The importance of soil dust for mixed-phase clouds in global climate models

Abstract:

Dust particles are an important driver of ice nucleation and glaciation in mixed-phase clouds. With that they influence precipitation and the hydrological cycle. Dust particles mostly originate from natural source regions, like deserts, and consist of different minerals, e.g. clay, feldspar, quartz. Soil dust particles, which originate from agricultural sites also consist of a small fraction of organic matter. It has been shown in different studies that this small fraction of organic matter influences the ice nucleating ability of the dust particles. Soil dusts have been found to be more efficient ice-nucleating particles (INPs) compared to mineral dusts. Currently global climate models do not consider a difference between soil dust and desert dust or the source of dust particles. Since soil dust is becoming increasingly important due to the increase of agricultural areas, we make a first attempt to quantify the importance of soil dust as an INP on a global scale in present and possible future conditions.

For our study we use a version of the global climate-aerosol model ECHAM6-HAM2, where it is possible to differentiate between soil dust and desert dust emissions. Furthermore, new parameterizations to describe the ice nucleation capability of desert and soil dusts are implemented. We present how the different parameterization schemes in combination with the dust type influence the freezing process and thus the properties of mixed-phase clouds, precipitation and their climate impact.