FAAM NON-CORE Droplet Measurement Technologies dual column cloud condensation nuclei counter
 
The CCN counter measures the number of cloud condensation nuclei in a sample for a given set point supersaturation. The column operates on the principle that the diffusion of water vapour in air is quicker than heat allowing a region in the center of the CCN column to be supersaturated when a vertical temperature gradient in is maintained.

System Components

 
The CCN instrument is mounted on the outboard side of the CCN rack and samples through a Rosemount inlet on the port side of the aircraft, this inlet is shared with the 3786 CPC. The sample is pumped down a 3.31 metre length of conductive tubing to the instrument. The sample pressure is controlled using a reduced constant pressure inlet.
 
The instrument has two bisque lined columns that are constantly wetted from a resevior. It operates at total system flow of 1 lpm, 500 sccm per column. The sample to sheath flow is maintained at 10:1. The reduced constant pressure is nominally set at 650 hPa. The data is stored internally on a PC-208 system.
 
ccn100 cps
 

Data

The CCN outputs column specific supersaturation and CCN concentration measurements at 1 Hz along with other diagnositc parameters. Uncertanties for these data are not yet available, thouhg this data will be available in the future. The data are routinely available in Nasa Ames format for supersaturation and concentrations at the BADC in faam-non-core data folders.
 
spreadsheet CCN and 3786 CPC data status (45 KB)