Abstract
In this paper, a novel method for rain rate estimation is researched by polarimetric phase shift of the Global Navigation Satellite System (GNSS). The physical process of GNSS signals propagating through rain-filled medium is investigated, by which the cause of polarimetric phase shift is explored. Then, a theoretical model between polarimetric phase shift Δ ϕ and rain rate R is established and simulated, which is based on the oblate spheroid raindrop model, four different popular raindrop size distribution models and raindrop canting angle distribution across the Space-Earth rain path. Additionally, effects of raindrop size distribution, rain path length, raindrop canting angle and temperature on the Δ ϕ -R relation are discussed systematically. Other factors in the slant path such as ice crystals, melting particles and ionosphere are also researched preliminarily. The results show that polarimetric phase shift of GNSS signals, which has a strong correlation with rain rate, can be used to estimate the rain rate, and these influencing factors, raindrop size distribution, rain path length, raindrop canting angle and temperature, are quite important in the process of rain rate measurement. It can be also found that the effect of ice crystals can be negligible, while that of melting particles should be considered, and though ionosphere effects are not obvious, the ionospheric anomalies cannot be neglected in future experiments. This method has potential applications in real-time, continuous, extreme precipitation reconnaissance and numerical weather prediction.
Highlights
Polarimetric characteristics of a microwave, when it propagates through a region containing raindrops, have been of great concern in many fields such as radio communication, remote sensing, and radar meteorology [1,2]
The relation between the polarimetric phase shift of Global Navigation Satellite System (GNSS) signals and rain rate is discussed in detail in Section 3; the effects of raindrop size distribution, rain path length, raindrop canting angle and temperature on the polarimetric phase shift and rain rate relation model are investigated systematically; we investigate the effects of ice crystals, melting particles and the ionosphere
Since the frequencies of GNSS signals are in the L-band, the raindrop scattering is in the range of applicability of the Rayleigh scattering hypothesis
Summary
Polarimetric characteristics of a microwave, when it propagates through a region containing raindrops, have been of great concern in many fields such as radio communication, remote sensing, and radar meteorology [1,2]. In radar meteorology, as the past decades have witnessed the rapid development of the polarimetric weather radar technique, rain rate estimation from radar polarization parameters has been investigated extensively and intensively [3,4,5]. In radar meteorology, its theoretical research mainly focuses on backward scattering characteristics of cloud particles or rain particles in the S-, C- and X-band, while the forward scattering properties of rain particles in the L-band, especially the forward-scattering polarimetric properties, have been investigated very little. The rain-induced polarimetric properties of GNSS signals, which are right-hand circularly polarized (RHCP) microwaves at frequencies from 1.164 GHz to 1.6155 GHz belonging to the L-band [9], have been systematically studied very little
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