Measurements and modeling of the interhemispheric differences of atmospheric chlorinated very short-lived substances

We tagged regional source emissions of CH2Cl2 and C2Cl4 in the model and found that Asian emissions dominate the global distributions of these species both at the surface (950 hPa) and at high altitudes (150 hPa). Overall, our results confirm relatively high mixing ratios of Cl-VSLS in the UTLS region and show that the CESM model does a reasonable job of simulating their global abundance but we also note the uncertainties with Cl-VSLS emissions and active chlorine sources in the model.

These findings will be used to validate future emission inventories and to investigate the fast convective transport of Cl-VSLS to the UTLS region and their impact on stratospheric ozone. Plain Language

Summary

The Montreal Protocol has phased down the consumption and production of a large number of halogenated compounds such as CFCs, due to their potential for depleting stratospheric ozone. However, the consumption and production of a class of halogenated compounds, referred to as very short-lived substances (VSLS), is not controlled by the Montreal Protocol. Evidence is growing that globally increasing emissions of human-produced chlorinated VSLS (Cl-VSLS) could have an impact on stratospheric ozone.

In this work, we present comprehensive aircraft measurements coupled to modeling of the major speciated Cl-VSLS that show their present day global distribution at altitudes up to 12 km and also show that Asian emissions are responsible for the majority of observed Cl-VSLS throughout the troposphere including the Southern Hemisphere.