Kinetic mass-transfer calculation of water isotope fractionation due to cloud microphysics in a regional meteorological model
<p>In conventional atmospheric models, isotope exchange between liquid, gas, and solid phases is usually assumed to be in equilibrium, and the highly kinetic phase transformation processes inferred in clouds are yet to be fully investigated. In this study, a two-moment microphysical scheme in...
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Copernicus Publications
2019-02-01
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| Series: | Atmospheric Chemistry and Physics |
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doaj-17e58aabfae7456793fb01398226d1b82020-11-25T00:36:11ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242019-02-01191753176610.5194/acp-19-1753-2019Kinetic mass-transfer calculation of water isotope fractionation due to cloud microphysics in a regional meteorological modelI.-C. Tsai0W.-Y. Chen1W.-Y. Chen2J.-P. Chen3J.-P. Chen4M.-C. Liang5Research Center for Environmental Changes, Academia Sinica, Taipei, TaiwanDepartment of Atmospheric Sciences, National Taiwan University, Taipei, TaiwanCentral Weather Bureau, Taipei, TaiwanDepartment of Atmospheric Sciences, National Taiwan University, Taipei, TaiwanInternational Degree Program on Climate Change and Sustainable Development, National Taiwan University, Taipei, TaiwanInstitute of Earth Sciences, Academia Sinica, Taipei, Taiwan<p>In conventional atmospheric models, isotope exchange between liquid, gas, and solid phases is usually assumed to be in equilibrium, and the highly kinetic phase transformation processes inferred in clouds are yet to be fully investigated. In this study, a two-moment microphysical scheme in the National Center for Atmospheric Research (NCAR) Weather Research and Forecasting (WRF) model was modified to allow kinetic calculation of isotope fractionation due to various cloud microphysical phase-change processes. A case of a moving cold front is selected for quantifying the effect of different factors controlling isotopic composition, including water vapor sources, atmospheric transport, phase transition pathways of water in clouds, and kinetic-versus-equilibrium mass transfer. A base-run simulation was able to reproduce the <span class="inline-formula">∼</span> 50 ‰ decrease in <span class="inline-formula"><i>δ</i>D</span> that was observed during the frontal passage. Sensitivity tests suggest that all the above factors contributed significantly to the variations in isotope composition. The thermal equilibrium assumption commonly used in earlier studies may cause an overestimate of mean vapor-phase <span class="inline-formula"><i>δ</i>D</span> by 11 ‰, and the maximum difference can be more than 20 ‰. Using initial vertical distribution and lower boundary conditions of water stable isotopes from satellite data is critical to obtain successful isotope simulations, without which the <span class="inline-formula"><i>δ</i>D</span> in water vapor can be off by about 34 ‰ and 28 ‰, respectively. Without microphysical fractionation, the <span class="inline-formula"><i>δ</i>D</span> in water vapor can be off by about 25 ‰.</p>https://www.atmos-chem-phys.net/19/1753/2019/acp-19-1753-2019.pdf |
| collection |
DOAJ |
| language |
English |
| format |
Article |
| sources |
DOAJ |
| author |
I.-C. Tsai W.-Y. Chen W.-Y. Chen J.-P. Chen J.-P. Chen M.-C. Liang |
| spellingShingle |
I.-C. Tsai W.-Y. Chen W.-Y. Chen J.-P. Chen J.-P. Chen M.-C. Liang Kinetic mass-transfer calculation of water isotope fractionation due to cloud microphysics in a regional meteorological model Atmospheric Chemistry and Physics |
| author_facet |
I.-C. Tsai W.-Y. Chen W.-Y. Chen J.-P. Chen J.-P. Chen M.-C. Liang |
| author_sort |
I.-C. Tsai |
| title |
Kinetic mass-transfer calculation of water isotope fractionation due to cloud microphysics in a regional meteorological model |
| title_short |
Kinetic mass-transfer calculation of water isotope fractionation due to cloud microphysics in a regional meteorological model |
| title_full |
Kinetic mass-transfer calculation of water isotope fractionation due to cloud microphysics in a regional meteorological model |
| title_fullStr |
Kinetic mass-transfer calculation of water isotope fractionation due to cloud microphysics in a regional meteorological model |
| title_full_unstemmed |
Kinetic mass-transfer calculation of water isotope fractionation due to cloud microphysics in a regional meteorological model |
| title_sort |
kinetic mass-transfer calculation of water isotope fractionation due to cloud microphysics in a regional meteorological model |
| publisher |
Copernicus Publications |
| series |
Atmospheric Chemistry and Physics |
| issn |
1680-7316 1680-7324 |
| publishDate |
2019-02-01 |
| description |
<p>In conventional atmospheric models, isotope exchange between
liquid, gas, and solid phases is usually assumed to be in equilibrium, and the
highly kinetic phase transformation processes inferred in clouds are yet to
be fully investigated. In this study, a two-moment microphysical scheme in
the National Center for Atmospheric Research (NCAR) Weather Research and Forecasting (WRF) model was modified to allow
kinetic calculation of isotope fractionation due to various cloud
microphysical phase-change processes. A case of a moving cold front is selected
for quantifying the effect of different factors controlling isotopic
composition, including water vapor sources, atmospheric transport, phase
transition pathways of water in clouds, and kinetic-versus-equilibrium mass
transfer. A base-run simulation was able to reproduce the
<span class="inline-formula">∼</span> 50 ‰ decrease in <span class="inline-formula"><i>δ</i>D</span> that was observed during the frontal
passage. Sensitivity tests suggest that all the above factors contributed
significantly to the variations in isotope composition. The thermal
equilibrium assumption commonly used in earlier studies may cause an
overestimate of mean vapor-phase <span class="inline-formula"><i>δ</i>D</span> by 11 ‰, and the maximum difference can be more than
20 ‰. Using initial vertical distribution and lower boundary
conditions of water stable isotopes from satellite data is critical to
obtain successful isotope simulations, without which the <span class="inline-formula"><i>δ</i>D</span> in water
vapor can be off by about 34 ‰ and 28 ‰, respectively.
Without microphysical fractionation, the <span class="inline-formula"><i>δ</i>D</span> in water vapor can be off
by about 25 ‰.</p> |
| url |
https://www.atmos-chem-phys.net/19/1753/2019/acp-19-1753-2019.pdf |
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