RT info:eu-repo/semantics/article
T1 Trend analysis and outlier distribution of CO2 and CH4: A case study at a rural site in northern Spain
A1 Pérez Bartolomé, Isidro Alberto
A1 García Pérez, María Ángeles
A1 Sánchez Gómez, María Luisa
A1 Pardo Gómez, Nuria
K1 Skewed distributions
K1 Greenhouse gases
K1 Efficiency estimators
K1 Distribution fitting
K1 Outlier distribution
K1 Emissions statistical control
K1 22 Física
AB CO2 and CH4 outliers may have a noticeable impact on the trend of both gases. Nine years of measurements since 2010 recorded at a rural site in northern Spain were used to investigate these outliers. Their influence on the trend was presented and two limits were established. No more than 23.5% of outliers should be excluded from the measurement series in order to obtain representative trends, which were 2.349 ± 0.012 ppm year−1 for CO2 and 0.00879 ± 0.00004 ppm year−1 for CH4. Two types of outliers were distinguished. Those above the trend line and the rest below the trend line. Outliers were described by skewed distributions where the Weibull distribution figures prominently in most cases. A qualitative procedure was presented to exclude the worst fits, although five statistics were considered to select the best fit. In this case, the modified Nash-Sutcliffe efficiency is prominent. Finally, three symmetrical distributions were added to fit the observations when outliers are excluded, with the Gaussian and beta distributions providing the best fits. As a result, certain skewed functions, such as the lognormal distribution, whose use is frequent for air pollutants, could be questioned in certain applications.
PB Elsevier
SN 0048-9697
YR 2022
FD 2022
LK https://uvadoc.uva.es/handle/10324/58628
UL https://uvadoc.uva.es/handle/10324/58628
LA eng
NO Science of The Total Environment, 2022, vol. 819, p. 153129
NO Producción Científica
DS UVaDOC
RD 11-jul-2024