Abstract
Abstract. The number and shape of ice crystals present in mixed-phase and ice clouds influence the radiation properties, precipitation occurrence and lifetime of these clouds. Since clouds play a major role in the climate system, influencing the energy budget by scattering sunlight and absorbing heat radiation from the earth, it is necessary to investigate the optical and microphysical properties of cloud particles particularly in situ. The relationship between the microphysics and the single scattering properties of cloud particles is usually obtained by modelling the optical scattering properties from in situ measurements of ice crystal size distributions. The measured size distribution and the assumed particle shape might be erroneous in case of non-spherical ice particles. There is a demand to obtain both information correspondently and simultaneously for individual cloud particles in their natural environment. For evaluating the average scattering phase function as a function of ice particle habit and crystal complexity, in situ measurements are required. To this end we have developed a novel airborne optical sensor (PHIPS-HALO) to measure the optical properties and the corresponding microphysical parameters of individual cloud particles simultaneously. PHIPS-HALO has been tested in the AIDA cloud simulation chamber and deployed in mountain stations as well as research aircraft (HALO and Polar 6). It is a successive version of the laboratory prototype instrument PHIPS-AIDA. In this paper we present the detailed design of PHIPS-HALO, including the detection mechanism, optical design, mechanical construction and aerodynamic characterization.
Highlights
Better understanding of the radiative impact of different clouds requires knowledge of the link between the cloud microphysics and the single scattering properties of the cloud particles which are used in radiative transfer models
In the past, sophisticated optical methods for the computation of the single scattering properties were developed and applied to non-axisymmetric and irregularly shaped ice particles. These included exact/near-exact methods like Tmatrix methods (e.g. Havemann and Baran, 2001), the finitedifference time-domain method (FDTD) (Yang and Liou, 1999) and discrete-dipole approximation (DDA; Draine and Flatau, 1994; Yurkin and Hoekstra, 2007), or methods based on the geometric optics’ approximation (Macke et al, 1996), improved geometric optics (IGO) (Bi et al, 2011; Liu et al, 2013; Yang and Liou, 1996) and ray tracing with diffraction on facets (RTDF; Hesse et al, 2009)
We presented a novel airborne optical probe (PHIPS-HALO) developed at the Karlsruhe Institute of Technology (KIT) for attachment to the German DLR HALO GV-SP aircraft as well as other research aircraft
Summary
Better understanding of the radiative impact of different clouds requires knowledge of the link between the cloud microphysics and the single scattering properties of the cloud particles which are used in radiative transfer models. The airborne polar nephelometer (PN) (Crépel et al, 1997; Gayet et al, 1997) measures the scattering function of the ice particles and was used in conjunction with results from the Cloud Particle Imager (CPI) probe (Lawson et al, 2001) to investigate the impact of the ice crystal habits on the radiative properties of cirrus clouds. This could be done only using a statistical approach with assumptions made about the particle shape within an ensemble of randomly oriented particles. Data acquisition and storage were required to be included within the same compartment
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