• 대기
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• 제20권3호
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• pp.333-341
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• 2010

The stratiform rain fraction is investigated in the tropical boreal winter Madden-Julian oscillation (MJO) and summer intraseasonal oscillation (ISO) using Tropical Rainfall Measuring Mission (TRMM) Precipitation Rader data for the 11-yr period from 1998 to 2008. Composite analysis shows that the MJO/ISO produces larger stratiform rain rate than convective rain rate for nearly all phases following the propagating MJO/ISO deep clouds, with the greatest stratiform rainfall amount when the MJO/ISO center is located over the central-eastern Indian Ocean and the western Pacific. The fraction of the intraseasonally filtered stratiform rainfall compared to total rainfall (i.e., convective plus stratiform rainfall) amounts to 53~56%, which is 13~16% larger than the stratiform rain fraction estimated for the same data on seasonal-to-annual time scales by Schumacher and Houze. This indicates that the MJO/ISO exhibits the organized rainfall process which is characterized by the shallow convection/heating at the incipient phase and the subsequent flare-up of strong deep convection, followed by the development of stratiform clouds at the upper troposphere.

• 대기
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• 제24권4호
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• pp.457-470
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• 2014

Thermodynamic conditions related with localized torrential rainfall in the middle west region of Korean peninsula are examined using radar rain rate and radiosonde observational data. Localized torrential rainfall events in this study are defined by three criteria base on 1) any one of Automated Synoptic Observing System (ASOS) hourly rainfall exceeds $30mmhr^{-1}$ around Osan, 2) the rain (> $1mmhr^{-1}$) area estimated from radar reflectivity is less than $20,000km^2$, and 3) the rain (> $10mmhr^{-1}$) cell is detected clearly and duration is short than 24 hr. As a result, 13 cases were selected during the summer season of 10 years (2004-13). It was found that the duration, the maximum rain area, and the maximum volumetric rain rate of convective cells (> $30mmhr^{-1}$) are less than 9hr, smaller than $1,000km^2$, and $15,000{\sim}60,000m^3s^{-1}$ in these cases. And a majority of cases shows the following thermodynamic characteristics: 1) Convective Available Potential Energy (CAPE) > $800Jkg^{-1}$, 2) Convective Inhibition (CIN) < $40Jkg^{-1}$, 3) Total Precipitable Water (TPW) ${\approx}$ 55 mm, and 4) Storm Relative Helicity (SRH) < $120m^2s^{-2}$. These cases mostly occurred in the afternoon. These thermodynamic conditions indicated that these cases were caused by strong atmospheric instability, lifting to overcome CIN, and sufficient moisture. The localized torrential rainfall occurred with deep moisture convection result from the instability caused by convective heating.

• 대기
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• 제18권4호
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• pp.317-338
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• 2008

Analyses of observational data and numerical simulations were performed to understand the mechanism of MCSs (Mesoscale Convective Systems) occurred on 13-14 July 2004 over Jindo area of the Korean Peninsula. Observations indicated that synoptic environment was favorable for the occurrence of heavy rainfall. This heavy rainfall appeared to have been enhanced by convergence around the Changma front and synoptic scale lifting. From the analyses of storm environment using Haenam upper-air observation data, it was confirmed that strong convective instability was present around the Jindo area. Instability indices such as K-index, SSI-index showed favorable condition for strong convection. In addition, warm advection in the lower troposphere and cold advection in the middle troposphere were detected from wind profiler data. The size of storm, that produced heavy rainfall over Jindo area, was smaller than $50{\times}50km^2$ according to radar observation. The storm developed more than 10 km in height, but high reflectivity (rain rate 30 mm/hr) was limited under 6 km. It can be judged that convection cells, which form cloud clusters, occurred on the inflow area of the Changma front. In numerical simulation, high CAPE (Convective Available Potential Energy) was found in the southwest of the Korean Peninsula. However, heavy rainfall was restricted to the Jindo area with high CIN (Convective INhibition) and high CAPE. From the observations of vertical drop size distribution from MRR (Micro Rain Radar) and the analyses of numerically simulated hydrometeors such as graupel etc., it can be inferred that melted graupels enhanced collision and coalescence process of heavy precipitation systems.

• 한국지구과학회지
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• 제23권1호
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• pp.59-71
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• 2002

Theoretical models of radiative transfer are developed to simulate the 85 GHz brightness temperature (T85) observed by the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) radiometer as a function of rain rate. These simulations are performed separately over regions of the convective and stratiform rain. TRMM Precipitation Radar (PR) observations are utilized to construct vertical profiles of hydrometeors in the regions. For a given rain rate, the extinction in 85 GHz due to hydrometeors above the freezing level is found to be relatively weak in the convective regions compared to that in the stratiform. The hydrometeor profile above the freezing level responsible for the weak extinction in convective regions is inferred from theoretical considerations to contain two layers: 1) a mixed (or mixed-phase) layer of 2 km thickness with mixed-phase particles, liquid drops and graupel above the freezing level, and 2) a layer of graupel extending from the top of the mixed layer to the cloud top. Strong extinction in the stratiform regions is inferred to result from slowly-falling, low-density ice aggregates (snow) above the freezing level. These theoretical results are consistent with the T85 measured by TMI, and with the rain rate deduced from PR for the convective and stratiform rain regions. On the basis of this study, the accuracy of the rain rate sensed by TMI is inferred to depend critically on the specification of the convective or stratiform nature of the rain.

