Observational ozone data over the global oceans and polar regions: The TOAR-II Oceans data set version 2024
Authors: Kanaya Yugo , Sommariva Roberto , Saiz-Lopez Alfonso , Mazzeo Andrea , Koenig Theodore K. , Kawana Kaori , Johnson James E. , Colomb Aurélie , Tulet Pierre , Molloy Suzie , Galbally Ian E. , Volkamer Rainer , Mahajan Anoop , Halfacre John W. , Shepson Paul B. , Schmale Julia , Angot Hélène , Blomquist Byron , Shupe Matthew D. , Helmig Detlev , Gil Junsu , Lee Meehye , Coburn Sean C. , Ortega Ivan , Chen Gao , Lee James , Aikin Kenneth C. , Parrish David D. , Holloway John S. , Ryerson Thomas B. , Pollack Ilana B. , Williams Eric J. , Lerner Brian M. , Weinheimer Andrew J. , Campos Teresa , Flocke Frank M. , Spackman J. Ryan , Bourgeois Ilann , Peischl Jeff , Thompson Chelsea R. , Staebler Ralf M. , Aliabadi Amir A. , Gong Wanmin , Van Malderen Roeland , Thompson Anne M. , Stauffer Ryan M. , Kollonige Debra E. , Gómez Martin Juan Carlos , Fujiwara Masatomo , Read Katie , Rowlinson Matthew , Sato Keiichi , Kurokawa Junichi , Iwamoto Yoko , Taketani Fumikazu , Takashima Hisahiro , Navarro Comas Monica , Panagi Marios , Schultz Martin G. 
Published: February 2025

Abstract. Studying tropospheric ozone over the remote areas of the planet, such as the open oceans and the polar regions, is crucial to understand the role of ozone as a global climate forcer and regulator of atmospheric oxidative capacity. A focus on the pristine oceanic and polar regions complements the available land-based data sets and provides insights into key photochemical and depositional loss processes that control the concentrations, spatio-temporal variability of ozone, and the physico-chemical mechanisms driving these patterns. However, an assessment of the role of ozone over the oceanic and polar regions has been hampered by a lack of comprehensive observational data sets. Here, 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 filtered by using backward trajectories calculated with the HYSPLIT model from the individual observation points to extract essentially oceanic observations, defined as air masses that have travelled over oceans for 72 hours or more, which were further tested with the coincident Radon observations. The oceanic and polar data thus selected showed typically flat diurnal patterns at high latitudes and daytime decreases (11–16 %) at low latitudes, indicating the adequacy of the data collection and processing procedures, as well as the potential for further studies of processes with statistical robustness and coverage. 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.