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Surface observations of ozone mixing ratio were conducted at the Henties Bay Aerosol Observatory (HBAO; http://www.hbao.cnrs.fr/), a regional station in the Global Atmosphere Watch (GAW) programme of the World Meteorological Organization (WMO). The research centre is located on the Sam Nujoma Marine and Coastal Resources Research Centre (SANUMARC) of the University of Namibia in Henties Bay. Henties Bay is a small town in an arid environment with no vegetation, no industrial activity and very little traffic. Energy usage is predominantly a mix of electricity and gas, with some solid fuel combustion (wood) due to low availability. The monitoring site, situated on the university campus, is located on the coast approximately 100 m from the shoreline. To the east are the Namibian gravel plains, 3 km to the south of the campus is the town of Henties Bay and to the north is the Omaruru riverbed (river mouth approximately 100 m from SANUMARC). The population of Henties Bay ranges between 4600 and 6000 inhabitants, according to the Namibia Population and Housing Census Main Report. The ozone mixing ratio (ppb) was measured by two instruments. From 23/07/2012 to 15/09/2017: O342 UV photometric monitor (Environnement S.A., France). From 15/09/2017 to 22/03/2019: APOA-370 analyser (HORIBA, Japan). Both instruments (continuously monitors atmospheric ozone concentrations using a cross flow modulated ultraviolet absorption method. They have detection limit=0.5 ppb, accuracy=1 ppb. The instruments operated at approximately 0.7 L min-1 through a Teflon tube (outside diameter 6 mm) using an internal pump. Data are acquired at 5-minute time resolution. Concentrations were inspected manually to eliminate excessive noise and erratic events.