Evaluation of satellite-based aerosol datasets and the CAMS reanalysis over the ocean utilizing shipborne reference observations
Jonas Witthuhn, Anja Hünerbein, and Hartwig Deneke
Atmos. Meas. Tech., 13, 1387–1412, https://doi.org/10.5194/amt-13-1387-2020, 2020
Reliable reference measurements over ocean are essential for the evaluation and improvement of satellite- and model-based aerosol datasets. Here, a uniqe set of shipborne reference aerosol products obtained from Microtops sunphotometer and GUVis-3511 shadowband radiometer observations are compared to aerosol products from the MODIS and SEVIRI satellite sensors, and the CAMS reanalysis over the Atlantic Ocean. The present evaluation highlights the importance of an aerosol-type based analysis.
A Phase Separation Inlet for Droplets, Ice Residuals, and Interstitial Aerosols
Libby Koolik, Michael Roesch, Lesly J. Franco Deloya, Chuanyang Shen, A. Gannet Hallar, Ian B. McCubbin, and Daniel J. Cziczo
Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-2020-42,2020
Preprint under review for AMT (discussion: open, 0 comments)
The phaSe seParation Inlet for Droplets icE residuals and inteRstitial aerosols (SPIDER) combines an omni-directional inlet, a Large-Pumped Counterflow Virtual Impactor, a flow tube evaporation chamber, and a Pumped Counterflow Virtual Impactor to separate droplets, ice crystals, and interstitial aerosols for simultaneous sampling. This new inlet for studying mixed-phase clouds is described here, with laboratory verification tests and a deployment at a mountain-top research facility.
Evaluation of satellite-based aerosol datasets and the CAMS reanalysis over the ocean utilizing shipborne reference observations
Jonas Witthuhn, Anja Hünerbein, and Hartwig Deneke
Atmos. Meas. Tech., 13, 1387–1412, https://doi.org/10.5194/amt-13-1387-2020, 2020
Reliable reference measurements over ocean are essential for the evaluation and improvement of satellite- and model-based aerosol datasets. Here, a uniqe set of shipborne reference aerosol products obtained from Microtops sunphotometer and GUVis-3511 shadowband radiometer observations are compared to aerosol products from the MODIS and SEVIRI satellite sensors, and the CAMS reanalysis over the Atlantic Ocean. The present evaluation highlights the importance of an aerosol-type based analysis.
A Phase Separation Inlet for Droplets, Ice Residuals, and Interstitial Aerosols
Libby Koolik, Michael Roesch, Lesly J. Franco Deloya, Chuanyang Shen, A. Gannet Hallar, Ian B. McCubbin, and Daniel J. Cziczo
Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2020-42,2020
Preprint under review for AMT (discussion: open, 0 comments)
The phaSe seParation Inlet for Droplets icE residuals and inteRstitial aerosols (SPIDER) combines an omni-directional inlet, a Large-Pumped Counterflow Virtual Impactor, a flow tube evaporation chamber, and a Pumped Counterflow Virtual Impactor to separate droplets, ice crystals, and interstitial aerosols for simultaneous sampling. This new inlet for studying mixed-phase clouds is described here, with laboratory verification tests and a deployment at a mountain-top research facility.
Retrieval of eddy dissipation rate from derived equivalent vertical gust included in Aircraft Meteorological Data Relay (AMDAR)
Soo-Hyun Kim, Hye-Yeong Chun, Jung-Hoon Kim, Robert D. Sharman, and Matt Strahan
Atmos. Meas. Tech., 13, 1373–1385, https://doi.org/10.5194/amt-13-1373-2020, 2020
We retrieve the eddy dissipation rate (EDR) from the derived equivalent vertical gust included in the Aircraft Meteorological Data Relay data for more reliable and consistent observations of aviation turbulence globally with the single preferred EDR metric. We convert the DEVG to the EDR using two methods (lognormal mapping scheme and best-fit curve between EDR and DEVG), and the DEVG-derived EDRs are evaluated against in situ EDR data reported by US-operated carriers.
Evaluation of UV Aerosol Retrievals from an Ozone Lidar
Shi Kuang, Bo Wang, Michael J. Newchurch, Paula Tucker, Edwin W. Eloranta, Joseph P. Garcia, Ilya Razenkov, John T. Sullivan, Timothy A. Berkoff, Guillaume Gronoff, Liqiao Lei, Christoph J. Senff, Andrew O. Langford, Thierry Leblanc, and Vijay Natraj
Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-2020-40,2020
Preprint under review for AMT (discussion: open, 0 comments)
Ozone lidar is a state-of-art remote sensing instrument to measure atmospheric ozone concentration with high spatio-temporal resolution. In this study, we show that an ozone lidar can also provide reliably aerosol measurements with high resolution by using the collocated data taken by the ozone lidar and an aerosol lidar. This means that ozone lidars are capable of providing simultaneous ozone and aerosol measurements.
