Plane-parallel Layer Research Articles

Fabry–Perot enhancement of liquid crystals birefringence effects in terahertz range

Abstract THz technology is a rapidly advancing field in both fundamental and applied research, integrating novel approaches from optical and microwave ranges. Despite the wide applications of liquid crystals (LCs) in the visible range, their efficiency in the THz range is limited due to the low optical path length of existing anisotropic LC materials. In this work, we propose and explore the advantages of incorporating a LC core layer into the Fabry-Perot resonator as a simple strategy to enhance the observed birefringence effects. This enhancement is achieved through multiple wave passes through the LC layer, effectively increasing the effective optical path length.
In particular, we demonstrate a more than tenfold improvement in the efficiency of wave transformation within a plane-parallel LC layer.
Our findings are well correlated with the THz response of an LC cell composed of two parallel thick quartz substrates infiltrated with commercially available E48 liquid crystal, as observed in our experiments. The low switching voltage for cells with pyrocarbon-based electrodes is also demonstrated.

NON-STATIONARY WAVES IN A FUNCTIONALLY GRADED VISCOELASTIC PLANE-PARALLEL LAYER2

The propagation of nonstationary disturbances in a plane-parallel layer of infinite extent, which arise as a result of normal dynamic loading of one of its surfaces when the other surface is stationary, is investigated. The material of the layer is assumed to be functionally graded and, at the same time, viscoelastic. The hereditary properties of such a material are taken into account using linear integral Boltzmann–Volterra relations with regular kernels in the form of partial sums of the Prony's series. The peculiarity of this work is that here the parameters of the relaxation kernels are considered continuous functions of the transverse coordinate in the same way as other physical and mechanical characteristics. A method was used for the study, which consists in replacing a functionally graded material with an approximating layered homogeneous structure with continuity conditions at the contact of homogeneous layers. The solution of the nonstationary dynamic linear viscoelasticity problem for a package of plane homogeneous viscoelastic layers is presented in a special form, which greatly simplifies its numerical implementation, especially with a large number of layers with different hereditary properties. This made it possible to successfully apply this method and carry out a series of calculations using an efficient algorithm. Transient wave processes are investigated in the case when the parameters of a functionally graded material are non-monotonic functions of the transverse coordinate, symmetrical with respect to the middle surface of the layer. A comparison of transient wave processes for different types of these functions is carried out. The convergence of the calculation results with an increase in the number of approximating homogeneous layers with a continuous dependence of the external load on time is confirmed. The significant influence of both heterogeneity and viscosity of the material on nonstationary wave processes has been established.

Unifying radiative transfer models in computer graphics and remote sensing, Part II: A differentiable, polarimetric forward model and validation

The constellation of Earth-observing satellites continuously collects measurements of scattered radiance, which must be transformed into geophysical parameters in order to answer fundamental scientific questions about the Earth. Retrieval of these parameters requires highly flexible, accurate, and fast forward and inverse radiative transfer models. Existing forward models used by the remote sensing community are typically accurate and fast, but sacrifice flexibility by assuming the atmosphere or ocean is composed of plane-parallel layers. Monte Carlo forward models can handle more complex scenarios such as 3D spatial heterogeneity, but are relatively slower. We propose looking to the computer graphics community for inspiration to improve the statistical efficiency of Monte Carlo forward models and explore new approaches to inverse models for remote sensing. In Part 2 of this work, we demonstrate that Monte Carlo forward models in computer graphics are capable of sufficient accuracy for remote sensing by extending Mitsuba 3, a forward and inverse modeling framework recently developed in the computer graphics community, to simulate simple atmosphere-ocean systems and show that our framework is capable of achieving error on par with codes currently used by the remote sensing community on benchmark results.

Unifying radiative transfer models in computer graphics and remote sensing, Part I: A survey

The constellation of Earth-observing satellites continuously collects measurements of scattered radiance, which must be transformed into geophysical parameters in order to answer fundamental scientific questions about the Earth. Retrieval of these parameters requires highly flexible, accurate, and fast forward and inverse radiative transfer models. Existing forward models used by the remote sensing community are typically accurate and fast, but sacrifice flexibility by assuming the atmosphere or ocean is composed of plane-parallel layers. Monte Carlo forward models can handle more complex scenarios such as 3D spatial heterogeneity, but are relatively slower. We propose looking to the computer graphics community for inspiration to improve the statistical efficiency of Monte Carlo forward models and explore new approaches to inverse models for remote sensing. In Part 1 of this work, we examine the evolution of radiative transfer models in computer graphics and highlight recent advancements that have the potential to push forward models in remote sensing beyond their current periphery of realism.

