Correlations Among the Optical Properties of Cirrus-Cloud Particles: Microphysical Interpretation

Cirrus measurements obtained with a ground-based polarization Raman lidar at 67.9° N in January 1997 reveal a strong positive correlation between the particle optical properties, specifically depolarization ratio apar and extinction-to-backscatter (lidar) ratio Spar, for apar ~ 40%. Over the duration of the measurements both particle properties vary systematically. This effect is particularly pronounced in the case of apar which decreases significantly with time. The analysis of lidar humidity and radiosonde temperature data shows that the measured op- tical properties stem from scattering by dry solid ice particles, while scattering by supercooled droplets, or by wetted or subliming ice particles can be excluded. For the microphysical interpretation of the lidar measurements, ray-tracing computations of par~ticle scattering properties have been used. The comparison with the theoretical data sug- gests that the observed cirrus data can be interpreted in terms of size, shape, and growth of the cirrus particles, the latter under the assumption that the lidar measurements of consecutive cloud segments can be mapped on the temporal development of a single cloud parcel moving along its trajectory: Near the cloud top in the early stage of cirrus de- velopment, light scattering by nearly isometric particles that have the optical characteristics of hexagonal columns (short, column-like particles) is dominant. Over time the ice particles grow, and as the cloud base height extends to lower altitudes characterized by warmer temperatures they become morphologically diverse. For large Spar and depolarization values of ~ 40%, the scattering contributions of column- and plate-like parti- cles are roughly the same. In the lower ranges of the cirrus clouds, light scattering is pre- dominantly by plate-like ice particles. This interpretation assumes random orientation of the cirrus particles. Simulations with a simple model suggest, however, that the positive correlation between Spar and apar, which is observed for depolarization ratios < 40% mainly at low cloud altitudes, can be alternatively explained by horizontal alignment of a fraction of the cirrus particle population.

[1]  J. Wettlaufer.  Impurity Effects in the Premelting of Ice , 1999 .

[2]  M. Baker,et al.  Cloud Microphysics and Climate , 1997 .

[3]  William L. Woodley,et al.  Deep convective clouds with sustained supercooled liquid water down to -37.5 °C , 2000, Nature.

[4]  B. J. Mason,et al.  The growth habits and surface structure of ice crystals , 1963 .

[5]  A. Macke,et al.  Scattering of light by polyhedral ice crystals. , 1993, Applied optics.

[6]  K. Sassen,et al.  Highly Supercooled Cirrus Cloud Water: Confirmation and Climatic Implications , 1985, Science.

[7]  Paivi Piironen,et al.  Measurements of Cirrus Cloud Optical Properties and Particle Size with the University of Wisconsin High Spectral Resolution Lidar , 1997 .

[8]  K. Sassen.  Evidence for Liquid-Phase Cirrus Cloud Formation from Volcanic Aerosols: Climatic Implications , 1992, Science.

[9]  A. Ansmann,et al.  Independent measurement of extinction and backscatter profiles in cirrus clouds by using a combined Raman elastic-backscatter lidar. , 1992, Applied optics.

[10]  Leopoldo Stefanutti,et al.  One year of cloud lidar data from Dumont d'Urville (Antarctica): 1. General overview of geometrical and optical properties , 1993 .

[11]  D. Althausen,et al.  Comprehensive particle characterization from three-wavelength Raman-lidar observations: case study. , 2001, Applied optics.

[12]  S. H. Melfi,et al.  OBSERVATION OF RAMAN SCATTERING BY WATER VAPOR IN THE ATMOSPHERE , 1969 .

[13]  J. Iaquinta,et al.  Cirrus Crystal Terminal Velocities , 2000 .

[14]  A. Ansmann,et al.  Retrieval of physical particle properties from lidar observations of extinction and backscatter at multiple wavelengths. , 1998, Applied optics.

[15]  C. Platt,et al.  Remote Sounding of High Clouds. IV: Observed Temperature Variations in Cirrus Optical Properties , 1981 .

[16]  Kenneth Sassen,et al.  A Midlatitude Cirrus Cloud Climatology from the Facility for Atmospheric Remote Sensing. Part II: Microphysical Properties Derived from Lidar Depolarization , 2001 .

[17]  K. Sassen,et al.  Tropical cirrus cloud properties derived from TOGA/COARE airborne polarization lidar , 2000 .

[18]  C. M. R. Platt.  Lidar Backscatter from Horizontal Ice Crystal Plates , 1978 .

