Characterization of the inter-annual, seasonal, and diurnal variations of condensation particle concentrations at Neumayer, Antarctica

R Weller,A Minikin,D Wagenbach,V Dreiling

doi:10.5194/acp-11-13243-2011

Abstract

Abstract. Continuous condensation particle (CP) observations were conducted from 1984 through 2009 at Neumayer Station under stringent contamination control. During this period, the CP concentration (median 258 cm−3) showed no significant long term trend but exhibited a pronounced seasonality characterized by a stepwise increase starting in September and reaching its annual maximum of around 103 cm−3 in March. Minimum values below 102 cm–3 were observed during June/July. Dedicated time series analyses in the time and frequency domain revealed no significant correlations between inter-annual CP concentration variations and atmospheric circulation indices like Southern Annular Mode (SAM) or Southern Ocean Index (SOI). The impact of the Pinatubo volcanic eruption and strong El Niño events did not affect CP concentrations. From thermodenuder experiments we deduced that the portion of volatile (at 125 °C) and semi-volatile (at 250 °C) particles which could be both associated with biogenic sulfur aerosol, was maximum during austral summer, while during winter non-volatile sea salt particles dominated. During September through April we could frequently observe enhanced concentrations of ultrafine particles within the nucleation mode (between 3 nm and 7 nm particle diameter), preferentially in the afternoon.

Highlights

Greenhouse gases and aerosols are atmospheric trace compounds determining decisively the radiation balance of the Earths’ atmosphere (Forster et al, 2007), thorough knowledge about atmospheric cycling are pivotal to predict their impact on global climate (Haywood and Boucher, 2000; Ramanathan et al, 2001; Hatzianastassiou et al, 2004; Forster et al, 2007)
Dedicated time series analyses in the time and frequency domain revealed no significant correlations between inter-annual condensation particle (CP) concentration variations and atmospheric circulation indices like Southern Annular Mode (SAM) or Southern Ocean Index (SOI)
From previous investigations we know that the ionic composition of the aerosol at NM shows a distinct seasonality with high portion of biogenic sulfur during summer, decreasing to less than 7 % from April through October while throughout the year sea salt aerosol is clearly dominating with a relative portion of around 50 % during summer increasing to 86 % in winter (Weller et al, 2008)

Summary

Introduction

Greenhouse gases and aerosols are atmospheric trace compounds determining decisively the radiation balance of the Earths’ atmosphere (Forster et al, 2007), thorough knowledge about atmospheric cycling are pivotal to predict their impact on global climate (Haywood and Boucher, 2000; Ramanathan et al, 2001; Hatzianastassiou et al, 2004; Forster et al, 2007). Unlike most of the important greenhouse gases (CO2, CH4, N2O), aerosols stand out due to short atmospheric lifetimes typically in the range of a few days, entailing a striking temporal and spatial concentration and radiation forcing variability (Raes et al, 2000; Ramanathan et al, 2001) In this regard the nearly completely ice covered Antarctic continent is a particular interesting case: Primary aerosol sources like sea spray, mineral dust, or soot, as well as aerosol sources due to gas to particle conversion (secondary aerosol) are virtually absent on this continent, apart from some insular rocky regions (on the Antarctic peninsula, in the coastal dry valleys and on high mountain ranges) and volcanic activity of Mt. Erebus.

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