The influence of the tropical Atlantic Ocean over the climate of
Europe, Africa and America is well known today. However,
several questions about high-frequency processes in this region
remain open. This thesis addresses the characterisation of the
diurnal and other short timescale variability of the meteo-ocean
variables measured in the tropical Atlantic Ocean by the PIRATA
array, as well as derived air-sea heat fluxes. By combining the
complementarity and mitigating the disadvantages of using the
high temporal resolution of in situ data in conjunction with the
excellent spatial coverage of satellite based data, this work also
aims to investigate the characteristics of the Tropical Instability
Waves in the tropical Atlantic. The satellite data validation
process used in this study assesses each of the buoys
individually, to take into account possible regional biases.

A complete picture of the mean diurnal cycle and the seasonal
variability of the diurnal signal is performed for the first time for
the whole tropical Atlantic basin. The SST diurnal signal presents
strong characteristics during the respective summer in both
hemispheres. However, through the wavelet technique used in
this analysis, a significant diurnal signal at the equator could be
noticed during the second half of each year, indicating a
possible modulation of the diurnal signal by processes with
different timescales. It is suggested that Tropical Instability
Waves could be one of these processes. The results presented
here show that the TIW clearly vary their position and time of
activity, depending on the degree of development of the
equatorial cold tongue. The most active year analysed in this
study was 2001, when the spectral characteristics could be
observed as far north as 4N. The imprints of the TIW are well
marked in the wind fields, showing that clearly there are coupled
mechanisms associated with the TIW. Moreover, this study
confirms that a coupling mechanism suggested for the Pacific
Ocean is also applicable to the tropical Atlantic basin. The
measurements made by the TMI sensor, in conjunction with the
Qscat wind data showed that the atmospheric fields are highly
correlated with the SST fields at the timescale associated with
the TIW.

The analysis of the cross-scale relationship suggests that the
passage of instability waves might affect the diurnal amplitude
of SST, skin-SST and latent heat flux. The mechanisms that
interact on the eastern and western side of the equatorial
Atlantic tend to be distinct, especially due to the local
oceanographic and meteorological conditions, and due to the
different level of TIW activity.