HISTORICAL DATA OF SURFACE OZONE AT TROPICAL LATITUDES

During the last decades of the 19th century day-time and night-time da ta of surface ozone were collected by means of the Schonbein method at the coastal observatories of Rio de Janeiro, Brazil (23-degrees-S) an d Manila, Philippines (14-degrees-N) and at the mountain observatory o f Oaxaca de Juarez, Mexico (17-degrees-N, 1574 m a.s.l.). Taking into account the uncertainties of the method, daily readings have been conv erted to ppbv concentrations by a procedure already applied to other s eries of historical data. The calculated time-averaged values show tha t 1 century ago the ozone levels at tropical latitudes were considerab ly lower than at mid-latitudes of the northern and southern hemisphere s, similar to the present-day measurements.