[A-AS11] Atmospheric Chemistry

[AAS11-11] Observational ozone data over the global oceans and polar regions: The TOAR-II Oceans dataset version 2024 with contribution from Japan

*Yugo Kanaya¹, Roberto Sommariva^2,3, Alfonso Saiz-Lopez⁴, Andrea Mazzeo⁵, Matthew Rowlinson⁶, Katie Read⁶, Theodore K. Koenig⁷, Martin G. Schultz⁸, Kaori Kawana^9,10, Masatomo Fujiwara¹¹, Keiichi Sato¹², Junichi Kurokawa¹², Yoko Iwamoto¹³, Fumikazu Taketani¹, Hisahiro Takashima¹⁴, Takashi Sekiya¹ (1.Research Institute for Global Change, Japan Agency for Marine-Earth Science and Technology, 2.University of Birmingham, 3.University of Leicester, 4.CSIC, 5.Lancaster University, 6.University of York, 7.The Hong Kong University of Science and Technology, 8.Forschungszentrum Jülich GmbH, 9.FORTH/ICE-HT, 10.EPFL, 11.Hokkaido University, 12.Asia Center for Air Pollution Research, 13.Hiroshima University, 14.Fukuoka University)

Keywords:Tropospheric ozone, Marine atmosphere, Global observations, Halogen chemistry

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 produced under the TOAR-II (Tropospheric Ozone Assessment Report Phase II) activity and highlight data contributed from Japan. 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, enabling studies of processes with statistical robustness and coverage. We will discuss seasonality and long-term trends for the defined 11 global regions and comparisons with global model simulations including those from CHASER.

Additional Team Members:
James E. Johnson, Aurélie Colomb, Pierre Tulet, Suzie Molloy, Ian E. Galbally, Rainer Volkamer, Anoop Mahajan, John W. Halfacre, Paul B. Shepson, Julia Schmale, Hélène Angot, Byron Blomquist, Matthew D. Shupe, Detlev Helmig, Junsu Gil, Meehye Lee, Sean C. Coburn, Ivan Ortega, Gao Chen, James Lee, Kenneth C. Aikin, David D. Parrish, John S. Holloway, Thomas B. Ryerson, Ilana B. Pollack, Eric J. Williams, Brian M. Lerner, Andrew J. Weinheimer, Teresa Campos, Frank M. Flocke, J. Ryan Spackman, Ilann Bourgeois, Jeff Peischl, Chelsea R. Thompson, Ralf M. Staebler, Amir A. Aliabadi, Wanmin Gong, Roeland Van Malderen, Anne M. Thompson, Ryan M. Stauffer, Debra E. Kollonige, Juan Carlos Gómez Martin, Monica Navarro Comas, Marios Panagi, Alba Badia, Maria Russo, Fernando Igresias-Suarez, Ulas Im, Mariano Mertens