Retrieval of eddy dissipation rate from derived equivalent vertical gust included in Aircraft Meteorological Data Relay (AMDAR)
Soo-Hyun Kim, Hye-Yeong Chun, Jung-Hoon Kim, Robert D. Sharman, and Matt Strahan
Atmos. Meas. Tech., 13, 1373–1385, https://doi.org/10.5194/amt-13-1373-2020, 2020
We retrieve the eddy dissipation rate (EDR) from the derived equivalent vertical gust included in the Aircraft Meteorological Data Relay data for more reliable and consistent observations of aviation turbulence globally with the single preferred EDR metric. We convert the DEVG to the EDR using two methods (lognormal mapping scheme and best-fit curve between EDR and DEVG), and the DEVG-derived EDRs are evaluated against in situ EDR data reported by US-operated carriers.
Evaluation of UV Aerosol Retrievals from an Ozone Lidar
Shi Kuang, Bo Wang, Michael J. Newchurch, Paula Tucker, Edwin W. Eloranta, Joseph P. Garcia, Ilya Razenkov, John T. Sullivan, Timothy A. Berkoff, Guillaume Gronoff, Liqiao Lei, Christoph J. Senff, Andrew O. Langford, Thierry Leblanc, and Vijay Natraj
Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2020-40,2020
Preprint under review for AMT (discussion: open, 0 comments)
Ozone lidar is a state-of-art remote sensing instrument to measure atmospheric ozone concentration with high spatio-temporal resolution. In this study, we show that an ozone lidar can also provide reliably aerosol measurements with high resolution by using the collocated data taken by the ozone lidar and an aerosol lidar. This means that ozone lidars are capable of providing simultaneous ozone and aerosol measurements.
Simultaneous leaf-level measurement of trace gas emissions and photosynthesis with a portable photosynthesis system
Mj Riches, Daniel Lee, and Delphine K. Farmer
Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-2020-45,2020
Preprint under review for AMT (discussion: open, 0 comments)
This manuscript presents a thorough characterization of a leaf emission sampling technique, coupling a portable photosynthesis system with different trace gas analyzers. We further provide several case studies using both online and offline gas analyzers to measure different types of leaf emissions. We further highlight both the capabilities and pitfalls of this method.
Simultaneous leaf-level measurement of trace gas emissions and photosynthesis with a portable photosynthesis system
Mj Riches, Daniel Lee, and Delphine K. Farmer
Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2020-45,2020
Preprint under review for AMT (discussion: open, 0 comments)
This manuscript presents a thorough characterization of a leaf emission sampling technique, coupling a portable photosynthesis system with different trace gas analyzers. We further provide several case studies using both online and offline gas analyzers to measure different types of leaf emissions. We further highlight both the capabilities and pitfalls of this method.
The limited-angle projection data of an object, in some practical applications of computed tomography (CT), are obtained due to the restriction of scanning condition.
In these situations, since the projection data are incomplete, some limited-angle artifacts will be presented near the edges of reconstructed image using some classical reconstruction algorithms, such as filtered backprojection (FBP).
The reconstructed image can be fine approximated by sparse coefficients under a proper wavelet tight frame, and the quality of reconstructed image can be improved by an available prior image. To deal with limited-angle CT reconstruction problem, we propose a minimization model that is based on wavelet tight frame and a prior image, and perform this minimization problem efficiently
by iteratively minimizing separately. Moreover, we show that each bounded sequence, which is generated by our method, converges to a critical or a stationary point. The experimental results indicate that our algorithm can efficiently suppress artifacts and noise and preserve the edges of reconstructed image, what's more, the introduced prior image will not miss the important information that is not included in the prior image.
Restoration of images contaminated by multiplicative noise (also
known as speckle noise) is a key issue in coherent image
processing. Notice that images under consideration are often highly compressible in certain suitably chosen
transform domains. By exploring this intrinsic feature embedded in images, this paper introduces a variational restoration model
for multiplicative noise reduction that consists of a term
reflecting the observed image and multiplicative noise, a quadratic
term measuring the closeness of the underlying image in a transform
domain to a sparse vector, and a sparse regularizer for removing
multiplicative noise. Being different from popular existing models
which focus on pursuing convexity, the proposed sparsity-aware model
may be nonconvex depending on the conditions of the parameters of
the model for achieving the optimal denoising performance. An algorithm for finding a critical point of the objective function of the model is developed based on coupled fixed-point equations expressed in terms of the proximity operator of functions that appear in the objective function. Convergence analysis of the algorithm is provided.
Experimental results are shown to demonstrate that the proposed iterative algorithm is sensitive to some initializations for obtaining the best restoration results. We observe that the proposed method with SAR-BM3D filtering images as initial estimates can remarkably outperform several state-of-art methods in terms of the
quality of the restored images.
In this paper, we propose a new augmented Lagrangian method for the mean curvature based image denoising model [33]. Different from the previous works in [21,35], this new method only involves two Lagrange multipliers, which significantly reduces the effort of choosing appropriate penalization parameters to ensure
the convergence of the iterative process of finding the associated saddle points. With this new algorithm, we demonstrate the features of the model numerically, including the preservation of image contrasts and object corners, as well as its capability of generating smooth patches of image graphs. The data selection property and the role of the spatial mesh size for the model performance are also discussed.
