A C T We investigated the variability of 210 Pb, 7 Be and 10 Be in coastal Antarctic aerosol samples based on continuous, monthly and annually resolved time series obtained from Neumayer Station over the period 1983 to 2008.Clear seasonal cycles peaking in the local summer half year stand out as a common feature of all three radionuclide records.Time series analyses suggest that significant multiannual changes are confined to a 4-6 yr periodicity resembling that of the Southern Annual Mode index in case of 210 Pb and to the expected decadal solar cycle in case of the cosmogenic Be-isotopes.Both, changes in the meridional transport and surface inversion strength appear to drive the seasonal 210 Pb cycle, which generally peaks in November.In contrast, stratospheric air mass intrusions are proved to be the main reason for the Be-isotopes seasonality.This finding is revealed by enhanced 10 Be/ 7 Be ratios occurring during late summer / early autumn broadly concurrently with the individual Be-isotopes and the 7 Be/ 210 Pb ratio.The 10 Be and 7 Be records clearly reflect the decadal, solar-modulated production signal but, for unknown reasons, they substantially differ in their detailed pattern.It is ruled out, that an excess 7 Be production by solar energetic particles was responsible for this mismatch.

The provenance of fine-grained eolian dust over East Asia is distinguished using a regional climate model. Five major source regions within China and Mongolia are considered: sandy lands in the northeastern China, deserts in the northern China, the Gobi deserts, the Taklimakan deserts in western China and deserts on the Tibet an Plateau. The contribution of each dust source is evaluated for the downwind eolian sediments in the Chinese Loess Plateau (CLP) and Japan Sea (JS). The results show that the adjoining northern and Gobi deserts dominate the dust depositions over CLP and over eastern China, although Taklimakan deserts are actually the largest emission source. On the marine deposits in JS, Taklimakan deserts exert a more significant role since the particles from Taklimakan tend to be raised into upper atmosphere and delivered for a longer distance. The agent for dust delivery also differs among different sources. Dust from northern deserts is dominantly carried by the local northwesterly winds in spring associated with the East Asian winter monsoon system and restricted in the low-level atmosphere, while the westerly winds in the midto high-level troposphere become of great importance and more likely to be responsible for the transport of Taklimakan dust.

A C T The work focuses on the analysis of CO 2 and O 3 surface variations observed during five summer experimental campaigns carried out at the 'Icaro Camp' clean air facility (74.7 • S, 164.1 • E, 41 m a.s.l.) of the 'Mario Zucchelli' Italian coastal research station.This experimental activity allowed the definition of summer average background O 3 values that ranged from 18.3 ± 4.7 ppbv (summer 2005-2006) to 21.3 ± 4.0 ppbv (summer 2003-2004).Background CO 2 concentrations showed an average growth rate of 2.10 ppmv yr -1 , with the highest CO 2 increase between the summer campaigns 2002-2003 and 2001-2002 (+2.85 ppmv yr -1 ), probably reflecting the influence of the 2002/2003 ENSO event.A comparison with other Antarctic coastal sites suggested that the summer background CO 2 and O 3 at MZS-IC are well representative of the average conditions of the Ross Sea coastal regions.As shown by the analysis of local wind direction and by 3-D back-trajectory calculations, the highest CO 2 and O 3 values were recorded in correspondence to air masses flowing from the interior of the Antarctic continent.These results suggest that air mass transport from the interior of the continent exerts an important influence on air mass composition in Antarctic coastal areas.

An observation-based numerical study of humidity-dependent aerosol optical properties of mixed marine and Saharan mineral dust aerosol is presented. An aerosol model was developed based on measured optical and microphysical properties to describe the marine and Saharan dust aerosol at Cape Verde. A wavelength-dependent optical equivalent imaginary part of the refractive index and a scattering non-sphericity factor for Saharan dust were derived. Simulations of humidity effects on optical properties by the aerosol model were validated with relative measurements of the extinction coefficient at ambient conditions. Parametrizations were derived to describe the humidity dependence of the extinction, scattering, and absorption coefficients as well as the asymmetry parameter and single scattering albedo. For wavelengths (300–950 nm) and dry dust volume fractions (0–1), aerosol optical properties as a function of relative humidity (RH = 0–90%) can be calculated from tabulated parameters. For instance, at a wavelength of 550 nm, a volume fraction of 0.5 of dust on the total particle volume (dry conditions) and a RH of 90%, the enhancements for the scattering, extinction and absorption coefficients are 2.55, 2.46 and 1.04, respectively, while the enhancements for the asymmetry parameter and single scattering albedo are 1.11 and 1.04. DOI: 10.1111/j.1600-0889.2011.00568.x

A C T Ground-based high spectral resolution measurements of downwelling radiances from 800 to 1200 cm -1 were conducted between 20 January and 6 February 2008 within the scope of the SAMUM-2 field experiment.We infer the spectral signature of mixed biomass burning/mineral dust aerosols at the surface from these measurements and at top of the atmosphere from IASI observations.In a case study for a day characterized by the presence of high loads of both dust and biomass we attempt a closure with radiative transfer simulations assuming spherical particles.A detailed sensitivity analysis is performed to investigate the effect of uncertainties in the measurements ingested into the simulation on the simulated radiances.Distinct deviations between modelled and observed radiances are limited to a spectral region characterized by resonance bands in the refractive index.A comparison with results obtained during recent laboratory studies and field experiments reveals, that the deviations could be caused by the aerosol particles' non-sphericity, although an unequivocal discrimination from measurement uncertainties is not possible.Based on radiative transfer simulations we estimate the aerosol's direct radiative effect in the atmospheric window region to be 8 W m -2 at the surface and 1 W m -2 at top of the atmosphere.