Backscatter and propagation signatures due to hydrometeors along the propagation path, either in earth space propagation links , or radar to target volumes has been studied for a long time specially since the beginnings of radar. However the interest in these propagation properties have seen renewed interest, especially due to innovative use of dual-polarized propagation properties. Since the advent of dual-polarization radars, the dual-polarization propagation properties have become very important. In addition, the innovative uses of dual-polarization propagation properties to mitigate attenuation effects have led to the building of weather radars at attenuating frequencies such as X band. The specific attenuation in precipitation is basically the manifestation of the extinction cross section of the precipitation particles in the path weighted by the size distribution. The specific differential phase between the two linear polarization states is the difference in forward scatter amplitudes, weighted by the size distribution. The attenuation due to rain can be corrected for by measuring the differential propagation phase. In addition the differential propagation properties are weighted closer to the volume of precipitation particles than the backscatter effects such as reflectivity. Therefore the propagation phase measurements are better suited for remote sensing applications. Thus the dual polarized signatures precipitation have become active area of research. Many radars are being built to remotely sense precipitation from the lower S band frequencies such as 3 GHz, to the mm wave range such as 35 GHz. Though it is useful to observe differential propagation phase, it is a challenging measurement. The differential propagation phase is a path integrated quantity and any observation of the characteristics at a small range is estimated as range derivatives that makes it noisy. This paper presents challenges and advantages of dual-polarization propagation measurements through precipitation from 3 to 95 GHz. Observations made at several frequency bands in between such as S, C, X, Ku and Ka will be presented. The impact of attenuation on the choice of polarization state will also be discussed. Subsequently differential propagation properties of multi-frequency systems will be shown for potential use in space borne observations of precipitation.
Dual-polarized Microwave Signatures of Precipitation from Earth and Space Between 3 GHz to 95 GHz
L Baldini;
2013
Abstract
Backscatter and propagation signatures due to hydrometeors along the propagation path, either in earth space propagation links , or radar to target volumes has been studied for a long time specially since the beginnings of radar. However the interest in these propagation properties have seen renewed interest, especially due to innovative use of dual-polarized propagation properties. Since the advent of dual-polarization radars, the dual-polarization propagation properties have become very important. In addition, the innovative uses of dual-polarization propagation properties to mitigate attenuation effects have led to the building of weather radars at attenuating frequencies such as X band. The specific attenuation in precipitation is basically the manifestation of the extinction cross section of the precipitation particles in the path weighted by the size distribution. The specific differential phase between the two linear polarization states is the difference in forward scatter amplitudes, weighted by the size distribution. The attenuation due to rain can be corrected for by measuring the differential propagation phase. In addition the differential propagation properties are weighted closer to the volume of precipitation particles than the backscatter effects such as reflectivity. Therefore the propagation phase measurements are better suited for remote sensing applications. Thus the dual polarized signatures precipitation have become active area of research. Many radars are being built to remotely sense precipitation from the lower S band frequencies such as 3 GHz, to the mm wave range such as 35 GHz. Though it is useful to observe differential propagation phase, it is a challenging measurement. The differential propagation phase is a path integrated quantity and any observation of the characteristics at a small range is estimated as range derivatives that makes it noisy. This paper presents challenges and advantages of dual-polarization propagation measurements through precipitation from 3 to 95 GHz. Observations made at several frequency bands in between such as S, C, X, Ku and Ka will be presented. The impact of attenuation on the choice of polarization state will also be discussed. Subsequently differential propagation properties of multi-frequency systems will be shown for potential use in space borne observations of precipitation.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
