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CLIMATOLOGICAL ANALYSIS OF OZONE AND RADIATION
MEASUREMENTS AT A BACKGROUND SITE IN THE SOUTHERN
HEMISPHERE SUBTROPICS Cerro Tololo 30ºS,70ºW,
2200 m.a.s.l.
A.M. Córdova 1, Melitta Fiebig-Wittmaack1,2,3,
J. Quintana4, L. Valle 4 and G. Torres
4   1.Centro de Estudios Avanzados en Zonas
Áridas (CEAZA) , Benavente 980, Casilla 599, La
Serena, Chile. acordova_at_inia.cl 2. Departamento
de Matemática, Universidad de La Serena,
Chile. 3. Centro de Investigación Atmosférica ,
La Serena (CIALS), Chile 4. Dirección
Meteorológica de Chile  
INTRODUCTION Several chemical and dynamical
processes regulate surface ozone (O3)
concentrations. Measurements of ultraviolet
spectral irradiance, tropospheric ozone and
meteorological parameters (temperature, wind
speed and direction, relative humidity, etc)
have been performed simultaneously at Cerro
Tololo (CT) (30º 10S, 70º 48O, 2200 m.a.s.l.)
by the Chilean Weather Office as part of the
Global Atmospheric Watch (GAW) program of the
World Meteorological Organization (WMO) since
November 1995.

• RESULTS AND DISCUSSION
• The ozone concentrations ranged from 11 ppb to 60
  ppb. Results showed that O3 concentrations
  measured during summer (DJF) were lower than
  spring season (SON) at Cerro Tololo.
• The average ozone concentrations do not show
  significant diurnal cycle at this site. The ozone
  concentrations during summer and autumn are 27
  ppb (SD ? 5.2 ppb). The increase of ozone
  concentrations are observed during of month of
  spring (SON) with the maximum concentration of 60
  ppb.
• The maximum solar radiation decrease from 1100
  Wm-2 in summer (DJF) to 620 Wm-2 in winter
  (JJA).
• Ozone concentrations do not show a positive
  correlation with solar and UV-B radiation. This
  indicates that in situ photochemical production
  is not the driving process at this site. In fact
  that, previous work suggest that synoptical
  features linked with stratosphere-troposphere
  exchange play a significant role in explaining
  the spring maximum and the sudden increases in
  ozone mixing ratios observed at Cerro Tololo.
• The index UV is higher than 11 (exposure category
  extreme) from November to February.
• Ozone concentrations do not show correlations
  with wind speed and wind direction at surface.
  The wind direction is principally from Northeast
  during all year.
• A inspection of the data do not shows temporal
  trends and ENOS do not influence significantly
  the ozone concentrations at this site. On the
  other hand, no significant change of O3 was
  observed in association to the El Niño 1997 and
  La Niña 1998.

 
Acknowledgements Dirección Meteorólogica de
Chile (DMC), Chilean Research Council
(CONICYT-FONDECYT 1030809).