rain gauges can account for the mountainous effects and becomes an important step for forecasting flash flood and calibrating of the radar rainfall. For this reason, in this study, we suggest a methodology for rain gauge network evaluation with consideration of the rain gauge's altitude. To explore the density of rain gauges at each level of altitude, the Equal-Altitude-Ratio of the density of rain gauges, which is based on the fixed amount of elevation and the Equal-Area-Ratio of the density of rain gauges, which is based on the fixed amount of basin area are designed. After these two methods are applied to a real watershed, it is found that the Equal-Area-Ratio generates better results for evaluation of a rain gauge network with consideration of rain gauge's altitude than the Equal-Altitude-Ratio does. In addition, for comparison between the soundness of rain gauge networks in other watersheds, the Coefficient of Variation (CV) of the rain gauge density by the Equal-Area-Ratio is served as the index for the evenness of the distribution of the rain gauge's altitude. The suggested method is applied to the five large watersheds in Korea and it is found that rain gauges installed in a watershed having less value of the CV shows more evenly distributed than the ones in a watershed having higher value of the CV.

Effect of Threshold on the Comparison of Radar and Rain Gauge Rain Rate (레이더 강우와 지상강우 비교에 대한 임계값의 영향 평가)

  • Yoon, Jungsoo;Ha, Eunho;Yoo, Chulsang
    • Proceedings of the Korea Water Resources Association Conference
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    • 2015.05a
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    • pp.522-522
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    • 2015
  • In this study, the effect of threshold applied to the radar rain rate on the comparison of the radar and rain gauge rain rate was theoretically examined. The result derived was also evaluated theoretically, using the Bernoulli random field, and empirically, using Mt. Kwanak weather radar data. The results are summarized as follows. (1) In the application to the Bernoulli random field, it was found that the comparison of the radar and rain gauge rain rate with threshold does not introduce any systematic bias. (2) The same results could also be derived in the application to Mt Kwanak weather radar data. In all cases with several radar bin sizes and thresholds considered, the bias was estimated to be far less than 10% of the mean of the rain gauge rain rate. (3) However, in the comparison with threshold applied to both the radar and rain gauge rain rate, the bias was estimated to be higher than 20%. That is, the systematic bias was introduced. This result indicates that the comparison with threshold applied to both the radar and rain gauge rain rate should not be used.

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Development of a smart rain gauge system for continuous and accurate observations of light and heavy rainfall

  • Han, Byungjoo;Oh, Yeontaek;Nguyen, Hoang Hai;Jung, Woosung;Shin, Daeyun
    • Proceedings of the Korea Water Resources Association Conference
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    • 2022.05a
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    • pp.334-334
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    • 2022
  • Improvement of old-fashioned rain gauge systems for automatic, timely, continuous, and accurate precipitation observation is highly essential for weather/climate prediction and natural hazards early warning, since the occurrence frequency and intensity of heavy and extreme precipitation events (especially floods) are recently getting more increase and severe worldwide due to climate change. Although rain gauge accuracy of 0.1 mm is recommended by the World Meteorological Organization (WMO), the traditional rain gauges in both weighting and tipping bucket types are often unable to meet that demand due to several existing technical limitations together with higher production and maintenance costs. Therefore, we aim to introduce a newly developed and cost-effective hybrid rain gauge system at 0.1 mm accuracy that combines advantages of weighting and tipping bucket types for continuous, automatic, and accurate precipitation observation, where the errors from long-term load cells and external environmental sources (e.g., winds) can be removed via an automatic drainage system and artificial intelligence-based data quality control procedure. Our rain gauge system consists of an instrument unit for measuring precipitation, a communication unit for transmitting and receiving measured precipitation signals, and a database unit for storing, processing, and analyzing precipitation data. This newly developed rain gauge was designed according to the weather instrument criteria, where precipitation amounts filled into the tipping bucket are measured considering the receiver's diameter, the maximum measurement of precipitation, drainage time, and the conductivity marking. Moreover, it is also designed to transmit the measured precipitation data stored in the PCB through RS232, RS485, and TCP/IP, together with connecting to the data logger to enable data collection and analysis based on user needs. Preliminary results from a comparison with an existing 1.0-mm tipping bucket rain gauge indicated that our developed rain gauge has an excellent performance in continuous precipitation observation with higher measurement accuracy, more correct precipitation days observed (120 days), and a lower error of roughly 27 mm occurred during the measurement period.

