RT Journal Article
T1 Assessment of atmospheric processes driving ozone variations in the subtropical North Atlantic free troposphere
A1 Cuevas, Emilio
A1 González, Y.
A1 Rodríguez González, Sergio
A1 Guerra, J. C.
A1 Gómez Pélaez, A. J.
A1 Alonso Pérez, Silvia
A1 Bustos, J.
A1 Milford, C.
AB An analysis of the 22-yr ozone (O3) series (1988–2009) at the subtropical high mountain Iza˜na station (IZO;2373m a.s.l.), representative of free troposphere (FT) conditions,is presented. Diurnal and seasonal O3 variations as wellas the O3 trend (0.19±0.05%yr−1 or 0.09 ppbvyr−1), are assessed.A climatology of O3 transport pathways using backwardtrajectories shows that higher O3 values are associatedwith air masses travelling above 4 km altitude from NorthAmerica and North Atlantic Ocean, while low O3 is transportedfrom the Saharan continental boundary layer (CBL).O3 data have been compared with PM10, 210Pb, 7Be, potentialvorticity (PV) and carbon monoxide (CO). A clear negativelogarithmic relationship was observed between PM10and surface O3 for all seasons. A similar relationship wasfound between O3 and 210Pb. The highest daily O3 values(90th percentile) are observed in spring and in the first half ofsummer time. A positive correlation between O3 and PV, andbetween O3 and 7Be is found throughout the year, indicatingthat relatively high surface O3 values at IZO originate fromthe middle and upper troposphere. We find a good correlationbetween O3 and CO in winter, supporting the hypothesisof long-range transport of photochemically generated O3from North America. Aged air masses, in combination withsporadic inputs from the upper troposphere, are observed inspring, summer and autumn. In summer time high O3 valuesseem to be the result of stratosphere-to-troposphere (STT)exchange processes in regions neighbouring the Canary Islands.Since 1995–1996, the North Atlantic Oscillation haschanged from a predominantly high positive phase to alternatingbetween negative, neutral or positive phases. Thischange results in an increased flow of the westerlies in themid-latitude and subtropical North Atlantic, thus favouringthe transport of O3 and its precursors from North America,and a higher frequency of storms over North Atlantic, witha likely higher incidence of STT processes in mid-latitudes.These processes lead to an increase of tropospheric O3 in thesubtropical North Atlantic region after 1996 that has been reflectedin surface O3 records at IZO.
PB European Geosciences Union
SN 1680-7324
YR 2013
FD 2013
LK http://hdl.handle.net/10272/7940
UL http://hdl.handle.net/10272/7940
LA spa
NO Cuevas, E., González, Y., Rodríguez González, S., Guerra, J.C., Gómez Pélaez, A.J., Alonso Pérez, S., Bustos, J., Milford, C.: "Assessment of atmospheric processes driving ozone variations in the subtropical North Atlantic free troposphere".  Atmospheric Chemistry and Physics. Vol. 13,, p. .1973–1998 (2013). ISSN 1680-7324
DS Repositorio Institucional de la Universidad de Huelva
RD 28 may 2026