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| Titel |
Continuous atmospheric boundary layer observations in the coastal urban area of Barcelona during SAPUSS |
| VerfasserIn |
M. Pandolfi, G. Martucci, X. Querol, A. Alastuey, F. Wilsenack, S. Frey, C. D. O'Dowd, M. Dall'Osto |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 13, no. 9 ; Nr. 13, no. 9 (2013-05-14), S.4983-4996 |
| Datensatznummer |
250018652
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| Publikation (Nr.) |
 copernicus.org/acp-13-4983-2013.pdf |
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| Zusammenfassung |
| Continuous measurements of surface mixed layer (SML), decoupled
residual/convective layer (DRCL) and aerosol backscatter coefficient were
performed within the Barcelona (Spain) boundary layer from September to
October 2010 (30 days) in the framework of the SAPUSS (Solving Aerosol
Problems by Using Synergistic Strategies) field campaign. Two near-infrared
ceilometers (Jenoptik CHM15K), vertically and horizontally probing (only
vertical profiles are herein discussed), were deployed. Ceilometer-based
DRCLs (1761 ± 363 m a.g.l.) averaged over the campaign duration were twice
as high as the mean SML (904 ± 273 m a.g.l.). Both DRCL and SML showed
a marked SML diurnal cycle. Ceilometer data were compared with potential
temperature profiles measured by daily radiosounding (twice a day, midnight
and midday) to interpret the boundary layer structure in the coastal urban
area of Barcelona. The overall agreement (R2 = 0.80) between the
ceilometer-retrieved and radiosounding-based SML heights (h) revealed
overestimation of the SML by the ceilometer (Δh=145 ± 145 m).
After separating the data in accordance with different atmospheric scenarios,
the lowest SML (736 ± 183 m) and DRCL (1573 ± 428 m) were
recorded during warm North African (NAF) advected air mass. By contrast,
higher SML and DRCL were observed during stagnant Regional (REG)
(911 ± 234 m and 1769 ± 314 m, respectively) and cold Atlantic
(ATL) (965 ± 222 m and 1878 ± 290 m, respectively) air masses.
In addition to being the lowest, the SML during the NAF scenario frequently
showed a flat upper boundary throughout the day possibly because of the
strong winds from the Mediterranean Sea limiting the midday SML convective
growth. The mean backscatter coefficients were calculated at two selected
heights representative of middle and top SML portions, i.e.
β500 = 0.59 ± 0.45 Mm−1 sr−1 and
β800 = 0.87 ± 0.68 Mm−1 sr−1 at 500 m and
800 m a.g.l., respectively. The highest backscatter coefficients were observed during NAF
(β500 = 0.77 ± 0.57 Mm−1 sr−1) when compared
with ATL (β500 = 0.51 ± 0.44 Mm−1 sr−1) and REG
(β500 = 0.64 ± 0.39 Mm−1 sr−1). The relationship
between the vertical change in backscatter coefficient and atmospheric
stability (∂θ/∂z) was investigated in the first
3000 m a.g.l., aiming to study how the unstable, stable or neutral
atmospheric conditions of the atmosphere alter the distribution of aerosol
backscatter with height over Barcelona. A positive correlation between
unstable conditions and enhanced backscatter and vice versa was found. |
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