 |
| Titel |
A new optical ice particle counter at LACIS |
| VerfasserIn |
Henner Bieligk, Georg Sebastian Voelker, Tina Clauss, Marius Grundmann, Frank Stratmann |
| Konferenz |
EGU General Assembly 2014
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250088631
|
| Publikation (Nr.) |
 EGU/EGU2014-2762.pdf |
|
|
|
|
|
| Zusammenfassung |
| Clouds play an important role within the climate system, especially for the radiative energy
budget of the earth. The radiative properties of a cloud depend strongly on the fractions of ice
crystals and water droplets, their size distributions, and the ice crystal shapes within the
particular cloud. One option to gain this kind of information is using optical particle
counters.
A new optical particle counter is developed for laboratory work and is based on the
concept of the Thermostabilized Optical Particle Spectrometer for the Detection of Ice
Particles (TOPS-Ice, Clauss et al., 2013). TOPS-Ice uses linearly polarized green laser light
and the depolarization of the scattered light at a scattering angle of 42.5° to discriminate
between liquid water droplets and ice crystals in the lower μm range. However, the
measurements are usually limited to ice fractions in the order of 1%. To improve the
determination of the ice fraction, several modifications of the original setup are implemented
including an additional detection system at another scattering angle. The new scattering angle
is optimized for least interference between the droplet and ice signals. This is achieved
by finding the angle with the maximum difference in scattered intensity of water
droplets compared to ice crystals with the same volume equivalent diameter. The
suitable scattering angle of 100° for linearly polarized light was chosen based on
calculations using T-Matrix method, Lorenz-Mie theory, Müller matrices and distribution
theory.
The new optical setup is designed to run in combination with a laminar flow tube, the
so-called Leipzig Aerosol Cloud Interaction Simulator (LACIS, Stratmann et al., 2004;
Hartmann et al., 2011). Using LACIS and its precisely controlled thermodynamic
conditions, we are able to form small water droplets and ice crystals which will then be
detected, classified and sized by our new optical device. This setup is planned to
be tested in ice measurements including Snomax® and several dusts (e.g. illite,
kaolinite, ATD) as ice nuclei which all show different behaviors in ice formation.
Furthermore, a detailed comparison of both instruments TOPS-Ice and the new setup is
planned.
This project is part of the Leipzig Graduate School on Clouds, Aerosols and Radiation
and is partly supported by the German Research Foundation (DFG project WE 4722/1-1)
within the DFG Research Unit FOR 1525 INUIT.
Clauss, T., Kiselev, A., Hartmann, S., Augustin, S., Pfeifer, S., Niedermeier, D., Wex, H.,
and Stratmann, F, 2013, Application of linear polarized light for the discrimination of
frozen and liquid droplets in ice nucleation experiments, Atmos. Meas. Tech., 6,
1041-1052.
Hartmann, S., Niedermeier, D., Voigtländer, J., Clauss, T., Shaw, R. A., Kiselev, A., and
Stratmann, F., 2011, Homogeneous and heterogeneous ice nucleation at LACIS: operating
principle and theoretical studies, Atmos. Chem. Phys., 11, 1753-1767.
Stratmann, F., Kiselev, A., Wurzler, S., Wendisch, M., Heintzenberg, J., Charlson, R. J.,
Diehl, K., Wex, H., and Schmidt, S., 2004, Laboratory Studies and Numerical Simulations of
Cloud Droplet Formation under Realistic Supersaturation Conditions, J. Atmos. Oceanic.
Technol., 21, 876-887. |
|
|
|
|
|
|