Effect of Particle Shape, Density, and Inhomogeneity on the Microwave Optical Properties of Graupel and Hailstones
| Autor: | Benjamin T. Johnson, R. Lee Panetta, Ping Yang, Leung Tsang, Guanglin Tang, Patrick G. Stegmann |
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| Rok vydání: | 2017 |
| Předmět: |
Materials science
010504 meteorology & atmospheric sciences business.industry 0211 other engineering and technologies 02 engineering and technology Dielectric 01 natural sciences Molecular physics Grain size Optics Particle-size distribution General Earth and Planetary Sciences Particle SPHERES Electrical and Electronic Engineering Porosity business Graupel Microwave 021101 geological & geomatics engineering 0105 earth and related environmental sciences |
| Zdroj: | IEEE Transactions on Geoscience and Remote Sensing. 55:6366-6378 |
| ISSN: | 1558-0644 0196-2892 |
| Popis: | Atmospheric ice particles can be rimed and contaminated (e.g., by soot attachments). Previous optical property calculations usually assume rimed particles such as graupel and hailstones to be homogeneous spheres with fixed densities. The relevant dielectric constants are estimated with the effective medium approximation (EMA), although such particles are predominately nonspherical, porous, and contain small interior grains. This paper assesses the effects of nonsphericity, density, and inhomogeneity of graupel and hailstones on their optical properties. The bicontinuous medium approximation (BMA) is employed to simulate the particle internal structure. Conical shapes are compared with spherical and spheroidal shapes to assess the effect of nonsphericity. At frequencies lower than 89 GHz, the optical properties are more sensitive to particle’s mass density than to overall particle shape, and the internal structure plays an insignificant role when the particle effective diameter (a quantity involving the particle size distribution) is smaller than approximately 10 mm, and the internal grain size is smaller than 0.2 mm. With a small grain size, the BMA phase function converges to the EMA phase function with an effective refractive index calculated with the Bruggeman formulation. Simulated top of atmosphere radiances at three microwave frequencies, 18.7, 36.5, and 89 GHz, are quite sensitive to ice particle effective diameter between 1 and 5 mm, ice fraction between 0.1 and 0.9, and ice water path between 1 and 5 kg/ $\text{m}^{2}$ . Thus, these frequencies are suitable for retrieving the microphysical properties. |
| Databáze: | OpenAIRE |
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