Evidence of Saharan dust in the marine boundary layer

A typical size distribution of marine aerosol was measured on April the 9^th at the ground-based measurement station at Ragged Point (red). The Aitken and accumulation mode, seperated by the so called Hoppel-minimum can be seen in the Figure. On April the 15^th a Saharan dust layer with a maximum total number concentration at 2-4 km height was situated above the measurement region. Through synoptic scale advection of these Saharan dust to the measurement region since 14/04/2011 and following downmixing of those particles into the boundary layer, the shape of the number size distribution has changed. Compared to the typical measured number concentration in this marine region (red), the entrainment of the Saharan dust causes an increased number concentration (black) and the typical shape of the Hoppel-minimum gets almost lost.