Observational ozone data over the global oceans and polar regions: The TOAR-II Oceans data set version 2024

We present the first comprehensive collection of ozone data over the oceans and the polar regions. The overall data set consists of 77 ship cruises/buoy-based observations and 48 aircraft-based campaigns. The data set, consisting of more than 630,000 independent ozone measurement data points covering the period from 1977 to 2022 and an altitude range from the surface to 5000 m (with a focus on the lowest 2000 m), allows systematic analyses of the spatio-temporal distribution and long-term trends over the defined 11 ocean/polar regions. The data sets from ships, buoys, and aircrafts are complemented with an ozonesonde data set from 29 launch sites or field campaigns, and by 21 non-polar and 17 polar ground-based stations data sets. The data were combined with information on how long the air masses have been over the oceans (LCL), based on backward trajectories. Here using the threshold of 72 hours or more (LCL >=72) is recommended to extract essentially oceanic observations. The ship/buoy- and aircraft-based data sets presented here will supplement the land-based ones in the TOAR-II database to provide a fully global assessment of tropospheric ozone.　See more at https://essd.copernicus.org/preprints/essd-2024-566/ (this URL will be changed after acceptance of discussion paper.)