Browsing University of Hertfordshire by Author "Ulanowski, Zbigniew"

Now showing items 1-20 of 38

    • Alignment of atmospheric dust observed by high-sensitivity optical polarimetry 

      Ulanowski, Zbigniew (Springer Nature, 2007)
      Optical polarimetry observations on La Palma, Canary Islands, during a Saharan dust episode showed dichroic extinction, indicating the presence of vertically aligned particles in the atmosphere. It is postulated that the ...

    • Application of global optimisation to particle identification using light scattering 

      Zakovic, S.; Ulanowski, Zbigniew; Bartholomew-Biggs, Michael (1998)
      Numerical methods of solving the inverse light scattering problem for spheres are presented. The methods are based on two stochastic global optimization techniques: Deep's random search and the multilevel single-linkage ...

    • Application of neural networks to the inverse light scattering problem for spheres 

      Ulanowski, Zbigniew; Wang, Z.; Kaye, Paul H.; Ludlow, Ian (1998)
      A new approach suitable for solving inverse problems in multi-angle light scattering is presented. The method takes advantage of multidimensional function approximation capability of radial basis function (RBF) neural ...

    • Characterization of small ice crystals using frequency analysis of azimuthal scattering patterns 

      Ulanowski, Zbigniew; Stopford, Chris; Hesse, Evelyn; Kaye, Paul H.; Hirst, Edwin; Schnaiter, M. (2007)
      Azimuthal scattering patterns obtained from ice crystals using the Small Ice Detector 2 are examined. They are converted to frequency spectra using Fast Fourier Transform. To classify the shape of the crystals, the spectra ...

    • Characterizing ice particles using two-dimensional reflections of a lidar beam 

      Goerke, Marissa; Ulanowski, Zbigniew; Ritter, Georg; Hesse, Evelyn; Neely, Ryan; Taylor, Laurence; Stillwell, Robert; Kaye, Paul (2017-07-01)
      We report a phenomenon manifesting itself as brief flashes of light on the snow surface near a lidar beam. The flashes are imaged and interpreted as specular reflection patterns from individual ice particles. Such patterns ...

    • Cirrus clouds 

      Heymsfield, Andrew J.; Kraemer, Martina; Brown, Philip; Cziczo, Dan; Franklin, Charmaine; Lawson, Paul; Lohmann, Ulrike; Luebke, Anna; McFarquhar, Greg; Ulanowski, Zbigniew; Van Tricht, Kristof (2017)
      The goal of this article is to synthesize information about what is now known about one of the three main types of clouds, cirrus, and to identify areas where more knowledge is needed. Cirrus clouds, composed of ice ...

    • Classifying atmospheric ice crystals by spatial light scattering 

      Kaye, Paul H.; Hirst, Edwin; Greenaway, Richard; Ulanowski, Zbigniew; Hesse, Evelyn; DeMott, P.; Saunders, C.; Connolly, P. (2008)
      We describe preliminary results from an optical scattering instrument designed to assess the shapes and sizes of microscopic atmospheric cloud particles, especially the smallest ice crystals, that can profoundly affect ...

    • Cloud chamber experiments on the origin of ice crystal complexity in cirrus clouds 

      Schnaiter, Martin; Järvinen, Emma; Vochezer, Paul; Abdelmonem, Ahmed; Wagner, Robert; Jourdan, Olivier; Mioche, Guillaume; Shcherbakov, Valery N.; Schmitt, Carl G.; Tricoli, Ugo; Ulanowski, Zbigniew; Heymsfield, Andrew J. (2016-04-25)
      This study reports on the origin of ice crystal complexity and its influence on the angular light scattering properties of cirrus clouds. Cloud simulation experiments were conducted at the AIDA (Aerosol Interactions and ...

    • Cloud characterization using a particle-counter dropsonde 

      Ulanowski, Zbigniew; Kaye, Paul; Hirst, Edwin; Wieser, Andreas; Stanley, Warren (2015-04-12)
      Routine meteorological data is obtained in the atmosphere using disposable radiosondes, giving temperature, pressure, humidity and wind speed. Additional measurements are obtained from dropsondes, released from research ...

    • Cloud Ice Properties: In Situ Measurement Challenges 

      Baumgardner, Darrel; Abel, Steve; Axisa, Duncan; Cotton, Richard; Crosier, Jonathan; Field, P.R.; Gurganus, Colin; Heymsfield, Andrew J.; Korolev, Alexei; Kraemer, Martina; Lawson, Paul; McFarquhar, Greg; Ulanowski, Zbigniew; Um, Junshik (2017-04-10)
      Understanding the formation and evolution of ice in clouds requires detailed information on the size, shape, mass and optical properties of individual cloud hydrometeors and their bulk properties over a broad range of ...

