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Samuel Takele Kenea,오영석,구태영,Jae-Sang Rhee,변영화,Lev D. Labzovskii,Shanlan Li 한국기상학회 2019 Asia-Pacific Journal of Atmospheric Sciences Vol.55 No.3
It is evident that evaluating the measurement of greenhouse gases (GHGs) obtained from multi-platform instruments against accurate and precise instrument such as aircraft in-situ is very essential when using remote sensing GHGs results for source/sink estimations with inverse modeling. The results of the inverse models are very sensitive even to small biases in the data (Rayner and O’Brien 2001). In this work, we have evaluated ground-based high resolution Fourier Transform Spectrometer (g-b FTS) and the Greenhouse gases Observing SATellite (GOSAT) column-averaged dry air mole fraction of methane (XCH4) through aircraft in-situ observations over Anmyeondo station (36.538o N, 126.331o E, 30 m above sea level). The impact of the spatial coincidence criteria was assessed by comparing GOSAT data against g-b FTS.We noticed there was no any systematic difference based on the given coincidence criteria. GOSATexhibited a bias ranging from 0.10 to 3.37 ppb, with the standard deviation from 4.92 to 12.54 ppb, against g-b FTS with the spatial coincidence criteria of ±1, ±3, ±5 degrees of latitude and longitude and ± 1 h time window. Data observed during ascent and descent of the aircraft is considered as vertical profiles within an altitude range of 0.2 to a maximum of 9.0 km so that some assumptions were applied for the construction of the profiles below 0.2 and above 9.0 km. In addition, the suitability of aircraft data for evaluation of remote sensing instruments was confirmed based on the assessment of uncertainties. The spatial coincidence criteria is ±1o latitude and ± 2o longitude and for temporal difference is ±1 h of the satellite observation overpass time were applied, whereas g-b FTS data are the mean values measured within ±30 min of the aircraft observation time. Furthermore, the sensitivity differences of the instruments were taken into account.With respect to aircraft, the g-b FTS data were biased by −0.19 ± 0.69%, while GOSAT data were biased by −0.42 ± 0.84%. These results confirm that both g-b FTS and GOSAT are consistent aircraft observations and assure the reliability of the datasets for inverse estimate of CH4.
Samuel Takele Kenea,Haeyoung Lee,Sangwon Joo,Shanlan Li,Lev D. Labzovskii,Chu-Yong Chung,Yeon-Hee Kim 한국대기환경학회 2021 한국대기환경학회 학술대회논문집 Vol.2021 No.10
To comprehend interannual variability of CH₄ and its drivers, we used integrated data from different platforms such as in situ measurements, TROPOMI, and GOSAT retrievals. A pronounced change of annual growth rate was detected at Anmyeondo (AMY), Korea, ranging from -16.8 to 31.3 ppb yr<SUP>−1</SUP> as captured in situ through 2015-2020. High growth rates were discerned in 2016 (31.3 ppb yr<SUP>−1</SUP> and 13.4 ppb yr<SUP>−1</SUP> from in situ and GOSAT, respectively) and 2019 (27.4 ppb yr<SUP>−1</SUP> and 16.4 ppb yr<SUP>−1</SUP> from in situ and GOSAT, respectively). The high growth in 2016 was essentially explained by the strong El Niño event in 2015–2016, whereas the large growth rate in 2019 was not related to ENSO. We suggest that the growth rate that appeared in 2019 was related to soil temperature. The stable isotopic composition of <SUP>13</SUP>C/<SUP>12</SUP>C in CH₄ (δ<SUP>13</SUP>-CH₄) collected by flask-air sampling at AMY during 2014-2019 supported the soil methane hypothesis. The isotopic values in 2019 exhibited the strongest depletion compared to other periods, which suggests even a stronger biogenic signal that was affected by the variations of soil temperature and soil moisture.