Publication Date:
2023-12-19
Description:
Predicting cirrus cloud properties with confidence requires a sound understanding of the relative roles of homogeneous and heterogeneous ice formation. This study explores the effect of mineral dust and contrail‐processed aviation soot particles as ice‐nucleating particles (INPs) competing with liquid solution droplets in cirrus formation. We study aerosol‐cirrus interactions by accounting for atmospheric variability in updraft speeds and INP number concentrations. Our results confirm the dominant role of mineral dust in ice nucleation events in cirrus clouds. In addition, we show that pre‐existing thin cirrus may suppress ice formation when updraft speeds are low. We find that homogeneous freezing of liquid solution droplets dominates clear‐sky aerosol‐cirrus interaction above a threshold updraft speed determined by total number concentrations and ice nucleation abilities of INPs. When mineral dust particles exceed number concentrations of 10 L〈sup〉−1〈/sup〉, they reduce homogeneously nucleated ice crystal numbers significantly and even prevent homogeneous freezing for frequently observed local updraft speeds between 10 and 20 cm s〈sup〉−1〈/sup〉. When both mineral dust and aviation soot particles coexist with solution droplets, dust typically prevents ice nucleation by aviation soot. Aviation soot exerts a notable impact on cirrus ice numbers only if updrafts are weak, large soot particles are present in number concentrations that are considerably higher than typically observed in emission measurements, and/or number concentrations of mineral dust and other INPs are low. Overall, our results elucidate the role of aviation soot‐cirrus interactions in the presence of other INP types.
Description:
Plain Language Summary:
Understanding ice formation from atmospheric aerosol particles in cirrus clouds is important to correctly predict the impact of cirrus on climate. Here, we study for the first time on the process level cirrus ice formation from freezing of liquid solution droplets in competition with ice nucleation on mineral dust and aviation‐produced soot particles. Our results show that in the majority of cloud‐forming updrafts, mineral dust particles dominate cirrus formation over droplet freezing and that they outcompete aviation soot in producing cloud ice. Moreover, already existing cirrus clouds often prevent ice formation from these particle types altogether. Our results help evaluate cirrus parameterizations within global models and constrain model‐based estimates of the global climate impact of aviation.
Description:
Key Points:
Mineral dust outcompetes contrail‐processed aviation soot in aerosol‐cirrus interactions.
Mineral dust reduces homogeneously nucleated ice crystal numbers more effectively than aviation soot.
Strong potential of pre‐existing cirrus clouds to suppress new cloud ice formation.
Description:
European Commission
http://dx.doi.org/10.13039/501100000780
Description:
https://doi.org/10.5281/zenodo.7404707
Keywords:
ddc:551.5
;
ice nucleating particles
;
cirrus
;
aerosol cloud interactions
Language:
English
Type:
doc-type:article
Permalink
