RT Journal Article
T1 Atmospheric nanoparticle observations in the low free troposphere during upward orographic flows at Izaña Mountain Observatory
A1 Rodríguez González, Sergio
A1 González, Y.
A1 Cuevas, Emilio
A1 Ramos, R.
A1 Romero, P. M.
A1 Abreu Afonso, J.
A1 Redondas, A.
AB This study investigates the processes andconditions favouring the formation of nanoparticles(diameter<10 nm) which are frequently observed on highmountains reaching the low free troposphere. This wasdone through an analysis of a data set collected at IzañaGlobal Atmospheric Watch Observatory (Canary Islands;2367mabove sea level). This high mountain supersite islocated well above the stratocumulus layer characteristic ofthe subtropical oceanic tropospheres. At night, when thecatabic flow regime is well established, free troposphereaerosols were measured. The development of orographicbuoyant upward flows during daylight resulted in an increaseof water vapour, SO2 and NOy concentrations. These ascendingairflows perturbed the free troposphere and resultedin high concentrations of 3–10 nm particles (N3−10) due tonew particle formation. An analysis of the 5-min averagetime series allowed the identification of two main types ofN3−10 event. In Type I events a linear relationship betweenN3−10 and SO2 was observed (r2 coefficients 0.70–0.95and a mean slope of 11 cm−3 ppt−1 for 5-min averageddata; SO2 concentrations from tens to hundreds of ppt).These particles seem to be formed during upward transport(probably within or after the outflows of clouds typicallylocated below Iza˜na). During Type II events, no correlationbetween SO2 and N3−10 was observed and 3–10 nm particleswere formed in-situ at noon and during the afternoon due tothe condensation of vapours linked to photochemistry. Newparticle formation was observed almost every day owingto the favourable conditions associated with the entry ofboundary layer air in the low free troposphere, even if SO2concentrations are rather low at Iza˜na (tens to hundreds ofppt). The low surface area of pre-existing particles, lowtemperature and high radiation intensity clearly favouredthe formation of nanoparticles. The low surface area ofpre-existing particles in the upward flows is furthered byin-cloud particles scavenging in the stratocumulus layertypically located below Iza˜na. The higher temperature andthe presence of coarse Saharan dust particles decrease theefficiency of the new particle formation mechanisms in summer.Thus, the “N3−10 versus SO2” slope (for r2>0.7 cases)was higher in autumn and winter ( 15 cm−3 ppt−1 asaverage) than in summer (2–8 cm−3 ppt−1). These fieldobservations suggest that elevated mounts that reaches thefree troposphere may act as source regions for new particles.
PB European Geosciences Union
SN 1680-7316
SN 1680-7324
YR 2009
FD 2009
LK http://hdl.handle.net/10272/7925
UL http://hdl.handle.net/10272/7925
LA eng
NO Rodríguez González, S., González, Y., Cuevas, E., Ramos, R., Romero, P. M., Abreu Afonso, J., Redondas, A.: "Atmospheric nanoparticle observations in the low free troposphere during upward orographic flows at Izaña Mountain Observatory". Atmospheric Chemistry and Physics. Vol. 9, págs. 6319–6335 (2009). ISSN 1680-7316
DS Repositorio Institucional de la Universidad de Huelva
RD 31 may 2026