气候变化领域集成服务门户(CCPortal): Cirrus cloud thinning using a more physically based ice microphysics scheme in the ECHAM-HAM general circulation model

CCPortal

DOI	10.5194/acp-22-11455-2022
	Cirrus cloud thinning using a more physically based ice microphysics scheme in the ECHAM-HAM general circulation model
	Tully, Colin; Neubauer, David; Omanovic, Nadja; Lohmann, Ulrike
发表日期	2022
ISSN	1680-7316
EISSN	1680-7324
起始页码	11455
结束页码	11484
卷号	22 期号:17 页码:30
英文摘要	Cirrus cloud thinning (CCT) is a relatively new radiation management proposal to counteract anthropogenic climate warming by targeting Earth's terrestrial radiation balance. The efficacy of this method was presented in several general circulation model (GCM) studies that showed widely varied radiative responses, originating in part from the differences in the representation of cirrus ice microphysics between the different GCMs. The recent implementation of a new, more physically based ice microphysics scheme (Predicted Particle Properties, P3) that abandons ice hydrometeor size class separation into the ECHAM-HAM GCM, coupled to a new approach for calculating cloud fractions that increases the relative humidity (RH) thresholds for cirrus cloud formation, motivated a reassessment of CCT efficacy. In this study, we first compared CCT sensitivity between the new cloud fraction approach and the original ECHAM-HAM cloud fraction approach. Consistent with previous approaches using ECHAM-HAM, with the P3 scheme and the higher RH thresholds for cirrus cloud formation, we do not find a significant cooling response in any of our simulations. The most notable response from our extreme case is the reduction in the maximum global-mean net top-of-atmosphere (TOA) radiative anomalies from overseeding by about 50 %, from 9.9 W m(-2) with the original cloud fraction approach down to 4.9 W m(-2) using the new cloud fraction RH thresholds that allow partial grid-box coverage of cirrus clouds above ice saturation, unlike the original approach. Even with this reduction with the updated cloud fraction approach, the TOA anomalies from overseeding far exceed those reported in previous studies. We attribute the large positive TOA anomalies to seeding particles overtaking both homogeneous nucleation and heterogeneous nucleation on mineral dust particles within cirrus clouds to produce more numerous and smaller ice crystals. This effect is amplified by longer ice residence times in clouds due to the slower removal of ice via sedimentation in the P3 scheme. In an effort to avoid this overtaking effect of seeding particles, we increased the default critical ice saturation ratio (S-i,S-seed) for ice nucleation on seeding particles from the default value of 1.05 to 1.35 in a second sensitivity test. With the higher Si,seed we drastically reduce overseeding, which suggests that S-i,S-seed is a key factor to consider for future CCT studies. However, the global-mean TOA anomalies contain high uncertainty. In response, we examined the TOA anomalies regionally and found that specific regions only show a small potential for targeted CCT, which is partially enhanced by using the larger S-i,S-seed. Finally, in a seasonal analysis of TOA responses to CCT, we find that our results do not confirm the previous finding that high-latitude wintertime seeding is a feasible strategy to enhance CCT efficacy, as seeding in our model enhances the already positive cirrus longwave cloud radiative effect for most of our simulations. Our results also show feedbacks on lower-lying mixed-phase and liquid clouds through the reduction in ice crystal sedimentation that reduces cloud droplet depletion and results in stronger cloud albedo effects. However, this is outweighed by stronger longwave trapping from cirrus clouds with more numerous and smaller ice crystals. Therefore, we conclude that CCT is unlikely to act as a feasible climate intervention strategy on a global scale.
学科领域	Environmental Sciences; Meteorology & Atmospheric Sciences
语种	英语
WOS研究方向	Environmental Sciences & Ecology ; Meteorology & Atmospheric Sciences
WOS记录号	WOS:000850452400001
来源期刊	ATMOSPHERIC CHEMISTRY AND PHYSICS
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/273393
作者单位	Swiss Federal Institutes of Technology Domain; ETH Zurich
推荐引用方式 GB/T 7714	Tully, Colin,Neubauer, David,Omanovic, Nadja,et al. Cirrus cloud thinning using a more physically based ice microphysics scheme in the ECHAM-HAM general circulation model[J],2022,22(17):30.
APA	Tully, Colin,Neubauer, David,Omanovic, Nadja,&Lohmann, Ulrike.(2022).Cirrus cloud thinning using a more physically based ice microphysics scheme in the ECHAM-HAM general circulation model.ATMOSPHERIC CHEMISTRY AND PHYSICS,22(17),30.
MLA	Tully, Colin,et al."Cirrus cloud thinning using a more physically based ice microphysics scheme in the ECHAM-HAM general circulation model".ATMOSPHERIC CHEMISTRY AND PHYSICS 22.17(2022):30.