[19]  J. Reichardt,et al.  High accuracy humidity measurements using the standardized frequency method with a research upper-air sounding system , 2001 .

[20]  Optical and geometrical properties of northern midlatitude cirrus clouds observed with a UV Raman lidar , 1999 .

[21]  Piet Stammes,et al.  Scattering matrices of imperfect hexagonal ice crystals , 1998 .

[22]  J. Klett,et al.  Microphysics of Clouds and Precipitation , 1978, Nature.

[23]  Ping Yang,et al.  Light scattering by hexagonal ice crystals: solutions by a ray-by-ray integration algorithm , 1997 .

[24]  A. Ansmann,et al.  Determination of stratospheric aerosol microphysical properties from independent extinction and backscattering measurements with a Raman lidar. , 1995, Applied optics.

[25]  J. Nelson.  Sublimation of Ice Crystals , 1998 .

[26]  G. McFarquhar,et al.  Sensitivity of cirrus bidirectional reflectance to vertical inhomogeneity of ice crystal habits and size distributions for two Moderate‐Resolution Imaging Spectroradiometer (MODIS) bands , 2001 .

[27]  Massimo Del Guasta,et al.  Simulation of LIDAR returns from pristine and deformed hexagonal ice prisms in cold cirrus by means of , 2001 .

[28]  T. Gonda,et al.  Morphology of ice droxtals grown from supercooled water droplets , 1978 .

[29]  K. Sassen.  Optical backscattering from near-spherical water, ice, and mixed phase drops. , 1977, Applied optics.

[30]  J. Reichardt,et al.  Atmospheric temperature profiling in the presence of clouds with a pure rotational Raman lidar by use of an interference-filter-based polychromator. , 2000, Applied optics.

[31]  Taneil Uttal,et al.  A Method for Determining Cirrus Cloud Particle Sizes Using Lidar and Radar Backscatter Technique , 1993 .

[32]  Ulla Wandinger,et al.  Combined Raman lidar for aerosol, ozone, and moisture measurements , 1996 .

[33]  M. Leutbecher,et al.  Particle microphysics and chemistry in remotely observed mountain polar stratospheric clouds , 1998 .

[34]  A. Heymsfield.  Laboratory and field observations of the growth of columnar and plate crystals from frozen droplets , 1973 .

[35]  N. L. Abshire,et al.  Some Microphysical Properties of an Ice Cloud from Lidar Observation of Horizontally Oriented Crystals , 1978 .

[36]  K. Liou,et al.  Single-scattering properties of complex ice crystals in terrestrial atmosphere , 1998 .

[37]  J P Wolf,et al.  Derivation of Mount Pinatubo stratospheric aerosol mean size distribution by means of a multiwavelength lidar. , 1994, Applied optics.

[38]  Gerald G. Mace,et al.  Cloud and Aerosol Research Capabilities at FARS: The Facility for Atmospheric Remote Sensing. , 2001 .

[39]  A. H. Auer,et al.  The Dimension of Ice Crystals in Natural Clouds , 1970 .

[40]  J. Reichardt,et al.  Correlations among the optical properties of cirrus‐cloud particles: Implications for spaceborne remote sensing , 2002 .

[41]  Kenneth Sassen,et al.  Remote Sensing of Planar Ice Crystal Fall Attitudes , 1980 .

[42]  T. Deshler,et al.  Type I PSC‐particle properties: Measurements at ALOMAR 1995 to 1997 , 1999 .

[43]  Yoshihide Takano,et al.  Radiative Transfer in Cirrus Clouds. Part III: Light Scattering by Irregular Ice Crystals , 1995 .

[44]  D. Donovan,et al.  First ice cloud effective particle size parameterization based on combined lidar and radar data , 2002 .

[45]  J. Comstock,et al.  A Midlatitude Cirrus Cloud Climatology from the Facility for Atmospheric Remote Sensing. Part III: Radiative Properties , 2001 .

[46]  Kenneth Sassen,et al.  Observations by Lidar of Linear Depolarization Ratios for Hydrometeors. , 1971 .

[47]  K. Sassen,et al.  Parry arc: a polarization lidar, ray-tracing, and aircraft case study. , 2000, Applied optics.

[48]  K. Sassen.  The Polarization Lidar Technique for Cloud Research: A Review and Current Assessment , 1991 .

[49]  Michael I. Mishchenko,et al.  Depolarization of lidar returns by small ice crystals: An application to contrails , 1998 .