  This study present a comparison of lidar observations of midlatitude cirrus
clouds over the SIRTA observatory between 2002 and 2006 with multiple
tropopauses (MT) retrieved from radiosounding temperature profiles. The
temporal variability of MT properties (frequency, thickness) are discussed.
Results show a marked annual cycle, with MT frequency reaching its lowest point
in May (~18% occurrence of MT) and slowly rising to more than 40% in DJF. The
average thickness of the MT also follows an annual cycle, going from less than
1 km in spring to 1.5 km in late autumn. Comparison with lidar observations
show that cirrus clouds show a preference for being located close below the 1st
tropopause. When the cloud top is above the 1st tropopause (7% of
observations), in 20% of cases the cloud base is above it as well, resulting in
a cirrus cloud "sandwiched" between the two tropopauses. Compared to the
general distribution of cirrus, cross-tropopause cirrus show a higher frequency
of large optical depths, while inter-tropopause cirrus show almost exclusively
low optical depths (Tau < 0.03 in 90% of cases) typical of subvisible clouds.
Results suggest the occurrence of inter-tropopause cirrus clouds is correlated
with the frequency of multiple tropopauses.
