  During the 2017 record-breaking burning season in Canada / United States,
intense wild fires raged during the first week of September in the Pacific
northwestern region (British Columbia, Alberta, Washington, Oregon, Idaho,
Montana and northern California) burning mostly temperate coniferous forests.
The heavy loads of smoke particles emitted in the atmosphere reached the
Iberian Peninsula (IP) a few days later on 7 and 8 September. Satellite imagery
allows to identify two main smoke clouds emitted during two different periods
that were injected and transported in the atmosphere at several altitude
levels. Columnar properties on 7 and 8 September at two Aerosol Robotic Network
(AERONET) mid-altitude, background sites in northern and southern Spain are:
aerosol optical depth (AOD) at 440 nm up to 0.62, Angstrom exponent of 1.6-1.7,
large dominance of small particles (fine mode fraction > 0.88), low absorption
AOD at 440 nm (<0.008) and large single scattering albedo at 440 nm (>0.98).
Profiles from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP)
show the presence of smoke particles in the stratosphere during the transport,
whereas the smoke is only observed in the troposphere at its arrival over the
IP. Portuguese and Spanish ground lidar stations from the European Aerosol
Research Lidar Network / Aerosols, Clouds, and Trace gases Research
InfraStructure Network (EARLINET/ACTRIS) and the Micro-Pulse Lidar NETwork
(MPLNET) reveal smoke plumes with different properties: particle depolarization
ratio and color ratio, respectively, of 0.05 and 2.5 in the mid troposphere
(5-9 km) and of 0.10 and 3.0 in the upper troposphere (10-13 km). In the mid
troposphere the particle depolarization ratio does not seem time-dependent
during the transport whereas the color ratio seems to increase (larger
particles sediment first).