We study a variational problem for simultaneous video inpainting and motion estimation.
We consider a functional proposed by Lauze and Nielsen [25] and we study, by means
of the relaxation method of the Calculus of Variations, a slightly modified version of this functional.
The domain of the relaxed functional is constituted of functions of bounded variation and
we compute a representation formula of the relaxed functional.
The representation formula shows the role of discontinuities of the various functions involved
in the variational model. The present study clarifies the variational properties of the
functional proposed in [25] for motion compensated video inpainting.
This work considers the problem of recovering small electromagnetic
inhomogeneities in a bounded domain $\Omega \subset \mathbb{R}^3$,
from a single Cauchy data, at a fixed frequency. This problem has
been considered by several authors, in particular in
[4]. In this paper, we revisit this work with the
objective of providing another identification method and
establishing stability results from a single Cauchy data and at a
fixed frequency. Our approach is based on the asymptotic expansion
of the boundary condition derived in [4] and the
extension of the direct algebraic algorithm proposed in
[1].
This paper develops two accelerated Bregman Operator Splitting (BOS) algorithms with backtracking for solving regularized large-scale linear inverse problems, where the regularization term may not be smooth. The first algorithm improves the rate of convergence for BOSVS [5] in terms of the smooth component in the objective function by incorporating Nesterov's multi-step acceleration scheme under the assumption that the feasible set is bounded. The second algorithm is capable of dealing with the case where the feasible set is unbounded. Moreover, it allows more aggressive stepsize than that in the first scheme by properly selecting the penalty parameter and jointly updating the acceleration parameter and stepsize. Both algorithms exhibit better practical performance than BOSVS and AADMM [21], while preserve the same accelerated rate of convergence as that for AADMM. The numerical results on total-variation based image reconstruction problems indicate the effectiveness of the proposed algorithms.
In this paper, we investigate the relations between the Radon and weighted divergent beam and cone transforms. Novel inversion formulas are derived for the latter two. The weighted cone transform arises, for instance, in image reconstruction from the data obtained by Compton cameras, which have promising applications in various fields, including biomedical and homeland security imaging and gamma ray astronomy. The inversion formulas are applicable for a wide variety of detector geometries in any dimension. The results of numerical implementation of some of the formulas in dimensions two and three are also provided.
In this paper, we introduce a direct method for the inverse scattering problems
in a periodic waveguide from near-field scattered data. The direct scattering problem is to simulate the point sources scattered by a sound-soft obstacle embedded in the periodic waveguide, and the aim of the inverse problem is to reconstruct the obstacle from the near-field data measured on line segments outside the obstacle. Firstly, we will approximate the scattered field by some solutions of a series of Dirichlet exterior problems, and then the shape of the obstacle can be deduced directly from the Dirichlet boundary condition. We will also show that the approximation procedure is reasonable as the solutions of the Dirichlet exterior problems are dense in the set of scattered fields. Finally, we will give several examples to show that this method works well for different periodic waveguides.
We extend the applicability of the Generalized Linear Sampling Method (GLSM)
[2] and the Factorization Method (FM)[16] to the case of
inhomogeneities where the contrast changes sign. Both methods give an exact characterization of the target shapes in
terms of the farfield operator (at a fixed frequency) using the
coercivity property of a special solution operator. We prove this property
assuming that the contrast has a fixed sign in a neighborhood of the
inhomogeneities boundary. We treat both isotropic and anisotropic scatterers with possibly different supports for the isotropic and anisotropic parts. We finally validate the methods through some numerical tests in two
dimensions.
Curvilinear surfaces in 3D Euclidean spaces are commonly represented by triangular meshes. The structure of the triangulation is important, since it affects the accuracy and efficiency of the numerical computation on the mesh. Remeshing refers to the process of transforming an unstructured mesh to one with desirable structures, such as the subdivision connectivity. This is commonly achieved by parameterizing the surface onto a simple parameter domain, on which a structured mesh is built. The 2D structured mesh is then projected onto the surface via the parameterization. Two major tasks are involved. Firstly, an effective algorithm for parameterizing, usually conformally, surface meshes is necessary. However, for a highly irregular mesh with skinny triangles, computing a folding-free conformal parameterization is difficult. The second task is to build a structured mesh on the parameter domain that is adaptive to the area distortion of the parameterization while maintaining good shapes of triangles. This paper presents an algorithm to remesh a highly irregular mesh to a structured one with subdivision connectivity and good triangle quality. We propose an effective algorithm to obtain a conformal parameterization of a highly irregular mesh, using quasi-conformal Teichmüller theories. Conformality distortion of an initial parameterization is adjusted by a quasi-conformal map, resulting in a folding-free conformal parameterization. Next, we propose an algorithm to obtain a regular mesh with subdivision connectivity and good triangle quality on the conformal parameter domain, which is adaptive to the area distortion, through the landmark-matching Teichmüller map. A remeshed surface can then be obtained through the parameterization. Experiments have been carried out to remesh surface meshes representing real 3D geometric objects using the proposed algorithm. Results show the efficacy of the algorithm to optimize the regularity of an irregular triangulation.
