Inter-hemispheric Tropospheric Vertical Distribution of Ozone Over the Atlantic Ocean: Multi-year assessment from shipboard observations during the NOAA AEROSE II –AEROSE VII Campaigns

The role of ozone in the troposphere is of utmost importance as it can affect atmospheric composition and radiative properties. Ozone (O3) is the primary source of hydroxyl radicals, which in turn are responsible to initiate most of the oxidation processes in the atmosphere. In the upper troposphere, ozone is a greenhouse gas that plays a key role in radiative forcing and potential climate change [Wang et al., 1980, 1993; Hansen et al., 2002, Thompson et al., 2002]. Previous studies have shown the significance of gravity and Rossby wave activity in the formation and transport of ozone and other constituents, due to vertical displacement and quasi-horizontal transport of material surfaces, respectively [Danielsen et al., 1991; Reid and Vaughan, 1991; Tsuda et al., 1994; Teitelbaum et al.,1996; Pierce and Grant, 1998; Grant et al., 1998; Fujiwara et al.,1998, Stone, 2006 and Thompson et al., 2007, 2011]. Based on this approach, Thompson et al. (2007, 2011) proposes 4 major dynamical ozone formation mechanisms responsible for the total tropospheric budget: stratospheric-tropospheric interactions, boundary layer processes, advection of pollutants and regional convection and lightning. Obtaining quantitative approximations of the contribution of each process towards the total tropospheric ozone budget is not known accurately and it is still an area of ongoing research, due to the extreme limitations in satellite retrievals and frequency of balloon-borne ozone measurements, especially over remote areas like the ocean.

Despite the logistical and opportunistic limitations in obtaining ozonesonde records, we describe an unprecedented data set acquired from oceanographic intensive observation periods (IOP) conducted onboard the NOAA Ship Ronald H. Brown, during seven years (2006-2011) of the NOAA Aerosols and Ocean Science Expeditions (AEROSE). A composite of well-resolved and accurate tropospheric profiles retrieved from daily ozonesondes, launched along latitudes between 33N to 34 S; aim to describe the Atlantic Ocean ozone geographical and vertical distribution during boreal Spring and Summer months. Laminae obtained applying the Pierce-Teitelbaum (PT) method are coupled to gravity waves (GW) and Rossby waves (RW). The ozone records are complemented with other RAOB parameters, ECMWF and NOAA NCEP meteorological and backtrajectory re/analysis and a myriad of in-situ and remote-sensing measurements collected daily during every cruise. Furthermore, we highlight ozone distribution patterns as a result of stratospheric folding events from storms and cut-off lows systems, effect of precursors from biomass burning regions and transport from continental airmasses and polluted areas, interactions with regions of deep convection (e.g. ITZC), boundary layer dynamics, possible enhancement by mineral aerosols and others. Finally we strive to address the contribution from each of the aforementioned mechanisms to the total tropospheric ozone budget over the tropical Atlantic.