Aerosol- und Wolkenphysik


Univ.-Prof. Dr. Stephan Borrmann


Upper Troposphere /
Lower Stratosphere 
Holography Atmospheric
Dr. Ralf Weigel Ph.D. Jacob Fugal Ph.D. Miklós Szákall
Marcus Klingebiel Oliver Schlenczek Dr. Karoline Diehl
Christoph Mahnke Alexander Jost
Max Port

former staff:

  • Dr. Wiebke Frey
  • Dr. Sergej Molleker
  • Dr. Subir K. Mitra
  • Nadine von Blohn


Upper Troposphere / Lower Stratosphere (UTLS)

  • Airborne measurements, in particular at up to Stratospheric altitudes (~21 km) concerning Aerosol number concentration and size distribution, chemical composition and morphology.
  • Sources, new particle formation and transport processes of aerosol.
  • Aerosol interaction with atmospheric water vapor and trace gases.
  • Aerosol spatial distribution.
  • Cloud particle microphysical properties, such as cloud particles size distributions and concentration, shape and phase in mixed phase clouds, ice clouds, subvisible cirrus, polar stratospheric clouds, volcanic plumes, clouds in the outflow of Mesoscale Convective Systems.


  • Airborne and ground-based (mountain-top) holographic measurements of cloud particles yielding a three-dimensional position, size and shadowgraph of each ice particle and cloud droplet in a local ~10 cm3 sample volume.
  • Holographic measurements of cloud particles in the vertical wind tunnel to observe cloud particle collision and coalescence.
  • Measurements of the structure (spatial distribution) of cloud droplets and filaments of dry air at cloud top using a simulated stratus cloud in the laboratory.
  • Development of holographic instruments and particle-hologram analysis technique.

Atmospheric Hydrometeors

  • Ice nucleation
  • Growth of ice particles by riming
  • Shape, oscillation, collision and internal circulation of raindrops
  • Uptake and retention of trace gases by raindrops and ice particles


Upper Troposphere / Lower Stratosphere (UTLS)

  • Mainly the field activities of the research group are oriented to aircraft measurements at UT/LS altitudes using platforms with advanced ceiling such as the Russian M55 Geophysica. Further instrumental applications were realized on board of the French ATR-42, the British BAe-143, and the German Falcon-20, Learjet 35A and Partenavia P68. The group works with condensation particle detectors and optical particle counters in the submicron particle size range. Impactors are used for sampling aerosols for offline analysis with SEM, ESEM, NanoSIMS techniques. Cloud particles are probed with forward scattering particle spectrometers, shadow cast imaging sensors and digital holography.


  • Holography is a tool to examine the local environment surrounding cloud particles, either in-situ in atmospheric clouds or in laboratory or wind-tunnel simulated clouds. One can examine, for example, the three-dimensional clustering of cloud particles due to turbulence and the local spatial structure of mixed phase clouds (i.e. how are water droplets distributed about the ice particles in mixed-phase clouds). Because one can measure thousands of particles in a local sample volume (a single hologram), one can also estimate a local size distribution on cm-scales and also how local size distributions vary with position inside a cloud.


  • The Mainz vertical wind tunnel allows one to freely suspend various hydrometeors as for example rain and cloud drops, ice particles, and snow flakes in a vertical air stream so that no wall effects are to be expected. As the hydrometeors are levitated at their terminal velocities the ventilation coefficients are in the real-atmospheric order. In the wind tunnel single events with individual hydrometeors are observed. Environmental conditions such as air speed, temperature, humidity and depending on the study, concentrations of trace gases or aerosol particles are controlled exactly and continuously recordered. To perform experiments with the ice phase the wind tunnel air can be cooled down to -30°C. The air humidifying is possible up to the saturation level. The air speed can reach values up to 40 m/s; allowing the whole range of hydrometeors, starting with small drops having radii between 30 und 500 µm, large drops with equivalent radii up to 3 or 4 mm, ice crystals, snow flakes, graupels and even large hailstones, can be floated. The Mainz vertical wind tunnel is therefore an outstanding tool for microphysical and chemical investigations of hydrometeors.