Secondary ice production affects tropical convective clouds under different aerosol conditions
- 1University of Manchester (Manchester, United Kingdom)
Abstract
Secondary ice production (SIP) modulates tropical convection, but its interactions with aerosol loading remain uncertain. Using the UK Met Office Unified Model with detailed SIP parameterizations, this study investigates how multiple SIP mechanisms affect a Hector storm under weak instability and varying cloud condensation nuclei (CCN) concentrations. A reference simulation including all SIP mechanisms at a prescribed droplet number concentration ( N d ) of 400 cm ⁻³ is first evaluated against satellite, radar and aircraft observations. At moderate aerosol loading ( N d = 400 cm ⁻³ ), SIP substantially enhances the ice phase. Ice number increases by over 3 orders of magnitude at temperatures warmer than −10 °C, and ice water content rises by up to ∼ 120 % in the anvil. SIP also reduces outgoing longwave radiation (OLR) by 6.8 W m ⁻² (−2.5 %), increases outgoing shortwave radiation (OSR) by 7.9 W m ⁻² (+2 %), over a 110 km × 110 km region in 6 h. For this case, precipitation becomes more organized near the convective core, with total accumulation increasing by ∼ 25 %. Under polluted ( N d = 800 cm ⁻³ ) and clean ( N d = 200 cm ⁻³ ) conditions, SIP effects are weaker or spatially fragmented, indicating non-linear aerosol dependence. Sensitivity experiments show that, when combined with rime-splintering (RS), Mode 1 (droplet fragmentation during freezing) weakens at high CCN owing to reduced supercooled raindrop supply in the mixed-phase layer, while Mode 2 (drop–ice collisions with splashing) is inhibited at low CCN due to fewer encounters with large rimed ice particles. In contrast, RS and its combination with ice–ice collisional breakup show relatively limited aerosol sensitivity in this case.
Versions
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BibTeX
@article{sun2026secondary,
title = {{Secondary ice production affects tropical convective clouds under different aerosol conditions}},
author = {Mengyu Sun and Paul J. Connolly and Paul R. Field and Declan L. Finney and Alan M. Blyth},
journal = {Atmospheric Chemistry and Physics},
year = {2026},
month = nov,
doi = {10.5194/acp-26-15349-2026},
url = {https://doi.org/10.5194/acp-26-15349-2026},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Secondary ice production affects tropical convective clouds under different aerosol conditions
AU - Mengyu Sun
AU - Paul J. Connolly
AU - Paul R. Field
AU - Declan L. Finney
AU - Alan M. Blyth
PY - 2026
DA - 2026/11/02
JO - Atmospheric Chemistry and Physics
DO - 10.5194/acp-26-15349-2026
UR - https://doi.org/10.5194/acp-26-15349-2026
AB - Secondary ice production (SIP) modulates tropical convection, but its interactions with aerosol loading remain uncertain. Using the UK Met Office Unified Model with detailed SIP parameterizations, this study investigates how multiple SIP mechanisms affect a Hector storm under weak instability and varying cloud condensation nuclei (CCN) concentrations. A reference simulation including all SIP mechanisms at a prescribed droplet number concentration ( N d ) of 400 cm ⁻³ is first evaluated against satellite, radar and aircraft observations. At moderate aerosol loading ( N d = 400 cm ⁻³ ), SIP substantially enhances the ice phase. Ice number increases by over 3 orders of magnitude at temperatures warmer than −10 °C, and ice water content rises by up to ∼ 120 % in the anvil. SIP also reduces outgoing longwave radiation (OLR) by 6.8 W m ⁻² (−2.5 %), increases outgoing shortwave radiation (OSR) by 7.9 W m ⁻² (+2 %), over a 110 km × 110 km region in 6 h. For this case, precipitation becomes more organized near the convective core, with total accumulation increasing by ∼ 25 %. Under polluted ( N d = 800 cm ⁻³ ) and clean ( N d = 200 cm ⁻³ ) conditions, SIP effects are weaker or spatially fragmented, indicating non-linear aerosol dependence. Sensitivity experiments show that, when combined with rime-splintering (RS), Mode 1 (droplet fragmentation during freezing) weakens at high CCN owing to reduced supercooled raindrop supply in the mixed-phase layer, while Mode 2 (drop–ice collisions with splashing) is inhibited at low CCN due to fewer encounters with large rimed ice particles. In contrast, RS and its combination with ice–ice collisional breakup show relatively limited aerosol sensitivity in this case.
SN - 1680-7324
ER -