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Integral quantities, wind run, S, and recirculation factor, R, useful for describing air flow, are calculated and combined with CO(2) mixing ratios. Meteorological observations were obtained from a RASS sodar and CO(2) mixing ratios from a continuous analyzer installed at a rural site in the upper Spanish plateau. The measuring campaign spread over 3 years and two approaches were followed. The first approach considered integral quantities on a daily basis and two classifications of air flow, to date scarcely used. The first classification distinguished among stagnation, recirculation, and ventilation, the second considering synoptic, meso-, and local scales. Moreover, 52.94% of daily values handled in this paper corresponded to ventilation and 49.70% to synoptic scale. The main goal of this approach is the subsequent link between the two classifications: the synoptic scale was associated with ventilation, mesoscale with recirculation and local scale partially with recirculation. CO(2) observations were distributed in air flow groups following these classifications and mesoscale processes were satisfactorily described since noticeable evidence of transport from nearby cities was observed. In the second approach, S and R pairs were used and CO(2) mixing ratios were distributed following percent intervals of ventilation, calculated by binning these pairs. The main goal of the second approach is to consider only three groups of mixing ratios. In the first group, with high ventilation, mixing ratios were low. With intermediate ventilation, mixing ratios were medium, and with low ventilation mixing ratios were high. A contrast of 21 ppm between the third and first groups was obtained at the 95th percentile. Finally, the second group provided a contrast of 3 ppm between north and south directions and also between east and west attributed to transport from nearby cities.

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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.