Long-range transport and mixing of aerosol sources during the 2013 North American biomass burning episode: analysis of multiple lidar observations in the western Mediterranean basin

Abstract

Abstract. Long-range transport of biomass burning (BB) aerosols between North America and the Mediterranean region took place in June 2013. A large number of groundbased and airborne lidar measurements were deployed in the western Mediterranean during the Chemistry-AeRosol Mediterranean EXperiment (ChArMEx) intensive observation period. A detailed analysis of the potential North American aerosol sources is conducted including the assessment of their transport to Europe using forward simulations of the FLEXPART Lagrangian particle dispersion model initialized using satellite observations by MODIS and CALIOP. The three-dimensional structure of the aerosol distribution in the ChArMEx domain observed by the ground-based lidars (Minorca, Barcelona and Lampedusa), a Falcon-20 aircraft flight and three CALIOP tracks, agrees very well with the model simulation of the three major sources considered in this work: Canadian and Colorado fires, a dust storm from western US and the contribution of Saharan dust streamers advected from the North Atlantic trade wind region into the westerlies region. Four aerosol types were identified using the optical properties of the observed aerosol layers (aerosol depolarization ratio, lidar ratio) and the transport model analysis of the contribution of each aerosol source: (i) pure BB layer, (ii) weakly dusty BB, (iii) significant mixture of BB and dust transported from the trade wind region, and (iv) the outflow of Saharan dust by the subtropical jet and not mixed with BB aerosol. The contribution of the Canadian fires is the major aerosol source during this episode while mixing of dust and BB is only significant at an altitude above 5 km. The mixing corresponds to a 20-30 % dust contribution in the total aerosol backscatter. The comparison with the MODIS aerosol optical depth horizontal distribution during this episode over the western Mediterranean Sea shows that the Canadian fire contributions were as large as the direct northward dust outflow from Sahara.

Microphysical characterization of long-range transported biomass burning particles from North America at three EARLINET stations

“…The summer of 2013 was one of the driest in the previous decades in the USA and Canada. Large forest fires caused by thunderstorms started at the end of June 2013 and continued being active during July and August, causing vast forest areas to burn up (Ancellet et al, 2016). In a previous work (Ortiz-Amezcua et al, 2014), a preliminary optical description was given for the lidar detection of a smoke event over Granada (Spain) in July 2013.…”

“…Markowicz et al (2016) used in situ measurements, passive and active remote sensing observations and numerical simulations to describe the temporal variability of aerosol optical properties for the same period over Poland, and Janicka et al (2016) studied the properties of the mixing of those smoke particles with dust particles over Warsaw. Ancellet et al (2016) reported optical properties of the smoke plumes transported over some stations in the western Mediterranean Basin in June 2013. Veselovskii et al (2015) described vertically resolved optical and microphysical properties of particles detected in Washington, DC coming from similar forest fires after regional transport in August 2013.…”

Intercontinental transport of biomass burning pollutants over the Mediterranean Basin during the summer 2014 ChArMEx-GLAM airborne campaign

“…Several studies have 60 already reported transatlantic transport of boreal forests fire emissions from North America to Central Europe Petzold et al, 2007) or to the MB (Formenti et al, 2002;Cristofanelli et al, 2013;Ancellet et al, 2016). Those studies were mainly focused on biomass burning aerosols except that of Forster et al (2001) which also addressed CO emissions, but with measurements made in Germany, thus, concerning Central Europe.…”

“…Over the MB, Formenti et al (2002) have found a forest fire haze layer up to 3.5 km coming from Canadian forest fires over the eastern Mediterranean. Ancellet et al (2016) have reported aerosol layers up to 7 km coming from North America over the western MB. The published cases we know of transatlantic transport to MB in the recent years are gathered in North America.…”

“…Transport between North America and the MB in Formenti et al (2002) and Ancellet et al (2016) lasts about 10 days (Table 2). A hypothesis of Forster et al (2001) is that those biomass burning emissions coming from North…”