Improvements for ground-based remote sensing of atmospheric aerosol properties by additional polarimetric measurements

Li, Zhengqiang; Goloub, Philippe; Dubovik, Оleg; Blarel, Luc; Zhang, Wenxing; Podvin, Thierry; Sinyuk, A.; Sorokin, M. G.; Chen, Hongbin; Holben, B. N.; Tanré, D.; Canini, Marius; Buis, Jean-Pierre

doi:10.1016/j.jqsrt.2009.04.009

Cited by 85 publications

(83 citation statements)

References 15 publications

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“…Standard operation of AERONET instruments does not require such knowledge, so we attempted to confirm our knowledge of instrument orientation with observations of U . This is equivalent to the method in Li et al (2009), who identify the reference frame by ensuring the polarization angle, χ , of skylight is consistently 90 • from the scattering plane. In the Appendix, we explore how polarizing filter orientation knowledge accuracy impacts overall measurement uncertainty.…”

Section: Data Explorationmentioning

confidence: 99%

“…More recently, Cimels have been developed that have multiple channels. These have been used to retrieve aerosol optical properties with DoLP (Li et al, 2004(Li et al, , 2006(Li et al, , 2007(Li et al, , 2009(Li et al, , 2010(Li et al, , 2013. A portion of these instruments also make zenith mode measurements in the cloud mode, although polarization data from these measurements are not currently utilized.…”

Section: Multiple-channel Polarimeter Site: Nasa Gsfcmentioning

confidence: 99%

“…The first polarization-sensitive Cimel instruments were constructed with sensitivity in a single channel (870 nm), while more recent versions are sensitive in all channels (typically 400, 500, 675, 870, 1020 and 1640 nm). Clear-sky measurements from these instruments are primarily used to determine aerosol optical properties (Li et al, 2004(Li et al, , 2006(Li et al, , 2007(Li et al, , 2009(Li et al, , 2010(Li et al, , 2013(Li et al, , 2009. Often, these algorithms use measures of quantity of polarization, and discard linear polarization direction information.…”

Section: Introductionmentioning

confidence: 99%

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Cloud thermodynamic phase detection with polarimetrically sensitive passive sky radiometers

et al. 2015

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Abstract. The primary goal of this project has been to investigate if ground-based visible and near-infrared passive radiometers that have polarization sensitivity can determine the thermodynamic phase of overlying clouds, i.e., if they are comprised of liquid droplets or ice particles. While this knowledge is important by itself for our understanding of the global climate, it can also help improve cloud property retrieval algorithms that use total (unpolarized) radiance to determine cloud optical depth (COD). This is a potentially unexploited capability of some instruments in the NASA Aerosol Robotic Network (AERONET), which, if practical, could expand the products of that global instrument network at minimal additional cost.We performed simulations that found, for zenith observations, that cloud thermodynamic phase is often expressed in the sign of the Q component of the Stokes polarization vector. We chose our reference frame as the plane containing solar and observation vectors, so the sign of Q indicates the polarization direction, parallel (positive) or perpendicular (parallel) to that plane. Since the fraction of linearly polarized to total light is inversely proportional to COD, optically thin clouds are most likely to create a signal greater than instrument noise. Besides COD and instrument accuracy, other important factors for the determination of cloud thermodynamic phase are the solar and observation geometry (scattering angles between 40 and 60 • are best), and the properties of ice particles (pristine particles may have halos or other features that make them difficult to distinguish from water droplets at specific scattering angles, while extreme ice crystal aspect ratios polarize more than compact particles).We tested the conclusions of our simulations using data from polarimetrically sensitive versions of the Cimel 318 sun photometer/radiometer that compose a portion of AERONET. Most algorithms that exploit Cimel polarized observations use the degree of linear polarization (DoLP

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Section: Data Explorationmentioning

confidence: 99%

Section: Multiple-channel Polarimeter Site: Nasa Gsfcmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Cloud thermodynamic phase detection with polarimetrically sensitive passive sky radiometers

et al. 2015

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“…Since aerosol scattering alters not only the sky radiance but also its polarization, polarization adds independent measurement degrees of freedom with respect to aerosols (e.g. Vermeulen et al, 2000;Boesche et al, 2006;Li et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

Feasibility of polarized all-sky imaging for aerosol characterization

Kreuter

Blumthaler

2013

Atmos. Meas. Tech.

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In this study, we investigate the method of polarized all-sky imaging with respect to aerosol characterization. As a technical frame work for image processing and analysis, we propose Zernike polynomials to decompose the relative Stokes parameter distributions. This defines a suitable and efficient feature vector which is also appealing because it is independent of calibration, circumvents overexposure problems and is robust against pixel noise. We model the polarized radiances of realistic aerosol scenarios and construct the feature vector space of the key aerosol types in terms of the first two principal components describing the maximal variances. We show that, using this representation, aerosol types can be clearly distinguished with respect to fine and coarse mode dominated size distribution and index of refraction. We further investigate the individual influences of varying aerosol properties and solar zenith angle. This suggests that polarized all-sky imaging may improve aerosol characterization in combination with sky scanning radiometers of the existing Aerosol Robotic Network (AERONET) especially at low aerosol optical depths and low solar zenith angles

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“…Recently, a commercially available ground-based polarimeter, CE318-DP, has been developed by the CIMEL Electronic (Paris, France). Li et al (2009) performed a preliminary analysis of the measurements and found that adding polarization can reduce retrieval errors in the fine mode of the size distribution, the real part of the refractive index and the particle shape parameters.…”

Section: Introductionmentioning

confidence: 99%

The impact of aerosols on polarized sky radiance: model development, validation, and applications

et al. 2010

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Abstract. Although solar radiation initially is unpolarized when entering the Earth's atmosphere, it is polarized by scattering processes with molecules, water droplets, ice crystals, and aerosols. Hence, measurements of the polarization state of radiation can be used to improve remote sensing of aerosols and clouds. The analysis of polarized radiance measurements requires an accurate radiative transfer model. To this end, a new efficient and flexible threedimensional Monte Carlo code to compute polarized radiances has been developed and implemented into MYSTIC (Monte Carlo code for the phYSically correct Tracing of photons In Cloudy atmospheres). The code has been extensively validated against published benchmark results. The polarized downwelling radiation field is calculated for various aerosol types showing the high sensitivity of polarized ultraviolet radiances to the particle microphysics. Model simulations are compared to ground based measurements and found to be qualitatively in good agreement. Quantitative differences can be attributed to the assumed aerosol models based on the OPAC aerosol database, which does not include exactly the types of aerosols that have been observed. This comparison to the measurements shows that there is a high potential to retrieve information about the aerosol type from polarized radiance measurements.

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Improvements for ground-based remote sensing of atmospheric aerosol properties by additional polarimetric measurements

Cited by 85 publications

References 15 publications

Cloud thermodynamic phase detection with polarimetrically sensitive passive sky radiometers

Cloud thermodynamic phase detection with polarimetrically sensitive passive sky radiometers

Feasibility of polarized all-sky imaging for aerosol characterization

The impact of aerosols on polarized sky radiance: model development, validation, and applications

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