After comparing each layer, it appears the middle troposphere layer shows the highest levels of sulfur dioxide in the center of the plume - this layer is recommended for use in studies on moderate eruptions and long-range transport of sulfur pollution. The planetary boundary layer is often used in studies on near-surface pollution, the lower troposphere can be used to study degassing from volcanic sources and, the upper troposphere and stratosphere is recommended for use in studies on explosive volcanic eruptions.