Atmospheric Chemistry and Physics Homogeneous nucleation of NAD and NAT in liquid stratospheric aerosols: insufficient to explain denitrification

• Main Authors: D. A. Knopf, T. Koop, B. P. Luo, U. G. Weers, T. Peter
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Arctic
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.404.7468; http://hal.archives-ouvertes.fr/docs/00/29/51/99/PDF/acp-2-207-2002.pdf

Abstract. The nucleation of NAD and NAT from HNO3/H2O and HNO3/H2SO4/H2O solution droplets is investigated both theoretically and experimentally with respect to the formation of polar stratospheric clouds (PSCs). Our analysis shows that homogeneous NAD and NAT nucleation from liquid aerosols is insufficient to explain the number densities of large nitric acid containing particles recently observed in the Arctic stratosphere. This conclusion is based on new droplet freezing experiments employing optical microscopy combined with Raman spectroscopy. The homogeneous nucleation rate coefficients of NAD and NAT in liquid aerosols under polar stratospheric conditions derived from the experiments are < 2 × 10−5 cm−3 s−1 and < 8 × 10−2 cm−3 s−1, respectively. These nucleation rate coefficients are smaller by orders of magnitude than the value of ∼ 103 cm−3 s−1 used in a recent denitrification