Observationally Constrained SO₂ Oxidation Rates from ACCLIP (2022): Toward Improved Sulfate Representation in CESM
Tambe, T., Smith, W. P., Nance, L. B., Myron-Karels, M.. (2026). Observationally Constrained SO₂ Oxidation Rates from ACCLIP (2022): Toward Improved Sulfate Representation in CESM. , doi:https://doi.org/10.5065/0tth-kz49
| Title | Observationally Constrained SO₂ Oxidation Rates from ACCLIP (2022): Toward Improved Sulfate Representation in CESM |
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| Genre | Manuscript |
| Author(s) | Trisha Tambe, Warren P. Smith, Louisa B. Nance, Meghan Myron-Karels |
| Abstract | Sulfate aerosol (SO42-) in the upper troposphere and lower stratosphere (UTLS) influences radiative balance, stratospheric chemistry, and air quality far from its source, with Asian summer monsoon deep convection delivering sulfur to this region. Version 2.2 of the Community Earth System Model reproduces observed SO₂ during the 2022 ACCLIP campaign but overestimates SO₄²⁻ above the boundary layer by nearly an order of magnitude. This study tests whether misrepresented gas-phase SO₂ oxidation in the UTLS accounts for any of that discrepancy. Backward trajectories are used to assign a time since convection to each observation and to isolate five validated Lagrangian air parcels. The campaign-wide dataset produces an observed SO₂ lifetime of 6.2 [5.1-7.9] days in the UTLS, which is validated by the Lagrangian parcels. A theoretical lifetime of 5.0 days, calculated from JPL kinetics and a steady-state OH concentration derived entirely from observations, nearly closes the sulfur budget through gas-phase chemistry alone and independently validates the model's OH field. The model lifetime of 4.7 days differs from the observed rate by a factor of 0.75, but applying this scalar improves SO₄²⁻ negligibly while degrading SO₂. Comparing the model and observations along the convective pathway localizes the bias: model-to-observation SO₄²⁻ ratios rise from 1.89 in inflow to 5.19 in fresh outflow, while CO falls from 0.86 to 0.63. The bias is therefore generated during convective transport, implicating wet scavenging and in-cloud production rather than outflow chemistry. |
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| Publication Date | Aug 1, 2026 |
| Publisher's Version of Record | https://doi.org/10.5065/0tth-kz49 |
| OpenSky Citable URL | https://n2t.net/ark:/85065/d79k4gtv |
| OpenSky Listing | View on OpenSky |