Monte Carlo radiative transfer simulation for the near-ocean-surface high-resolution downwelling irradiance statistics

Abstract. The OSIRIS instrument on board the Odin spacecraft has been measuring limb scattered radiance since 2001. The vertical radiance profiles measured as the instrument nods are inverted, with the aid of the SASKTRAN radiative transfer model, to obtain vertical profiles of trace atmospheric constituents. Here we describe two newly developed modes of the SASKTRAN radiative transfer model: a high spatial resolution mode, and a Monte Carlo mode. The high spatial resolution mode is a successive orders model capable of modelling the multiply scattered radiance when the atmosphere is not spherically symmetric; the Monte Carlo mode is intended for use as a highly accurate reference model. It is shown that the two models agree in a wide variety of solar conditions to within 0.2%. As an example case for both models, Odin-OSIRIS scans were simulated with the Monte Carlo model and retrieved using the high resolution model. A systematic bias of up to 4% in retrieved ozone number density between scans where the instrument is scanning up or scanning down was identified. It was found that calculating the multiply scattered diffuse field at five discrete solar zenith angles is sufficient to eliminate the bias for typical Odin-OSIRIS geometries.

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Monte Carlo simulation of polarized radiative transfer over the ocean surface

10.5194/egusphere-egu2020-10377 ◽

2020 ◽

Author(s):

Tatiana Russkova ◽

Konstantin Shmirko

Keyword(s):

Monte Carlo ◽

Radiative Transfer ◽

Optical Measurement ◽

Polarization State ◽

Ocean Surface ◽

Distribution Model ◽

Radiative Transfer Model ◽

Transfer Model ◽

Atmospheric Conditions ◽

Russian Science

<p>An increasing number of remote sensing instruments measure the polarization state of electromagnetic radiation. The polarization state contains all the information about the sensing object that is available to optical measurement methods. Taking into account the polarization during the radiative transfer simulation leads to a redistribution of energy between the components of the Stokes vector, thereby introducing a correction to the scalar approximation, the value of which may be significant. This information potentially can be used to improve algorithms for removal of surface glint, underwater visibility, to improve radiative transfer retrieval methods if the polarization-sensitive sensors are employed.</p><p>A Monte Carlo polarized radiative transfer model termed MCPOLART for the ocean-atmosphere system that is able to predict the total and the polarized signals has been developed. &#160;Since the ocean surface is not smooth, the radiation model must take into account waves that occur under the influence of wind. The Cox-Munk ocean wave slope distribution model is used in calculation of the reflection matrix of a wind-ruffled ocean surface. Sensitivity studies are conducted for various ocean-surface and atmospheric conditions, geometric schemes of lighting and observation. &#160;</p><p>This work was supported by the Russian Science Foundation (project No. 19-77-10022).</p>

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High-resolution and Monte Carlo additions to the SASKTRAN radiative transfer model

Atmospheric Measurement Techniques ◽

10.5194/amt-8-2609-2015 ◽

2015 ◽

Vol 8 (6) ◽

pp. 2609-2623 ◽

Cited By ~ 22

Author(s):

D. J. Zawada ◽

S. R. Dueck ◽

L. A. Rieger ◽

A. E. Bourassa ◽

N. D. Lloyd ◽

...

Keyword(s):

Monte Carlo ◽

High Resolution ◽

Radiative Transfer ◽

Spatial Resolution ◽

High Spatial Resolution ◽

Imaging System ◽

Monte Carlo Model ◽

Radiative Transfer Model ◽

Transfer Model ◽

Systematic Bias

Abstract. The Optical Spectrograph and InfraRed Imaging System (OSIRIS) instrument on board the Odin spacecraft has been measuring limb-scattered radiance since 2001. The vertical radiance profiles measured as the instrument nods are inverted, with the aid of the SASKTRAN radiative transfer model, to obtain vertical profiles of trace atmospheric constituents. Here we describe two newly developed modes of the SASKTRAN radiative transfer model: a high-spatial-resolution mode and a Monte Carlo mode. The high-spatial-resolution mode is a successive-orders model capable of modelling the multiply scattered radiance when the atmosphere is not spherically symmetric; the Monte Carlo mode is intended for use as a highly accurate reference model. It is shown that the two models agree in a wide variety of solar conditions to within 0.2 %. As an example case for both models, Odin–OSIRIS scans were simulated with the Monte Carlo model and retrieved using the high-resolution model. A systematic bias of up to 4 % in retrieved ozone number density between scans where the instrument is scanning up or scanning down was identified. The bias is largest when the sun is near the horizon and the solar scattering angle is far from 90°. It was found that calculating the multiply scattered diffuse field at five discrete solar zenith angles is sufficient to eliminate the bias for typical Odin–OSIRIS geometries.

