• 한국농림기상학회지
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• 제1권1호
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• pp.60-71
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• 1999

The micrometeorological tower flux network is the cornerstone of the global terrestrial vegetation monitoring. The eddy covariance technique used for tower fluxes is derived from the conservation of mass and is most applicable for steady-state conditions over flat, extended, and uniform vegetation. This technique allows us to obtain surface fluxes of energy budget components, greenhouse and trace gases, and other pollutants. The quality-controlled flux data are invaluable to validate various models with temporal scales ranging from minutes to years and spatial scales ranging from a few meters to hundreds of kilometers. In this paper, we review the theoretical background of this important eddy covariance technique, examine the measurement criteria and corrections, and finally suggest some measurement strategies that may facilitate coordinated flux measurements among different disciplines and provide a strong infrastructure for the global flux network.

• 대기
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• 제26권3호
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• pp.483-492
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• 2016

We have examined the random error of eddy covariance (EC) measurements on the basis of two-tower approach during daytime. Two EC towers were placed on the grassland with different vegetation density near Gumi-weir. We calculated the random error using three different methods. The first method (M1) is two-tower method suggested by Hollinger and Richardson (2005) where random error is based on differences between simultaneous flux measurements from two towers in very similar environmental conditions. The second one (M2) is suggested by Kessomkiat et al. (2013), which is extended procedure to estimate random error of EC data for two towers in more heterogeneous environmental conditions. They removed systematic flux difference due to the energy balance deficit and evaporative fraction difference between two sites before determining the random error of fluxes using M1 method. Here, we introduce the third method (M3) where we additionally removed systematic flux difference due to available energy difference between two sites. Compared to M1 and M2 methods, application of M3 method results in more symmetric random error distribution. The magnitude of estimated random error is smallest when using M3 method because application of M3 method results in the least systematic flux difference between two sites among three methods. An empirical formula of random error is developed as a function of flux magnitude, wind speed and measurement height for use in single tower sites near Nakdong River. This study suggests that correcting available energy difference between two sites is also required for calculating the random error of EC data from two towers at heterogeneous site where vegetation density is low.

• Ocean and Polar Research
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• 제26권2호
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• pp.145-154
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• 2004

Surface energy and $CO_2$ fluxes have been measured over an ocean at Ieodo Ocean Research Station of KORDI since May 2003. Eddy covariance technique, which is a direct flux measurement, is used to quantitatively understand the interaction between the ocean surface and the atmospheric boundary layer. Although fluxes were continuously measured during the period from May 2003 to February 2004, the quality control of these data yielded <20% of data retrieval. The atmospheric stability did not show any distinct dirunal patterns and remained near-neutral to stable from May to June but mostly unstable during fall and winter in 2003. Sensible heat flux showed a good correlation with the difference between the sea water temperature and the air temperature. The maximum fluxes of sensible heat and latent heat were $120Wm^{-2}$ and $350Wm^{-2}$ respectively, with an averaged Bowen ratio of 0.2. The ocean around the tower absorbed $CO_2$ from the atmosphere and the uptake rates showed seasonal variations. Based our preliminary results, the daytime $CO_2$ flux was steady with an average of $-0.1 mgCO_2m^{-2}s^{-1}$ in summer and increased in winter. The nighttime $CO_2$ uptake was greater and fluctuating, reaching up to $-0.1 mgCO_2m^{-2}s^{-1}$ but these data require further examination due to weak turbulent mixing at nighttime. The magnitude of $CO_2$ flux was positively correlated with the half hourly changes in horizontal mean wind speed. Due to the paucity of quality data, further data collection is needed for more detailed analyses and interpretation.

• 한국대기환경학회지
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• 제28권5호
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• pp.485-494
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• 2012

The purpose of this study is to monitor the flux of $CO_2$ and BVOCs (biogenic volatile organic compounds) between the atmosphere and forest. The main research activities are conducted at Taehwa Research Forest (TRF), managed by the College of Agriculture and Life Sciences at Seoul National University. The TRF site is located 60 km north-east from the center of Seoul Metropolitan Area. The TRF flux tower is in the middle of a Korean Pine (Pinus Koraiensis) plantation ($400m{\times}400m$), surrounded by a mixed forest. Eddy covariance method was used for $CO_2$ flux above the forest and REA (Relaxed eddy accumulation) method applying eddy covariance was used for BVOCs flux. BVOCs flux that was measured in spring (from May 16 to 18) had distribution of 84 to $2917{\mu}g/m^2{\cdot}h$. Especially, it showed that d-limonene being strong reactivity composed the largest fraction of monoterpene. Ambient $CO_2$ concentration measured in Mt. Taehwa was 399 ppm and observed $CO_2$ fluxes between the atmosphere and forest suggested that during the day, $CO_2$ is absorbed by plants through photosynthesis and released during the night.

