Abstract
Abstract. Europe is a densely populated region that is a significant global source of black carbon (BC) aerosol, but there is a lack of information regarding the physical properties and spatial/vertical distribution of rBC in the region. We present the first aircraft observations of sub-micron refractory BC (rBC) aerosol concentrations and physical properties measured by a single particle soot photometer (SP2) in the lower troposphere over Europe. The observations spanned a region roughly bounded by 50° to 60° N and from 15° W to 30° E. The measurements, made between April and September 2008, showed that average rBC mass concentrations ranged from about 300 ng m−3 near urban areas to approximately 50 ng m−3 in remote continental regions, lower than previous surface-based measurements. rBC represented between 0.5 and 3% of the sub-micron aerosol mass. Black carbon mass size distributions were log-normally distributed and peaked at approximately 180 nm, but shifted to smaller diameters (~160 nm) near source regions. rBC was correlated with carbon monoxide (CO) but had different ratios to CO depending on location and air mass. Light absorption coefficients were measured by particle soot absorption photometers on two separate aircraft and showed similar geographic patterns to rBC mass measured by the SP2. We summarize the rBC and light absorption measurements as a function of longitude and air mass age and also provide profiles of rBC mass concentrations and size distribution statistics. Our results will help evaluate model-predicted regional rBC concentrations and properties and determine regional and global climate impacts from rBC due to atmospheric heating and surface dimming.
Highlights
Black carbon (BC) aerosol emitted during incomplete combustion is the major light absorbing component of atmospheric aerosols and has important impacts on the atmosphere and climate
The data presented here were obtained from 21 FAAM aircraft flights and 12 DLR Falcon flights over the UK and Europe that spanned a geographic range from approximately 15◦ W to 30◦ E and from 50◦to 60◦ N
The aircraft observations were lower than measured and modelled surface refractory BC (rBC) mass concentrations, but the comparison was complicated by both variability in measurement times and locations and by differences in the rBC measurement method, the latter highlighting the need for a systematic comparison of SP2 measurements to filter-based OC/elemental carbon (EC) approaches
Summary
Black carbon (BC) aerosol emitted during incomplete combustion is the major light absorbing component of atmospheric aerosols and has important impacts on the atmosphere and climate. Surface- and aircraft-based observations have relied on filter and/or optical based methods to measure BC. Both approaches suffer from low sensitivity and resolution (temporal and/or spatial) and both are prone to a number of artefacts arising from the deposition of material to the filter (e.g., Kirchstetter et al, 2001; Weingartner et al, 2003; Chow et al, 2008). Filter-based absorption measurements require corrections for the additional absorption by particles of light scattered by filter fibres and deposited particles and the enhancement of absorption arising from organic coatings on sampled absorbing particles. The low resolution and sensitivity of filter-based measurements is problematic for aircraft studies, which often probe regions of low BC concentrations and that
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