Atmospheric black carbon and warming effects influenced by the source and absorption enhancement in central Europe

Abstract

Particles containing black carbon (BC), a strong absorbing substance, exert a rather uncertain direct and indirect radiative forcing in the atmosphere. To investigate the mass concentration and absorption properties of BC particles over central Europe, the model WRF-Chem was used at a resolution of 12 km in conjunction with a high-resolution BC emission inventory (EUCAARI 42-Pan-European Carbonaceous Aerosol Inventory; 1/8 degrees x 1/16 degrees). The model simulation was evaluated using measurements of equivalent soot carbon, absorption coefficients and particle number concentrations at seven sites within the German Ultrafine Aerosol Network, PM10 mass concentrations from the dense measurement network of the German Federal Environmental Agency at 392 monitoring stations, and aerosol optical depth from MODIS and AERONET. A distinct time period (25 March to 10 April 2009) was chosen, during which the clean marine air mass prevailed in the first week and afterwards the polluted continental air mass mainly from the southeast dominated with elevated daily average BC concentration of up to 4 mu g m(-3). The simulated PM10 mass concentration, aerosol number concentration and optical depth were in good agreement with the observations, while the modelled BC mass concentrations were found to be a factor of 2 lower than the observations. Together with back trajectories, detailed model bias analyses suggested that the current BC emission in countries to the east and south of Germany might be underestimated by a factor of 5, at least for the simulation period. Running the model with upscaled BC emissions in these regions led to a smaller model bias and a better correlation between model and measurement. In contrast, the particle absorption coefficient was positively biased by about 20% even when the BC mass concentration was underestimated by around 50 %. This indicates that the internal mixture treatment of BC in the WRF-Chem optical calculation is unrealistic in our case, which overamplifies the light absorption by BC-containing particles. By adjusting the modelled mass absorption cross-section towards the measured values, the simulation of particle light absorption of BC was improved as well Finally, the positive direct radiative forcing of BC particles at the top of the atmosphere was estimated to be in the range of 0 to +4 W m(-2) over Germany for the model mn with improved BC mass concentration and adjusted BC light absorption cross-section. This adjustment lowered the positive forcing of BC by up to 70 %, compared with the internal mixing treatment of BC in the model simulation

Long-term observations of tropospheric particle number size distributions and equivalent black carbon mass concentrations in the German Ultrafine Aerosol Network (GUAN)

“…Ma and Birmili, 2015). Black carbon, on the other hand, is an essential parameter that is linked to atmospheric particulate light absorption (Bond et al, 2013;Nordmann et al, 2014). Number size distributions of refractory particles (300 • C) represent particle cores that are of likely relevance for health studies and which have been associated with harmful soot particles (Nordmann et al, 2009;Poulain et al, 2014).…”

“…Some studies, however, have suggested that the massbased metrics might not be the most favourable parameter to characterise PM-induced health effects (HEI Review Panel on Ultrafine Particles, 2013). Some epidemiological studies have associated health endpoints with the number of ultrafine particles or the particle surface area rather than particle mass (Ibald-Mulli et al, 2002;Franck et al, 2011;Rückerl et al, 2011). Ultrafine particles are ubiquitous in urban atmospheres (Kumar et al, 2014), and their ability to penetrate deep into the human body after inhalation has been forwarded as a rationale for their adverse health effects.…”

Sea salt emission, transport and influence on size-segregated nitrate simulation: a case study in northwestern Europe by WRF-Chem

“…The parameterization scheme (GO03) for SSA emission coupled in the WRF-Chem model follows the Gong (2003) scheme. GO03 was developed based on the semi-empirical formulation (Monahan et al, 1986) and field measurements (O'Dowd et al, 1997), including two drop types produced by bursting bubbles (jet drop and film drop). The SSA flux from the ocean to the atmosphere is described as a function of 10 m wind speed and particle radius.…”

Quantifying black carbon light absorption enhancement with a novel statistical approach

“…The Mie calculations are implemented with a customized program (Wu, 2017e) written in Igro Pro (WaveMetrics, Inc. Lake Oswego, OR, USA) and it is available from https://sites.google.com/site/wuchengust. It should be noted that the core-shell-type mixing state of particles is still rare in 3-D atmospheric models like WRF-Chem (Matsui et al, 2013;Nordmann et al, 2014) due to computational cost limitation.…”