• Journal of Astronomy and Space Sciences
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• 제25권4호
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• pp.415-424
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• 2008

곽영실 등(2008)의 연구로부터 고위도 하부 열권의 평균 수평바람 형태는 발산적인 흐름보다는 회전적인 흐름에 더 강하게 지배된다는 것이 확인되었다. 이 연구에서는, 곽영실 등(2008)의 연구의 연장으로, 회전적인 흐름의 척도인 소용돌이도(vorticity)를 유지시켜주는 강제(forcing)항들을 정량화하고 서로 비교 분석함으로써, 고위도 하부 열권에서의 전체 수평 바람장의 강한 회전 흐름을 유발시키는 주된 물리적인 과정을 규명하였다. 이 연구를 위하여 미 국립대기연구소(NCAR)의 열권-이온권 전기역학적 대순환 모델(Thermosphere-ionosphere Electrodynamic General Circulation Model, TIEGCM)을 이용하였다. 고위도 하부 열권의 소용돌이의 변화를 결정하고 유지시켜 주는 주된 강제항은 이온항력(ion drag)항과 수평 이류(horizontal advection)항으로 확인되었다. 늘림(stretching)항 또한 뚜렷한 기여를 하는 것으로 확인되었다. 소용돌이도 강제에 대한 IMF의 영향이 고도 105-110km부근까지 뚜렷하게 나타남이 확인되었다.

• 한국해양학회지
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• 제30권5호
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• pp.512-521
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• 1995

표면혼합층의 단기(2시간~24시간)변화를 조사하기 위하여 대한해협의 한 정점에 서 1983년 10월 12일에서 10월 14일까지 48시간 동안 주로 1시간 간격으로 해양과 기 상에 대한 관측을 실시하였다. 표면혼합층의 깊이와 수온을 시간당 변동률이 평균적으 로 각각 5.2 m/hour, 0.2$^{\circ}C$/hour로 해표면에서의 바람 응력, 부력속과의 상관관계가 매우 적다. 표면 혼합층은 표면혼합층의 수온와 염분이 높을 때 깊고, 낮을 때 얕다. 한편, 표면혼합층 수온의 급격한 하강 또는 상승이 관측되었다. 인공위성 자료와 XBT 자료 분석에 의하면 표면혼합층 수온의 급격한 상승은 고온의 해수의 이류에 의한 일 어남을 알 수 있었다. 위의 결과들은 해류가 비교적 강하고 해수물성이 서로 다른 수 괴가 존재하는 가을철 대한해협에서는 해수의 이류가 표면혼합층의 단기변화에 크게 영향을 준다는 것을 나타낸다.

• Journal of Astronomy and Space Sciences
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• 제22권2호
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• pp.139-146
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• 2005

A model of advection-dominated accretion flows has been highlighted in the last decade. Most of calculations are based on self-similar solutions of equations governing the accreting flows. We revisit self-similar solutions of the simplest form of advection-dominated accretion flows. We explore the parameter space thoroughly and seek another category of self-similar solutions. In this study we allow the parameter f less than zero, which denotes the fraction of energy transported through advection. We have found followings: 1. For f > 0, in real ADAF solutions the ratio of specific heats ${\gamma}$ satisfies 1 < ${\gamma}$ < 5/3 for O ${\leq}$ f ${\leq}$ 1. On the other hands, in wind solutions a rotating disk does not exist. 2. For f < 0, in real ADAF solutions with ${\epsilon}$ greater than zero ${\gamma}$ requires rather exotic range, that is, ${\gamma}$ < 1 or ${\gamma}$ > 5/3. When -5/2 < ${\epsilon}$' < 0, however, allowable ${\gamma}$ can be found in ${\gamma}$ < 5/3, in which case 4{\Omega}_0$,_ is imaginary. 3. For a negative $u_0$,+ with f > 0, solutions are only allowed with exotic ${\gamma}$, that is, 1 < ${\gamma}$ or ${\gamma}$ > (5f/2-5/3)/(5f/2-1)when O < f < 2/5, (5f/2-5/3)/(5f/2-1) < ${\gamma}$ < 1 when f > 2/5. Since ${\epsilon}$' is negative, 4{\Omega}_0$,+ is again an imaginary quantity. For a negative $u_0$,+ with f < 0, ${\gamma}$ is allowed in 1 < 7 < (5|f|/2 + 5/3)/(5|f|/2 + 1). We briefly discuss physical implications of what we have found.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2006년도 Proceedings of ISRS 2006 PORSEC Volume I
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• pp.21-24
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• 2006

