Abstract. Ground-based high spectral resolution Fouriertransform infrared (FTIR) solar absorption spectroscopy is a powerful remote sensing technique to obtain information on the total column abundances and on the vertical distribution of various constituents in the atmosphere. This work presents results from two FTIR measurement campaigns in 2002 and 2004, held at Ile de La Réunion (21 • S, 55 • E). These campaigns represent the first FTIR observations carried out at a southern (sub)tropical site. They serve the initiation of regular, long-term FTIR monitoring at this site in the near future. To demonstrate the capabilities of the FTIR measurements at this location for tropospheric and stratospheric monitoring, a detailed report is given on the retrieval strategy, information content and corresponding full error budget evaluation for ozone (O 3 ), methane (CH 4 ), nitrous oxide (N 2 O), carbon monoxide (CO), ethane (C 2 H 6 ), hydrogen chloride (HCl), hydrogen fluoride (HF) and nitric acid (HNO 3 ) total and partial column retrievals. Moreover, we have made a thorough comparison of the capabilities at sea level altitude (St.-Denis) and at 2200 m a.s.l. (Maïdo). It is proved that the performances of the technique are such that the atmospheric variability can be observed, at both locations and in distinctCorrespondence to: C. Senten (cindy.senten@aeronomie.be) altitude layers. Comparisons with literature and with correlative data from ozone sonde and satellite (i.e., ACE-FTS, HALOE and MOPITT) measurements are given to confirm the results. Despite the short time series available at present, we have been able to detect the seasonal variation of CO in the biomass burning season, as well as the impact of particular biomass burning events in Africa and Madagascar on the atmospheric composition above Ile de La Réunion. We also show that differential measurements between St.-Denis and Maïdo provide useful information about the concentrations in the boundary layer.

International audienceThe study of the variability of stratospheric aerosols and the transfer between the diierent atmospheric regions improves our understanding of dynamical processes involved in isentropic exchanges that take place episodically in the lower stratosphere through the subtropical barrier. One useful approach consists in combining in situ ground-based and global measurements with numerical analyses. The present paper reports on a case study of a horizontal transfer evidenced ÿrst by Rayleigh–Mie LIDAR observations over Durban (29:9 • S, 31:0 • E, South Africa). Additional data from MeteoSat and SAGE-2 experiments, and from ECMWF meteorological analysis have been used in this study. Contour advection maps of potential vorticity from the MIMOSA model derived from ECMWF ÿelds, were also used. By the end of April, 1999, LIDAR observations showed that aerosol extinction, in the lower stratosphere, has increased signiÿcantly and abnormally in comparison with other LIDAR and SAGE-2 observations recorded for the period from April 20 to June 14, 1999. The dynamical context of this case study seems to exclude the possibility of a local innuence of the subtropical jet stream or tropical convection, which could inject air masses enriched with tropospheric aerosols into the stratosphere. On the contrary, a high-resolution model based on PV advection calculations and ECMWF meteorological analyses shows that air masses are isentropically advected from the equatorial zone close to Brazil. They cross the southern barrier of the tropical reservoir due to laminae stretching and reach the southern subcontinent of Africa 5–6 days later

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The time and spatial evolution of gravity‐wave characteristics are analysed using wavelets in vertical profiles of temperature and winds at Tromelin Island (15.53°S, 54.31°E) during the passage of the intense tropical cyclone Hudah in the Southern Ocean Indian Basin in 2000. Inertia‐gravity waves were observed in the upper troposphere and the lower stratosphere with dominant vertical wavelengths of 1.5–3 km, horizontal wavelengths <2000 km and periods of 0.6–1.6 days. Large amounts of gravity‐wave energy were detected during landfalls of the tropical cyclone. The distribution of total energy indicates that mesoscale convective structures such as tropical cyclones are important gravity‐wave sources in the upper troposphere.

Rayleigh-Mie lidar measurements of stratospheric temperature and aerosol profiles have been carried out at Reunion Island (southern tropics) since 1993. Since June 1998, an operational extension of the system is permitting additional measurements of tropospheric ozone to be made by differential absorption lidar. The emission wavelengths (289 and 316 nm) are obtained by stimulated Raman shifting of the fourth harmonic of a Nd:YAG laser in a high-pressure deuterium cell. A mosaic of four parabolic mirrors collects the backscattered signal, and the transmission is processed by the multiple fiber collector method. The altitude range of ozone profiles obtained with this system is 3¿17 km. Technical details of this lidar system working in the southern tropics, comparisons of ozone lidar profiles with radiosondes, and scientific perspectives are presented. The significant lack of tropospheric ozone measurements in the tropical and equatorial regions, the particular scientific interest in these regions, and the altitude range of the ozone measurements to 16¿17 km make this lidar supplement useful and its adaptation technically conceivable at many Rayleigh-Mie lidar stations.