• 한국전자파학회논문지
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• 제10권5호
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• pp.701-710
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• 1999

To predict rain attenuation accurately, we must know scattering characteristics of rain-drops for real drop shapes. In this paper, the scattering characteristics of rain-drops are analyzed by an analytical model, and the differences in the characteristics of the forward scattering amplitudes for three different rain-drop shapes are compared. Using the results for the Pruppacher-Pitter's real rain-drop shaper, the specific rain attenuation in domestic environment is predicted, and the difference from the ITU-R model is compared and analyzed.

• 한국전자파학회논문지
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• 제9권1호
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• pp.52-59
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• 1998

빗방울이 랜덤하게 분포한 대기를 하나의 실효유전율을 가진 단일 매질로 가정하고 그 매질 내에서 전파가 진행시 감쇠량을 계산하였다. 실효유전율은 빗방울의 유전율과 빗방울이 대기 중에 차지하는 체적 동의 함수로 표현되는데, 주파수와 온도에 따라 변하는 빗방울의 유전율을 계산하고 Marshall-Palmer의 빗방울 크기분포를 이용하여 대기 중 빗방울이 차지하는 체적을 계산하였다. 빗방울이 산재한 대기를 단일 매질로 가정하고 실효유전율을 이용하여 강우에 의한 강우감죄량을 예측한 본 모델과 ITU가 권고하는 강우에 의한 전파감쇠모텔과 비교 하였는데 두 모델의 결과값이 비교적 일치하며 50 GHz 이하에서는 실효유전율 모텔이 낮게, 50 GHz 이상의 주 파수대역에서는높게 강우감쇠량을평가하고 있다.

• 대한원격탐사학회지
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• 제29권3호
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• pp.293-306
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• 2013

Hydrometeor type and Drop Size Distribution (DSD) in cloud are the fundamental properties that may help explain the rain formation processes and determine the parameters of radar meteorology. This study presents a preliminary analysis of hydrometeor types and DSD data of cloud measured with a PARSIVEL (PARticle SIze and VELocity) optical disdrometer at the site of Cloud Physics Observation System (CPOS, $37^{\circ}41^{\prime}N$, $128^{\circ}45^{\prime}E$, 843 m from sea level) in Daegwallyeong mountainside of Korea. The method has been validated by comparing the observed rainfall rates with the computed ones from the fitted distribution, using the physical data such as DSD, terminal velocity, and rain intensity which were measured by a Micro-Rain Radar (MRR) and a PARSIVEL optical disdrometer. The analysis period started in three cases: on rainy days with light rain (15.5 mm), moderate rain (76 mm), and heavy rain (121 mm), from March to November 2007, respectively.

• 한국환경과학회지
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• 제25권3호
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• pp.345-359
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• 2016

This study analyze the synoptic meteorological cause of rainfall, rainfall intensity, drop size distribution(DSD), fall velocity and oblateness measured by the 2D-Video distrometer(2DVD) by comparing two cases which are heavy rainfall event case and a case that is not classified as heavy rainfall but having more than $30mm\;h^{-1}$ rainrate in July, 2014 at Gimhae region. As a results; Over the high pressure edge area where strong upward motion exists, the convective rain type occurred and near the changma front, convective and frontal rainfall combined rain type occurred. Therefore, rainrate varies based on the synoptic meteorological condition. The most rain drop distribution appeared in the raindrops with diameters between 0.4 mm and 0.6 mm and large particles appeared for the convective rain type since strong upward motion provide favorable conditions for the drops to grow by colliding and merging so the drop size distribution varies based on the location or rainfall types. The rainfall phases is mainly rain and as the diameter of the raindrop increase the fall velocity increase and oblateness decrease. The equation proposed based on the 2DVD tends to underestimated both fall velocity and oblateness compared with observation. Since these varies based on the rainfall characteristics of the observation location, standard equation for fall velocity and oblateness fit for Gimhae area can be developed by continuous observation and data collection hereafter.

• 한국대기환경학회지
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• 제15권1호
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• pp.1-11
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• 1999

In this work, a theoretical model has been formulated which allows the study of the scavenging efficiencies of aerosol particles by the rain drops. Aerosol particles are scavenged by the simultaneous brownian diffusion, interception and inertial impaction force. In addition the calculations based on the collision efficiency model are carried out for the collision of aerosol particles with diameter range 0.01~30 $mu extrm{m}$ and rain drops with diameter 0.02$\times$$2^{n/3}$(n=1, 2, …, 17)cm. The results indicate that: (1) the below-cloud scavenging affects mainly the coarse particles (＞3 ${\mu}{\textrm}{m}$), the fine particles remaining almost unchanged; (2) the scavenging efficiencies by below-cloud in the heavy rain (rain intensity, 10 mm/hr) surpass the efficiency found in the drizzle rain (rain intensity, 1 mm/hr).

