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The Stratospheric Regular Sounding project was planned to measure regularly the vertical profiles of several tracers like ozone, water vapor, NOx, ClOx and BrOx radicals, aerosol, pressure and temperature, at three latitudes, to discriminate between the transport and photochemical terms which control their distribution. As part of this project, the "Istituto di Fisica dell'Atmosfera" launched nine laser backscattersondes (LABS) on board stratospheric balloons to make observations of background aerosol and PSCs. LABS was launched with an optical particle counter operated by the University of Wyoming. Observations have been performed in the arctic, mid-latitudes and tropical regions in different seasons. Polar stratospheric clouds have been observed in areas inside and outside the polar vortex edge. A background aerosol was observed both in mid-latitudes and in arctic regions with a backscattering ratio of 1.2 at 692 nm. Very stratified aerosol layers, possibly transported into the lower stratosphere by deep convective systems, have been observed in the lower stratosphere between 20 and 29 km in the tropics in the Southern Hemisphere. Key words. Atmospheric composition and structure (aerosols and particles; middle atmosphere – composition and chemistry; instruments and techniques)

International audience; We present an evaluation of observations from the Lidar Ozone and Aerosol for NDACC in Antarctica (LOANA) at the Dumont d'Urville station, Antarctica. This instrument is part of the Network for the Detection of Atmospheric Composition Change (NDACC), and ensures continuity with lidar measurements made since 1989 with the previous instrument at this site. This study is based on the dataset from 2008 to 2009, and comparisons are made with observations from balloon soundings, and from three satellite experiments: Aura/MLS, TIMED/SABER, and CALIOP/CALIPSO. The lidar ozone data are in very good agreement with the balloon sounding data (ECC sensor), revealing a bias of less than 3% between 17 and 34 km. For temperature, the lidar shows a low bias of −3 K at 20 km when compared with Aura/MLS. Between 30 and 50 km, the bias is less than 2 K. We also present our initial results showing diurnal variations in temperature. The amplitude of these diurnal cycles is on the order of 1 K and is unlikely to account for the temperature biases between LOANA and the reference instruments. Comparisons of total attenuated backscatter reveal good qualitative agreement between LOANA and CALIOP, with differences of less than 30% in the derived optical depth.

Three ground-based portable low power consumption micro lidars (MULID) have been built and deployed at three remote sites in Banizoumbou (Niger), Cinzana (Mali) and M'Bour (Senegal) in the framework of the African Monsoon Multidisciplinary Analyses (AMMA) project for the characterization of aerosols optical properties. A description of the instrument and a discussion of the data inversion method, including a careful analysis of measurement uncertainties (systematic and statistical errors), are presented. Some case studies of typical lidar profiles observed over the Banizoumbou site during 2006 are shown and discussed with respect to the Aerosol Robotic Network (AERONET) 7-day back-trajectories and the biomass burning emissions from the Combustion Emission database for the AMMA campaign.

An FSSP-100 Optical Particle Counter designed to count and size particles in the micron range and a backscattersonde that measures in-situ particle optical properties such as backscatter and depolarization ratio, are part of the payload of the high altitude research aircraft M55 Geophysica. This aircraft was deployed in tropical field campaigns in Bauru, Brasil (TROCCINOX, 2004) Darwin, Australia (SCOUT-Darwin, 2005) and Ouagadougou, Burkina Faso (SCOUT-AMMA, 2006). In those occasions, measurements of particle size distributions and optical properties within cirrus cloud were performed. Scope of the present work is to assess and discuss the consistency between the particle volume backscatter coefficient observed by the backscattersonde and the same parameter retrieved by optical scattering theory applied to particle size distributions as measured by the FSSP-100. In addition, empirical relationships linking the optical properties measured in-situ by the backscattersonde, which generally can be obtained by remote sensing techniques (LIDAR), and microphysical bulk properties like total particle number, surface and volume density will be presented and discussed.

PFS is a two-channel Fourier spectrometer operating in the infra-red wavelengths between 1.25 and 45 μm. The instrument will be used mainly in the study of the Martian atmosphere. The principal goals are the measurements of the atmospheric temperature and pressure, atmospheric constituents, aerosol and clouds, ground pressure for surface topography, optical and thermophysics properties of the Martian soil. PFS will fly on the Mars 94 spacecraft which should be launched in 1994 and reach the planet in 1995. It is essentially constituted by two different interferometers located in the same box which is divided into two parts. A dichroic placed on the PFS entrance is used to separate the spectral range into two parts, a division needed by the different optical materials which have to be used in each spectral range. The optical layout of the experiment is very compact. Each channel uses two cubic mirrors mounted on an L-structure pivoted on a motor. The motor moves the mechanics and permits the optical-path difference between the arms to be varied. Each interformeter operates in a different spectral range, respectively, between (1.25÷4.8) μm (8000÷2083cm−1) and (6÷45)μm (1666÷220)cm−1). The spectral resolution is 2 cm−1. The entrance aperture area is 30 cm2 per channel and the field of view is 2 and 4 degrees. Every measurement lasts about 4 s. The time and, therefore, the relative optical-path difference for the measurement of every point of the interferogram is given by the zero crossings of the interferogram of a reference monochromatic channel at 1.2 μm which uses a laser diode as source. The two interferograms are double-sided and will have 16384 and 4096 points, respectively, corresponding to spectra of 6250 and 1823 useful points.