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Method for Analysis on Optimization of Averaging Interval of Rainfall Rate Measured by Tipping-Bucket Rain Gauges

  • Nam, Kyung-Yeub;Chang, Ki-Ho;Kim, Kyung-Eak;Oh, Sung-Nam;Choi, Young-Jean;Kim, Kyung-Sik;Lee, Dong-In;Kim, Kum-Lan
    • Korean Journal of Remote Sensing
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    • v.24 no.1
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    • pp.17-24
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    • 2008
  • Rainfall data from three different types of rain gauge system have been collected for the summertime rain event at Mokpo in the Korean peninsula. The rain gauge system considered in this paper is composed of three tipping-bucket rain gauges with 0.1, 0.2, and 0.5 mm measuring resolutions, the Optical Rain Gauge (ORG), and the PARSIVEL (PARticle SIze and VELocity). The PARSIVEL rainfall rate has been considered as the reference for comparison since it gave good resolution and performance on this event. Comparison with the PARSIVEL rainfall rate gives the results that the error and temporal variation of rainfall rate are simultaneously reduced with increasing the averaging interval of rainfall rate or decreasing the size of tipping bucket. This suggests that the estimated rainfall rate must be optimized, differently for the type of tipping-bucket rain gages, by minimizing the averaging interval of rainfall rate under the condition satisfying the given performance of rainfall rate.

Effect of Combined Rainfall Observation with Radar and Rain Gauge (강우 레이더와 지상 우량계의 통합관측효과)

  • Yoo, Chul-Sang;Kim, Kyoung-Jun
    • Journal of Korea Water Resources Association
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    • v.40 no.11
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    • pp.841-849
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    • 2007
  • This study evaluated the effect of combined rainfall observation of using rain gauge and rain radar. The effect of combined observations is to be evaluated by considering the decrease of measurement error due to combined use of design orthogonal observation methods. As an example, this study evaluated the rain gauge network of the Keum river basin, and showed how the density of rain gauges could be decreased by combining the radar observation. This study applied the researches on sampling error by North and Nakamoto(1989), Yoo et al. (1996) and Yoo (1997), also the simple NFD model for representing the rainfall field. The model parameters were decided using the rainfall characteristics (correlation time and length) estimated using the data collected in the Keum River Basin by 28 rain gauges and the operation rule of radar was assumed arbitrarily. This study considered the rain gauge density criteria provided by WMO(1994) and the rain gauge density installed in the Keum river basin to decrease the rain gauge density under the condition of introducing the radar.

Evaluation of Rain Gauge Distribution Characteristics by Altitude using Optimization Technique (최적화 기법을 통한 강우관측소의 고도별 분포특성 검토)

  • Lee, Ji Ho;Kim, Jong Geun;Joo, Hong Jun;Jun, Hwan Don
    • Journal of Wetlands Research
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    • v.19 no.1
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    • pp.103-111
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    • 2017
  • In this study, we estimate the NNI(Nearest Neighbor Index) which is considered altitude of rain gauge network as a method for evaluating appropriateness of spatial distribution and the current rain gauge network is evaluated. The altitude is divided by equal-area-ratio and optimal NNI within given basin condition is estimated using harmony search method for considering geographical conditions that vary from altitude to altitude. After calculating current state and optimal NNI for each altitude, the distribution of the rain gauge network is evaluated based on the difference between the two NNIs. As a result, it founds that the density of rain gauge networks is relatively thin as the altitude increases. Furthermore, it will be possible to construct an efficient rain gauge network if the characteristics of different altitudes are considered when a new rain gauge network is newly constructed.

A Study on Confidence Evaluation of the Observed Data According to the Rain Gauges Installation Conditions (우량계 설치조건에 따른 관측치 신뢰성 평가 연구)

  • Park, Ji-Chang;Kim, Nam;Kang, Myeong-Ju;Ryoo, Kyong-Sik
    • Journal of Environmental Science International
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    • v.18 no.10
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    • pp.1115-1121
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    • 2009
  • The purpose of this study is to estimate the impact of rainfall measurement according to the installation conditions of rain gauges: windbreak, grass mat, installation elevation or obstacle. Rain gauges were installed by the standards of Korea Meteorological Administration(KMA), and the rainfall measurement was conducted daily unit during two years(2007~2008). In conclusion, observed error of rain gauge did not affect whether windbreak was installed or not. If there is the obstacle around rain gauge, average error rate was increased about 3.3%: (2007year-2.49%, 2008year-4.10%). If rain gauge is located in a high place, average error rate was increased about 4.89%. Additionally, the observed error of rain gauge according to the wind speed has a positive correlation with obstacle and installation elevation and has a negative correlation with windbreak and has no affection with grass mat.

