  Tropospheric ozone (O3T) is a secondary pollutant whose formation involved
primarily solar radiation, NOx and volatile organic compounds. The North of the
Buenos Aires Province has great agricultural-industrial activity; therefore,
O3T study is an important issue in the area. In this paper, we present the
first results tend to estimate and characterize O3T in San Nicol\'as de los
Arroyos, North of Buenos Aires. Due to a lack of in situ data, we analyse the
observations of the instrument OMI (Ozone Monitoring Instrument) of land remote
sensing satellite AURA (GSFC/NASA). The data cover the years 2004-2013.
Applying the multitaper technique (MTM), very suitable for short and noisy data
series, spectral analysis is performed on a grid corresponding 1{\deg} in
latitude by 1.5{\deg} in longitude, centred South of the Province of Santa Fe.
The most remarkable result is the emergence of a significant peak (95%) of four
months cycle. To test the validity of this signal in San Nicol\'as, daily solar
radiation data (Q) were analysed in the area. The application of MTM to the
daily values of Q, yields a spectral peak of 120 days. It is concluded that
atmospheric opacity on the site has four months variations that modify the
solar radiation at the troposphere, and consequently, the production rate of
O3T. Evidence that these variations are due to teleconnection process
originated in the Maritime Continent are presented.