• Asian Journal of Atmospheric Environment
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• 제7권3호
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• pp.161-168
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• 2013

In this study, an investigation was conducted to assess the washout mechanism of Asian dust particles through both laboratory-scale experiment and model calculation. To artificially simulate Asian dust particle, $CaCO_3$ particles were generated inside an experimental chamber. They were then scavenged by the artificial rain drops. The abundant $CaCO_3$ particles scavenged on a rain drop were successively identified by SEM observation. The concentrations of Ca in residual $CaCO_3$ particles on individual droplet were quantified by PIXE analysis. There was a tendency toward a high accumulation of Ca on a relatively small drop (e.g., <1.0 mm diameter). It is thus suggested that smaller rain drops can effectively scavenge a significant amount of Asian dust particles in ambient atmosphere. The numerical estimation can account for 92.1% and 83.2% of Ca that were measured in small (<1.0 mm diameter) and large (>2.0 mm diameter) size drops, respectively.

• 한국전자파학회논문지
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• 제16권8호
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• pp.848-854
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• 2005

본 논문에서는 국내 환경에 적용할 수 있는 EHF(44 GHz) 대역의 강우 감쇠 특성을 예측하기 위한 연구를 수행하였다. 일반적으로 10 GHz 이상에서 동작하는 무선 통신 시스템이 강우에 의한 영향을 많이 받는 것으로 알려져 있다. 이러한 강우 감쇠는 빗방울의 크기 분포를 통해서 예측이 가능하다. 따라서 무선 통신 시스템을 설계하거나 강우에 의한 감쇠 영향을 분석하기 위해서는 국내 환경에 적용 가능한 정확한 빗방울 크기 분포 예측 모델 개발이 중요하다. 본 논문에서는 충남대학교에서 측정을 통해 얻어진 데이터를 바탕으로 일반적인 확장 감마 분포를 이용하여 빗방울 크기 분포 예측 모델을 제시하였으며, 실제 강우 감쇠 측정 데이터와 잘 일치하는 결과를 얻었다.

• Asian Journal of Atmospheric Environment
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• 제9권3호
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• pp.222-227
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• 2015

The environmental education with ideal teaching tools (e.g., a small-scaled experimental kit) is essential for raising the public's, especially student's, awareness of many environmental issues. This study was undertaken to develop a do-it-yourself model instrument of acid rain and estimating its applicability to the environmental education. Our novel model tool consists of a body (17 cm width, 6 cm depth, and 17 cm height), an acid gas injector, acid four rain reservoirs, and a drop supply pump. An alternative model instrument that can be more readily assembled was also suggested. Based on our novel approach, we carried out several model experiments with educatees (i.e., high school and college students, and adults). The results of questionnaires indicated that educatees achieved a very deep understanding of acid rain through an experienced model experiment. A 77 to 89% of educatees experienced the reappearance experiment of acid rain by our model instrument felt that it was very useful as a teaching tool of environmental education.

• 한국전자파학회논문지
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• 제11권2호
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• pp.242-251
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• 2000

Ka 및 mm파 대역에서의 강우감쇠는 무선회선설계에 큰 영향을 미친다. 본 논문에서는 전반적인 기초가 되는 Mie 산란이론을 이용하여 국내환경에 적합한 강우감쇠를 추정하기 위해 중요한 요소인 빗방울 크기분포를 여러 자료를 비교하여 분석하였고. 일반화된 식을 통해 수치해석적 접근을 시도함으로써 각 파라미터별 강우감 쇠에 미치는 정도를 분석하여 이론적으로 국내 강우환경에서의 강우감쇠를 추정하기 위한 근거를 제공하고자 하였다.

• 한국전자통신학회논문지
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• 제15권1호
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• pp.153-160
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• 2020

Brazil Alagoas 주의 동부 지역에서 우적 크기를 측정하는 디즈드로미터(disdrometer)로 산출한 강우량과 강우율의 관계로 우적의 역학 에너지가 예측되었다. 강우의 시작과 끝에서 측정되는 약한 강우 강도에서는 지수 형태의 방정식이 큰 우적의 영향을 억제하였다. 빗방울의 역학 에너지는 거의 모든 강우 강도 범위에서 과소평가 되었다. 결정 계수, 평균 절대 오차, 상대 오차 비율, 평균 절대 오차, 평균 제곱 오차, Willmott의 일치 지수 및 신뢰 지수와 같은 성과 지표에 기반을 두어 예측된 강우 역학 에너지가 유용한 결과로 평가되었다.