• 한국수자원학회논문집
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• 제46권2호
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• pp.111-122
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• 2013

최근 들어 기후변화로 인해 물과 에너지 순환에 관한 정확한 이해가 요구되고 있다. 현재 미기상학적 플럭스 타워 네트워크는 수문학적, 생태학적 분석에 있어서 주춧돌역할을 하고 있다. 하지만 플럭스 타워의 에디공분산 방법을 활용한 잠열 플럭스 측정은 여러 가정사항에 따른 시스템적 오류를 내포하고 있고 이에 따라 과소평가된 잠열 플럭스 원시자료의 보정이 필요하다. 몇몇의 보정방법 중 보엔비를 활용한 방법이 가장 유용한 방법 중 하나로서 여기에는 플럭스타워에서 측정한 순 복사에너지 및 기타 플럭스(현열, 지열) 등이 요구되며 이러한 자료에 대한 정확한 측정 및 검증이 필요하다. 본 연구에서는 설마천, 청미천 유역의 플럭스타워에서 측정된 순 복사에너지를 검증하기 위해 두 가지 형태의 이론적으로 계산된 순 복사에너지와의 비교검증을 실시하였다-(1) FAO 56 기반의 일평균 순 복사에너지 (2) Bastiaansen (1995)가 제안한 순간 순 복사에너지. 본 연구의 결과는 플럭스타워에서 측정된 순 복사에너지는 이론적으로 계산된 순 복사에너지와 상당히 비슷한 경향성을 보인다는 것을 제시했다. 또한, 측정된 순 복사에너지를 이용하여 관측된 잠열플럭스를 보엔비 보정방법에 적용시킨 결과 에너지수지에 더욱 부합하는 것을 알 수 있었다.

• 한국농공학회논문집
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• 제57권3호
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• pp.109-120
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• 2015

Spatial heterogeneous characteristics of solar radiation energy from Climate Change gives rise to energy imbalance in the general ecological system including water resources. This study is to estimate the $CO_2$ flux of South Korea using Terra MODIS image and to assess the reliability of MODIS data from the ground measured $CO_2$ flux by eddy covariance flux tower data at 3 locations (two at mixed forest area and one at rice paddy area). The MODIS Gross Primary Productivity (GPP) product (MOD17A2), 8-day composite at 1-km spatial resolution was adopted for the spatial $CO_2$ flux generation. The MOD17A2 data by noise like cloud and snow in a day were tried to fill by Inverse Distance Weighted (IDW) method from valid pixels and the damping effect of MOD17A2 data were corrected by Quality Control (QC) flag. The MODIS $CO_2$ flux was estimated as the sum of GPP and Re (ecosystem respiration) by Lloyd and Taylor method (1994). The determination coefficient ($R^2$) between MODIS $CO_2$ and flux tower $CO_2$ for 3 years (2011~2013) showed 0.55 and 0.60 in 2 mixed forests and 0.56 in rice paddy respectively. The $CO_2$ flux generally fluctuated showing minus values during summer rainy season (from July to August) and maintaining plus values for other periods. The MODIS $CO_2$ flux can be a useful information for extensive area, for example, as a reliable indicator on ecological circulation system.

• 대기
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• 제34권1호
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• pp.69-81
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• 2024

In this paper, Annual flux variations in the Boseong Tall Tower (BTT) from 2016 to 2020 were analyzed using data from three levels (2.5 m, 60 m, and 300 m). BTT was installed in Boseong-gun, Jeollanam-do in February 2014 and continued to conduct energy exchange observations such as CO2, sensible heat, and latent heat using the eddy covariance method until March 2023. The BTT was located in a very flat and uniform paddy field, and flux observations were conducted at four levels: 2.5 m, 60 m, 140 m, and 300 m above ground. Surface energy balance was confirmed from observed data of net radiation flux, soil heat flux, sensible heat flux, and latent heat flux. Additionally, 2.5 m height surface fluxes, which are most influenced by agricultural land, were compared with data from Local Data Assimilation and Prediction System (LDAPS) of the Korea Meteorological Administration to evaluate the accuracy of LDAPS flux data. The correlation coefficient between LDAPS flux data and observed values was 0.95 or higher. Excluding summer latent heat flux data, there was a general tendency for LDAPS data to be higher than observed values. The footprint areas estimated below 60 m height mainly covered agricultural land, and flux observations at 2.5 m and 60 m heights showed typical agricultural characteristics. In contrast, the footprint estimated at 300 m height did not show agricultural characteristics, indicating that observations at this height encompassed a wide range, including mountains, sea, and roads. The analysis results of long-term flux observations can contribute to understanding the energy and carbon dioxide fluxes in agricultural fields. Furthermore, these results can be utilized as essential data for validating and improving numerical models related to such fluxes.

