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HNO 3 partitioning in cirrus clouds

1999; American Geophysical Union; Volume: 26; Issue: 14 Linguagem: Inglês

10.1029/1999gl900423

1944-8007

Stefanie Meilinger, A. Tsias, V. Dreiling, Michael Kühn, C. Feigl, H. Ziereis, Hans Schlager, Joachim Curtius, B. Sierau, Frances H. Arnold, Martin Zöger, C. Schiller, Thomas Peter,

Atmospheric and Environmental Gas Dynamics

During the 1997 POLSTAR‐1 winter campaign in northern Sweden a flight was performed across a cold trough of air (≃ 196 K) in the tropopause region. Measurements of total water vapour, nitric acid, particles and reactive nitrogen (NO y ) were taken. The particle measurements indicate that about 3% of the particles in the moist tropospheric air were ice particles. Forward and backward facing NO y inlets were used simultaneously to determine condensed phase HNO 3 . The combined NO y and particle measurements reveal that less than 1% of a monolayer of NO y could have resided on the ice particles. This casts doubt on the hypothesis that sedimenting cirrus particles generally lead to a strong downward flux of NO y . In addition to the NO y measurements, independent HNO 3 measurements were used to determine total HNO 3 . Although quantitative uncertainties do not allow to completely rule out that the NO y uptake on ice was limited by total HNO 3 , the combined NO y and HNO 3 data suggest that there was low uptake of NO y on ice despite abundant HNO 3 in the gas phase. Model studies indicate, that the most likely explanation of the measured nitric acid partitioning is given by HNO 3 in ternary solution droplets coexisting with almost HNO 3 free ice in the same air mass.