Physical and optical properties of atmospheric aerosols by in-situ and radiometric measurements

Abstract

Abstract. Physical and optical properties of atmospheric aerosols collected by using a high resolution (1.5 nm) spectroradiometer (spectral range 400-800 nm), a 13-stage Dekati Low Pressure Impactor (size range 30 nm-10 µm), and an AE31 Aethalometer (7 wavelenghts from 370 nm to 950 nm), have been examined in a semi-rural site in Southwest Italy (Tito Scalo, 40 • 35 N, 15 • 41 E, 750 m a.s.l.). In particular, daily averaged values of AOD andÅngström turbidity parameters from radiometric data together with masssize distributions from impactor data and Black Carbon (BC) concentrations have been analyzed from May to October 2008. Furthermore, by inverting direct solar radiances, aerosol columnar number and volume size distributions have been obtained for the same period. The comparison of different observation methods, allowed to verify if, and in what conditions, changes in aerosol properties measured at ground are representative of columnar properties variations. Agreement between columnar and in-situ measurements has been obtained in case of anthropogenic aerosol loading, while in case of Saharan dust intrusions some discrepancies have been found when dust particles were located at high layers in the atmosphere (4-8 km) thus affecting columnar properties more than surface ones. For anthropogenic aerosols, a good correlation has been confirmed through the comparison of fine aerosol fraction contribution as measured by radiometer, impactor and aethalometer, suggesting that, in this case, the particles are more homogeneously distributed over the lower layers of atmosphere and columnar aerosol optical properties are dominated by surface measured component.

Black Carbon and Organic Components in the Atmosphere of Southern Italy: Comparing Emissions from Different Sources and Production Processes of Carbonaceous Particles

“…In fact, as reported in Calvello et al (2010), to widely describe and compare aerosol optical and physical properties with the above mentioned instruments, both at the ground and over the atmospheric column, cloudless atmospheric conditions are requested. For this reason, the biggest part of data has been collected during spring-summer seasons of years 2008, 2009, 2010. In Table 1 The urban site considered by Raghavendra et al (2011) was characterized by the lowest mean values of BC during the monsoon season (1040 ± 470 ng/m 3 ) and the highest ones during winter time (3310 ± 610 ng/m 3 ).…”

Comparison of surface and column measurements of aerosol scattering properties over the western North Atlantic Ocean at Bermuda

“…To obtain coincident data sets and reduce associated problems due to temporal variability of meteorological conditions (such as wind speed, relative humidity) and air mass transport (Calvello et al, 2010), we report column aerosol data that correspond to the periods of near-surface measurements. The paired hourly averaged data (AOD at 500 nm, τ 500 , and b bulk-surf ) correspond to those having a minimum of three AOD measurements and thus are restricted to clear-sky situations.…”

Aerosol optical properties and precipitable water vapor column in the atmosphere of Norway

“…The use of Ångström exponents provides a qualitative description of the particle size distribution, valid only for a Junge-type aerosol distribution. The coarse-size aerosols observed in summer are likely to be characterized by two particle modes, a fineparticle mode with radii in the range 0.1-0.3 μm, and a coarse-particle mode with radii in the range, say, 2-3 μm (see e.g., Calvello et al [52]). The particles in the latter mode are expected to grow with humidity.…”