• Title, Summary, Keyword: precipitation process

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A Stochastic Model for Precipitation Occurrence Process of Hourly Precipitation Series (시간강수계열의 강수발생과정에 대한 추계학적 모형)

  • Lee, Jae-Jun;Lee, Jeong-Sik
    • Journal of Korea Water Resources Association
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    • v.35 no.1
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    • pp.109-124
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    • 2002
  • This study is an effort to develop a stochastic model of precipitation series that preserves the pattern of occurrence of precipitation events throughout the year as well as several characteristics of the duration, amount, and intensity of precipitation events. In this study an event cluster model is used to describe the occurrence of precipitation events. A logarithmic negative mixture distribution is used to describe event duration and separation. The number of events within each cluster is also described by the Poisson cluster process. The duration of each event within a cluster and the separation of events within a single cluster are described by a logarithmic negative mixture distribution. The stochastic model for hourly precipitation occurrence process is fitted to historical precipitation data by estimating the model parameters. To allow for seasonal variations in the precipitation process, the model parameters are estimated separately for each month. an analysis of thirty-four years of historical and simulated hourly precipitation data for Seoul indicates that the stochastic model preserves many features of historical precipitation. The seasonal variations in number of precipitation events in each month for the historical and simulated data are also approximately identical. The marginal distributions for event characteristics for the historical and simulated data were similar. The conditional distributions for event characteristics for the historical and simulated data showed in general good agreement with each other.

A Stochastic Simulation Model for the Precipitation Amounts of Hourly Precipitation Series (시간강수계열의 강수량 모의발생을 위한 추계학적 모형)

  • Lee, Jung-Sik;Lee, Jae-joon;Park, Jong-Young
    • Journal of Korea Water Resources Association
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    • v.35 no.6
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    • pp.763-777
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    • 2002
  • The objective of this study is to develop computer simulation model that produces precipitation patterns from stochastic model. The hourly precipitation process consists of the precipitation occurrence and precipitation amounts. In this study, an event cluster model developed by Lee and Lee(2002) is used to describe the occurrence process of events, and the hourly precipitation amounts within each event is described by a nonstationary form of a first-order autoregressive process. The complete stochastic model for hourly precipitation is fitted to historical precipitation data by estimating the model parameters. An analysis of historical and simulated hourly precipitation data for Seoul indicates that the stochastic model preserves many of the features of historical precipitation. The autocorrelation coefficients of the historical and simulated data are nearly identical except for lags more than about 3 hours. The precipitation intensity, duration, marginal distributions, and conditional distributions for event characteristics for the historical and simulated data showed in general good agreement with each other.

Development of Radar-Based Multi-Sensor Quantitative Precipitation Estimation Technique (레이더기반 다중센서활용 강수추정기술의 개발)

  • Lee, Jae-Kyoung;Kim, Ji-Hyeon;Park, Hye-Sook;Suk, Mi-Kyung
    • Atmosphere
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    • v.24 no.3
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    • pp.433-444
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    • 2014
  • Although the Radar-AWS Rainrate (RAR) calculation system operated by Korea Meteorological Administration estimated precipitation using 2-dimensional composite components of single polarization radars, this system has several limitations in estimating the precipitation accurately. To to overcome limitations of the RAR system, the Korea Meteorological Administration developed and operated the RMQ (Radar-based Multi-sensor Quantitative Precipitation Estimation) system, the improved version of NMQ (National Mosaic and Multi-sensor Quantitative Precipitation Estimation) system of NSSL (National Severe Storms Laboratory) for the Korean Peninsula. This study introduced the RMQ system domestically for the first time and verified the precipitation estimation performance of the RMQ system. The RMQ system consists of 4 main parts as the process of handling the single radar data, merging 3D reflectivity, QPE, and displaying result images. The first process (handling of the single radar data) has the pre-process of a radar data (transformation of data format and quality control), the production of a vertical profile of reflectivity and the correction of bright-band, and the conduction of hydrid scan reflectivity. The next process (merger of 3D reflectivity) produces the 3D composite reflectivity field after correcting the quality controlled single radar reflectivity. The QPE process classifies the precipitation types using multi-sensor information and estimates quantitative precipitation using several Z-R relationships which are proper for precipitation types. This process also corrects the precipitation using the AWS position with local gauge correction technique. The last process displays the final results transformed into images in the web-site. This study also estimated the accuracy of the RMQ system with five events in 2012 summer season and compared the results of the RAR (Radar-AWS Rainrate) and RMQ systems. The RMQ system ($2.36mm\;hr^{-1}$ in RMSE on average) is superior to the RAR system ($8.33mm\;hr^{-1}$ in RMSE) and improved by 73.25% in RMSE and 25.56% in correlation coefficient on average. The precipitation composite field images produced by the RMQ system are almost identical to the AWS (Automatic Weather Statioin) images. Therefore, the RMQ system has contributed to improve the accuracy of precipitation estimation using weather radars and operation of the RMQ system in the work field in future enables to cope with the extreme weather conditions actively.

