Aerosol particle number concentration measurements during ISDAC flights

Description

The Indirect and Semi-Direct Aerosol Campaign (ISDAC) took place in Alaska in the vicinity of Fairbanks and Barrow, near the Atmospheric Radiation Measurement (ARM) North Slope of Alaska site during April 1–30, 2008. Profiles of the total number concentration and size distributions of aerosol particles at different altitudes are studied in a variety of conditions, including polluted and clean environments when there were no clouds or precipitation present. Averaging all clean scenario profiles reveals a mean aerosol number concentration of 120 with a standard deviation (s.d.) of 40 cm-3, over the vertical altitude range 500–6500 m. The polluted days, April 18–22, have a mean aerosol number concentration of 720 with a s.d. of 360 cm-3 over the altitude range 500–6500 m. Horizontally, there is also large variation over constant altitude legs. For example, a polluted case, flight 25 on April 19, 2008, has the aerosol total number concentrations 656 with a s.d. of 191 cm-3 at 5500 m, 636 with a s.d. of 292 cm-3 at 4500 m, and 1029 with a s.d. of 446 cm-3 at 2900 m. Aerosol size distributions at various altitudes are also presented. Future work includes determining the aerosol effects on different types of clouds encountered during flights. Cloud and aerosol physical and chemical properties are used for comparing and contrasting ice, liquid, and mixed-phase clouds.