• 한국지구과학회지
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• 제32권1호
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• pp.33-45
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• 2011

이 연구는 TRMM(Tropical Rainfall Measuring Mission) 위성의 강수레이더인 PR(Precipitation Radar)의 5년간 (2002-2006) 6-8월 동안의 산출물을 분석하여 한반도 주변 지역과 동아시아의 아열대 및 열대 지역의 강우와 강우구름의 연직 구조 특성을 강우유형별로 분류하여 조사하였다. 한반도 주변 지역은 12.2%의 대류형 강우 비율로 다른 지역과 비교하여 약 6% 작았으며, 단위면적당의 강우 발생 빈도는 특히 열대지역의 50% 정도였다. 또한 한반도 주변 지역은 대류형에서 40% 더 강한 강우강도(10.4 mm/h)를 만들어내며, 층운형의 경우 세 지역 모두 비슷한 강우강도를 나타냈다. 평균적으로 강우강도는 운정고도와 비례하는 관계를 보였다. 레이더 반사도의 연직 구조를 통해 한반도 주변의 대류운은 연직적으로 매우 발달한 구름으로 더 높은 강우강도와 연관되어 있었다. 특히 열대지역의 대류형 강우구름들은 약 5 km의 고도 이하에서 지표에 접근함에 따라 수적들의 충돌병합에 의해 뚜렷한 레이더 반사도의 증가를 보였으며, 층운형 강우구름들은 더욱 뚜렷한 밝은 띠를 갖고 있었다. 한편 대류형에서 레이더 반사도의 첫 번째 경험직교함수 구조는 세 지역이 매우 비슷하지만, 두 번째 경험직교함수는 조금 다른 모습을 보였다. 한반도 주변 지역과 열대지역은 각각 상층과 하층에 큰 변동성을 보였다.

• 한국지구과학회지
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• 제31권7호
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• pp.749-761
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• 2010

본 연구에서는 2006-2007년 여름(6-8월)동안의 기상청 낙뢰 관측자료와 자동관측소 강우량 자료를 사용하여 여름철 낙뢰와 강우의 관계에 대해 분석하였다. 대부분의 부극성 낙뢰는 대류가 활발한 중심에 집중되어 발생하고 낙뢰빈도가 높고 강한 강우를 동반하였다. 반면 대부분의 정극성 낙뢰는 구름의 가장자리 또는 모루운에서 발생하고 낙뢰빈도는 낮으며, 약한 강우를 동반하였다. 일반적으로 강우강도는 부극성과 정극성이 함께 발생했을 경우 가장 강하고 부극성 낙뢰, 정극성 낙뢰, 그리고 낙뢰가 발생하지 않은 순으로 나타나고 있다. 여름철 전체 낙뢰 중 정극성 낙뢰의 비율은 평균 10% 이하이며 강우를 유발하지 않는 낙뢰의 비율은 평균 34%이다. 강우강도는 특히 부극성 낙뢰빈도와 높은양의 상관을 보였고, 낙뢰는 강우와 동시에 발생하거나 약 10분정도 선행하는 경향을 보였다. 낙뢰를 동반한 강우를 대류성 강우로 정의하여 분석한 결과 우리나라 여름철 강우 중 적어도 20% 이상은 대류성 강우이며 6, 7월보다는 8월에 대류성 강우가 많이 발생하고 있다. 또한 강우 및 낙뢰와 같이 대류성 강우의 비율도 오후에 최대치를 보이는 일변동을 보인다.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2002년도 Proceedings of International Symposium on Remote Sensing
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• pp.361-365
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• 2002

Rain-rate retrieval using the NOAA/AMSU (Advanced Microwave Sounding Unit) (Zaho et al., 2001) has been implemented at METRI/KMA since 2001. Here, we present the results of the AMSU derived rain-rate and validation result, especially for the rainfall associated with the tropical cyclone for 2001. For the validation, we use rain-rate derived from the ground based radar and/or rainfall observation from the rain gauge in Korea. We estimate the bias score, threat score, bias, RMSE and correlation coefficient for total of 16 tropical cyclone cases. Bias score shows around 1.3 and it increases with the increasing threshold value of rain-rate, while the threat score extends from 0.4 to 0.6 with the increasing threshold value of precipitation. The averaged rain-rate for at all 16 cases is 3.96mm/hr and 1.41mm/hr for the retrieved from AMSU and the ground observation, respectively. On the other hand, AMSU rain-rate shows a much better agreement with the ground based observation over inner part of tropical cyclone than over the outer part (Correlation coefficient for convective region is about 0.7, while it is only about 0.3 over the stratiform region). The larger discrepancy of tile correlation coefficient with the different part of the tropical cyclone is partly due to the time difference in between ice water path and surface rainfall. This results indicates that it might be better to develop the algorithm for different rain classes such as convective and stratiform.

