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

Abstract

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.

Analysis of CO2 and CH4 temporal patterns and the Valladolid urban plume influence over the upper Spanish plateau

“…These results were in line with those reported by other authors (e.g. García et al, 2016;Lozano et al, 2012;Pérez et al, 2018a) who stated that local trajectories (i.e. trajectories confined within the Peninsula) are normally characterized by stagnant conditions, leading to higher mixing ratio values.…”

“…Some of the most recent studies of the group involve those concerning the analysis of the role played by meteorological variables in CO2 and CH4 trend and seasonal evolution (Pérez et al, 2017;2018b;. To conclude, several backward analyses have been conducted in order to link their characteristics to the final CO2 and CH4 mixing ratio measured at the CIBA station (García et al, 2016;Pérez et al, 2017;2018a;. The current thesis aims to study CO2 and CH4 temporal patterns by employing different statistical techniques whilst at the time exploring the possible influence of the city of Valladolid on final CO2 and CH4 mixing ratio values collected at the CIBA station.…”

“…Furthermore, many authors have also highlighted the effect of the orography (e.g. Hernández-Ceballos et al, 2015a;Izquierdo et al, 2017;Pérez et al, 2018a;Valverde et al, 2016) on the transport, accumulation and dispersal of air substances. The mountain ranges surrounding the monitoring station led to restrictions in the movement of the arriving flow.…”