CO2 transport by urban plumes in the upper Spanish plateau

Sánchez

Intl Journal of Climatology

et al. 2017

Self Cite

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.

Section: Introductionmentioning

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

Sánchez

Intl Journal of Climatology

et al. 2017

Self Cite

“…This daily evolution has also been observed in other environments, such as boreal regions (Chen et al, 2005(Chen et al, , 2006Gryning et al, 2009). Another noticeable atmospheric process is CO 2 transport, which has been described by Levy et al (1999) for a forested site in Sweden, and in northern Finland (Eneroth et al, 2005), as well as at this measuring site (Pérez et al, 2009c).…”

Section: Introductionmentioning

confidence: 66%

Analysis of two atmospheric dispersion schemes from CO₂ surface concentrations at a rural site

Quart J Royal Meteoro Soc

Paredes

et al. 2011

Self Cite

Two atmospheric dispersion schemes, the transport index and the Bultynck-Malet scheme, have been analysed and combined by means of a three-year database obtained at a rural site comprising CO 2 surface concentrations and meteorological variables (wind and temperature profiles) from a RASS sodar. The most noticeable feature of the transport index is its ability to split the influence of local effects and transport, whereas the Bultynck-Malet scheme is based on seven stability classes and requires temperature gradient and wind data not too close to the surface. The transport index was obtained in the layer from 40 to 100 m. Medians of the transport index were below 600 m, particularly at night, revealing that local effects prevailed during this period. CO 2 concentrations were parametrized as a function of distance, and a boundary of the transport index was calculated to establish two regions, the inner region affected by local effects and the outer, affected by transport. Dependence of this boundary on height was also analysed. The original Bultynck-Malet scheme was adapted to the database by modifying the limit of high winds. As a result, only a few observations were transferred to more stable classes. A successful relationship between CO 2 concentrations and stability classes was obtained and a detailed analysis revealed the noticeable influence of temperature gradient on the two most stable classes. Finally, the relationship between both dispersion schemes enabled us to propose an extremely simplified scheme retaining the two most stable Bultynck-Malet classes and grouping the remaining observations into a third class with lower concentrations. Copyright c 2011 Royal Meteorological Society Key Words: transport index; Bultynck-Malet scheme; stability classification; RASS sodar; CO 2 statistics.

“…Directional calculations aim to determine the source of the concentrations recorded [24]. However, directions obtained at the measurement site may be affected by local flows.…”

Section: Calculation Of the Trajectory Directionmentioning

confidence: 99%

“…Directional analyses have proved useful for identifying pollution sources. Pérez et al [24] obtained the histogram for CO 2 concentrations above the 95 th percentile to determine sources affecting the measurement site. Ashbaugh et al [25] used conditional probability to determine the location of major pollutant sources.…”

Section: Introductionmentioning

confidence: 99%

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

Sánchez

Advances in Meteorology

et al. 2019

Self Cite

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.