• 한국농림기상학회지
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• 제20권1호
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• pp.18-33
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• 2018

기후스마트농업의 관점에서 무논점파 농법의 경쟁력을 평가하기 위하여 플럭스 타워(HPK)를 설치, 에디 공분산 방법으로 이산화탄소, 메탄 그리고 에너지의 교환량을 지속적으로 관측하고 있다. 본 통신문에서는 HPK 관측지에 대한 소개와 관측 자료의 처리과정 및 품질 관리에 대하여 문서화 하였다. KoFlux 표준화 방법에 따른 10단계 자료 처리 및 품질 관리과정을 거쳤으며, 이 과정에서 HPK 관측지의 자료 사용자들이 알아야 할 중요한 보정 단계를 이해하기 쉽도록 각 방법에 대한 개념과 일반적인 예를 들어 설명하였다. 자료 처리 과정에서 생성된 모든 자료들을 정리하여 데이터 서버에 저장하였으며, 모든 처리 과정을 거친 최종 자료를 사용하여 HPK 관측지에서 2016년 생장기간 동안 관측된 주 요소들에 대해 간략히 정량화 하였다.

• 대한원격탐사학회지
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• 제28권4호
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• pp.435-448
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• 2012

증발산은 토양 표면에서 일어나는 증발 과정과 식물의 광합성 작용으로 인해 일어나는 증산 작용을 포함하는 수문기상인자로 외부 환경에 민감하게 작용한다. 현재 국내외에서는 이를 정확하게 관측하여 활용하기 위해 증발접시(evaporation pan), 침루계(lysimeter) 등을 이용하여 실측하거나 Eddy covariance technique, Bowen ratio method 등을 이용하여 경험적으로 산정하고 있으나 공간적인 제약이 따른다. 따라서 본 연구에서는 Terra 인공위성에 탑재된 Moderate Resolution Imaging Spectroradiometer (MODIS) 다중분광 센서를 이용, 원격탐사 기술을 적용함으로써 이러한 지상 관측의 단점을 보완하고자 하였다. 이전 연구들에서 소개가 되었던 원격탐사 기반 증발산 산정 모형을 개선하여 별도의 외부 입력자료 없이 MODIS 위성 이미지 자료만을 이용, 우리나라의 지역적 특성을 반영한 Penman-Monteith 기반 증발산을 산정하였다. 유량조사사업단에서 운영 및 관리하고 있는 설마천/청미천 플럭스 타워의 증발산 관측치와 MODIS 기반 증발산 산정값과의 비교를 통해 각각 0.69, 0.74의 높은 상관계수를 보여 산정 방법의 적용성을 검증하였다.

• 한국농림기상학회지
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• 제7권1호
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• pp.45-50
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• 2005

우리나라의 주요 농업 생태계인 논에서 벼 생육기간 중의 CO₂와 에너지 교환을 정량화하고 분석(평가하기 위하여 미기상학적인 방법인 에디 공분산법으로 물질/에너지 플럭스를 측정하였다. 측정장소는 한반도 중부 지방의 대표적인 벼농사 지대인 경기도 이천시 부발읍 신원리 농업과학기술원 이천 시험지 플럭스 측정 지점 (37°18'20.34"N, 127°30'40.46"E)에서 수행되었다. 벼군락 장파복사의 방출은 대기로부터의 장파복사량보다 100Wm/sup -2/정도 많았다. 벼논에서 이앙 후 에너지 배분은 잠열 플럭스로 더 많이 배분되었고, 보웬 비는 0.3-0.7 정도였다. 이앙 후 대기중의 수증기 농도는 이 앙 전에 비하여 2gm/sup -3/ 정도 높아졌다. 벼논에서 CO₂ 농도는 야간이 780～820gm/sup -3/, 주간에는 약 650gm/sup -3/ 정도였다. 일사량 증가에 따른 이산화탄소 흡수량은 엽면적 지수가 높을수록 높았으며 특히 유수 형성기-출수기에서 가장 높았다.