Stratospheric transport and tropospheric sink of solar geoengineering aerosol: a Lagrangian analysis

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Jun 3, 2024, 8:30:25 AMJun 3
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https://www.nature.com/articles/s41612-024-00664-8

Authors 
Hongwei Sun, Stephen Bourguet, Lan Luan & David Keith 

30 May 2024

Citations: Sun, H., Bourguet, S., Luan, L. et al. Stratospheric transport and tropospheric sink of solar geoengineering aerosol: a Lagrangian analysis. npj Clim Atmos Sci 7, 115 (2024). https://doi.org/10.1038/s41612-024-00664-8

Abstract
Stratospheric aerosol injection (SAI) aims to reflect solar radiation by increasing the stratospheric aerosol burden. To understand how the background circulation influences stratospheric transport of injected particles, we use a Lagrangian trajectory model (lacking numerical diffusion) to quantify particles’ number, flux, lifetime, and tropospheric sinks from a SAI injection strategy under present-day conditions. While particles are being injected, stratospheric particle number increases until reaching a steady-state. During the steady-state, the time series of particle number shows a dominant period of ~2 years (rather than a 1-year cycle), suggesting modulation by the quasi-biannual oscillation. More than half of particles, injected in the tropical lower stratosphere (15° S to 15° N, 65 hPa), undergo quasi-horizontal transport to the midlatitude. We find a zonal asymmetry of particles’ tropospheric sinks that are co-located with tropopause folding beneath the midlatitude jet stream, which can help predict tropospheric impacts of SAI (e.g., cirrus cloud thinning).

figure 1

Time series of the number of particles (black line) in the stratosphere, with three stages divided by the red dashed lines.

Evaluations of particle distribution and transport in the stratosphere.
figure 4

a Spatial distribution (latitude vs. altitude) of zonally integrated particle number concentration (with a unit of particles per square meter). b Particle number N (red values with the unit of particles), number flux F (blue values with a unit of particles per year), and lifetime L (purple values with a unit of years) in or between different regions (black boxes) during the steady-state stage (2005.01–2010.01). The injection rate is scaled to 100 particles per year and all other values are scaled correspondingly.

Source: Nature
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