Tropospheric trace gas slant column densities derived from MAX-DOAS measurements on pacific transit cruises of the German research vessel Sonne in 2019

Between January and July 2019 the German research vessel Sonne was on several cruises in the Pacific, crossing the ocean from Suva, Fiji to Manzanillo, Mexico in February (SO267-2) and from Vancouver, Canada to Singapore in June (SO268-3). A Multi Axis-Differential Optical Absorption Spectroscopy (MAX-DOAS) instrument was in operation outside the national exclusive economic zone (EEZ) regions allowing for profile measurements of trace gases and aerosol on the open seas under background conditions. Both transit cruises cover a wide range of marine biomes and climatic zones affecting the trace gas and particle composition of the atmosphere.

Ship measurements of Nitrogen Dioxide (NO₂) and Sulphur Dioxide (SO₂) are especially important for the validation of satellite measurements as the remote Pacific Ocean is typically used as a reference region. Off the coast of North America an enhanced signal of halogen species, i.e. bromine oxide (BrO) and iodine oxide (IO) was observed. The abundance of formaldehyde (HCHO) and its interrelation with the marine bio-activity could also be observed.