Trend analysis of CO2 and CH4 recorded at a semi-natural site in the northern plateau of the Iberian Peninsula

Pérez, Isidro A.; Sánchez, M. Luisa; García, M. Ángeles; Pardo, Núria

doi:10.1016/j.atmosenv.2016.11.068

Cited by 10 publications

(12 citation statements)

References 54 publications

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“…A well-defined increasing pattern over the years was inferred from Fig. 4, which is partially related with a rise in anthropogenic emissions from industrial activities and from the urban landfill near the monitoring station for CH4, as well as from farming vehicle emissions [8]. The same behaviour was described by García et al [18].…”

Section: Data Trend Evolutionsupporting

confidence: 59%

“…where wi are the weights and and are weighted mean values, calculated according to the procedure described by Pérez et al [8]. It should be considered that in this case, the Epanechnikov kernel was used, since it is the most widely used kernel in atmospheric studies and also because of its simplicity.…”

Section: Local Linear Functionmentioning

confidence: 99%

“…This procedure involves fitting appropriate mathematical functions to the data [2].pollution analysis. Cleveland [7] suggested local regression methods to obtain visual information from scatterplots [8]. Kernel smoothing functions are an extension of the locally weighted average method which has been widely used in atmospheric temporal series [9].…”

Section: Introductionmentioning

confidence: 99%

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Trend Assessment for a CO2 and CH4 Data Series in Northern Spain

Fernández-Duque

Pérez

Garcia

et al. 2017

Proceedings of the 2nd International Electronic Conference on Atmospheric Sciences

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Abstract:The main objective of this paper is to implement different methods to assess the salient features of the data trend for a CO2 and CH4 data series. Said series was obtained at the Low Atmosphere Research Centre (41°48′49″ N, 4°55′59″ W) using a Picarro analyser (G1301). Different functions were employed to determine and quantify the data trend. The first was a harmonic function based on a third-degree polynomial. An increasing trend, below 2.30 ppm year -1 for CO2 and below 11.90 ppb year -1 for CH4, was reported. Epanechnikov, Gaussian, biweight, tricubic, rectangular and triangle kernels, were applied with a 500-day bandwidth for the trend. The best fit was obtained by the biweight kernel (r>0.20), with an increasing trend around 1.80 ppm year -1 for CO2 and around 7.15 ppb year -1 for CH4. The final analysis, which included local linear regression functions also applying a 500-day bandwidth, revealed increasing trends for both CO2, around 1.98 ppm year -1 , and CH4, around 10.85 ppb year -1 . Trend values were far more accelerated in the latter years of the series, regardless of the chosen function. This paper demonstrated the usefulness of the mathematical functions, allowing for an accurate determination of the data trend.

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Section: Data Trend Evolutionsupporting

confidence: 59%

Section: Local Linear Functionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Trend Assessment for a CO2 and CH4 Data Series in Northern Spain

Fernández-Duque

Pérez

Garcia

et al. 2017

Proceedings of the 2nd International Electronic Conference on Atmospheric Sciences

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“…The evolution of CO 2 and CH 4 has often been described by composite equations comprising two parts (Fern andez-Duque et al, 2017;P erez et al, 2017), one being harmonic to include daily and yearly cycles, which lies outside the scope of this study, and the other being responsible for the concentration trend.…”

Section: Introductionmentioning

confidence: 99%

The influence of meteorological variables on CO2 and CH4 trends recorded at a semi-natural station

Pérez

Sánchez

García

et al. 2018

Journal of Environmental Management

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CO and CH evolution is usually linked with sources, sinks and their changes. However, this study highlights the role of meteorological variables. It aims to quantify their contribution to the trend of these greenhouse gases and to determine which contribute most. Six years of measurements at a semi-natural site in northern Spain were considered. Three sections are established: the first focuses on monthly deciles, the second explores the relationship between pairs of meteorological variables, and the third investigates the relationship between meteorological variables and changes in CO and CH. In the first section, monthly outliers were more marked for CO than for CH. The evolution of monthly deciles was fitted to three simple expressions, linear, quadratic and exponential. The linear and exponential are similar, whereas the quadratic evolution is the most flexible since it provided a variable rate of concentration change and a better fit. With this last evolution, a decrease in the change rate was observed for low CO deciles, whereas an increasing change rate prevailed for the rest and was more accentuated for CH. In the second section, meteorological variables were provided by a trajectory model. Backward trajectories from 1-day prior to reaching the measurement site were used to calculate distance and direction averages as well as the recirculation factor. Terciles of these variables were determined in order to establish three intervals with low, medium and high values. These intervals were used to classify the variables following their interval widths and skewnesses. The best correlation between pairs of meteorological variables was observed for the average distance, in particular with horizontal wind speed. Sinusoidal relationships with the average direction were obtained for average distance and for vertical wind speed. Finally, in the third section, the quadratic evolution was considered in each interval of all the meteorological variables. As regards the main result, the greatest increases were obtained for high potential temperature for both gases followed by low and medium boundary layer height for CO and CH, respectively. Combining both meteorological variables provided increases of 22 ± 9 and 0.070 ± 0.019 ppm for CO and CH, respectively, although the number of observations affected is small, around 7%.

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“…The analysis presented in the current study expands that research by using all the percentiles. Although most of the measurements follow the evolution given by the trend and the yearly cycle [24], outliers are frequently observed due to local sources or sinks and transport from cities [25]. The shape of the annual cycle and the distribution of outliers are specific to the site.…”

Section: Observations and Outliersmentioning

confidence: 99%

Statistical Analysis of the CO2 and CH4 Annual Cycle on the Northern Plateau of the Iberian Peninsula

et al. 2020

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Outliers are frequent in CO2 and CH4 observations at rural sites. The aim of this paper is to establish a procedure based on the lag-1 autocorrelation to form measurement groups, some of which include outliers, and the rest include regular measurements. Once observations are classified, a second objective is to determine the number of harmonics in order to suitably describe the annual evolution of both gases. Monthly CO2 and CH4 percentiles were calculated over a six-year period. Linear trends for most of the percentiles were around 2.24 and 0.0097 ppm year−1, and the interquartile ranges of residuals calculated from detrended concentrations were 6 and 0.02 ppm for CO2 and CH4, respectively. Five concentration groups were proposed for CO2 and six were proposed for CH4 from the lag-1 autocorrelation applied to detrended observations. Monthly medians were calculated in each group, and combinations of harmonics were applied in an effort to fit the annual cycle. Finally, adding annual and semi-annual harmonics successfully described the cycle where one step was observed in the concentration decrease in spring, not only for high CO2 percentiles but also for low CH4 percentiles.

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Trend analysis of CO2 and CH4 recorded at a semi-natural site in the northern plateau of the Iberian Peninsula

Cited by 10 publications

References 54 publications

Trend Assessment for a CO2 and CH4 Data Series in Northern Spain

Trend Assessment for a CO2 and CH4 Data Series in Northern Spain

The influence of meteorological variables on CO2 and CH4 trends recorded at a semi-natural station

Statistical Analysis of the CO2 and CH4 Annual Cycle on the Northern Plateau of the Iberian Peninsula

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