한국농림기상학회지, 제 10권 제3호(2008) (pISSN 1229-5671, eISSN 2288-1859)
Korean Journal of Agricultural and Forest Meteorology, Vol. 10, No. 3, (2008), pp. 82~93
DOI: 10.5532/KJAFM.2008.10.3.082
ⓒ Author(s) 2014. CC Attribution 3.0 License.


광릉 산림의 플럭스 자료 처리와 품질 관리

임희정, 이영희
경북대학교 천문대기과학과

(2008년 05월 23일 접수; 2008년 09월 20일 수정; 2008년 09월 29일 수락)

Processing and Quality Control of Flux Data
at Gwangneung Forest

Hee-jeong Lim, Young-Hee Lee
Department of Astronomy and Atmospheric Sciences, Kyungpook National University,
Daegu 702-701, Republic of Korea

(Received May 23, 2008; Revised September 20, 2008; Accepted September 29, 2008)

ABSTRACT
In order to ensure a standardized data analysis of the eddy covariance measurements, Hong and Kim’s quality control program has been updated and used to process eddy covariance data measured at two levels on the main flux tower at Gwangneung site from January to May in 2005. The updated program was allowed to remove outliers automatically for CO2 and latent heat fluxes. The flag system consists of four quality groups(G, D, B and M). During the study period, the missing data were about 25% of the total records. About 60% of the good quality data were obtained after the quality control. The number of record in G group was larger at 40m than at 20m. It is due that the level of 20m was within the roughness sublayer where the presence of the canopy influences directly on the character of the turbulence. About 60% of the bad data were due to low wind speed. Energy balance closure at this site was about 40% during the study period. Large imbalance is attributed partly to the combined effects of the neglected heat storage terms, inaccuracy of ground heat flux and advection due to local wind system near the surface. The analysis of wind direction indicates that the frequent occurrence of positive momentum flux was closely associated with mountain valley wind system at this site. The negative CO2 flux at night was examined in terms of averaging time. The results show that when averaging time is larger than 10min, the magnitude of calculated CO2 fluxes increases rapidly, suggesting that the 30min CO2 flux is influenced severely by the mesoscale motion or nonstationarity. A proper choice of averaging time needs to be considered to get accurate turbulent fluxes during nighttime.

Keyword: Quality control, Energy balance, Turbulent flux, Gwangneung forest

MAIN

적요

보다 자동화된 방법으로 신뢰성 있는 난류 플럭스의 자료를 생산하기 위해서 Hong and Kim(2002)의 난류 품질 관리 프로그램을 개선하고 개선된 프로그램을 광릉산림에 적용하여 복잡한 산림지역에서 난류 플럭스의 특성을 조사하였다. 개선된 프로그램을 이용하여 2005년 1월부터 5월까지 광릉 수목원에 위치한 주 타워의 두 고도 (20m와 40m)에서 관측된 난류 자료에 대하여 품질 검사를 실시하였다. 개선전과 비교해 개선된 프로그램은 이상점(outlier)에 해당되는 자료들을 많이 제거하였다. 자료의 품질체계는 4등급(Good, Dubious, Missing, Bad)으로 분류하였으며 본 분석에서 사용된 기간의 자료 중 25%는 결측이었고 (Missing 등급), 60%는 Good 등급으로 분류되었다. 고도 별로는 40m에서 관측된 자료가 20m에서 관측된 자료보다 Bad 등급의 자료수가 적었는데 이는 20m가 식생 꼭 대기에 인접한 거칠기 아층에 해당하고 또한 풍속도 더 낮은데 기인한다. Bad 등급으로 분류된 자료의 주원인은 낮은 풍속으로 나타났다. 분석 기간 동안의 에너지 수지의 닫힘은 약 40%로 나타났고 이러한 에너지 불균형의 부분적인 이유로는 열 저장항들이 고려되지 않은 점, 토양열 플럭스 측정의 불확실성, 복잡한 지형 등에 의한 국지풍에 의한 이류 등이 복합적으로 작용했을 것으로 생각된다. 광릉에서 발생하는 상향 운동량 플럭스는 국지풍의 발달 시 높은 발생률을 보여 이 둘이 밀접히 관련되어 있음을 나타낸다. 야간에 낮은 음의 CO2 플럭스가 발생하는 경우에 대하여 평균 시간을 증가시킴에 따른 CO2 flux의 변화를 조사한 결과 평균시간이 10분 이상 증가함에 따라 CO2 flux의 절대값이 빠르게 증가하는 경향을 보였다. 이는 야간에 CO2 플럭스는 중규모 운동이나 비정상성(nonstationarity) 등의 영향을 많이 받고 있음을 시사한다. 그러므로 야간에 보다 정확한 난류 플럭스 값을 산출하기 위해서는 평균시간의 적절한 조절이 필요할 것으로 보인다.

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