Preprints
https://doi.org/10.5194/acp-2021-148
https://doi.org/10.5194/acp-2021-148

  01 Mar 2021

01 Mar 2021

Review status: this preprint is currently under review for the journal ACP.

Estimating the potential cooling effect of cirrus thinning achieved via the seeding approach

Jiaojiao Liu and Xiangjun Shi Jiaojiao Liu and Xiangjun Shi
  • School of Atmospheric Sciences, Nanjing University of Information Science and Technology, 210044, Nanjing, China

Abstract. Cirrus thinning is a newly emerging geoengineering approach to mitigate global warming. To sufficiently exploit the potential cooling effect of cirrus thinning with the seeding approach, a flexible seeding method is used to calculate the optimal seeding number concentration, which is just enough to prevent homogeneous ice nucleation from occurring. A simulation using the Community Atmosphere Model version 5 (CAM5) with the flexible seeding method shows a global cooling effect of 1.36 ± 0.18 W m−2, which is approximately two-thirds of that from artificially turning off homogeneous nucleation (−1.98 ± 0.26 W m−2). However, simulations with fixed seeding ice nuclei particle number concentrations of 20 and 200 L−1 show a weak cooling effect of −0.27 ± 0.26 W m−2 and warming effect of 0.35 ± 0.28 W m−2, respectively. Further analysis shows that cirrus seeding leads to a significant warming effect of liquid and mixed-phase clouds, which counteracts the cooling effect of cirrus clouds. This counteraction is more prominent at low latitudes and leads to a pronounced net warm effect over some low latitude regions. The sensitivity experiment shows that cirrus seeding carried out at latitudes with solar noon zenith angles greater than 12° could yields a stronger global cooling effect of −2.00 ± 0.25 W m−2. Overall, the potential cooling effect of cirrus thinning is considerable, and the flexible seeding method is essential.

Jiaojiao Liu and Xiangjun Shi

Status: open (until 29 Apr 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

Jiaojiao Liu and Xiangjun Shi

Data sets

Model code, simulation output data, and all scripts for the paper "Estimating the potential cooling effect of cirrus thinning achieved via the seeding approach" Jiaojiao Liu and Xiangjun Shi https://doi.org/10.5281/zenodo.4507001

Jiaojiao Liu and Xiangjun Shi

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Short summary
Cirrus thinning, which reduces the warming effect of cirrus clouds, has been investigated as a new geoengineering approach. In this study, a flexible seeding method is used to exploit the potential cooling effect of cirrus thinning. Simulation results show that the seeding method is essential for estimating the cooling effect. Cirrus thinning with the flexible seeding method could produce a considerable cooling effect, which is much stronger than the fixed seeding method.
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