Studies of Ice Nucleating Aerosol Particles in the Arctic

The CFD instrument was used on the NCAR C-130 research aircraft during May 1998 for studies of ice nucleation in Arctic clouds. A few examples of the measurements are presented here. An article describing the science and field projects, FIRE-III and SHEBA, was published in the AMS Bulletin (Curry et al., 2000).

Components for an article about the ice nuclei measurements (May 04, 1998) are available for viewing here. Airborne measurements are described for 34 minutes during low level passes over the pack ice near the SHEBA ship. In the middle of the time period, the CFD was adjusted to sample at very high supersaturations (>20% w.r.t. water). The development of new particles in response to the high supersaturations is dramatically depicted in the optical particle counter data. The interpretation of these data is not straightforward, since (1) such high supersaturations are not expected to occur in natural clouds, and (2) there are questions about the what the CFD instrument is responding to (residual droplets or ice crystals?). Studies are underway to address (2).

Vertical profiles of IN and clouds on May 18 show ice nuclei concentrations generally increasing with altitude, along with occasional high values near cloud base.

Another example of measurements, from a flight on May 7, shows a number of interesting features, including low concentrations of CN and IN, and a small region of unexpectedly high IN concentrations.

During May, there were three CN counters on the C-130 aircraft, plus other aerosol instrumentation. A brief comparison of CN measurements shows some common features and instrumental differences.

The May 18 case provided data illustrating the effects of riming on the performance of the air sample inlet.

Other information about the ice nuclei measurements:

See also FIRE.ACE (NASA) or SHEBA (NSF, University of Washington)

Project data are available for viewing or as ftp downloads from the FIRE III ACE Archive

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