This project is supported by the European Commission - DG XII - Environment and Climate Programme

Objective

The objective of the project is to collect the atmospheric data needed to check step by step the GCM simulations of temperature and transport as well as box and CTM (Chemistry Transport Model) and micro physical and photochemical codes, in use int he simulation of ozone depletion, by Lagrangian measurements for several weeks, in the vortex and over a wide geographical area, using a combination of constant level and altitude excursion long duration balloons.

Brief description of the research project

The Lagrangian experiment is a combination of measurements onboard long duration balloons with novel appropriate light instruments and state of the art transport, radiative, microphysical and photochemical modelling.


The experiment will make use of two types of balloons, constant level and variable altitude together, carrying the same basic gondola plus several sensors of various types depending on the balloon capacity and of the requirements of the instruments:

- superpressure balloons, able to carry a 15 kg payload, at constant density level around 70 hPa, where the PSC frequency is the largest, with temperature, pressure, localisation, IR radiation, PSC, and small ozone and water vapour in-situ sensors which all can perform in the polar night;

- infrared-Montgolfier (MIR), able to perform large vertical excursions from 18-20 km at night to 30 km during daytime, with a 50kg payload including the same basic gondola plus a uv-visible spectrometer for O3, NO2, OClO and BrO profiles and CH4 and H2O in-situ sensors. The IR Montgolfier as well as the uv-visible spectrometer require some sunlight for operating.


Three superpressure balloons and two infrared Montgolfier will be flown together for several weeks inside the polar vortex during the winter in the frame of THESEO. The superpressure balloons will be launched during the second half of January in the polar night (depending on the presence of the vortex above the station), while the IR Montgolfier, requiring some sunlight, will follow by mid-February.


Their data will be confronted to the GCM analysis of ECMWF and UKMO, and to state of the art, inertia-gravity, gravity and orographic waves, radiative transfer, microphysical and photochemical simulations.

Balloons

SUPERPRESSURE Balloons (BP) : spherical 10 m diameter Mylar balloons carrying a 25 kg payload at constant density level at about 56 hPa or 19 km.
Measurements : temperature, pressure, GPS location and altitude (CNES), IR flux (CNRS), ozone (solid state semiconductor sensor, UCL / UCAM), water vapour (surface acoustic wave crystals, UCAM) and PSC (laser diode CNR).

IR MONTGOLFIER (MIR) : hot air balloons of 36 000 m3 volume heated by upwelling IR flux, carrying two payloads of 60 kg in total at 26 km during daytime and 16 - 20 km during nighttime.
Measurements : temperature, pressure, GPS location and altitude (CNES), IR flux (global radiometer CNRS), ozone (solid state semiconductor sensor, UCL / UCAM), water vapour (surface acoustic wave crystals, UCAM) and PSC (laser diode CNR), O3, NO2, OClO and BrO (SAOZ uv-vis spectrometer, CNRS), CH4 (Tunable Diode Laser, NPL / UCAM), water vapour (Lyman alpha hygrometer, CAO).

Operation / Schedule

- Launch from Kiruna (Sweden) in the polar vortex (BP after 15 January 1999; MIR after 10 February)

- Duration : cut down for recovery after 22 days if flying above Scandinavia, maximum duration : 28 days.

- Safety : automatic cut-down if: - altitude lower than 16 km

- latitude south of 55°N

Participants

CNRS - Service d'Aéronomie, France	Dr J.P. Pommereau, Coordinator Dr A. Garnier, Project Manager
CNR - IFA, Italy	Dr A. Adriani
University of Cambridge (UCAM), UK	Dr R.L. Jones
Danish Meteorological Institute, DMI, Denmark	Dr B. Knudsen
National Physical Laboratory (NPL), UK	Dr P. Woods
CNRS - Laboratoire de meteorologie Dynamique	Dr F. Vial
University College of London	Prof D.E. Williams
British Antarctic Survey	Dr H.K. Roscoe
Central Aerological Observatory (CAO)	Dr V.Yuskhov
Balloon operations:	CNES