Modeling variability in dendritic ice crystal backscattering cross sections at millimeter wavelengths using a modified Rayleigh–Gans theory
نویسندگان
چکیده
Using the Generalized Multi-particle Mie-method (GMM), Botta et al. (in this issue) [7] created a database of backscattering cross sections for 412 different ice crystal dendrites at X-, Kaand W-band wavelengths for different incident angles. The Rayleigh–Gans theory, which accounts for interference effects but ignores interactions between different parts of an ice crystal, explains much, but not all, of the variability in the database of backscattering cross sections. Differences between it and the GMM range from −3.5 dB to +2.5 dB and are highly dependent on the incident angle. To explain the residual variability a physically intuitive iterative method was developed to estimate the internal electric field within an ice crystal that accounts for interactions between the neighboring regions within it. After modifying the Rayleigh–Gans theory using this estimated internal electric field, the difference between the estimated backscattering cross sections and those from the GMM method decreased to within 0.5 dB for most of the ice crystals. The largest percentage differences occur when the form factor from the Rayleigh–Gans theory is close to zero. Both interference effects and neighbor interactions are sensitive to the morphology of ice crystals. Improvements in ice-microphysical models are necessary to predict or diagnose internal structures within ice crystals to aid in more accurate interpretation of radar returns. Observations of the morphology of ice crystals are, in turn, necessary to guide the development of such ice-microphysical models and to better understand the statistical properties of ice crystal morphologies in different environmental conditions. & 2013 Elsevier Ltd. All rights reserved.
منابع مشابه
Radar backscattering properties of nonspherical ice crystals at 94 GHz
[1] The millimeter wavelength radar backscattering properties at 94 GHz for six nonspherical ice crystals, which include hexagonal column, hollow, plate, bullet rosette, aggregate, and droxtal with 46 maximum dimensions ranging from 2 to 10,500 mm, are investigated using the discrete dipole approximation (DDA) method and Lorenz-Mie theory. It is found that the radar backscattering cross section...
متن کاملApplicability of the Rayleigh-Gans approximation for scattering by snowflakes at microwave frequencies in vertical incidence
[1] The applicability of the Rayleigh-Gans approximation (RGA) for scattering by snowflakes is studied in the microwave region of the electromagnetic spectrum. Both the shapes of the single ice crystals, or monomers, and their amounts in the modeled snowflakes are varied. For reference, the discrete-dipole approximation (DDA) is used to produce numerically accurate solutions to the single-scatt...
متن کاملLinking snowflake microstructure to multi-frequency radar observations
[1] Spherical or spheroidal particle shape models are commonly used to calculate numerically the radar backscattering properties of aggregate snowflakes. A more complicated and computationally intensive approach is to use detailed models of snowflake structure together with numerical scattering models that can operate on arbitrary particle shapes. Recent studies have shown that there can be sig...
متن کاملManifestations of interference fluctuations of phase functions and backscattering cross sections for ice crystals with specific orientations
The ray-by-ray integration technique is applied to investigate the effect of the phase interference between rays on the scattering phase functions and backscattering cross sections of pristine hexagonal ice plates and columns with specific orientations. Numerical computations are carried out at 0.532 and 1.064 μm wavelengths. The results demonstrate that strong fluctuations of the phase functio...
متن کامل95-GHz Scattering by Terrain at Near-Grazing Incidence
This study, consisting of three complimentary topics, examines of the millimeter-wave backscattering behavior of terrain at incidence angles extending between 70 and 90 , corresponding to grazing angles of 20 to 0 . The first topic addresses the character of the statistical variability of the radar backscattering cross section per unit area A. Based on an evaluation of an extensive data set acq...
متن کامل