Extended high altitude cirrus were observed during a cruise of the German research vessel POLARSTERN by a Mobile Aerosol Raman Lidar (MARL). The clouds occurred between 8°S and 12°N along 22°W during 34 h of observations from May 30th to June 3rd 2000. The altitude, vertical and optical depth at 532 nm and 355 nm of the cloud are determined from the Lidar data, as well as depolarisation characteristics at both this wavelength. The clouds appear in an altitude around 16 km and are between 0.5 and 2 km thick. The optical depth at 532 nm lies between 0.01 an 0.1. The data of radiosondes launched aboard POLARSTERN on a daily basis allow the determination of the temperatures, humidity and airmass of the clouds. Obviously the high-altitude cirrus appear in two distinct layers of purely tropospheric air separeted by wind direction and speed. The poster will discuss the lidar observations of the tropical cirrus in respect to this dynamical situation. Comparison of the depolarisation behavior measured for the tropical clouds with those of midlatitudinal cirrus allow some insight in the particle characterisitics.