Chemistry and Mixing in the Convective Boundary Layer: Insights from Mathematics and Computation

Chemistry in the convective boundary layer (CBL) involves multiple reacting species of different origin (biogenic, anthropogenic) generated by surface sources and brought down from the overlying free troposphere. Their dynamics is driven by coupled processes of chemical kinetics and turbulent (CBL) mixing. One approach to modeling such systems assumes a "well mixed" state (box chemistry) and concentrates on reactants and their pathways. On the opposite extreme are (computationally intensive) LES-based schemes for passive or reactive species. While LES models can naturally accommodate spatial heterogeneity (species distribution and convective mixing), they have limitations, particularly near the surface layer where concentrations and the mixing process change rapidly with height. Here we propose an intermediate approach based on parameterized CBL (vertical) mixing. Such a scheme offers several advantages: in simple cases it can be analyzed mathematically; in other (more involved) cases it requires only modest computational resources (Mathematica or Matlab) for efficient implementation and numeric experiments. We outline the general scheme and apply it to several cases, including the NOx-Ozone triad, and more general systems that include "organic chemistry" (VOCs).