The occurrence of a springtime ozone depletion over Antarctica appears to be the result of a chain of processes leading to catalitic destruction of the gas by the action of halogen radicals, in particular chlorine oxide. High abundances of ClO in the stratosphere are determined by abnormally low concentrations of nitrogen compounds; such denitrification is likely to be caused by heterogeneous reactions and transport carried out by the clouds present in the polar stratosphere. Stratospheric clouds form during most of the winter and the beginning of spring over the polar regions. Due to scarce accessibility, knowledge of their properties is still poor. Information on extent, particles shape and size distributions is, however, fundamental for the understanding of the magnitude of their contribution to the destruction chain. A balloon-borne experiment, aimed at thein situ observation of cloud particles from 2 to 200 microns in radius, is presented. This would be the first system to provide on-line TV images of cloud particles. The first measurement campaign in Antarctica is planned for the period August–October 1990.

An experiment for measuring the electric field along 2 axes from quasi-static DC to kHz called OPERA is being produced at IFSI for the USSR mission Interball. An experiment description is given here. The experiment is in collaboration with ESTEC (ESA) and LPCE (Orleans, France).

We describe the participation of the “Istituto di Fisica dello Spazio Interplanetario» in the Infrared Space Observatory (ISO) Project. We comtribute to the international consortium of Institutes to build the Long Wavelength Spectrometer (LWS): in particular we have responsability for the construction of the data processing unit,i.e. the on-board computer.

Multiwavelength laser backscattersondes (MAS) have been widely used from a variety of airborne platforms for in situ measurements of optical properties of clouds and atmospheric particulate as well as their phase and com- position. Recently, a new miniaturized LIDAR (MULID) has been developed using state-of-art technology for balloon borne profiling of the same quantities. A description of the two instruments, a survey of preliminary re- sults obtained during test flights and indications for future use are given.

International audience; A comprehensive investigation of polar stratospheric clouds was performed on 25 January 2000 with instruments onboard a balloon gondola flown from Kiruna, Sweden. Cloud layers were repeatedly encountered at altitudes between 20 and 24 kilometers over a wide range of atmospheric temperatures (185 to 197 kelvin). Particle composition analysis showed that a large fraction of the cloud layers was composed of nitric acid trihydrate (NAT) particles, containing water and nitric acid at a molar ratio of 3:1; this confirmed that these long-sought solid crystals exist well above ice formation temperatures. The presence of NAT particles enhances the potential for chlorine activation with subsequent ozone destruction in polar regions, particularly in early and late winter.

An innovative balloonborne microjoule lidar (MULID) has been developed within the framework of the HIBISCUS project to provide nighttime measurements of visible and subvisible cirrus and aerosols. MULID has been designed to be a low-cost and an ultralow consumption instrument, due to the remote possibilities of payload recovery and the necessity of a low-weight battery power supply. Ground tests have been performed at the Observatory of Haute Provence (France), and the first technical flight has been made from Trapani, Italy, on a stratospheric balloon; finally, the instrument has been scientifically deployed during the pre-HIBISCUS and HIBISCUS tropical campaigns in Bauru, Brazil, in February 2003 and February 2004, respectively. A description of the instrument is provided together with the results of the ground-based and flight tests as well as an overview and discussion of the first results.

A novel approach to single-photon detection by means of an avalanche photodiode is described and preliminary results obtained by implementation of a prototype are reported. The electronic circuit (breakdown voltage follower) avoids the use of complex temperature controls typically used with these devices, thus reducing system complexity and cost. Data obtained without any thermoregulation show the same behavior with respect to systems thermoregulated to within a few hundredths of a degree celsius.

An instrument for photon counting measurements in a Lidar experiment is described. Single events can be stored up to rates of 25 MHz and it is capable of 4096 data acquisitions for each measurement. Time information by two successive photons is achieved with an accuracy better than 14 ns. The system is interfaced with an HP 1000F series computer. A window discriminator/shaper for formatting the photomultiplier pulses is also described.

