Classification of Arctic, midlatitude and tropical clouds in the mixed-phase temperature regime
The degree of glaciation of mixed-phase clouds constitutes one of the largest uncertainties in climate prediction. In order to better understand cloud glaciation, cloud spectrometer observations are presented in this paper, which were made in the mixed-phase temperature regime between 0 and −38 ...
| Main Authors: | , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-10-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/17/12219/2017/acp-17-12219-2017.pdf |
| Summary: | The degree of glaciation of mixed-phase clouds constitutes one
of the largest uncertainties in climate prediction. In order to better
understand cloud glaciation, cloud spectrometer observations are presented in
this paper, which were made in the mixed-phase temperature regime between 0 and
−38 °C (273 to 235 K), where cloud particles can either be frozen
or liquid. The extensive data set covers four airborne field campaigns
providing a total of 139 000 1 Hz data points (38.6 h within clouds) over
Arctic, midlatitude and tropical regions. We develop algorithms, combining
the information on number concentration, size and asphericity of the observed
cloud particles to classify four cloud types: liquid clouds, clouds in which
liquid droplets and ice crystals coexist, fully glaciated clouds after the
Wegener–Bergeron–Findeisen process and clouds where secondary ice formation
occurred. We quantify the occurrence of these cloud groups depending on the
geographical region and temperature and find that liquid clouds dominate
our measurements during the Arctic spring, while clouds dominated by the
Wegener–Bergeron–Findeisen process are most common in midlatitude spring.
The coexistence of liquid water and ice crystals is found over the whole
mixed-phase temperature range in tropical convective towers in the dry
season. Secondary ice is found at midlatitudes at −5 to −10 °C
(268 to 263 K) and at higher altitudes, i.e. lower temperatures in the
tropics. The distribution of the cloud types with decreasing temperature is
shown to be consistent with the theory of evolution of mixed-phase clouds.
With this study, we aim to contribute to a large statistical database on
cloud types in the mixed-phase temperature regime. |
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| ISSN: | 1680-7316 1680-7324 |