 |
| Titel |
The micro-orifice uniform deposit impactor–droplet freezing technique (MOUDI-DFT) for measuring concentrations of ice nucleating particles as a function of size: improvements and initial validation |
| VerfasserIn |
R. H. Mason, C. Chou, C. S. McCluskey, E. J. T. Levin, C. L. Schiller, T. C. J. Hill, J. A. Huffman, P. J. DeMott, A. K. Bertram |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1867-1381
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 8, no. 6 ; Nr. 8, no. 6 (2015-06-15), S.2449-2462 |
| Datensatznummer |
250116432
|
| Publikation (Nr.) |
 copernicus.org/amt-8-2449-2015.pdf |
|
|
|
|
|
| Zusammenfassung |
| The micro-orifice uniform deposit impactor–droplet freezing
technique (MOUDI-DFT) combines particle collection by inertial impaction
(via the MOUDI) and a microscope-based immersion freezing apparatus (the
DFT) to measure atmospheric concentrations of ice nucleating particles
(INPs) as a function of size and temperature. In the first part of this
study we improved upon this recently introduced technique. Using optical
microscopy, we investigated the non-uniformity of MOUDI aerosol deposits at
spatial resolutions of 1, 0.25 mm, and for some stages when necessary 0.10
mm. The results from these measurements show that at a spatial resolution of
1 mm and less, the concentration of particles along the MOUDI aerosol
deposits can vary by an order of magnitude or more. Since the total area of
a MOUDI aerosol deposit ranges from 425 to 605 mm2 and the area
analyzed by the DFT is approximately 1.2 mm2, this non-uniformity needs
to be taken into account when using the MOUDI-DFT to determine atmospheric
concentrations of INPs. Measurements of the non-uniformity of the MOUDI
aerosol deposits were used to select positions on the deposits that had
relatively small variations in particle concentration and to build substrate
holders for the different MOUDI stages. These substrate holders improve
reproducibility by holding the substrate in the same location for each
measurement and ensure that DFT analysis is only performed on substrate
regions with relatively small variations in particle concentration. In
addition, the deposit non-uniformity was used to determine correction
factors that take the non-uniformity into account when determining
atmospheric concentrations of INPs. In the second part of this study, the
MOUDI-DFT utilizing the new substrate holders was compared to the
continuous flow diffusion chamber (CFDC) technique of Colorado State University. The
intercomparison was done using INP concentrations found by the two
instruments during ambient measurements of continental aerosols. Results
from two sampling periods were compared, and the INP concentrations
determined by the two techniques agreed within experimental uncertainty. The
agreement observed here is commensurate with the level of agreement found in
other studies where CFDC results were compared to INP concentrations
measured with other methods. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|