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

Abstract

Abstract. 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 convective 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 singlemoment 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.

Stratospheric water vapour budget and convection overshooting the tropopause: modelling study from SCOUT-AMMA

“…This might be due to the use in our study of a double moment microphysical scheme and a budget calculation time step of 5 min instead of a single moment scheme. Marécal et al (2010) have shown in a convective cell simulation that the amount of ice of the cell core was higher for a single moment microphysical scheme than for a similar simulation using a double moment microphysical scheme. Another possible explanation is a difference in the vertical velocities computed in each simulation.…”

The Chemistry CATT-BRAMS model (CCATT-BRAMS 4.5): a regional atmospheric model system for integrated air quality and weather forecasting and research

“…CATT-BRAMS has been used operationally by the Brazilian Center for Weather Prediction and Climate Studies (CPTEC, http://meioambiente. cptec.inpe.br) since 2003 and as a research tool by several groups around the world (e.g., Marécal et al, 2007Marécal et al, , 2010Longo et al, 2009;Landulfo et al, 2009;Arteta et al, 2009a, b;Liu et al, 2010;Ramos, 2006;Gevaerd, 2005;Herrmann, 2004;Gácita, 2011;Munchow, 2008;Hernández, 2010;Alonso, 2011), which demonstrates its good performance.…”

Collision dynamics and uptake of water on alcohol-covered ice

“…Such particle and molecular scale processes are poorly integrated into larger cloud and climate scale models, that generally have poorly constrained ice surface interaction schemes (Marécal et al, 2010). Furthermore the bundling of complex microphysical chemistry into parameters like surface tension can result in errors from oversimplification (Prisle et al, 2012).…”