optical properties of PSC Ia‐enhanced at UV and visible wavelengths: Model and observations

Model calculations suggest that PSC-Ia optical properties measured by lidar at ultraviolet and visible wavelengths are strongly correlated; particle depolarization ratios and backscatter coefficients are 17% smaller and 41% larger at a wavelength of 532 nm than at 355 nm, respectively. The model relations are used to compute 532-nm particle backscatter and depolarization ratios from 355-nm lidar data of a PSC Ia-enhanced, i.e., a PSC of type Ia with unusually high backscatter ratios, measured with a UV Raman lidar over Esrange, Sweden (67.9° N, 21.1° E), on 20 Jan 1997. The calculated optical properties agree well with lidar observations at 532 nm of this PSC type.

[1]  Takashi Shibata,et al.  Polar stratospheric clouds observed by lidar over Spitsbergen in the winter of 1994/1995: Liquid particles and vertical “sandwich” structure , 1997 .

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

[3]  N. S. Higdon,et al.  Airborne lidar observations in the wintertime Arctic stratosphere: Polar stratospheric clouds , 1990 .

[4]  B. Carlson,et al.  Improved T-matrix computations for large, nonabsorbing and weakly absorbing nonspherical particles and comparison with geometrical-optics approximation. , 1997, Applied optics.

[5]  K. Kelly,et al.  Particle size distributions in Arctic polar stratospheric clouds, growth and freezing of sulfuric acid droplets, and implications for cloud formation , 1992 .

[6]  Roland Neuber,et al.  Polar stratospheric cloud threshold temperatures in the 1995–1996 arctic vortex , 1997 .

[7]  Michael I. Mishchenko,et al.  Light scattering by randomly oriented axially symmetric particles , 1991 .

[8]  H. Jacobowitz.  A method for computing the transfer of solar radiation through clouds of hexagonal ice crystals , 1971 .

[9]  Martin Wirth,et al.  Aircraft lidar observations of an enhanced type Ia polar stratospheric clouds during APE‐POLECAT , 1999 .

[10]  Paul J. Crutzen,et al.  Stratospheric aerosol growth and HNO3 gas phase depletion from coupled HNO3 and water uptake by liquid particles , 1994 .

[11]  Steven M. George,et al.  Refractive Indices of Amorphous and Crystalline HNO3/H2O Films Representative of Polar Stratospheric Clouds , 1994 .

[12]  K. Liou,et al.  Light scattering by hexagonal ice crystals: comparison of finite-difference time domain and geometric optics models , 1995 .