Processes controlling the interannual variation of mixed layer temperature (MLT) averaged over the NINO3 domain ($150-90^{\circ}W$, $5^{\circ}N-5^{\circ}S$) are studied using an ocean data assimilation product that covers the period of 1993 to 2003. Advective tendencies are estimated here as the temperature fluxes through the domain's boundaries, with the boundary temperature referenced to the domain-averaged temperature to remove the dependence on temperature scale. The overall balance is such that surface heat flux opposes the MLT change but horizontal advection and subsurface processes assist the change. The zonal advective tendency is caused primarily by large-scale advection of warm-pool water through the western boundary of the domain. The meridional advective tendency is contributed mostly by Ekman current advecting large-scale temperature anomalies though the southern boundary of the domain. Unlike many previous studies, we explicitly evaluate the subsurface processes that consist of vertical mixing and entrainment. In particular, a rigorous method to estimate entrainment allows an exact budget closure. The vertical mixing across the mixed layer (ML) base has a contribution in phase with the MLT change. The entrainment tendency due to temporal change in ML depth is negligible comparing to other subsurface processes. The entrainment tendency by vertical advection across the ML base is dominated by large-scale changes in wind-driven upwelling and temperature of upwelling water. Tropical instability waves (TIWs) result in smaller-scale vertical advection that warms the domain during La Ni? cooling events. When the advective tendencies are evaluated by spatially averaging the conventional local advective tendencies of temperature, the apparent effects of currents with spatial scales smaller than the domain (such as TIWs) become very important as they redistribute heat within the NINO3 domain. However, such internal redistribution of heat does not represent external processes that control the domain-averaged MLT.

• 한국해양학회지:바다
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• 제8권2호
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• pp.121-131
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• 2003

동해안에서 지난 20년 동안 발생한 월별 안개 발생빈도와 지속시간 분석에 의하면 1월, 2월, 11월, 12월의 안개 발생빈도는 거의 전무함을 알 수 있다. 이 현상은 태백산맥으로부터 동쪽으로 경사를 이루어 복사 안개의 발생이 어려운 지형 특징을 가지고 있기 때문으로 사료된다. 반면에 안개발생빈도의 90%이상을 차지하는 봄, 여름철의 안개 발생 원인은 크게 3가지로 분류된다. 첫 번째는 증기해무로서 오호츠크해 고기압의 확장으로 찬 북동기류가 동해상으로 이류하여 발생한다. 두 번째는 이류해무로서 따뜻한 기단이 상대적으로 찬 해수면 위로 이류하여 냉각, 포화되어 발생한다. 세 번째는 전선해무로써 저기압이 동해상으로 이동하여 수증기가 공급된 상태에서 한랭 전선 후면의 찬공기가 이류하면서 발생한다 한편, 해상풍, 상대습도, 운저고도, 시정 등의 예측과 동해 해역의 수직단면에서 안개 예측이 가능한 해무예측시스템(DUT-METRI)을 구축하여 사례기간의 해무를 모사하였, 위성자료로부터 이를 검증하였다.

• 한국지구과학회지
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• 제43권6호
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• pp.712-736
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• 2022

To understand the characteristics of low-level clouds (CLs), environmental variables are composited on each CL using individual surface observations and six-hourly upper-air meteorologies around the globe. Individual CLs has its own distinct environmental conditions. Over the eastern subtropical and western North Pacific Ocean in JJA, stratocumulus (CL5) has a colder sea surface temperature (SST), stronger and lower inversion, and more low-level cloud amount (LCA) than the climatology whereas cumulus (CL12) has the opposite characteristics. Over the eastern subtropical Pacific, CL5 and CL12 are influenced by cold and warm advection within the PBL, respectively but have similar cold advection over the western North Pacific. This indicates that the fundamental physical process distinguishing CL5 and CL12 is not the horizontal temperature advection but the interaction with the underlying sea surface, i.e., the deepening-decoupling of PBL and the positive feedback between shortwave radiation and SST. Over the western North Pacific during JJA, sky-obscuring fog (CL11), no low-level cloud (CL0), and fair weather stratus (CL6) are associated with anomalous warm advection, surface-based inversion, mean upward flow, and moist mid-troposphere with the strongest anomalies for CL11 followed by CL0. Over the western North Pacific during DJF, bad weather stratus (CL7) occurs in the warm front of the extratropical cyclone with anomalous upward flow while cumulonimbus (CL39) occurs on the rear side of the cold front with anomalous downward flow. Over the tropical oceans, CL7 has strong positive (negative) anomalies of temperature in the upper troposphere (PBL), relative humidity, and surface wind speed in association with the mesoscale convective system while CL12 has the opposite anomalies and CL39 is in between.

