Abstract

The major goal of the Tropospheric Ozone Production about the Spring Equinox (TOPSE) field campaign (2000) was to study the cause of the spring Arctic ozone maximum in the free troposphere. Sources for tropospheric ozone (O₃) are transport of O₃ from the stratosphere and in-situ photochemical pro... Show moreThe major goal of the Tropospheric Ozone Production about the Spring Equinox (TOPSE) field campaign (2000) was to study the cause of the spring Arctic ozone maximum in the free troposphere. Sources for tropospheric ozone (O₃) are transport of O₃ from the stratosphere and in-situ photochemical production. Peroxyacetyl Nitrate (PAN) can be used as a tropospheric indicator, since it is formed photochemically along with ozone and there are no sources of PAN in the stratosphere. This study focused on examining the evolution of O₃ and PAN along air mass trajectories, calculated using the HYSPLIT© model, from the source region of the air mass to the point of observation in the Arctic on board the C-130 aircraft. By step-wise “backwards” modeling along sections of the air mass trajectory, NCAR’s Master Mechanism could be utilized to estimate initial conditions in the source area, which were within the expectations for a typical urban air mass. The Master Mechanism was then used to model the photochemistry along the trajectory forward to the point of observation. The observed O₃ to PAN ratio and the modeled ratio were within 5%. Thus, it was concluded that the modeling approach was successful. Based on the evolution of the O₃ to PAN ratio from a city mix at the source to a value very close to that observed, it was also concluded that no stratospheric O₃ input was needed for the trajectory case studied. The comparison of more trajectories and source regions will help to further constrain the Arctic ozone budget. Show less