L. Stefanutti1, V. Santacesaria1, A. Adriani2, F. Cairo2, G. Didonfranceso2, V. Mitev3, H. Flentje4 and C. Kiemle4

1Istituto di Ricerca sulle Onde Elettromagnetiche of CNR, via Pancaldo 21, 50127 Firenze, Italy
2Istituto di Fisica dell'Atmosfera-CNR, via del Fosso del Cavaliere, Roma, Italy
3Observatoire Neuchatel, Switzerland
4Deutsches Zentrum für Luft- und Raumfahrt (DLR), Oberpfaffenhofen, Germany

APE-THESO campaign was held from 15 February to 15 March 1999 from the Seychelles in the western Indian Ocean. The principal goal of the campaign was the study of the tropical upper troposphere and lower stratosphere in the tropical region. Two aircraft were used simultaneously in order to perform remote and in situ measurement. They were the high altitude research aircraft M-55 Geophysica, which can fly up to 21 km and the DLR Falcon. The scientific payload of the DLR Falcon consisted of the OLEX lidar and a suite of radiometers. OLEX, the DLR ozone Lidar experiment, is an airborne 4-wavelength lidar. The M-55 Geophysica scientific payload included among the others the following systems: ABLE a high-power lidar emitting at 532 and 355 nm, MAL a microjoule lidar emitting at 532 nm and MAS a miniaturised Aerosol Sampler operating like a backscattersonde. At altitudes between 380 and 410 K, thin clouds were observed almost during every flight. The role of these layers in the climate change is not yet clear. Furthermore a very cold temperature at the tropopause has been observed during the campaign and a detailed analysis of the relationship, in the tropical area, among tropopause, ozonopause and hygropause has been performed. During the campaign a tropical cyclone "Davina" was analysed by the two aircraft. The Falcon could fly directly into the eye of Davina and the M-55 Geophysica entered the cyclone in different areas, sampling directly clouds and trace gases present in Davina. Results from this flight will also be presented.