VACC - Volatility Aerosol Composition and Concentration

1. VACC - Volatility Aerosol Composition and Concentration

2. VACC – Science Summary • Is CN mixed into cloud from above and/or below? • Out of cloud deep profiles • Porpoise through area to look for variation in CN • Characterise CN concentration and composion below and above cloud • If isolated cloud available characterise CN concentration and composition of inflow and outflow • orbits at different levels or straight and level legs perpendicular to wind. (depends on the extent of the cloud)

3. VACC – flight leg requirements • CPC – N (R > 5 nm) • 10 Hz data • flow controlled at 3 l/min all levels • No special flight requirements • SMPS – dN/dR (5 nm < R < ~200 nm) • Scan every 2.5 minutes • Sample flow controlled at 1 l/min all levels • Sheath flow controlled at 10 l/min all levels • Flight requirements: • Constant altitude for duration of scan • Preferably straight but can deal with wide angle turn/orbit • OPC – Volatility – constant temperature – dN/dR (50 nm < R < 1 µm) • 1 Hz data • Sample flow controlled at 0.12 l/min at all levels • No special flight requirements • OPC – Volatility – scanning temperature - dN/dR (50 nm < R < 1 µm) • Scan every 8 minutes • Sample flow controlled at 0.12 l/min at all levels • Flight requirements: • Constant altitude for duration of scan • Preferably straight but can deal with wide angle turn/orbit • Summary • Flight speed as slow as possible • Altitude profiles of CPC and OPC-volatility-set temperature obtainable • For SMPS or OPC-volatility – scanning temperature: require straight and level or level in slow turn flight legs. • Minimum operational pressure 500 mb ~6000m • Cannot operate in cloud

4. B047 – 09:22 (UTC)

5. 75°C 100°C Sample can be considered dry. MSA / Sulphuric acid 130°C 160°C Ammonium Hydrogen Sulphate 200°C 230°C Ammonium Nitrate 260°C 300°C Ammonium Sulphate Sodium Hydrogen Carbonate No particles R > 0.55μm

6. External/Internal Mixing.