The difference of vertical advection and convection process for chemistry species
The difference between advection and convection in Chemistry Transport models (CTMs) is a question of scale:


Advection is driven by winds that are provided by the meteorological input dataset. Thus, the wind is resolved in the meteorological data.
Convection is driven by sub grid processes (e.g. temperature gradients) and is paramterized in CTMs.


See for example:


Pleim, 2007a. doi: 10.1175/JAM2539.1
Pleim, 2007b. doi: 10.1175/JAM2534.1
Rasch et al., 1997. doi: 10.1029/97JD02087