2 research outputs found

    Continuous atmospheric boundary layer observations in the coastal urban area of Barcelona during SAPUSS

    Get PDF
    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 viceversa was found.This study was supported by FP7-PEOPLE- 2009-IEF, Project number 254773, SAPUSS – Solving Aerosol Problems Using Synergistic Strategies (Marie Curie Actions – Intra European Fellowships. Manuel Dall’Osto), the Spanish Ministry of Science and Innovation and FEDER funds under the project PRISMA (CGL2012-39623-C02/00), GRACCIE (CSD2007-00067), VAMOS (CLG2010-19464), and the Generalitat de Catalunya (2009 SGR8). M. Pandolfi was funded by the JAE-Doc CSIC program, co-funded by the European Social Fund (ESF). The authors gratefully acknowledge the NOAA Air Resources Laboratory (ARL) for the provision of the HYSPLIT transport and dis- persion model and/or READY website (http://www.arl.noaa.gov/ready.html) used in this publication. Thanks are also due to Jose Ma. Baldasano and staff for their help in establishing and maintaining the Barcelona AERONET measurement site. The authors wish to thank the Catalan Meteorological Service for providing the BCN radiosounding data. The authors wish to thank D. C. Carslaw and K. Ropkins for providing the Openair software used in this paper (Carslaw and Ropkins, 2012; Carslaw, 2012).Peer reviewe
    corecore