Tropopause and Cirrus Clouds Tops Heights

Cirrus clouds have recently garnered much attention due to their important role and impact on the atmospheric radiative balance. This stresses the need for active remote sensing such as lidar, whose capability to perceive high and optically thin cirrus makes it one of the most accurate systems for cirri study. The dynamic range of backscatter lidar signals enable to measure the altitude as well as the evolution of cirrus clouds in real time. By means of the retrievals profiles of the cirrus clouds parameters derived from lidar (light Detection and Ranging) system, particularly of those close to the upper troposphere, it is possible to analyze the evolution of tropopause layer using the top of cirrus clouds present as a tropopause tracer. A random selected dataset of 80 diurnal tropopause cirrus clouds collected during 2001-2006 were analyzed in order to estimate tropopause height and its temporal evolution with the altitude of the cirrus tops. We present here the preliminary results of the comparison between the cirrus top altitudes measured by lidar and the tropopause altitudes derived from rawinsonde data. Results show that cirrus tops can be viewed as tropopause tracers with an accuracy close to 1km.