Ten years (1986-95) of global analyses from the European Centre for Medium-Range Weather Forecasts are used to investigate the temporal and spatial distributions of Rossby wave breaking (RWB) at 350 K along the tropopause, herein defined by the Ϯ1.5 potential vorticity (PV) unit (10 Ϫ6 K m 2 s Ϫ1 kg Ϫ1) contours. Though many studies acknowledge RWB as an important contributor to the complex of mixing processes in the atmosphere, there exists no prior climatological study of its distribution near the tropopause. As in previous studies, RWB is identified in the global analyses by southward directed PV gradients. At 350 K, RWB along the tropopause occurs preferentially during summer over the midoceans, in relative proximity to the planetary-scale high pressure systems in the subtropics. Isentropic trajectories at 350 K show that outflow from the tops of these subtropical highs directly participates in RWB over the adjacent, downstream oceanic regions. Two regions are highlighted in this study: the North Pacific during boreal summer and the South Atlantic during austral summer. Synoptic maps of breaking Rossby waves in these regions are provided to reveal the acute tropopause folding in the meridional plane, which characteristically accompanies RWB. The rich interaction between the tropical flow and the extratropical westerly current exhibited by these cases suggests that the subtropical highs serve as important agents in the coupling between the tropical troposphere and the extratropical stratosphere. As expected from theoretical considerations, the locations where RWB occurs most frequently, known as ''surf zones,'' are shown to coexist with regionally weak time-mean wind speeds and horizontal gradients of PV at 350 K.

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We describe the construction of a continuous 38-year record of stratospheric aerosol optical properties. The Global Space-based Stratospheric Aerosol Climatology, or GloSSAC, provided the input data to the 15 construction of the Climate Model Intercomparison Project stratospheric aerosol forcing data set (1979 to 2014) and we have extended it through 2016 following an identical process. GloSSAC focuses on the Stratospheric Aerosol and Gas Experiment (SAGE) series of instruments through mid-2005 and on the Optical Spectrograph and InfraRed Imager System (OSIRIS) and the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) data thereafter. We also use data from other space 20 instruments and from ground-based, air and balloon borne instruments to fill in key gaps in the data set. The end result is a global and gap-free data set focused on aerosol extinction coefficient at 525 and 1020 nm and other parameters on an 'as available' basis. For the primary data sets, we developed a new method for filling the post-Pinatubo eruption data gap for 1991 to 1993 based on data from the Cryogenic Limb Array Etalon Spectrometer. In addition, we developed a new method for populating wintertime high 25 latitudes during the SAGE period employing a latitude-equivalent latitude conversion process that greatly improves the depiction of aerosol at high latitudes compared to earlier similar efforts. We report data in the troposphere only when and where it is available. This is primarily during the SAGE II period except the most enhanced part of the Pinatubo period. It is likely that the upper troposphere during Pinatubo was greatly enhanced over non-volcanic periods and that domain remains substantially under characterized. 30 We note that aerosol levels during the OSIRIS/CALIPSO period in the lower stratosphere at mid and high latitudes is routinely higher than what we observed during the SAGE II period. While this period had nearly continuous low-level volcanic activity, it is possible that the enhancement in part reflects deficiencies in the data set. We also expended substantial effort to quality assess the data set and the product is by far the best we have produced. GloSSAC version 1.0 is available in netCDF format at the NASA Atmospheric 35 Data Center at https://eosweb.larc.nasa.gov/. GloSSAC users should cite this paper and the data set DOI

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