A Simulation Model for the Intermittent Hydrologic Process(I) - Alternate Renewal Process (ARP) and Continuous Probability Distribution - (간헐(間歇) 수문과정(水文過程)의 모의발생(模擬發生) 모형(模型)(I) - 교대재생과정(交代再生過程)(ARP)과 연속확률분포(連續確率分布) -)

  • Lee, Jae Joon;Lee, Jung Sik
    • Journal of The Korean Society of Civil Engineers
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    • v.14 no.3
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    • pp.509-521
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    • 1994
  • This study is an effort to develop computer simulation model that produce precipitation patterns from stochastic model. A stochastic model is formulated for the process of daily precipitation with considering the sequences of wet and dry days and the precipitation amounts on wet days. This study consists of 2 papers and the process of precipitation occurrence is modelled by an alternate renewal process (ARP) in paper (I). In the ARP model for the precipitation occurrence, four discrete distributions, used to fit the wet and dry spells, were as follows; truncated binomial distribution (TBD), truncated Poisson distribution (TPD), truncated negative binomial distribution (TNBD), logarithmic series distribution (LSD). In companion paper (II) the process of occurrence is developed by Markov chain. The amounts of precipitation, given that precipitation has occurred, are described by a Gamma. Pearson Type-III, Extremal Type-III, and 3 parameter Weibull distribution. Daily precipitation series model consists of two models, A-Wand A-G model, by combining the process of precipitation occurrence and a continuous probability distribution on the precipitation of wet days. To evaluate the performance of the simulation model, output from the model was compared with historical data of 7 stations in the Nakdong and Seomjin river basin. The results of paper (1) show that it is possible to design a model for the synthetic generation of IX)int precipitation patterns.

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A Simulation Model for the Intermittent Hydrologic Process (II) - Markov Chain and Continuous Probability Distribution - (간헐(間歇) 수문과정(水文過程)의 모의발생(模擬發生) 모형(模型)(II) - Markov 연쇄와 연속확률분포(連續確率分布) -)

  • Lee, Jae Joon;Lee, Jung Sik
    • Journal of The Korean Society of Civil Engineers
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    • v.14 no.3
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    • pp.523-534
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    • 1994
  • The purpose of this study is to develop computer simulation model that produce precipitation patterns from stochastic model. In the paper(I) of this study, the alternate renewal process(ARP) is used for the daily precipitation series. In this paper(Il), stochastic simulation models for the daily precipitation series are developed by combining Markov chain for the precipitation occurrence process and continuous probability distribution for the precipitation amounts on the wet days. The precipitation occurrence is determined by first order Markov chain with two states(dry and wet). The amounts of precipitation, given that precipitation has occurred, are described by a Gamma, Pearson Type-III, Extremal Type-III, and 3 parameter Weibull distribution. Since the daily precipitation series shows seasonal variation, models are identified for each month of the year separately. To illustrate the application of the simulation models, daily precipitation data were taken from records at the seven locations of the Nakdong and Seomjin river basin. Simulated data were similar to actual data in terms of distribution for wet and dry spells, seasonal variability, and precipitation amounts.

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Study on New Process of Zero Discharge of Cyanide Wastewater

  • Qiu, Ting-Sheng;Tang, Guan-Zhong;Hao, Zhi-Wei;Cheng, Xian-Xiong
    • Proceedings of the IEEK Conference
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    • pp.135-139
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    • 2001
  • According to the requirement of cyanide precipitation-purification technology, adopt the acidized sulfate to precipitate cyanide. Studying the influence of acidity and the dosage of sulfate on precipitation rate of impurity ion in cyanide wastewater, and, on the basis of synthetic precipitation experiments, we obtain principle process of cyanide precipitation-purification to technology.

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Synthesis and Piezoelectric Properties of PZT Ceramics will Improved Process (공정개선을 통한 PZT 세라믹스의 합성 및 압전특성)

  • 윤철수;송태권;박태곤;박인용;김명호
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.14 no.11
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    • pp.904-911
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    • 2001
  • High-density lead zirconate titanate(Pb(Zr$\_$0.53/Ti$\_$0.47/)O$_3$, PZT) ceramics were fabricated by a new milling-precipitation(MP) process improved from the conventional solid state process. This process was progressed by a milling impregnation through mixing ZrO$_2$ and TiO$_2$ powders with lead nitrate(Pb(NO$_3$)$_2$) water solution in zirconia ball media, and then milling precipitation was induced from precipitation of PbC$_2$O$_4$ by adding ammonium of oxalate monohydrate((NH$_4$)$_2$C$_2$O$_4$$.$H$_2$O) as a precipitant. As a result of this process, single-phase perovskite structure was formed at the calcination temperature of 750$\^{C}$ for Pb(Zr$\_$0.53/Ti$\_$0.47/)O$_3$ powders. In addition, the highest density at the sintering temperature of 1100$\^{C}$ was obtained, because of the highly sinterable PZT Powders ground through the re-milling process. Piezoelectric and dielectric properties of sintered sample were improved by MP process.