    • Discussion of a physical optics method and its application to absorbing smooth and slightly rough hexagonal prisms 

      Hesse, Evelyn; Taylor, Laurence; Collier, Christopher T.; Penttila, Antti; Nousiainen, Timo; Ulanowski, Zbigniew (2018-10-01)
      Three different mathematical solutions of a physical optics model for far field diffraction by an aperture due to Karczewski and Wolf are discussed. Only one of them properly describes diffraction by an aperture and can, ...

    • Effects of Surface Roughness with Two Scales on Light Scattering by Hexagonal Ice Crystals Large Compared to the Wavelength: DDA Results 

      Collier, Christopher T.; Hesse, Evelyn; Taylor, Laurence; Ulanowski, Zbigniew; Penttila, Antti; Nousiainen, Timo (2016-10-01)
      The effect of ice crystal surface roughness on light scattering by ice crystals which are large compared to the wavelength was studied, in particular changes to the 2D scattering patterns, azimuthally averaged phase ...

    • Exploring the surface roughness of small ice crystals by measuring high resolution angular scattering patterns. 

      Schnaiter, M.; Kaye, Paul H.; Hirst, Edwin; Ulanowski, Zbigniew; Wagner, Robert (2011)
      Surface roughness of atmospheric ice particles is an important yet poorly investigated microphysical property in the context of the climate impact of cirrus and mixed-phase clouds. Measurements of single particle two-dimensional ...

    • Halo ratio from ground based all-sky imaging 

      Dandini, Paolo; Ulanowski, Zbigniew; Campbell, David; Kaye, Richard (2019-02-28)
      The halo ratio (HR) is a quantitative measure characterizing the occurrence of the 22 halo peak associated with cirrus. We propose to obtain it from an approximation to the scattering phase function (SPF) derived from ...

    • Improved understanding of the vertical distribution of simulated dust distribution in the Saharan Air Layer during the ICE-D field campaign with the WRF-CHEM model 

      Chiao, Sen; Jenkins, Gregory; Ulanowski, Zbigniew; Smith, Helen (2016-01-11)
      During the period of 4-27 August of 2015, the UK Ice in dust clouds experiment will take place in Cape Verde. UK_ICE-D will characterize aerosol particles and their ability to act as ice nuclei (IN) and cloud condensation ...

    • In-situ observations of volcanic ash clouds from the FAAM aircraft during the eruption of Eyjafjallajökull in 2010 

      Johnson, Ben; Turnbull, Kate; Brown, Phil; Burgess, Rachel; Dorsey, James; Baran, Anthony J.; Webster, Helen; Haywood, Jim; Cotton, Richard; Ulanowski, Zbigniew; Hesse, Evelyn; Wolley, Alan; Rosenberg, Philip (2012)
      During April–May 2010 the UK Facility for Airborne Atmospheric Measurements (FAAM) BAe-146 aircraft flew 12 flights targeting volcanic ash clouds around the UK. The aircraft observed ash layers between altitudes of 2–8 km ...

    • Incidence of rough and irregular atmospheric ice particles from Small Ice Detector 3 measurements 

      Ulanowski, Zbigniew; Kaye, Paul H.; Hirst, Edwin; Greenaway, Richard; Cotton, Richard J.; Hesse, Evelyn; Collier, Christopher T. (2013)
      The knowledge of properties of ice crystals such as size, shape, concavity and roughness is critical in the context of radiative properties of ice and mixed phase clouds. Limitations of current cloud probes to measure these ...

    • Introducing phase tracing into a computational method which combines ray-tracing with diffraction on facets 

      Hesse, Evelyn; Ulanowski, Zbigniew; Clarke, A.J.M.; Havemann, S.; Kaye, Paul H. (University of Bremen, 2005)
      The viability of introducing phase tracing into our ray tracing with diffraction on facets model is investigated. In order to prove the method, Monte Carlo ray-tracing results for a slit, based on our diffraction formula ...

    • Laser diffractometer for single particle scattering measurements 

      Ulanowski, Zbigniew; Greenaway, Richard; Kaye, Paul H.; Ludlow, Ian (2002)
      A laser diffractometer (polar nephelometer) constructed for single-particle studies is described. It takes advantage of an array of optical fibres and a scanning disc to allow the use of a single photomultiplier tube for ...

    • Light scattering by complex ice-analogue crystals 

      Ulanowski, Zbigniew; Hesse, Evelyn; Kaye, Paul H.; Baran, A.J. (2006)
      Angle-dependent light scattering measurements on single ice analogues crystals are described. Phase functions and degree of linear polarization are measured for electrodynamically levitated crystals. A procedure for ...