Tropospheric ozone trends at Mauna Loa Observatory tied to decadal climate variability

The GFDL AM3 model is the atmospheric component of a global coupled atmosphere-ocean-land-sea ice model (CM3) [Donner et al., 2011; Griffies et al., 2011; John et al., 2012]. The unique feature of interactive stratosphere-troposphere chemistry and dynamics [Naik et al., 2013; Austin et al., 2013] distinguishes the GFDL AM3 model from most current generation global and regional tropospheric chemical transport models. Table S1 provides a summary of the GFDL AM3 model simulations analyzed here. We conduct two types of hindcast simulations at ~200x200 km horizontal resolution: Nudged to reanalysis winds or driven by the observed evolution of sea surface temperatures (SSTs) and atmospheric radiative forcing agents (“AMIP” simulations). The BASE, FIXEMIS, and IAVFIRE with modified emissions of ozone and aerosol precursors are nudged to NCEP-NCAR reanalysis winds over 1980 to 2012. We implement a pressure-dependent nudging technique, relaxing the model to NCEP zonal and meridional wind with a time scale of 6 hour in the surface level, but weakening the nudging strength with decreasing pressure (e.g., relaxing with a time scale of ~60 hours by 100 hPa and ~600 hours by 10 hPa). Tropospheric ozone trends at Mauna Loa Observat ry tied to decadal climate vari bility SUPPLEMENTARY INFORMATION DOI: 10.1038/NGEO2066