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Studies of Ice Nucleating Aerosol Particles in Arctic Cloud Systems |
(definition: Ice nuclei (IN) are aerosol particles that catalyze the formation of ice in the atmosphere.)
The CFD chamber consists of two concentric cylinders. Sample air is sandwiched between particle-free sheath air and flows downward through the space between the cylinders. The cylinder walls are coated with ice and held at different temperatures to create a supersaturation. Ice nuclei activate, grow as ice crystals to ~3-8µm and are detected at the exit with an optical particle counter. Voltage pulses from the detector are also recorded by a multichannel analyzer for size distribution analysis. The crystals can be collected on electron microscope grids with an inertial impactor.
| Date | FAI t/o | Land | Hours | Mb Data | #CFD | #PIXE | #IN Filter |
|---|---|---|---|---|---|---|---|
| 980504 | 1851 | 0350 | 9.0 | 3.4 | 1 | 1 | 1 |
| 980507 | 1849 | 0315 | 8.4 | 5.9 | 4 | 2 | 2 |
| 980511 | 1809 | 0312 | 9.1 | 3.3 | 3 | 2 | 1 |
| 980515 | 1824 | 0256 | 8.5 | 5.0 | 4 | 3 | 2 |
| 980518 | 1830 | 0336 | 9.1 | 3.5 | 4 | 3 | 2 |
| 980520 | 1826 | 0300 | 8.6 | 6.1 | 5 | 3 | 2 |
| 980524 | 1802 | 0326 | 9.4 | 6.2 | 3 | 3 | 2 |
| 980527 | 1820 | 0345 | 9.4 | 7.4 | 2 | 2 | 2 |
| Total | 71.5 | 40.8 | 26 | 19 | 14 | ||
| # PIXE = number of samples collected with PIXE impactor. All aerosol particles are collected on transmission electron microscope (TEM) grids for later examination. | |||||||
| # CFD = number of samples collected with impactor at outlet of CFD chamber. These are IN particles only and are collected on TEM grids | |||||||
| # IN Filter = number of filter samples collected. These are polycarbonate membrane filters that collect all aerosol particles; they are processed later in the laboratory. | |||||||
Time series plot shows descent through clear sky near SHEBA ship and low altitude passes over pack ice and leads. CFD found IN ~5-10/L at -10 to -16°C, 2 to 8% supersaturation. Most leads appeared to have a skin of ice. CN spikes could be from aircraft or ship exhaust.
Same time period, plotted as a vertical profile.
Time series plot shows low altitude pass over open water during return flight from SHEBA ship. CFD found IN ~5-30/L at -18 to -23°C, 2 to 8% supersaturation. CN spike at 01:19 corresponds to pass over Barrow, Alaska.