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Modelling high-resolution transmission spectra of the ultra-hot jupiter wasp-76b with 3D Monte-Carlo radiative transfer

10.5194/epsc2020-1118 ◽

2020 ◽

Author(s):

Joost Wardenier ◽

Vivien Parmentier ◽

Graham Lee

Keyword(s):

Monte Carlo ◽

High Resolution ◽

Radiative Transfer ◽

Cross Correlation ◽

Circulation Model ◽

High Spectral Resolution ◽

Cloud Formation ◽

Time Varying ◽

Hot Jupiters ◽

3D Monte Carlo

<div class="c-message_kit__gutter"> <div class="c-message_kit__gutter__right" data-qa="message_content"> <div class="c-message_kit__blocks c-message_kit__blocks--rich_text"> <div class="c-message__message_blocks c-message__message_blocks--rich_text"> <div class="p-block_kit_renderer" data-qa="block-kit-renderer"> <div class="p-block_kit_renderer__block_wrapper p-block_kit_renderer__block_wrapper--first"> <div class="p-rich_text_block" dir="auto"> <div class="p-rich_text_section">Ultra-hot Jupiters are tidally-locked gas giants with two chemical regimes: on the scorching dayside molecular species are dissociated and metals are ionised, while the permanent nightside is cool enough for cloud formation to occur. This means that the abundances of particular chemical species, such as iron, will exhibit a sharp gradient across the terminator region, which can be probed by transmission spectroscopy. We present a state-of-the-art 3D Monte-Carlo radiative transfer framework, adapted from Lee et al. (2017, 2019), that allows for the 3D modelling of high-resolution spectra of ultra-hot Jupiters. We use this tool to post-process the output of the SPARC/MITgcm global circulation model, with the aim to better understand how inhomogeneous chemistry, clouds and Doppler shifts due to atmospheric dynamics impact the appearance of a transit spectrum and its cross-correlation signal.</div> <div class="p-rich_text_section">&#160;</div> <div class="p-rich_text_section">In this talk, we apply our model to the transit of WASP-76b, for which Ehrenreich et al. (2020) recently presented a time-varying iron signature at high spectral resolution. The observation suggests that iron condenses on the nightside of the planet. We show that different parts of the limb lead to very different cross-correlation signals and we show that the relative contributions from the east and west limb change during the transit, resulting in a time-varying cross-correlation signal. Finally, we explore different atmospheric scenarios for WASP-76b and we demonstrate that the occurrence of iron condensation, combined with the specific time-varying geometry during the transit, can quantitatively reproduce the Ehrenreich et al. (2020) result.</div> </div> </div> </div> </div> </div> </div> </div> <div class="c-message_actions__container c-message__actions" role="group" aria-label="Message shortcuts" data-qa="message-actions">&#160;</div>

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A COMBINED P1 AND MONTE CARLO MODEL FOR MULTIDIMENSIONAL RADIATIVE TRANSFER PROBLEMS IN SCATTERING MEDIA

Computational Thermal Sciences An International Journal ◽

10.1615/computthermalscien.v2.i6.60 ◽

2010 ◽

Vol 2 (6) ◽

pp. 549-560 ◽

Cited By ~ 10

Author(s):

Wojciech Lipinski ◽

Leonid A. Dombrovsky

Keyword(s):

Monte Carlo ◽

Radiative Transfer ◽

Monte Carlo Model ◽

Scattering Media ◽

Transfer Problems

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Exploring the robustness of Keplerian signals to the removal of active and telluric features

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3180 ◽

2020 ◽

Vol 500 (1) ◽

pp. 548-557

Author(s):

M Lisogorskyi ◽

H R A Jones ◽

F Feng ◽

R P Butler ◽

S Vogt

Keyword(s):

Monte Carlo ◽

High Resolution ◽

Monte Carlo Simulations ◽

Large Amplitude ◽

Absorption Cell ◽

Stellar Rotation ◽

Long Period ◽

Active Line ◽

Low Amplitude ◽

Rotation Signal

ABSTRACT We examine the influence of activity- and telluric-induced radial velocity (RV) signals on high-resolution spectra taken with an iodine absorption cell. We exclude 2-$\mathring{\rm A}$ spectral chunks containing active and telluric lines based on the well-characterized K1V star α Centauri B and illustrate the method on Epsilon Eridani – an active K2V star with a long-period, low-amplitude planetary signal. After removal of the activity- and telluric-sensitive parts of the spectrum from the RV calculation, the significance of the planetary signal is increased and the stellar rotation signal disappears. In order to assess the robustness of the procedure, we perform Monte Carlo simulations based on removing random chunks of the spectrum. Simulations confirm that the removal of lines impacted by activity and tellurics provides a method for checking the robustness of a given Keplerian signal. We also test the approach on HD 40979, which is an active F8V star with a large-amplitude planetary signal. Our Monte Carlo simulations reveal that the significance of the Keplerian signal in the F star is much more sensitive to wavelength. Unlike the K star, the removal of active lines from the F star greatly reduces the RV precision. In this case, our removal of a K star active line from an F star does not a provide a simple useful diagnostic because it has far less RV information and heavily relies on the strong active lines.

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