Journal article
A molecular perspective for global modeling of upper atmospheric NH3 from freezing clouds
Proceedings of the National Academy of Sciences - PNAS, Vol.115(24), pp.6147-6152
06/12/2018
DOI: 10.1073/pnas.1719949115
PMCID: PMC6004466
PMID: 29848636
Abstract
The retentions of gases upon freezing of water from available studies are conflicting. Using molecular dynamic simulations, we have revealed that the retention efficiency of NH
3
upon freezing cloud is close to 0 rather than 1 during deep convection. Our results further provide theoretical framework to explain the first-ever satellite-observed high concentration of NH
3
in the upper troposphere and lower stratosphere (UTLS). As NH
3
emission continues to increase, this study calls upon the emergent need to assess the role of NH
3
in UTLS chemistry especially in the deep convective regions. Methodologically, the molecular dynamics simulation is demonstrated as a tool for improving parameterization of interactions between trace gases and cloud (including ice) particles in global atmospheric models.
Ammonia plays a key role in the neutralization of atmospheric acids such as sulfate and nitrates. A few in situ observations have supported the theory that gas-phase NH
3
concentrations should decrease sharply with altitude and be extremely low in the upper troposphere and lower stratosphere (UTLS). This theory, however, seems inconsistent with recent satellite measurements and is also not supported by the aircraft data showing highly or fully neutralized sulfate aerosol particles by ammonium in the UTLS in many parts of the world. Here we reveal the contributions of deep convective clouds to NH
3
in the UTLS by using integrated cross-scale modeling, which includes molecular dynamic simulations, a global chemistry transport model, and satellite and aircraft measurements. We show that the NH
3
dissolved in liquid cloud droplets is prone to being released into the UTLS upon freezing during deep convection. Because NH
3
emission is not regulated in most countries and its future increase is likely persistent from agricultural growth and the warmer climate, the effect of NH
3
on composition and phase of aerosol particles in the UTLS can be significant, which in turn can affect cirrus cloud formation, radiation, and the budgets of NOx and O
3
.
Details
- Title: Subtitle
- A molecular perspective for global modeling of upper atmospheric NH3 from freezing clouds
- Creators
- Cui Ge - Department of Chemical and Biochemical EngineeringChongqin Zhu - Department of ChemistryJoseph S Francisco - Department of ChemistryXiao Cheng Zeng - Department of ChemistryJun Wang - Department of Chemical and Biochemical Engineering
- Resource Type
- Journal article
- Publication Details
- Proceedings of the National Academy of Sciences - PNAS, Vol.115(24), pp.6147-6152
- DOI
- 10.1073/pnas.1719949115
- PMID
- 29848636
- PMCID
- PMC6004466
- NLM abbreviation
- Proc Natl Acad Sci U S A
- ISSN
- 0027-8424
- eISSN
- 1091-6490
- Publisher
- National Academy of Sciences
- Grant note
- NNX17AF63G / National Aeronautics and Space Administration (NASA) CHE1665325 / National Science Foundation (NSF) NNX17AF77G / National Aeronautics and Space Administration (NASA)
- Language
- English
- Date published
- 06/12/2018
- Academic Unit
- Electrical and Computer Engineering; Civil and Environmental Engineering; Iowa Technology Institute; Physics and Astronomy; Chemical and Biochemical Engineering
- Record Identifier
- 9984104808602771
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