Compare the four Sulfur Dioxide layers to see at which level of the vertical column density where Sulfur Dioxide levels were the highest by clicking on the "eye" icon next to each layer. The planetary boundary layer corresponds to the center of mass altitude (CMA) of 0.9 km. The lower troposphere corresponds to CMA of 3 km, middle troposphere corresponds to CMA of 8 km, the upper troposphere and stratosphere corresponds to CMA of 18 km.