• 한국대기환경학회지
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• 제19권1호
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• pp.13-23
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• 2003

A local wind model and a three dimensional local environmental model including advection, diffusion, deposition. and photochemical reactions were performed at Gwangyang Bay, Korea, to predict air flow and air pollutants concentrations. A large grid was used, and nesting method was employed for small grid calculation. From the meterological module simulation, we were able to reproduce local wind characteristics such as sea/land winds and mountain/valley winds simulation at Gwangyang Bay. In addition, the concentration module showed high concentration regions at Yosu industrial complex, Gwangyang steel company. and Container anchor. It was also seen that air pollutants were dispersed by sea/land winds. A comparison between the measurement and the prediction of sulfur dioxide and nitric oxide, which are relatively low-reacted pollutants, was performed. However, the measured nitrogen dioxide and ozone concentrations were higher than the simulated ones. Particularly, ozone concentration between 8 a..m. and 8 p.m. agreed well, but the measured ozone during the rest of time were generally higher.

• Journal of Radiation Protection and Research
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• 제12권2호
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• pp.28-36
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• 1987

원자력 시설에서 대기중으로 방출되는 방사성 구름에 의한 환경선량계산에는 Gaussian plume model 주로 사용되고 있으나, 바람의 분포나 대기의 흐트러짐이 공간적으로 일정하지 않은 복잡 지형에의 적용에는 문제가 있다. 복잡 지형을 고려한 기류계산에는 MATTEW, WIND04 코드가 그 타당성을 인정받고 있다. 이러한 코드의 원리를 기초로 하여, 질량보존법칙을 만족하는 이류 확산 방정식을 유한차분법으로 계산하고 풍속장을 구하였다. 입자 농도와 피폭선량은 방사성 구름을 입자군으로 근사시키는 PIC model을 이용하여 계산하였으며, 입자의 대기 확산은 Random Walk법을 이용하였다. 계산 결과, 지형에 의한 풍속, 풍향의 변화를 알 수 있었으며, 피폭선량분포를 구할 수 있었다.

• 한국대기환경학회지
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• 제16권2호
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• pp.151-158
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• 2000

Since Pusan metropolitanarea where is composed complex terrain is connected to sea the sea-land breeze circulation and the mountain-valley circulation are apt to form A regional scale circulation system is formed at a region which has complex terrain because of curves of its and affect to the dispersion and advection of air pollutants. LCM Local Circulation Model which a propriety was verified described that sea breeze and valley wind at the daytime and land breeze and mountain wind at the nighttime were well devellped over the Pusan metropolital area. Next for the investigation of accuracy of simulated results an observed value at Kae-Kum and Su-Young on the pusan metropolitan area were compared with it at those points. From the comparison of the temperature and horizontal velocity between the results of LCM and an observed values they have a similar trend of a diurnal variation. For the prediction of dispersion and transportation of air pollutants the wind field should be calculated with high accuracy. A numerical simulation using LCM can provide more accuracy results around Pusan metropolitan area.

• 수산해양기술연구
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• 제13권1호
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• pp.17-25
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• 1977

For four calender years (1971-1974), daily observations of weather conditions (air temperature, humidity, wind speed, wind direction, cloud amount, fog, precipitation etc.) at six stations in the north western Pacific Ocean are used to calculate mean monthly values and to check extra-conditions. At Petropavlosk and Miko'skoe, where indicate the characteristics of modified continental climate, the temperature and humidity are high in summer, and Iow in winter. At A Dak and She Mya, where indicate the characteristics of warm current type maritime climate, humidity is high in all season and annual range of air temperature is nearly negligible. At Simusir and Vasi!' eva, where indicate the characteristics of cold current type maritime climate, humidity is high in all season and annual range of air temperature is $15^{\circ}C.$ As dry cooling power is relatively high in winter, working condition on deck is bad. Most of fogs are advection fog in the area of cold current type climate in summer.