In-situ instrumentation: Clouds
The Institute for Atmospheric Physics operates a variety of different sensors for the detection and characterization of cloud particles on the research aircraft HALO and Falcon. The instruments are attached under the wing of the aircraft or directly on the fuselage so that liquid and ice particles can be measured in the atmosphere undisturbed. In addition to aircraft measurements, the probes are also used to characterize cloud particle properties generated in wind tunnels.
The size range of the measured particles expands from sub-micrometers to several millimeters and thus covers all types of clouds and their growth phases.
The particles are detected and analyzed using various methodologies: Small particles are measured with a scattering spectrometer (e.g. the FFSSP or FCDP). When particles traverse a laser beam of a certain wavelength, light is scattered in the process. The scattered light pulse is registered on a detector and assigned to a particle size based on calibration data. Larger particles are captured as shadow images on diode arrays (e.g. with the 2DS and the PIP). The images recorded by the diodes moving in the direction of flight give information on the size, shape and thus also the phase of the particle. The water or ice mass content of the particles is measured using so-called hotwire instrument (e.g. the Nevzorov). The liquid droplets are evaporated when they hit the hot wire and the sublimation cooling is measured. Ice particles are collected in a small cylinder and evaporated similar to the droplets.
The combination of the instruments enables classification and analysis of many types of clouds from mixed-phase and liquid clouds to contrails and cirrus clouds in order to answer central questions of climate research. The microphysical parameters derived with these instruments serve to validate remote sensing instruments and numerical models and thus help to determine the unresolved question of the role of clouds in climate sensitivity.