title: Analysis of the vertical radon structure at the Spanish "El Arenosillo" tower station.
abstract: This paper presents an analysis of one year of hourly radon and meteorological measurements at 10 m and 100 m a.g.l. at El Arenosillo tall-tower station, in the south-west of the Iberian Peninsula. Whole-year and seasonal composites of the diurnal radon cycle show the expected behaviour, with larger concentrations at 10 m than at 100 m during the night, due to poor vertical mixing, and similar concentrations at both heights during the daylight hours. Wind speed and wind direction analyses by sector show the prevailing contributions for each season. Sectors with air which has spent a longer period over the ocean and high wind speeds will lead to low concentrations at both levels, whereas inland sectors show a clear increase of the concentrations with similar overall averages for the two levels. The Sierra Morena, Guadalquivir and Bethics System sectors (continental pathways) are the sectors that show higher concentrations for mild to large wind speeds. The daily evolution of radon concentration differences at both heights has been grouped into four clusters by using a K-means algorithm method. The four clusters have been selected so that they sufficiently describe different characteristics in terms of stability. The temporal evolution of the mixing height (MH) and of the bulk diffusivity parameter (Kb) during the nocturnal period has been calculated by using the temporal variation of (222)Rn concentration at 10 m and the concentration gradient with height, respectively.
authors.affiliation: Institute of Energy Technologies (INTE), Technical University of Catalonia, Barcelona, Spain. Electronic address: arturo.vargas@upc.edu.
authors.forename: A
authors.initials: A
authors.lastname: Vargas
authors.affiliation: Central Institute for Meteorology and Geodynamics (ZAMG), Vienna, Austria.
authors.forename: D
authors.initials: D
authors.lastname: Arnold
authors.affiliation: Atmospheric Sounding Station, El Arenosillo. National Institute for Aerospace Technology (INTA), Mazagón-Huelva, Spain.
authors.forename: J A
authors.initials: JA
authors.lastname: Adame
authors.affiliation: Catalan Institute of Climate Science (IC3), Barcelona, Spain.
authors.forename: C
authors.initials: C
authors.lastname: Grossi
authors.affiliation: European Commission, Joint Research Centre (JRC), Institute for Transuranium Elements (ITU), Nuclear Security Unit, Karlsruhe, Germany.
authors.forename: M A
authors.initials: MA
authors.lastname: Hernández-Ceballos
authors.affiliation: Department of Applied Physics, University of Huelva, Huelva, Spain.
authors.forename: J P
authors.initials: JP
authors.lastname: Bolivar
mesh_terms: D000396:Air Pollutants, Radioactive / Q000032:analysis*; D004784:Environmental Monitoring / Q000379:methods*; D011886:Radon / Q000032:analysis*
chemical_list: D000396:Air Pollutants, Radioactive; D011886:Radon
keywords: Atmospheric tracer; Cluster; Mixing height; Outdoor (222)Rn; Tall tower