FREEZING OF STRATOSPHERIC AEROSOL DROPLETS

被引:49
作者
LUO, BP
PETER, T
CRUTZEN, P
机构
[1] Max-Planck-Institut für Chemie, Mainz
关键词
D O I
10.1029/93GL03076
中图分类号
P [天文学、地球科学];
学科分类号
07 ;
摘要
Theoretical calculations are presented for homogeneous and heterogeneous freezing of sulfuric acid droplets under stratospheric conditions, based on classical nucleation theory. In contrast to previous results it is shown that a prominent candidate for freezing, sulfuric acid tetrahydrate (SAT = H2SO4.4H2O), does not freeze homogeneously. The theoretical results limit the homogeneous freezing rate at 200 K to much less than 1 cm-3s-1, a value that may be estimated from bulk phase laboratory experiments. This suggests that the experimental value is likely to be a measure of heterogeneous, not homogeneous nucleation. Thus, under statospheric conditions, freezing of SAT can only occur in the presence of suitable nuclei; however, even for heterogeneous nucleation experimental results impose strong constraints. Since a nitric acid trihydrate (NAT) embryo probably needs a solid body for nucleation, these results put an important constraint on the theory of NAT formation in polar stratospheric clouds.
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页码:1447 / 1450
页数:4
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