Using depolarization to quantify ice nucleating particle concentrations: a new method
We have developed a new method to determine ice nucleating particle (INP) concentrations observed by the Texas A&M University continuous flow diffusion chamber (CFDC) under a wide range of operating conditions. In this study, we evaluate differences in particle optical properties detec...
| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-12-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | https://www.atmos-meas-tech.net/10/4639/2017/amt-10-4639-2017.pdf |
| Summary: | We have developed a new method to determine ice nucleating particle (INP)
concentrations observed by the Texas A&M University continuous flow diffusion
chamber (CFDC) under a wide range of
operating conditions. In this study, we evaluate differences in particle
optical properties detected by the Cloud and Aerosol Spectrometer with
POLarization (CASPOL) to differentiate between ice crystals, droplets, and
aerosols. The depolarization signal from the CASPOL instrument is used to
determine the occurrence of water droplet breakthrough (WDBT) conditions in
the CFDC. The standard procedure for determining INP concentration is to
count all particles that have grown beyond a nominal size cutoff as ice
crystals. During WDBT this procedure overestimates INP concentration, because large droplets are miscounted as
ice crystals. Here we design a new analysis method based on depolarization
ratio that can extend the range of operating conditions of the CFDC. The
method agrees reasonably well with the traditional method under non-WDBT
conditions with a mean percent error of ±32.1 %. Additionally, a
comparison with the Colorado State University CFDC shows that the new
analysis method can be used reliably during WDBT conditions. |
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| ISSN: | 1867-1381 1867-8548 |