Distributed Sky Imaging Radiometry and Tomography

Aides, Amit; Levis, Aviad; Holodovsky, Vadim; Schechner, Yoav Y.; Althausen, Dietrich; Vainiger, Adi

doi:10.1109/iccp48838.2020.9105241

Cited by 17 publications

(17 citation statements)

References 55 publications

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“…They are a valuable basis for further studies on the aerosol radiative impact on climate and investigations towards aerosol-cloud interaction. In the frame of the collaboration with the Technion, the lidar measurements were also used as an anchor for a 3D wide-field sky scatterer tomography study (Aides et al, 2020). During the lidar observations, extensive sky-view images were taken by all-sky cameras from multiple views, to observe and map clouds in 3D across time.…”

Section: Discussionmentioning

confidence: 99%

The vertical aerosol type distribution above Israel – 2 years of lidar observations at the coastal city of Haifa

et al. 2022

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Abstract. For the first time, vertically resolved long-term lidar measurements of the aerosol distribution were conducted in Haifa, Israel. The measurements were performed by a PollyXT multi–wavelength Raman and polarization lidar. The lidar was measuring continuously over a 2-year period from March 2017 to May 2019. The resulting data set is a series of manually evaluated lidar optical property profiles. To identify the aerosol types in the observed layers, a novel aerosol typing method that was developed at TROPOS is used. This method applies optimal estimation to a combination of lidar-derived intensive aerosol properties to determine the statistically most-likely contribution per aerosol component in terms of relative volume. A case study that shows several elevated aerosol layers illustrates this method and shows, for example, that coarse dust particles are observed up to 5 km height over Israel. From the whole data set, the seasonal distribution of the observed aerosol components over Israel is derived. Throughout all seasons, coarse spherical particles like sea salt and hygroscopically grown continental aerosol were observed. These particles originate from continental Europe and were transported over the Mediterranean Sea. Sea-salt particles were observed frequently due to the coastal site of Haifa. The highest contributions of coarse spherical particles are present in summer, autumn, and winter. During spring, mostly coarse non-spherical particles that are attributed to desert dust were observed. This is consistent with the distinct dust season in spring in Israel. An automated time–height-resolved air mass source attribution method identifies the origin of the dust in the Sahara and the Arabian deserts. Fine-mode spherical particles contribute significantly to the observed aerosol mixture during all seasons. These particles originate mainly from the industrial region at the bay of Haifa.

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Section: Discussionmentioning

confidence: 99%

The vertical aerosol type distribution above Israel – 2 years of lidar observations at the coastal city of Haifa

et al. 2022

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“…Our approach seeks an optimal fit of observed data to a physical model based on droplet microphysical and density parameters. Our work here generalizes our prior inversion approaches, which have been based on intensity-only observations [61][62][63][64][65]. Our generalization takes advantage of polarimetric measurements, thereby providing the benefits described in Section 1.1.…”

Section: Outlinementioning

confidence: 95%

Multi-View Polarimetric Scattering Cloud Tomography and Retrieval of Droplet Size

et al. 2020

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Tomography aims to recover a three-dimensional (3D) density map of a medium or an object. In medical imaging, it is extensively used for diagnostics via X-ray computed tomography (CT). We define and derive a tomography of cloud droplet distributions via passive remote sensing. We use multi-view polarimetric images to fit a 3D polarized radiative transfer (RT) forward model. Our motivation is 3D volumetric probing of vertically-developed convectively-driven clouds that are ill-served by current methods in operational passive remote sensing. Current techniques are based on strictly 1D RT modeling and applied to a single cloudy pixel, where cloud geometry defaults to that of a plane-parallel slab. Incident unpolarized sunlight, once scattered by cloud-droplets, changes its polarization state according to droplet size. Therefore, polarimetric measurements in the rainbow and glory angular regions can be used to infer the droplet size distribution. This work defines and derives a framework for a full 3D tomography of cloud droplets for both their mass concentration in space and their distribution across a range of sizes. This 3D retrieval of key microphysical properties is made tractable by our novel approach that involves a restructuring and differentiation of an open-source polarized 3D RT code to accommodate a special two-step optimization technique. Physically-realistic synthetic clouds are used to demonstrate the methodology with rigorous uncertainty quantification.

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“…This section describes the forward model which is used in the first and last stages of the simulation (see III). It starts with the radiative-transfer simulation by pySHDOM as in [9], [13], [23]. Then, the image formation model of a polarized camera is used to generate the multi-view images.…”

Section: Forward Modelmentioning

confidence: 99%

“…( 6), radiative-transfer would be run multiple times to calculate I λ in the spectral band in which Γ λ is significant (with certain wavelength resolution). There is common approximation that simplify these calculations [9], [23]. It is valid if wavelength dependencies within a spectral band are weak.…”

Section: A Imager Modelmentioning

confidence: 99%

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Advances in 3D scattering tomography of cloud micro-physics

Tzabari,

Holodovsky,

Shubi

et al. 2021

Preprint

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We introduce new adjustments and advances in space-borne 3D volumetric scattering-tomography of cloud micro-physics. The micro-physical properties retrieved are the liquid water content and effective radius within a cloud. New adjustments include an advanced perspective polarization imager model, and the assumption of 3D variation of the effective radius. Under these assumptions, we advanced the retrieval to yield results that (compared to the simulated ground-truth) have smaller errors than the prior art. Elements of our advancement include initialization by a parametric horizontally-uniform micro-physical model. The parameters of this initialization are determined by a grid search of the cost function. Furthermore, we added viewpoints corresponding to single-scattering angles, where polarization yields enhanced sensitivity to the droplet micro-physics (i.e., the cloudbow region). In addition, we introduce an optional adjustment, in which optimization of the liquid water content and effective radius are separated to alternating periods. The suggested initialization model and additional advances have been evaluated by retrieval of a set of large-eddy simulation clouds.

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Distributed Sky Imaging Radiometry and Tomography

Cited by 17 publications

References 55 publications

The vertical aerosol type distribution above Israel – 2 years of lidar observations at the coastal city of Haifa

The vertical aerosol type distribution above Israel – 2 years of lidar observations at the coastal city of Haifa

Multi-View Polarimetric Scattering Cloud Tomography and Retrieval of Droplet Size

Advances in 3D scattering tomography of cloud micro-physics

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