scispace - formally typeset
Search or ask a question
Topic

Polarimetry

About: Polarimetry is a research topic. Over the lifetime, 4637 publications have been published within this topic receiving 72147 citations.


Papers
More filters
Peer ReviewDOI
17 May 2022
TL;DR: In this article , the authors exploit a unique three months dataset of mid-latitude winter clouds observed with vertically pointing triple-frequency (X-, Ka-, W-Band) and polarimetric W-band Doppler radars.
Abstract: The dendritic growth layer (DGL), defined as the temperature region between -20 and -10 °C, plays an important role for ice depositional growth, aggregation, and likely also secondary ice processes. The DGL has been found in the past to exhibit specific observational signatures in polarimetric and vertically pointing radar observations. However, consistent conclusions about their physical interpretation have often not been reached. In this study, we exploit a unique three months dataset of mid-latitude winter clouds observed with vertically pointing triple-frequency (X-, Ka-, W-Band) and polarimetric W-Band Doppler radars. In addition to standard radar moments, we also analyse the multi-wavelength and polarimetric Doppler spectra. New variables, such as the maximum of the spectral ZDR (sZDRmax), allows us to analyse the ZDR signal of asymmetric ice particles independent of the presence of low-ZDR producing aggregates. This unique dataset enables us to investigate correlations between enhanced aggregation and evolution of small ice particles in the DGL. For this, the multi-frequency observations are used to classify all profiles according to their maximum average aggregate size within the DGL. The strong correlation between aggregate class and KDP confirms the expected link between ice particle concentration and aggregation. Interestingly, no correlation between aggregation class and sZDRmax is visible. This indicates that aggregation is rather independent of the aspect ratio and density of ice crystals. A distinct reduction of mean Doppler velocity in the DGL is found to be strongest for cases with largest aggregate sizes. Analyses of spectral edge velocities suggest that the reduction is the combined result of the formation of new ice particles with low fall velocity and a weak updraft. It appears most likely that this updraft is the result of latent heat released by enhanced depositional growth. Clearly, the strongest correlations of aggregate class with other variables are found inside the DGL. Surprisingly, no correlation between aggregate class and concentration or aspect ratio of particles falling from above into the DGL could be found. Only a weak correlation between the mean particle size falling into the DGL and maximum aggregate size within the DGL is apparent. In addition to the correlation analysis, the dataset also allows to study the evolution of radar variables as a function of temperature. We find the ice particle concentration continuously increasing from -18 °C towards the bottom of the DGL. Aggregation increases more rapidly from -15 °C towards warmer temperatures. Surprisingly, KDP and sZDRmax are not reduced by the intensifying aggregation below -15 °C but rather reach their maximum values in the lower half of the DGL. Also below the DGL, KDP and sZDRmax remain enhanced until -4 °C. Only there, additional aggregation appears to deplete ice crystals and therefore reduce KDP and sZDRmax. The simultaneous increase of aggregation and particle concentration inside the DGL necessitates a source mechanism for new ice crystals. As primary ice nucleation is expected to decrease towards warmer temperatures, secondary ice processes are a likely explanation for the increase in ice particle concentration. Previous laboratory experiments strongly point towards ice collisional fragmentation as a possible mechanism for new particle generation. The presence of an updraft in the temperature region of maximum depositional growth might also suggest an important positive feedback mechanism between ice microphysics and dynamics which might further enhance ice particle growth in the DGL.
Proceedings ArticleDOI
24 Jul 2011
TL;DR: The polarimetric GB-SAR can validate the scattering mechanism of buildings by using dielectric dihedral object like a concrete block by detecting the dependency of the azimuth angles by evaluating the polarization orientation angle based on circular polarization basis.
Abstract: The electromagnetic wave scattering from a dielectric dihedral structure is discussed in this paper. In order to measure the scattering mechanism, we measured a scattering from a brick by using a polarimetric GB-SAR system. And we found three scattering characteristics of the dielectric dihedral structure. Especially, separated scattering at the center of the target in HV component and penetration of electromagnetic wave in VV component may be used to extract information of a target. Then, we validated a scattering from a concrete block at different azimuth angles and detected the dependency of the azimuth angles by evaluating the polarization orientation angle based on circular polarization basis. Therefore, the polarimetric GB-SAR can validate the scattering mechanism of buildings by using dielectric dihedral object like a concrete block.
17 Sep 2017
TL;DR: In this article, the polarization of the light is very sensitive to the size, morphology, porosity and composition of the scattering particles, and polarimetric observations could significantly complement observations performed in total light intensity.
Abstract: Many objects of the Solar System have been observed in polarized light [1]. The polarization of the light is very sensitive to the size, morphology, porosity and composition of the scattering particles. As a consequence, polarimetric observations could significantly complement observations performed in total light intensity, providing additional constraints to interpret remote sensing observations.
Posted Content
TL;DR: In this paper, a static, single-shot Stokes polarimeter based on a Fresnel cone is presented, which is the direct spatial analogue to the popular rotating quarter-wave plate approach.
Abstract: Light's polarisation contains information about its source and interactions, from distant stars to biological samples. Polarimeters can recover this information, but reliance on birefringent or rotating optical elements limits their wavelength range and stability. Here we present a static, single-shot polarimeter based on a Fresnel cone - the direct spatial analogue to the popular rotating quarter-wave plate approach. We measure the average angular accuracy to be 2.9 (3.6) degrees for elliptical(linear) polarisation states across the visible spectrum, with the degree of polarisation determined to within 0.12(0.08). Our broadband full Stokes polarimeter is robust, cost-effective, and could find applications in hyper-spectral polarimetry and scanning microscopy.
Posted Content
TL;DR: In this article, a complementary MOS pixel detector with small pixel size was employed as an x-ray photoelectron tracking polarimeter, which achieved an energy resolution of 176 eV (FWHM) at room temperature and the atmospheric condition.
Abstract: X-ray polarimetry in astronomy has not been exploited well, despite its importance. The recent innovation of instruments is changing this situation. We focus on a complementary MOS (CMOS) pixel detector with small pixel size and employ it as an x-ray photoelectron tracking polarimeter. The CMOS detector we employ is developed by GPixel Inc., and has a pixel size of 2.5 $\mathrm{\mu}$m $\times$ 2.5 $\mathrm{\mu}$m. Although it is designed for visible light, we succeed in detecting x-ray photons with an energy resolution of 176 eV (FWHM) at 5.9 keV at room temperature and the atmospheric condition. We measure the x-ray detection efficiency and polarimetry sensitivity by irradiating polarized monochromatic x-rays at BL20B2 in SPring-8, the synchrotron radiation facility in Japan. We obtain modulation factors of 7.63% $\pm$ 0.07% and 15.5% $\pm$ 0.4% at 12.4 keV and 24.8 keV, respectively. It demonstrates that this sensor can be used as an x-ray imaging spectrometer and polarimeter with the highest spatial resolution ever tested.

Network Information
Related Topics (5)
Radar
91.6K papers, 1M citations
85% related
Radiative transfer
43.2K papers, 1.1M citations
83% related
Pixel
136.5K papers, 1.5M citations
83% related
Polarization (waves)
65.3K papers, 984.7K citations
81% related
Light scattering
37.7K papers, 861.5K citations
77% related
Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023419
20221,017
2021166
2020188
2019266
2018212