Influence of atmospheric stability and transport on CH 4 concentrations in northern Spain

Advances in Meteorology

et al. 2019

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The focus of the current paper is to explore the influence of meteorological variables on atmospheric CO2 and CH4 mean annual cycles at a rural site. Four variables were investigated: boundary layer height, recirculation factor, trajectory direction, and wind speed modelled at the altitude of the site. Boundary layer height and wind speed were provided by the METeorological data EXplorer (METEX) model. Recirculation factor and trajectory direction were obtained from calculations based on this trajectory model, and a nonparametric procedure was used to obtain a smooth evolution. The main results are higher concentrations obtained during the night, attributed to lower dispersion in this period. The smoothed values of the boundary layer height reached nearly 1200 m AGL during the day in August, and its low values caused high concentrations in spring. During the night, the recirculation factor and wind speed showed a sharp contrast between summer and winter. The average recirculation factor was low, 0.10, and average wind speed was 5.1 m·s−1. Trajectories were directionally distributed in four quadrants. Different tests were performed by selecting values of meteorological variables above or below certain thresholds. The influence of these variables reached values around 6.3 and 0.023 ppm for CO2 and CH4 average concentrations, respectively, during the day when the boundary layer was below 400 m. The main conclusion of this study is that the influence of meteorological variables should not be ignored. In particular, extremely low boundary layer heights may have noticeable effects on both gases.

Section: Calculation Of the Trajectory Directionsupporting

confidence: 92%

Sensitivity of CO₂ and CH₄ Annual Cycles to Different Meteorological Variables at a Rural Site in Northern Spain

Advances in Meteorology

et al. 2019

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“…CO 2 and CH 4 evolution is affected by various factors such as sources, sinks and atmospheric dynamics (Sánchez et al, 2010;García et al, 2016). Consequently, establishing a direct relationship between the concentration recorded and each factor is not easy.…”

Section: Relationship Between Trajectory Groups and Trace Gasesmentioning

confidence: 99%

Analysis of the airflow at the centre of the upper plateau on the Iberian Peninsula and its link to CO₂ and CH₄ concentrations

Intl Journal of Climatology

et al. 2017

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Air trajectories are useful tools to investigate the airflow and transport of substances released into the atmosphere. Web‐based models are widely used to calculate trajectories reaching places that are being studied. This article considers 6 years of air trajectories as of October 2010 together with CO2 and CH4 concentrations. A bivariate smoothing function that employs the radial distance and direction of the trajectory to the measuring site was used to form trajectory groups from the minima of this function. Varied radial and angular windows were assayed to investigate the behaviour of the smoothing function. Curves associated with the number of minima were L‐shaped and the windows selected corresponded to the ‘knee’ of the curves. Seven trajectory groups were considered to observe the response of the procedure against the radial distance and the direction. Seasonal evolution revealed the greatest radial extent for winter and the lowest for summer. Moreover, trajectories from the Atlantic Ocean were the most frequent. CO2 and CH4 concentrations were detrended using a linear function, and average trends were 2.34 and 0.0085 ppm year−1, respectively. Annual cycles of detrended concentrations were very soft and were linked to the site's ecosystem. CO2 presented one maximum in spring linked to substantial vegetation growth, and one minimum in summer, when vegetation dies and dispersion is maximum. CH4 maximum was observed in winter although the minimum was found in summer and attributed to oxidation with the hydroxyl radical in the troposphere and to dispersion in this season. Analysis of concentration trends for the groups proposed revealed the opposite behaviour of both gases in summer. Finally, maximum CO2 concentrations were marked by trajectories from North Africa affected by nearby cities, whereas minimum concentrations for both gases were noticeable for trajectories from the ocean in summer.

“…Seasonal evolution was slightly more accentuated in the Northern Hemisphere, where the maximum was reached in winter and the minimum in summer. Recently, S anchez et al (2014) investigated its directional behaviour as well as daily and yearly cycles in the upper Spanish plateau, and García et al (2016) considered the influence of atmospheric stability and transport on its concentrations at the same site. In the current research, CH 4 analysis will run parallel to that of CO 2 .…”

Section: Introductionmentioning

confidence: 99%

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

Atmospheric Environment

et al. 2017

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