방위산업 수출을 위한 국내 기업의 Communication 강화 방안

엄효식 한국방위산업진흥회 2022 國防과 技術 Vol.- No.517

Trends of Stability Indices and Environmental Parameters Derived from the Rawinsonde Data over South Korea

엄효식,서명석 한국지구과학회 2011 韓國地球科學會誌 Vol.32 No.5

In this paper, trends of the widely used stability indices (SIs) and environmental parameters (EPs) were examined by using the 30-year routine rawinsonde data observed in three upper air observatories (Osan, Gwangju and Pohang) over South Korea. To take into account of the contribution of water vapor to a parcel density, we applied the virtual temperature correction in calculating the SIs and EPs. The trends of SIs and EPs indicated significant increases of temperature and moisture contents, especially at the low-to-mid troposphere during the last 10 years. The warming trend in the lower troposphere shows about 3 times greater than that of the global average (+0.10- +0.20oC/10 years), whereas the cooling trend of lower stratosphere demonstrates a similar trend with the global average (−0.33- −0.60oC/10 years). The vertical stability is clearly reduced due to the unsymmetrical change of atmospheric elements. The unstabilizing trend with the increased moisture contents gradually changed the atmospheric environment in South Korea into the conditions favorable for the occurrence of severe weather or intensifications of such events. These trends are consistent with the recent observations, which showed clear increase in the intensity and frequency of heavy rainfalls.

Seasonal and Diurnal Variations of Stability Indices and Environmental Parameters Using NCEP FNL Data over East Asia

엄효식,서명석 한국기상학회 2011 Asia-Pacific Journal of Atmospheric Sciences Vol.47 No.2

Seasonal and diurnal variations of commonly used stability indices (SIs) and environmental parameters (EPs) over East Asia were examined by using eight years (2000~2007) 6-hr National Centers for Environmental Prediction (NCEP) final (FNL) global reanalysis data. The quality of the FNL data was also evaluated by using the routine rawinsonde data over South Korea. Most of the SIs and EPs shows significant seasonal variation (SV) and diurnal variation (DV), but their magnitudes are dependent on the geographic locations and seasons. In general, the SV and DV of SIs and EPs are greater over the inland area than that over the waters around the Korean peninsula, and the magnitude of DV is significantly larger during summer than during other seasons. The mid-to-upper atmosphere of the East Sea also exhibits relatively stable conditions during the summer due to the extended Okhotsk sea air mass. As a result, the SIs and EPs of the summer show a “C” shape with a minimum instability over the East Sea. The spatial distribution of the SIs and EPs also shows that the eastern and south-eastern region of China is the most favorable for deep convection during the summer. The DV of SIs and EPs are more significant in the inland area than on the coast with maximum (minimum) at 0600 UTC (1800 UTC). Although the spatial distribution of DV pattern is well suited to that of rawinsonde data, the time of the maximum and minimum instability over South Korea does not correspond to that of the rawinsonde data, which occurred at 1200UTC and 0000 UTC (Eom et al., 2008). Compared to the rawinsonde data, the FNL data have a large RMSE in the temperature, wind, and mixing ratio especially at the lower troposphere. Therefore, the FNL data should be used with caution, especially for the perfect boundary condition experiments with various numerical simulation models.