• 한국지구과학회지
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• 제37권7호
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• pp.420-433
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• 2016

본 연구의 목적은 2011년 4월 22일부터 10월 22일까지 우리나라에서 강수가 있는 총 75일 동안 COMS 위성의 적외 채널 $10.8{\mu}m$ 휘도 온도(IR), 적외 채널 $10.8{\mu}m$와 수증기 채널 $6.7{\mu}m$의 휘도 온도차(IR-WV), 정규화 된 가시반사도(VIS)와 기상 레이더의 강우강도를 이용하여 2-D와 3-D 대류운의 강우강도 (CRR) 조견표를 향상시키는 것이다. 특별히 한국형 2-D와 3-D CRR 조견표를 검증하기 위해 2011년 강수가 있는 24일 동안의 기상 레이더 강우강도 자료가 사용된다. 2-D와 3-D CRR 조견표는 각 채널의 등급 범주별 강우 총수와 비강우 총수의 행렬을 이용하여 구한 강우 확률에 평균 누적강우강도와 최대 강우강도를 각각 곱함으로써 2-D (IR, IR-WV)와 3-D (IR, IR-WV, VIS) 조견표의 기본과 최대 행렬을 얻을 수 있다. 최종적으로 새로운 2-D와 3-D의 CRR 조견표는 경험적으로 기본과 최대 강우강도 행렬의 회귀 분석으로 얻어진다. 그 결과 새로운 CRR 조견표는 기존보다 낮은 IR 휘도 온도, 낮은 IR-WV 휘도 온도차일 때에도 비교적 많은 강우 현상을 나타내며, $10mm\;h^{-1}$ 이상의 강우강도 영역이 확대되어 나타난다. 정확도와 범주별 통계가 주어진 기간 동안 발생했던 CRR 자료에 대해 계산된다. 새로운 2-D와 3-D CRR 조견표의 평균 오차, 평균절대 오차, 제곱근평균 오차가 기존 조견표보다 작게 나타나며, 예측 거짓경고비율은 감소하고, 탐지확률은 증가하며, 임계성공지수는 개선된다. 태풍과 뇌우와 같은 기상 이변에서의 강한 호우를 고려하기 위해서 습윤 보정 계수를 교정한다. 이 인자는 수치모델이나 COMS에서 복원한 지면에서 500 hPa까지 평균한 총가강수량과 상대습도의 곱 (PW RH)으로 정의된다. 이 연구에서는 PW RH에 근거하여 IR 운정 휘도 온도가 210 K 이하일 때, 상대습도가 40% 이상일 때 1에서 2사이를 경험적으로 정한다. 새로운 2-D와 3-D CRR 조견표를 적용한 결과 평균 오차, 평균 절대 오차, 제곱근 평균 오차가 줄어든다.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 1999년도 Proceedings of International Symposium on Remote Sensing
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• pp.117-121
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• 1999

Relations between GMS-5 infrared brightness temperature with SSM/I retrieved rain rate are determined by a probability matching method similar to Atlas et al. and Crosson et al. For this study, coincident data sets of the GMS-5 infrared measurements and SSM/I data during two summer seasons of 1997 and 1998 are constructed. The cumulative density functions (CDFs) of infrared brightness temperature and rain rate are matched at pairs of two variables which give the same percentile contribution. The method was applied for estimating rain rate on 31 July 1998, examining heavy rainfall estimation of a flash flood event over Mt. Jiri. Results were compared with surface gauge observations run by Korean Meteorological Administration. It was noted that the method produced reasonably good quality of rain estimate, however, there was large area giving false rain due to the anvil type clouds surrounding deep convective clouds. Extensive validation against surface rain observation is currently under investigation.

• 대기
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• 제14권1호
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• pp.24-43
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• 2004

This paper describes the detailed characteristics of heavy rainfall events occurred in Chungcheong province on 15 and 16 April and from 6 to 8 August 2002 based on the analysis of raingauge rainfall rate and radar reflectivity from the METRI's X-band Weather Radar located in Cheongju. A synoptic analysis of the case is carried out, first, and then the analysis is devoted to seeing how the radar observes the case and how much information we obtain. The highly resolved radar reflectivity of horizontal and vertical resolutions of 1 km and 500 m, respectively shows a three-dimensional structure of the precipitating system, in a similar sequence with the ground rainfall rate. The radar echo classification algorithm for convective/stratiform cloud is applied. In the convectively-classified area, the radar reflectivity pattern shows a fair agreement with that of the surface rainfall rate. This kind of classification using radar reflectivity is considered to be useful for the precipitation forecasting. Another noteworthy aspect of the case includes the effect of topography on the precipitating system, following the analysis of the surface rainfall rate, topography, and precipitating system. The results from this case study offer a unique opportunity of the usefulness of weather radar for better understanding of structural and variable characteristics of flash flood-producing heavy rainfall events, in particular for their improved forecasting.