The Stratospheric Regular Sounding project was planned to measure regularly the vertical profiles of several tracers like ozone, water vapor, NOx, ClOx and BrOx radicals, aerosol, pressure and temperature, at three latitudes, to discriminate between the transport and photochemical terms which control their distribution. As part of this project, the "Istituto di Fisica dell'Atmosfera" launched nine laser backscattersondes (LABS) on board stratospheric balloons to make observations of background aerosol and PSCs. LABS was launched with an optical particle counter operated by the University of Wyoming. Observations have been performed in the arctic, mid-latitudes and tropical regions in different seasons. Polar stratospheric clouds have been observed in areas inside and outside the polar vortex edge. A background aerosol was observed both in mid-latitudes and in arctic regions with a backscattering ratio of 1.2 at 692 nm. Very stratified aerosol layers, possibly transported into the lower stratosphere by deep convective systems, have been observed in the lower stratosphere between 20 and 29 km in the tropics in the Southern Hemisphere. Key words. Atmospheric composition and structure (aerosols and particles; middle atmosphere – composition and chemistry; instruments and techniques)

We discuss 223 middle atmosphere lidar temperature observations. The record was collected at Frascati (42°N–13°E), during the 41-month period January 1989-May 1992, corresponding to the maximum of solar cycle 22. The choice of this interval was aimed at minimizing the temperature variability induced by the 11-year solar cycle. The average climatology over the 41-month period and comparison with a reference atmosphere (CIRA86) are presented. Monthly temperature variability over the full period, during opposite quasi-biennial oscillation phases and on a short-term scale (0.5–4 h), is analyzed. Results indicate the 50–55-km region as less affected by variability caused by the natural phenomena considered in the analysis. Due to this minimum in natural noise characterizing the atmospheric temperature just above the stratopause, observations of that region are well suited to the detection of possible temperature trends induced by industrial activities.

Lidar measurements of atmospheric density and temperature in the stratosphere and middle atmosphere are presented. The lidar system operating in Frascati is described and some results of high altitude soundings are reported.

A balloonborne sonde and a polarization lidar have been developed to make combined observations of thin tropospheric and stratospheric clouds. In their first application these instruments have been used in a campaign organized to study Antarctic polar stratospheric clouds (PSCs), which are deeply involved in the process of ozone depletion. The sonde collects cloud particles larger than 4 µm in diameter on a transparent impactor and observes them by means of a CCD (charge coupled device) camera microscope. Images are transmitted in real time to the ground station for recording and analysis. Shape, dimension, and size distribution of the particles are obtained from these frames. The lidar provides complementary information about the cloud optical depth, backscattering, depolarization, vertical distribution, and temporal evolution. Characteristics of both instruments are described. The experiments performed during the 1990 spring campaign at McMurdo Station, Antarctica, are discussed, and some resul...

In the recent past the role of polar stratospheric clouds (PSCs) and of stratospheric aerosol in polar ozone depletion raised the attention of the scientific community (Solomon 1990; Fiocco et al. 1997). The understanding of PSCs in terms of concentrations of particles, sizes, optical parameters, formation processes, and microphysics is relevant for evaluating their contribution to chlorine activation, dehydration, and denitrification of the lower polar stratosphere. In view of a better understanding of PSC properties, during the last few years joint lidar and optical particle counters (OPC) measurements were carried out in Antarctica (Deshler et al. 1991; Adriani et al. 1992). While the OPC was able to assess particle concentrations and sizing, the lidar could give a contemporary measurement of the aerosol volume cross section for backscattered signals and information on the depolarizing properties of the particles, hence their thermodynamical phase. In the approximation of the Mie theory, the two measurement techniques were compared to estimate the refractive index of the particles (Adriani et al. 1995). However, the comparison between lidar and balloon-borne measurements needs some care, due to differences in the sampling technique. The lidar is a ground-based instrument and the OPC is carried by balloons and moves with respect to the ground, so that the two measurements are not taken on the same air mass. Ancillary information about the wind speed profile have to be used to choose, among the lidar temporal sequence, the best lidar profile to be compared—at a given altitude—with data from the balloon-borne OPC, drifting with the

[1] In this work, observations of polar stratospheric clouds (PSC) carried out during one flight of the stratospheric research aircraft Geophysica deployed in the Airborne Polar Experiment–Geophysica Aircraft in Antarctica (APE-GAIA) campaign in September–October 1999 are presented. An analysis of data from the two lidars and a backscatter sonde on board the Geophysica aircraft is presented, coupled with temperature measurements. The observations are analyzed with the aid of a mesoscale model to provide air mass thermal histories and a microphysical box model to simulate PSC formation. The results obtained from this comparison are discussed in view of the theories for PSC formation processes.

A multichannel scaler for photon counting is described. Single photon pulses can be collected up to rates of 100 MHz during a programmed dwell time and an integration versus time can be done for each of the 999 channels on a user‐programmable number of successive measurements. A live, dynamic display is provided. Data can be easily sent to any computer for recording or to a telemetry system for remote transmission.