Precision and application range of quasi-single scattering approximation

2005 ◽  
Author(s):  
V.P. Boudak ◽  
A.V. Lubenchenko
Keyword(s):  
Single Scattering ◽  
Application Range ◽  
Scattering Approximation ◽  
Single Scattering Approximation

scholarly journals Fast Hyper-Spectral Radiative Transfer Model Based on the Double Cluster Low-Streams Regression Method

2021 ◽  
Vol 13 (3) ◽  
pp. 434
Author(s):  
Ana del Águila ◽  
Dmitry S. Efremenko
Keyword(s):  
Radiative Transfer ◽  
Single Scattering ◽  
Atmospheric Composition ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Absorption Bands ◽  
Acceleration Techniques ◽  
Scattering Approximation ◽  
Fine Resolution ◽  
Single Scattering Approximation

Fast radiative transfer models (RTMs) are required to process a great amount of satellite-based atmospheric composition data. Specifically designed acceleration techniques can be incorporated in RTMs to simulate the reflected radiances with a fine spectral resolution, avoiding time-consuming computations on a fine resolution grid. In particular, in the cluster low-streams regression (CLSR) method, the computations on a fine resolution grid are performed by using the fast two-stream RTM, and then the spectra are corrected by using regression models between the two-stream and multi-stream RTMs. The performance enhancement due to such a scheme can be of about two orders of magnitude. In this paper, we consider a modification of the CLSR method (which is referred to as the double CLSR method), in which the single-scattering approximation is used for the computations on a fine resolution grid, while the two-stream spectra are computed by using the regression model between the two-stream RTM and the single-scattering approximation. Once the two-stream spectra are known, the CLSR method is applied the second time to restore the multi-stream spectra. Through a numerical analysis, it is shown that the double CLSR method yields an acceleration factor of about three orders of magnitude as compared to the reference multi-stream fine-resolution computations. The error of such an approach is below 0.05%. In addition, it is analysed how the CLSR method can be adopted for efficient computations for atmospheric scenarios containing aerosols. In particular, it is discussed how the precomputed data for clear sky conditions can be reused for computing the aerosol spectra in the framework of the CLSR method. The simulations are performed for the Hartley–Huggins, O2 A-, water vapour and CO2 weak absorption bands and five aerosol models from the optical properties of aerosols and clouds (OPAC) database.

Seismo-Acoustic Benchmark Problems Involving Sloping Solid–Solid Interfaces and Variable Topography

2016 ◽  
Vol 24 (03) ◽  
pp. 1650019 ◽  
Author(s):  
Katherine Woolfe ◽  
Michael D. Collins ◽  
David C. Calvo ◽  
William L. Siegmann
Keyword(s):  
Finite Element ◽  
Wave Equation ◽  
Parabolic Equation ◽  
Finite Element Model ◽  
Element Model ◽  
Single Scattering ◽  
Benchmark Problems ◽  
Scattering Approximation ◽  
Single Scattering Approximation ◽  
Variable Topography

The accuracy of the seismo-acoustic parabolic equation is tested for problems involving sloping solid–solid interfaces and variable topography. The approach involves approximating the medium in terms of a series of range-independent regions, using a parabolic wave equation to propagate the field through each region, and applying a single-scattering approximation to obtain transmitted fields across the vertical interfaces between regions. The accuracy of the parabolic equation method for range-dependent problems in seismo-acoustics was previously tested in the small slope limit. It is tested here for problems involving larger slopes using a finite-element model to generate reference solutions.

The Effect Of Scattered Radiation On Capabilities Of Laser Beam Guidance

2020 ◽  
pp. 110-117
Author(s):  
Gennady A. Kaloshin ◽  
Vladimir P. Budak ◽  
Sergey A. Shishkin ◽  
Vladislav V. Zhukov
Keyword(s):  
Laser Radiation ◽  
Laser Beam ◽  
Single Scattering ◽  
Remote Detection ◽  
Field Observations ◽  
Continuous Laser ◽  
Axial Zone ◽  
Scattering Approximation ◽  
Detection Capabilities ◽  
Single Scattering Approximation

The paper discusses the possibility of remote detection of a continuous laser beam propagating in a scattering continental and coastal atmosphere, when it is recorded outside the axial zone. In the single scattering approximation, estimates of the radianceat the registration site are carried out, which are compared with the threshold characteristics of existing photodetectors in the visible and IR spectral regions. It is shown that the laser radiation (LR) of the beam is reliably recorded in the range of angles (0–180)° at metrological range of visibility equal (5–20) km at night conditions. At twilight, under the same conditions, detection capabilities are significantly reduced. A significant increase of the LR beam radiance contrast with a decrease in its divergence has been shown experimentally in the field observations. At twilight, a decrease in the beam’s radiance contrast is seen. A beam with a divergence equal to 2 ceases to be distinguishable at angles equal to (80–90)°, and a beam with a divergence of 4 – at angles (60–70)°.In this case, the contrast difference reaches up to 10 times.

Sign in / Sign up

Export Citation Format

Share Document