RCP 시나리오 기반 미래 국방기후지수 개발 - 활주로 온도

엄효식,김성,서남섭,황재돈,임병문,기균도,김종모 한국기상학회 2015 한국기상학회 학술대회 논문집 Vol.2015 No.4

MTSAT-1R 휘도온도를 이용한 낙뢰발생 특성 분석 및 예측

엄효식,서명석,이윤정,김효준 한국기상학회 2009 한국기상학회 학술대회 논문집 Vol.2009 No.4

최근 남한지역에서 발생한 낙뢰의 통계적 특성

엄효식,서명석 한국지구과학회 2009 한국지구과학회지 Vol.30 No.2

Lightning data, observed from total lightning detection system (TLDS) of KMA, for the recent five years (2002-2006) have been analyzed for temporal and spatial characteristics of frequency, intensity, duration, and flash rate. Lightning frequency varies largely with years (most frequent in 2006) and the lightning during the summer accounts for 75% of total flashes and only 0.6% of lightnings strike in cold season. In rainy season (JJAS), the ratio of positive flashes to negative ones is as low as 0.15, but it increases up to 0.98 in February. The seasonal variation of lightning duration is strongly linked with lightning occurrences, whereas flashes rates show weak seasonal variability. In a daily scale, lightning, on average, occurs more often at dawn (2 am, 5-7 am) and in the mid-afternoon (15 pm), and the lightning at dawn (around 5 am) is most intense during the day. The western inland areas and the West/South Sea show high lightning density during JJAS, whereas eastern part and the East Sea exhibit a low density of lightning. Considering the low ratio of positive flashes (0.15) for the whole analysis domain during summer period, Chungnam and Jeonbuk areas have a high ratio of flashes over 0.4. However, these should be analyzed with much caution because weak positive cloud-to-cloud discharges can be regarded as cloud-to-ground flashes. The western inland also exhibits long annual flash hours (15-24). And the West Sea has high flash rates as a result of large density and low flash hours. The most frequent time of lightning occurrence over most inland areas lies between mid-afternoon and early-evening, whereas mountainous and coastal areas, and the northern Kyoungki and Hwanghae provinces show the maximum lightning strikes in the morning and at dawn, respectively. 최근(2002-2006) 발생한 낙뢰의 빈도, 강도, 지속시간 및 낙뢰율의 시·공간적 특성을 분석하였다. 빈도는 경년변동이 크게 나타났으며, 여름과 겨울에 각각 전체 낙뢰의 75%, 0.6%가 발생하였다. 정극성 낙뢰는 우기(6-9월)에 부극성 낙뢰의 0.15 비율로 발생했으나 동계에는 그 비율이 증가하여 2월경에 부극성 낙뢰의 0.98까지 증가하였다. 낙뢰 지속시간은 여름에 집중되는 계절변동이 크게 나타났으나 낙뢰율의 변동은 이에 비해 작았다. 낙뢰는 새벽(2시, 5-7시)과 오후 중반(15시)에 두 번의 최대 빈도가 나타났으며 5시경에는 낙뢰강도가 강하였으나, 15시를 전후로 하는 오후 중반에는 낙뢰 강도가 약했다. 낙뢰밀도는 남한 서부 내륙 및 서·남해상에 높으며, 영동 및 동해지역은 낮았다. 충남 및 전북지역에서 0.4 이상으로 높게 나타났는데, 구름내 방전일 가능성이 있어 해석의 주의를 요한다. 낙뢰 밀도가 높은 서부내륙에서는 우기 낙뢰 지속시간이 연 평균 15-24시간으로 나타났으나, 서해상에서는 낙뢰 발생 시의 집중도가 높고 강도가 강하였다. 대부분의 내륙에서는 오후 중반에서 저녁 사이에 낙뢰 발생 빈도가 최대였으나 산악 및 해안, 중서부 지역은 각각 오전과 새벽에 최대로 발생하였다.

2015년 하계 MCSs 발생환경 분석

엄효식,박상환,황재돈,임병문,기균도,김종모 한국기상학회 2015 한국기상학회 학술대회 논문집 Vol.2015 No.10

팬텀을 이용한 환자 전면의 방사선 감수성 장기에 대한 자동장기기준선량제어장치의 유용성 평가 : 수정체, 갑상선, 유방에 대해

엄효식(Hyo Sic Um),이상우(Sang Woo Lee),김선기(Sun Ki Kim),하동윤(Dong Yoon Ha) 대한전산화단층기술학회 2014 대한CT영상기술학회지 Vol.16 No.2

