  We investigate, through simulation, the evolution of polarization states
during atmospheric propagation of high power, ultrashort laser pulses. A
delayed rotational response model handling arbitrary, transverse polarization
couples both the amplitude and phase of the polarization states. We find that,
while circularly and linearly polarized pulses maintain their polarization,
elliptically polarized pulses become depolarized due to energy equilibration
between left and right circularly polarized states. The depolarization can be
detrimental to remote radiation generation schemes and obscures time-integrated
polarization measurements.
