Low concentrations of fine dust aerosols may influence the occurrence of glaciated stratiform clouds in the Southern Ocean
Abstract
Clouds affect the earth's climate in different ways depending mainly on their radiative properties and altitude. These radiative properties depend strongly on their thermodynamic phase. Between 0°C and -40°C cloud droplets can freeze via heterogeneous nucleation trough the interaction with ice nuclei such as dust particles. However, current climate models show a large bias in the representation of such aerosol-cloud interactions. Therefore, it is crucial to improve the understanding of these processes using satellite measurements and high-quality reanalysis products.
The A-Train satellite products DARDAR-MASK and CALIOP-GOCCP were analysed together with the MACC reanalysis and the Cloudsat cloud scenario classification to assess the day-to-day variability of cloud thermodynamic phase. This variability was analysed at different loadings of fine dust and for different stratiform cloud types during the period 2007-2010. It was found that the most important factors controlling the stratiform cloud phase were the temperature and latitude. However, at constant temperature, latitude and season much of the day-to-day variability in stratiform cloud phase can be explained by the simulated variations of fine dust loading. This changes in day-to-day cloud phase can be additionally explained by the relative distributions of the four stratiform cloud types defined by the Cloudsat scenario classification: Cirrus, Altocumulus, Altostratus and Stratocumulus. This is especially evident for the latter two cloud types and for temperatures between 10°C and 20°C at mid- and high latitudes. Despite the great differences in average dust loading between the north and south hemisphere, the observed increase in cloud phase at higher dust loading was very similar at different latitudes, even in the remote sub-polar regions of the Southern Ocean.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.A13G2526V
- Keywords:
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- 0305 Aerosols and particles;
- ATMOSPHERIC COMPOSITION AND STRUCTUREDE: 0320 Cloud physics and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTUREDE: 3310 Clouds and cloud feedbacks;
- ATMOSPHERIC PROCESSESDE: 3349 Polar meteorology;
- ATMOSPHERIC PROCESSES