  The Radiation Assessment Detector (RAD), on board Mars Science Laboratory's
(MSL) rover Curiosity, measures the {energy spectra} of both energetic charged
and neutral particles along with the radiation dose rate at the surface of
Mars. With these first-ever measurements on the Martian surface, RAD observed
several effects influencing the galactic cosmic ray (GCR) induced surface
radiation dose concurrently: [a] short-term diurnal variations of the Martian
atmospheric pressure caused by daily thermal tides, [b] long-term seasonal
pressure changes in the Martian atmosphere, and [c] the modulation of the
primary GCR flux by the heliospheric magnetic field, which correlates with
long-term solar activity and the rotation of the Sun. The RAD surface dose
measurements, along with the surface pressure data and the solar modulation
factor, are analysed and fitted to empirical models which quantitatively
demonstrate} how the long-term influences ([b] and [c]) are related to the
measured dose rates. {Correspondingly we can estimate dose rate and dose
equivalents under different solar modulations and different atmospheric
conditions, thus allowing empirical predictions of the Martian surface
radiation environment.