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Study on Radar Detection of One Stratiform Cloud Precipitation Process in the Central Part of the Tianshan Mountains in China

  • Wang, Minzhong;Ming, Hu
    • Asia-Pacific Journal of Atmospheric Sciences
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    • v.54 no.3
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    • pp.511-524
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    • 2018
  • In order to investigate the physical structure characteristics of the clouds and precipitation over the Tianshan Mountains in summer, the Urumqi Institute of Desert Meteorology of China Meteorological Administration (CMA) carried out an atmospheric detection experiment in Bayanbulak from 1st to 31st August 2012 by means of a wind-profiling radar and a Doppler weather radar. Using the radar observation data, this paper analyzes the dynamic, thermodynamic, radar echo intensity and macro-micro structure characteristics of the 2-3 August precipitation process. The results show that: (1) The radar echo intensity of this rainfall process changes within 5-38 dBZ, and the precipitation cloud system is under the height of 6500 m, with notable $0^{\circ}C$ level echo bright band between 1200 m and 2000 m height. NCEP analysis data shows that the cloud top temperature ranges from $-25^{\circ}C$ to $-32^{\circ}C$. These indicate the features of typical stratiform cold cloud precipitation. (2) Atmospheric motion during the precipitation process presents the multi-layer structure with wind velocity varying within the range of 3.0-8.0 m/s. The temperature advection is presented with the vertical structure distribution of "cold-warm-cold", which indicates relative stability of the atmospheric stratification. (3) By retrieving and analyzing the raindrop size distributions below $0^{\circ}C$ level bright band within 600-1200 m height, when the precipitation evolve from early stage to its peak stage, the concentration of the tiny particle zone ($D{\leq}2.5mm$) changes a little while the concentration of the medium particle zone ($2.5<D{\leq}4mm$) and the concentration of the large particle(D > 4 mm) increase considerably; but after peak stage the concentration in the medium particle zone and the concentration in the large particle zone decline first, then the concentration in the tiny particle zone reduces. (4) Raindrop size distribution data is used to calculate the precipitation intensity and the liquid water content, whose spatial-temporal variation characteristics are the same. During peak stage of the precipitation, the instantaneous precipitation intensity reaches 5.0 mm/h, and the liquid water content reaches $0.35g/m^3$. This study would help deepen the understanding on the physical structure of the clouds and precipitation over the Tianshan Mountains in summer, and also provide some scientific basis for cloud seeding operation over this area.

Acid Precipitation and Water Cycling (산성강수와 물의 순환)

  • ;M. Krieter
    • Journal of Korean Society for Atmospheric Environment
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    • v.10 no.3
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    • pp.159-169
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    • 1994
  • This paper describes the process of acidic precipitation from the atmosphere to the ground water, The net deposition of wet precipitation to the ground surface is obtained by subtracting the interception loss due to plant leaves and evaporation from the amount of total precipitation. As the water immerses through the vegetation and the different soil layers the various chemical reactions take place. The relationship between the acidic precipitation by increasing industrial emissions and the soil acidification mechanism is discussed. The report focuses on the buffering action that involves the proton budget in soil and rocks. Based on the soil constituents, the six buffer ranges of the soil are classified and each buffering process is illustrated. In addition, the Possibility of the contamination of drinking-water reservoirs by continuous acid burden is emphasized.

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Prepurification of paclitaxel by micelle and precipitation

  • Seong, Ju-Ri;An, Hui-Bun;Kim, Jin-Hyeon
    • 한국생물공학회:학술대회논문집
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    • pp.501-504
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    • 2003
  • A novel prepurification method was developed aiming at increasing yield and purity, also reducing solvent usage for purification of paclitaxel. This method was a simple and efficient procedure, for the isolation and prepurification of paclitaxel from the biomass of Taxus chinensis, consisting of micelle formation, followed by two steps of precipitation. The use of a micelle and precipitation in the prepurification process allows for rapid separation of paclitaxel from interfering compounds and dramatically reduces solvent usage compared to alternative methodologies. This prepurification process serves to minimize the size and complexity of the HPLC operations for paclitaxel purification. This process is readily scalable to a pilot plant and eventually to a production environment where multikilogram quantities of material are expected to be produced. As much as possible, the process has been optimized to minimize solvent usage, complexity, and operating costs.

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