Stratosphere (ICE-4)

Small balloons equipped with in-situ instruments probe the atmosphere from the ground to the middle stratosphere (up to 35 km altitude, i.e. far above all aircraft) at high vertical resolution. Soundings can be organized flexibly, at short notice and at reasonable cost.

Flying such instruments in modular sensor packages offers cutting edge ob- servational capabilities that can be used in targeted flights and campaigns to investigate transport/mixing processes, or as part of regular monitoring pro- grams to detect trends and establish climatologies. Of particular importance are observations in the upper troposphere/lower stratosphere (UTLS) where small changes of greenhouse gas concentrations, aerosol loading, or cloud fre- quency can have a significant radiative impact. A special objective is to ensure rapid response in the case of events like forest fires and volcanic eruptions: bal- loon soundings into the plumes are indispensable to quantify the massive and rapid perturbations and to assess their radiative impact. Our sensors have par- ticipated successfully in many national and international field campaigns, e.g. in Chile, Finland, France, Sweden, and South Africa.

ICE-4 not only operates such balloon-borne in-situ instruments, but also de- velops, modifies and optimizes them to achieve the best possible performance. A part of the instrumentation is implemented and developed within the Helmholtz project MOSES - Modular Observation Solutions for Earth Systems.

Our balloons instruments are:

• Radiosondes measuring temperature, pressure, humidity and wind.
• Electrochemical Concentration Cell (ECC) Ozone sondes to measure the ozone concentration in the troposphere and stratosphere.
• Cryogenic Frostpoint Hygrometer (CFH) modified to be operated with liq- uid nitrogen capable for precise water vapor observation even in the very dry stratosphere (H2O : 1−20000ppmv).
• Compact Optical Particle Counter (OPC) for complementary information on aerosols particle size distribution.
• Cloud particle analyzer containing OPCs for aerosol and small cloud particle detection up to 40 μm in combination with an instrument to record real micro- scopic images of ice crystals (in development).
• AirCores: Collection of air samples from the stratophere down to the tropo- sphere. The air is analyzed for trace gases in the laboratory directly after the balloon flight. This enables the determination of multiple species, e.g., CFCs, SF₆, CH₄, CO₂, CO, N₂O , and in the future H₂.