Quantitative Analysis of Arctic Ozone Loss Using EOS MLS and SD-WACCM

Arctic ozone loss rates are quantitatively investigated using SD-WACCM (Specified Dynamics Whole Atmosphere Community Climate Model) initialized with EOS MLS (Earth Observing System Microwave Limb Sounder) ozone data. EOS MLS onboard the Aura satellite provides well-proven data since August 2004 and is thus appropriate for monitoring the evolution of measured atmospheric constituents and for initializing and validating models. SD-WACCM is nudged daily by GEOS (Goddard Earth Observing System) horizontal winds and temperature reanalysis data in order to simulate realistic dynamical behavior. Ozone loss rates due to heterogeneous chemistry in Arctic winters are investigated by applying the passive ozone method. With this method two model simulations are compared. The first includes complete gas-phase and heterogeneous chemistry, while in the second simulation heterogeneous chemistry, in particular surface reactions on polar stratospheric clouds (PSCs), is turned off. Ozone in the first simulation is referred to as “active” ozone, whereas ozone in the second simulation is referred to as a “pseudo-passive” tracer. A comparison of active ozone to the pseudo-passive tracer enables quantification of ozone loss due to heterogeneous chemical processes, presuming the modeled ozone is well validated and heterogeneous chemistry is comprehensively implemented in the model. Repetition of the described method for available Arctic winter seasons allows for a quantitative trend analysis over the past 5 years in order to show the evolution of anthropogenic contributions to ozone loss in the Arctic.