A Novel Framework to Study Trace Gas Transport in Deep Convective Clouds

摘要

Deep convective clouds reach the upper troposphere (8–15 km height). In addition to moisture and aerosol particles, they can bring aerosol precursor gases and other reactive trace gases from the planetary boundary layer to the cloud top. In this paper, we present a method to estimate trace gas transport based on the analysis of individual air parcel trajectories. Large eddy simulation of an idealized deep convective cloud was used to provide realistic environmental input to a parcel model. For a buoyant parcel, we found that the trace gas transport approximately follows one out of three scenarios, determined by a combination of the equilibrium vapor pressure (containing information about water‐solubility and pure component saturation vapor pressure) and the enthalpy of vaporization. In one extreme, the trace gas will eventually be completely removed by precipitation. In the other extreme, there is almost no vapor condensation on hydrometeors and most of the gas is transported to the top of the cloud. The scenario in between these two extremes is also characterized by strong gas condensation, but a small fraction of the trace gas may still be transported aloft. This approach confirms previously suggested patterns of inert trace gas behavior in deep convective clouds, agrees with observational data, and allows estimating transport in analytically simple and computationally efficient way compared to explicit cloud‐resolving model calculations. Plain Language Summary Gas transport by deep convective clouds can impact many atmospheric processes including new particle formation, which increases the amount of aerosols in the upper troposphere (8–15 km altitude). In this paper, we suggest a method for calculating the amount of trace gas that can survive transport inside a deep convective cloud. The model is applied to an idealized cloud event, and the results show that among other parameters, transport strongly depends on the physical properties of the gas. The model framework allows us to identify boundaries of the main gas properties defining two extreme scenarios for the gas: full removal by precipitation or complete transport of the gas aloft.