Polarimetric Emission of Rain Events: Simulation and Experimental Results at X-Band

Remote Sensing

Nuria Duffo¹  Mercedes Vall·llossera²  Adriano Camps²  Ignasi Corbella² 

[1] Dept. of Signal Theory and Communications, Universitat Politècnica de Catalunya, UPC Campus Nord D3, E-08034 Barcelona, Spain, and SMOS Barcelona Expert Centre, Pg. Marítim de la Barceloneta 37-49, E-08003, Barcelona, Spain;

关键词: polarimetric radiometry;    Stokes parameters;    emission;    scattering;    rain;    drops;   

DOI  :  10.3390/rs1020107

来源: mdpi

【 摘 要 】

Accurate models are used today for infrared and microwave satellite radiance simulations of the first two Stokes elements in the physical retrieval, data assimilation etc. of surface and atmospheric parameters. Although in the past a number of theoretical and experimental works have studied the polarimetric emission of some natural surfaces, specially the sea surface roughened by the wind (Windsat mission), very limited studies have been conducted on the polarimetric emission of rain cells or other natural surfaces. In this work, the polarimetric emission (four Stokes elements) of a rain cell is computed using the polarimetric radiative transfer equation assuming that raindrops are described by Pruppacher-Pitter shapes and that their size distribution follows the Laws-Parsons law. The Boundary Element Method (BEM) is used to compute the exact bistatic scattering coefficients for each raindrop shape and different canting angles. Numerical results are compared to the Rayleigh or Mie scattering coefficients, and to Oguchi’s ones, showing that above 1-2 mm raindrop size the exact formulation is required to model properly the scattering. Simulation results using BEM are then compared to the experimental data gathered with a X-band polarimetric radiometer. It is found that the depolarization of the radiation caused by the scattering of non-spherical raindrops induces a non-zero third Stokes parameter, and the differential phase of the scattering coefficients induces a non-zero fourth Stokes parameter.

【 授权许可】

CC BY   
© 2009 by the authors; licensee Molecular Diversity Preservation International, Basel, Switzerland.