Surface ozone measurements in the Venezuelan tropical savannah

A one-year set of surface ozone measurements in a four-station network located in the Venezuelan savannah is reported. The diurnal ozone variation is typical of continental stations with a maximum in the afternoon, when vertical turbulent mixing is strongest. The annual O₃ average concentration, based on the monthly averages of daily maxima, was 17±2 ppb, which is in good agreement with values reported for similar latitudes. The boundary-layer ozone levels did not fall below 8 ppb, in contrast with previous sporadic measurements made in tropical latitudes. No evidence was found that mesoscale O₃ downdrafts in the ITCZ in the South American continent are an important source of surface ozone. Finally, it is suggested that the relatively high ozone levels observed at the end of the dry season are probably of photochemical origin.