Preprints
https://doi.org/10.5194/egusphere-2024-821
https://doi.org/10.5194/egusphere-2024-821
02 Apr 2024
 | 02 Apr 2024
Status: this preprint is open for discussion and under review for Atmospheric Chemistry and Physics (ACP).

Response of cirrus clouds to idealised perturbations from aviation

Ella Gilbert, Jhaswantsing Purseed, Yun Li, Martina Krämer, Beatrice Altamura, and Nicolas Bellouin

Abstract. Aviation is a rapidly growing source of climate forcing, and the non-CO2 effective radiative forcing of aviation is approximately twice that of aviation CO2. However, considerable uncertainty remains regarding aviation’s non-CO2 effects because the radiative forcing of aviation aerosol-cloud interactions, especially with cirrus clouds, is poorly known. Here, we use a large eddy simulation model to quantify the impact of ice crystal number concentration (ICNC) perturbations on the water budget and microphysics of pre-existing cirrus clouds. These perturbations aim to represent the second half of the chain of effects linking aircraft aerosol emissions to changes in ICNC and ice water path. We examine two types of cirrus: warm conveyor belt outflow and gravity wave cirrus, which represent different updraft regimes and formation mechanisms. In both cases, the primary effect of an idealised increase in ICNC is to extend cloud lifetime, with the increase proportional to the magnitude of the ICNC perturbation applied. The effect is more pronounced in the gravity wave cirrus case than in the warm conveyor belt outflow cirrus case because the latter has lower initial ICNC and ice water contents. Quantitatively, the sensitivity of ice water path (IWP) to changes in ICNC, expressed as ∆ln(IWP)/∆ln(ICNC), is 0.06 for gravity wave cirrus and 0.35 for warm conveyor belt outflow cirrus when calculated 45 minutes after imposing the ICNC perturbation. These results suggest that aviation has the potential to increase the lifetime and radiative effects of pre-existing cirrus clouds.

Ella Gilbert, Jhaswantsing Purseed, Yun Li, Martina Krämer, Beatrice Altamura, and Nicolas Bellouin

Status: open (until 14 May 2024)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
Ella Gilbert, Jhaswantsing Purseed, Yun Li, Martina Krämer, Beatrice Altamura, and Nicolas Bellouin

Data sets

LES simulations Ella Gilbert, Jhaswantsing Purseed, and Nicolas Bellouin https://zenodo.org/records/10845637

Ella Gilbert, Jhaswantsing Purseed, Yun Li, Martina Krämer, Beatrice Altamura, and Nicolas Bellouin

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Short summary
We use a simple experiment to explore the non-CO2 impacts of aviation on climate, which are considerably larger than the impact of the sector’s carbon emissions alone. We show that the main effect of our experiments – which intend to mimic the effect of aircraft soot emissions reaching existing high-altitude cirrus clouds – is to extend cloud lifetime, thereby enhancing their effect on climate.