A global analysis of climate-relevant aerosol properties retrieved from the network of GAW near-surface observatories

Abstract

Aerosol particles are essential constituents of the Earth's atmosphere, impacting the earth radiation balance directly by scattering and absorbing solar radiation, and indirectly by acting as cloud condensation nuclei. In contrast to most 105 greenhouse gases, aerosol particles have short atmospheric residence time resulting in a highly heterogeneous distribution in space and time. There is a clear need to document this variability at regional scale through observations involving, in particular, the in-situ near-surface segment of the atmospheric observations system. This paper will provide the widest effort so far to document variability of climate-relevant in-situ aerosol properties (namely wavelength dependent particle light scattering and absorption coefficients, particle number concentration and particle number size distribution) from all sites 110 connected to the Global Atmosphere Watch network. High quality data from almost 90 stations worldwide have been collected and controlled for quality and are reported for a reference year in 2017, providing a very extended and robust view of the variability of these variables worldwide. The range of variability observed worldwide for light scattering and absorption coefficients, single scattering albedo and particle number concentration are presented together with preliminary information on their long-term trends and comparison with model simulation for the different stations. The scope of the 115 present paper is also to provide the necessary suite of information including data provision procedures, quality control and analysis, data policy and usage of the ground-based aerosol measurements network. It delivers to users of the World Data Centre on Aerosol, the required confidence in data products in the form of a fully-characterized value chain, including uncertainty estimation and requirements for contributing to the global climate monitoring system.

Cézeaux-Aulnat-Opme-Puy De Dôme: a multi-site for the long-term survey of the tropospheric composition and climate change

“…Deeper investigation of this trend is currently being performed and will include a more detailed discussion of these aspects. The variability of atmospheric aerosol number concentration at PUY shows a marked seasonal variation with a maximum during the summer, consistent with observations from other high-altitude sites where a stronger seasonal contrast is usually observed compared to continental lowland sites (Laj et al, 2020). A daily cycle is also very clear, with peak concentrations during the day.…”

“…A median scattering coefficient of ∼ 10 Mm −1 , in the range of values observed at other mountain sites, was obtained by Pandolfi et al (2018) for the period 2007-2014 at PUY. Seasonal medians in the range 0.7-9 Mm −1 were in addition more recently reported by Laj et al (2020) for the year 2017, together with median absorption coefficients of 0.92 and 0.44 Mm −1 for spring and fall, respectively. The climatology of these scattering and absorbing properties shows that, quite logically, compared to the results presented previously, the height of the boundary layer strongly influences the optical properties of the aerosol at the puy de Dôme, since it influences the concentrations in number, mass concentrations, and chemical composition.…”

“…The total particle number concentration (>10 nm) currently measured at PUY is on average ∼ 2×10 3 cm −3 , which corresponds to intermediate values compared to observations reported from neighboring mountain stations in Europe (Laj et al, 2020), such as for instance Montseny (Spain, 700 m a.s.l., ∼ 3 × 10 3 cm −3 ) or Jungfraujoch (Switzerland, 3578 m a.s.l, ∼ 2 × 10 2 cm −3 ). As illustrated in Fig.…”

Multidecadal trend analysis of in situ aerosol radiative properties around the world

“…As of 2017 absorption has been measured for at least 1 year (yr) at 50 sites, for 5 years at 37 sites and for 10 years at 20 sites, while scattering has been measured for at least 1 year at 56 sites, for 5 years at 45 sites and for 10 years at 30 sites. The companion paper (Laj et al, 2020) provides a historical view and a complete description of the present networks for aerosol measurements. The longest datasets cover up to 40 years of measurements, BRW (40 years), SPO (40 years), and MLO (31 years) (see Table 1 for station acronyms), whereas some stations with long time series recently closed or moved (THD, SGP, MUK, CPT).…”

“…To our knowledge, no further trend analyses of surface in situ aerosol optical properties involving a network of stations or several stations have been published up to now. This study is part of the SARGAN (in-Situ AeRosol GAW observing Network) initiative (see the companion paper by Laj et al, 2020) with the objective of supporting a global aerosol monitoring network to become a GCOS (Global Climate Observing System) associated network. This trend analysis is intended to answer the following questions.…”