  An accurate knowledge of the fluorescence yield and its dependence on
atmospheric properties such as pressure, temperature or humidity is essential
to obtain a reliable measurement of the primary energy of cosmic rays in
experiments using the fluorescence technique. In this work, several sets of
fluorescence yield data (i.e. absolute value and quenching parameters) are
described and compared. A simple procedure to study the effect of the assumed
fluorescence yield on the reconstructed shower parameters (energy and shower
maximum depth) as a function of the primary features has been developed. As an
application, the effect of water vapor and temperature dependence of the
collisional cross section on the fluorescence yield and its impact on the
reconstruction of primary energy and shower maximum depth has been studied.
