Health & Environmental Research Online (HERO)


Print Feedback Export to File
2695015 
Journal Article 
Cirrus cloud susceptibility to the injection of ice nuclei in the upper troposphere 
Storelvmo, T; Herger, N 
2014 
Yes 
Journal of Geophysical Research: Atmospheres
ISSN: 2169-897X
EISSN: 2169-8996 
119 
5 
2375-2389 
WOS:000333885700023 
Due to their net warming effect, cirrus clouds play a crucial role in the climate system. A recently proposed climate engineering mechanism (CEM) intends to reduce high cloud cover by seeding cirrus clouds with efficient ice nuclei (IN) and therefore cool climate. Here, the susceptibility of cirrus clouds to the injection of ice nuclei in the upper troposphere is investigated in the extended Community Atmospheric Model version 5 (CAM5). Due to large uncertainties associated with the dominant ice nucleation mechanism in cirrus clouds, different control cases were simulated. In addition to pure homogeneous and heterogeneous nucleation, cases with competition between homogeneous and heterogeneous nucleation and different fractions of mineral dust active as IN were considered. Whereas seeding in the pure heterogeneous case leads to a strong warming due to overseeding, an optimal seeding IN concentration of approximately 18 l(-1) was found for the other cases. For the optimal seeding concentration, a reduction in the net cloud forcing (NCF) of up to 2 W m(-2) was simulated, corresponding to a strong cooling effect. To optimize the cooling and minimize the amount of seeding material, globally nonuniform seeding strategies were tested, with minimal seeding in the summer hemisphere and in the tropics. With seeding applied to less than half the globe, an even stronger reduction in the NCF was achieved. This suggests that the CEM could work for an atmosphere even with considerable heterogeneous ice nucleation and that the desired cooling could be obtained without seeding the entire globe.



Key Points <list list-type="bulleted"> <list-item id="jgrd51177-li-0001">Cirrus cloud seeding in the upper troposphere was simulated in CAM5 <list-item id="jgrd51177-li-0002">Both cirrus cloud susceptibility and short-term climate response were analyzed <list-item id="jgrd51177-li-0003">Even globally non-uniform injection of IN leads to the desired cooling 
geoengineering; cirrus; climate; aerosol; susceptibility; dust