Melting of H 2 SO 4 ⋅4H 2 O Particles upon Cooling: Implications for Polar Stratospheric Clouds
- 14 June 1996
- journal article
- other
- Published by American Association for the Advancement of Science (AAAS) in Science
- Vol. 272 (5268) , 1638-1641
- https://doi.org/10.1126/science.272.5268.1638
Abstract
Polar stratospheric clouds (PSCs) are important for the chemical activation of chlorine compounds and subsequent ozone depletion. Solid PSCs can form on sulfuric acid tetrahydrate (SAT) (H2SO4·4H2O) nuclei, but recent laboratory experiments have shown that PSC nucleation on SAT is strongly hindered. A PSC formation mechanism is proposed in which SAT particles melt upon cooling in the presence of HNO3 to form liquid HNO3-H2SO4-H2O droplets 2 to 3 kelvin above the ice frost point. This mechanism offers a PSC formation temperature that is defined by the ambient conditions and sets a temperature limit below which PSCs should form.Keywords
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