Optimal Rain Gauge Density and Sub-basin Size for SWAT Model Application (SWAT 모형의 적용을 위한 적정 강우계밀도의 추정)

  • Yoo, Chul-Sang;Kim, Kyoung-Jun;Kim, Nam-Won
    • Journal of Korea Water Resources Association
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    • v.38 no.5 s.154
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    • pp.415-425
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    • 2005
  • This study estimated the optimal rain gauge density and sub-basin size for the application of a daily rainfall-runoff analysis model called SWAT (Soil and Water Assessment Tool). Simulated rainfall data using a WGR multi-dimensional precipitation model (Waymire et al., 1984) were applied to SWAT for runoff estimation, and then the runoff error was analyzed with respect to various rain gauge density and sub-basin size. As results of the study, we could find that the optimal sub-basin size and the representative area of one rain gauge are similar to be about $80km^2$ for the Yong-Dam dam basin.

Non-Destructive Material Analysis and Comparative Study of the Changdeok Palace "Chugudae" and National Designated "Chugudae" (창덕궁 이문원 측우대의 비파괴 재질 분석과 국가지정 측우대와의 비교)

  • Ahn, Yubin;Yoo, Jihyun;Lee, Myeongseong
    • Korean Journal of Heritage: History & Science
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    • v.53 no.3
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    • pp.244-257
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    • 2020
  • State-designated rain gauge pedestals, including a rain gauge support, were installed in front of the "Imunwon" at Changdeok Palace, made from various rock types. Some of those pedestals provide exact information on their production dates. These rain gauge pedestals are highly valuable as scientific instruments; however, there has been insufficient scientific research carried out on them. Therefore, precise analysis and conservative consideration are required. As a result of petrographic character analysis, the Changdeokgung rain gauge pedestal has been classified as marble. Furthermore, comparison of the results of P-XRF analysis with GSJ reference samples (JLs-1, JDo-1) has determined it to be dolomitic marble. Applying the same analysis to other state-designated rain gauge pedestals, it was presumed that the rain gauge supports at Gyeongsand-do Provincial Office and Gwansanggam were each made from aplite, pinkish medium-to-coarse biotite granite. Results confirmed that only the Changdeokgung rain gauge pedestal was made from marble. Marble is viewed as having an identity specificity rooted in a certain historical background. According to the tendency towards stone figures being made from marble, especially dolomitic marble, it is necessary to further studies whether particular rocks were used to make royal stone figures in Joseon Dynasty.

Evaluation of Spatially Disproportionate Rain Gauge Network for the Correction of Mean-Field Bias of Radar Rainfall: A Case Study of Ganghwa Rain Radar (레이더 강우의 편의 보정을 위한 지역적으로 편중된 우량계망의 평가: 강화 강우레이더의 사례 연구)

  • Yoo, Chul-Sang;Yoon, Jung-Soo;Kim, Byoung-Soo;Ha, Eun-Ho
    • Journal of Korea Water Resources Association
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    • v.42 no.6
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    • pp.493-503
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    • 2009
  • Estimation of the mean-field bias of radar rainfall is to determine the difference between the areal means of radar and rain gauge rainfall, where the rain gauge rainfall is assumed to be the truth. To exactly determine this bias, the variance of the difference between two observations must be small enough, thus, enough number of observations is indispensible. So, the problem becomes to determine the number of rain gauges to satisfy the level of variance of the difference between two observations. Especially, this study focuses on the case when the rain gauges are disproportionate spatially. This is the problem for the Ganghwa rain radar for the observation of rainfall within the Imjin river basin and the same problem also occurs when a radar is located in between land and ocean. This study considered the Imjin river basin, and compared two cases when rain gauges are available only within the downstream part, about one third of the whole basin, and over the whole basin. Based on the results derived, the rain gauge density within the downstream part of the Imjin river basin was proposed to secure the same accuracy obtained when the rain gauges are available over the whole Imjin river basin.