Oxalic acid as a heterogeneous ice nucleus in the upper troposphere and its indirect aerosol effect

B. Zobrist (1) , C. Marcolli (1) , T. Koop (2) , B. P. Luo (1) , D. M. Murphy (3) , U. Lohmann (1) , A. A. Zardini (1) , U. K. Krieger (1) , T. Corti (1) , D. J. Cziczo (1) , S. Fueglistaler (1) , P. K. Hudson (3) , D. S. Thomson (3) , T. Peter (1)

1 IAC - Institute for Atmospheric and Climate Science [Zürich]
2 Department of Chemistry
3 ESRL - NOAA Earth System Research Laboratory

Heterogeneous ice freezing points of aqueous solutions containing various immersed solid dicarboxylic acids (oxalic, adipic, succinic, phthalic and fumaric) have been measured with a differential scanning calorimeter. The results show that only the dihydrate of oxalic acid (OAD) acts as a heterogeneous ice nucleus, with an increase in freezing temperature between 2 and 5 K depending on solution composition. In several field campaigns, oxalic acid enriched particles have been detected in the upper troposphere with single particle aerosol mass spectrometry. Simulations with a microphysical box model indicate that the presence of OAD may reduce the ice particle number density in cirrus clouds by up to ~50% when compared to exclusively homogeneous cirrus formation without OAD. Using the ECHAM4 climate model we estimate the global net radiative effect caused by this heterogeneous freezing to result in a cooling as high as ?0.3 Wm^?2.

Domaines: Océan, Atmosphère

B. Zobrist, C. Marcolli, T. Koop, B. P. Luo, D. M. Murphy, et al.. Oxalic acid as a heterogeneous ice nucleus in the upper troposphere and its indirect aerosol effect. Atmospheric Chemistry and Physics, 2006, 6 (10), pp.3115-3129. ⟨hal-00295992⟩