목적 : 자동장기기준선량제어장치(Automated organ-based current modulation, 이하 AOBCM)을 이용하였을 때 환자 전면에 위치한 감수성 장기에 대한 선량 감소 효과와 화질을 평가하기 위함이다. 대상 및 방법 : 환자 전면에서의 표면 선량을 줄여주는 AOBCM 기능을 사용하여 흉부, 두부, 경부에서의 선량 감소효과와 화질 변화를 평가하였다. 선량 감소효과와 화질 변화를 평가하기 위해 조직 등가물질로 구성된 성인 인체모형 팬텀(ART-200X, Fluke biomedical, Nevada, USA)을 사용하였다. 검사에 사용된 장비는 Siemens사의 Somatom Definition AS(Siemens Healthcare, Munich, Germany)와 GE사의 Optima CT 660(GE Healthcare, Milwaukee, Wisconsin, USA)가 사용되었다. 각 제조사 장비마다 Reference scan과 AOBCM 기능을 사용한Experimental scan을 각각 행하였다. 선량을 측정하기 위해 열형광소자 GD-352M(Asahi TechcoGlass, Kansahi, Japan)를 사용하였고 화질 평가를 위해 영상 잡음(Image Noise, ROI에서의 CT number의 Standard Deviation)을 이용하였다. 결과 : Siemens사의 경우 흉부검사에서 전면선량이 평균 21.1%, 두부검사의 경우 평균 29.6%, 경부검사에서 32.9% 감소하였다. GE사는 흉부에서 전면 선량이 평균 23.2%,두부에서는 평균 29.0%, 경부의 경우는 54.2% 감소하였다(p≤0.034). AOBCM 기능을 사용하였을 때 Siemens사의 경우 잡음이 유방 위치에서 0.2, 흉벽에서는 0.2, 폐 실질에서는 2.5, 안구에서는 0.4, 뇌 실질에서는 0.8, 갑상선의 경우 0.4, 두판상근 위치의 연부조직에서는 0.8이 증가하였다. GE사의 경우 유방에서 3.6, 흉벽에서는 2.4, 폐 실질에서는 9.5, 안구에서는 0.9, 뇌 실질에서 2.5, 갑상선에서 3.0, 두판상근 위치의 연부조직에서 3.4가 증가하였다. 결론 : 환자 전면에서의 선량은 모든 실험에서 의미 있게 감소하였다. 각 제조사마다 선량 기준이 다르기 때문에 다른 제조사 장비로 동일한 검사를 수행할 시 검사 조건 설정을 일정하게 유지하고 또한 ODM 기능을 사용할 때에는 화질 유지를 위해 적절한 Noise Index를 선택한다면 인체 전면에 위치한 방사선 감수성 장기에 대한 피폭선량을 줄일 수 있을 것으로 사료된다. 하지만 경부검사의 경우 전면과 후면의 선량이 모두 감소하였는데 이는 후행 연구의 필요가 있다. Purpose : To evaluate image quality and dose reduction rate at radio-sensitive organs located on patient’s anterior surface when using Automated organ-based current modulation(AOBCM). Materials and Methods : By using AOBCM which can reduce surface dose at patient’s anterior surface, dose reduction rate and image quality in chest, head, neck were evaluated. To estimate dose reduction rate and image quality, anthropomorphic phantom(ART-200X, Fluke biomedical, Nevada, USA) made of tissue equivalent materials was used. Somatom Definition AS(Siemens Healthcare, Munich, Germany) and Optima CT 660(GE Healthcare, Milwaukee, Wisconsin, USA) were used. Reference scan and experimental scan which use AOBCM, were performed with each CT scanner. Fluorescence glass dosimeter, GD- 352M(Asahi TechnoGlass, Kansahi, Japan), was used to measure dose and image noise which is equal to CT number’s standard deviation in ROI was used to evaluate image quality. Results : The rate of dose reduction on anterior surface when performing chest, head, and neck scan was 21.1%, 29.6% and 32.9% on average(p≤0.034), respectively, and for Siemens, 23.2%, 29.0% and 54.2% on average(p≤0.004), respectively, for GE. When using AOBCM, numerical values that increase in noise are 0.2, 0.2, 2.5, 0.4, 0.8, 0.4, 0.8 for Siemens and 3.6, 2.4, 9.5, 0.9, 2.5, 3.0, 3.4 for GE at breast, chest wall, lung parenchyma, eyeball, cerebral parenchyma, thyroid soft tissue of neck respectively. Conclusion : Dose at patient’s anterior surface was decreased when using AOBCM. When performing same examination by different CTs, maintainin same conditions, and select appropriate noise index when using ODM, then exposure dose at radio-sensitive organs can be reduced. For neck scan however, dose at anterior and posterior surface were both decreased so it needs to be studied further.

남한에서 낙뢰발생시 근접 고층기상관측 자료를 이용한 안정도 지수 분석

엄효식(Hyo-Sik Eom),서명석(Myoung-Seok Suh) 한국기상학회 2010 대기 Vol.20 No.4

RCP 시나리오 기반 미래 국방기후지수 개발

김성,엄효식,홍선영,김준식,이창훈 한국기상학회 2014 한국기상학회 학술대회 논문집 Vol.2014 No.10