Modelling the reversible uptake of chemical species in the gas phase by ice particles formed in a convective cloud

V. Marécal (1) , Michel Pirre (1) , E. Riviere (2) , N Pouvesle (3) , J N Crowley (3) , S. Freitas (4) , K M Longo (4)

1 LPC2E - Laboratoire de Physique et Chimie de l'Environnement et de l'Espace
2 Association pour la Surveillance et l'Etude la Pollution Atmosphérique en Alsace
3 Max-Planck-Institut für Biophysikalische Chemie - Max Planck Institute for Biophysical Chemistry [Göttingen]
4 CPTEC - Center for Weather Forecasting and Climate Studies [São Paulo]

The present paper is a preliminary study preparing the introduction of reversible trace gas uptake by ice particles into a 3-D cloud resolving model. For this a 3-D simulation of a tropical deep convection cloud was run with the BRAMS cloud resolving model using a two-moment bulk microphysical parameterization. Trajectories within the con-vective clouds were computed from these simulation outputs along which the variations of the pristine ice, snow and aggregate mixing ratios and concentrations were extracted. The reversible uptake of 11 trace gases by ice was examined assuming applicability of Langmuir isotherms using recently evaluated (IUPAC) laboratory data. The results show that ice uptake is only significant for HNO 3 , HCl, CH 3 COOH and HCOOH. For H 2 O 2 , using new results for the partition coefficient results in significant partitioning to the ice phase for this trace gas also. It was also shown that the uptake is largely dependent on the temperature for some species. The adsorption saturation at the ice surface for large gas mixing ratios is generally not a limiting factor except for HNO 3 and HCl for gas mixing ratio greater than 1 ppbv. For HNO 3 , results were also obtained using a trapping theory, resulting in a similar order of magnitude of uptake, although the two approaches are based on different assumptions. The results were compared to those obtained using a BRAMS cloud simulation based on a single-moment microphysical scheme instead of the two moment scheme. We found similar results with a slightly more important uptake when using the single-moment scheme which is related to slightly higher ice mixing ratios in this simulation. The way to introduce these results in the 3-D cloud model is discussed.

Domaines: Physique Atmosphérique et Océanique [physics.ao-ph]; Météorologie

V. Marécal, Michel Pirre, E. Riviere, N Pouvesle, J N Crowley, et al.. Modelling the reversible uptake of chemical species in the gas phase by ice particles formed in a convective cloud. Atmospheric Chemistry and Physics, 2010, 10 (10), pp.4977-5000. ⟨10.5194/acp-10-4977-2010⟩. ⟨insu-02878512⟩