Liquid cloud optical property retrieval and associated uncertainties using multi-angular and bispectral measurements of the airborne radiometer OSIRIS

Abstract. In remote sensing applications, clouds are generally characterized by two properties: cloud optical thickness (COT) and effective radius of water–ice particles (Reff), as well as additionally by geometric properties when specific information is available. Most of the current operational passive remote sensing algorithms use a mono-angular bispectral method to retrieve COT and Reff. They are based on pre-computed lookup tables while assuming a homogeneous plane-parallel cloud layer. In this work, we use the formalism of the optimal estimation method, applied to airborne near-infrared high-resolution multi-angular measurements, to retrieve COT and Reff as well as the corresponding uncertainties related to the measurement errors, the non-retrieved parameters, and the cloud model assumptions. The measurements used were acquired by the airborne radiometer OSIRIS (Observing System Including PolaRization in the Solar Infrared Spectrum), developed by the Laboratoire d'Optique Atmosphérique. It provides multi-angular measurements at a resolution of tens of meters, which is very suitable for refining our knowledge of cloud properties and their high spatial variability. OSIRIS is based on the POLDER (POlarization and Directionality of the Earth's Reflectances) concept as a prototype of the future 3MI (Multi-viewing Multi-channel Multi-polarization Imager) planned to be launched on the EUMETSAT-ESA MetOp-SG platform in 2024. The approach used allows the exploitation of all the angular information available for each pixel to overcome the radiance angular effects. More consistent cloud properties with lower uncertainty compared to operational mono-directional retrieval methods (traditional bispectral method) are then obtained. The framework of the optimal estimation method also provides the possibility to estimate uncertainties of different sources. Three types of errors were evaluated: (1) errors related to measurement uncertainties, which reach 6 % and 12 % for COT and Reff, respectively, (2) errors related to an incorrect estimation of the ancillary data that remain below 0.5 %, and (3) errors related to the simplified cloud physical model assuming independent pixel approximation. We show that not considering the in-cloud heterogeneous vertical profiles and the 3D radiative transfer effects leads to an average uncertainty of 5 % and 4 % for COT and 13 % and 9 % for Reff.

Casimir-Polder interaction with Chern-Simons boundary layers

Green functions scattering method is generalized to consider mixing of electromagnetic polarizations after reflection from the plane boundary between different media and applied to derivation of the Casimir-Polder potential in systems with Chern-Simons plane boundary layers. The method is first applied to derive the Casimir-Polder potential of an anisotropic atom in the presence of a Chern-Simons plane boundary layer on a dielectric half-space. Then a general result for the Casimir-Polder potential of an anisotropic atom between two dielectric half-spaces with Chern-Simons plane parallel boundary layers is derived. The Casimir-Polder potential of an anisotropic atom between two Chern-Simons plane parallel layers in vacuum is expressed through special functions. Novel P-odd three-body vacuum effects are discovered and analyzed in the system of two Chern-Simons plane parallel layers and a neutral atom in its ground state between the layers. Remarkably, P-odd three-body vacuum effects arising due to 180 degree rotation of one of the Chern-Simons layers can be verified in experiments with neutral atoms having QED dipole interaction with an electromagnetic field.

Influence of nano-sized horizontal inhomogeneities on surface profiling by means of XPS

Quantitative analysis of thin films surface is performed by means of X-ray electron spectroscopy (XPS) according to a calculation model assuming surface layers of the target to be homogeneous and parallel. However, almost every surface of an ultra-thin film is rough. A study of such surface using the plane-parallel layer model will lead to incorrect results. This work proposes to use the model of inhomogeneous stochastic nano-structured surface layer for ultra-thin film profiling. Surface stochastic nano-structured inhomogeneities are described by the normal Gauss distribution function. To determine these inhomogeneities, three parameters are specified: dispersion (spread of thicknesses by the layer), mean and maximal thickness of the surface layer. For the first time, the type of X-ray photoelectron spectrum of an inhomogeneous stochastic nano-structured surface is found that is determined by functions of photoelectron production and transmission through that surface layer. The designed model is based on the following assumptions: photoelectrons are produced in substance and travel straight-forward (Straight Line Approximation) along the surface, photoelectron flux density decreases in the layer according to the Bouguer–Lambert law, photoelectrons of different energies lose energy differently, photoelectron energy losses in bulk and on surface differ. Modeling of X-ray photoelectron spectra of an oxidized metal film is performed using different models: homogeneous plane-parallel layers, an island nano-structured surface layer and an inhomogeneous stochastic nano-structured surface layer. Ranges of applicability of plane-parallel layer models and simple periodical nano-structured island surface layer for inhomogeneous stochastic nano-structured surface profiling are determined. The model of homogeneous plane-parallel layers shows satisfactory profiling results by some values of parameters of an inhomogeneous stochastic surface layer. It is shown that the model of a simple periodically nano-structured island layer leads to inadequate results by profiling of an inhomogeneous stochastic surface. The investigation shows that for more accurate profiling of an inhomogeneous ultra-thin film, it is necessary to consider inhomogeneity of a real surface, otherwise the calculated results would not match the true profile.

Introduction of the DISAMAR radiative transfer model: determining instrument specifications and analysing methods for atmospheric retrieval (version 4.1.5)

Abstract. DISAMAR (determining instrument specifications and analysing methods for atmospheric retrieval) is a computer model developed to simulate retrievals of properties of atmospheric trace gases, aerosols, clouds, and the ground surface from passive remote sensing observations in a wavelength range from 270 to 2400 nm. It is being used for the TROPOMI/Sentinel-5P and Sentinel-4/5 missions to derive Level-1b product specifications. DISAMAR uses the doubling–adding method and the layer-based orders of scattering method for radiative transfer calculations. It can perform retrievals using three different approaches: optimal estimation (OE), differential optical absorption spectroscopy (DOAS), and the combination of DOAS and OE, called DISMAS (differential and smooth absorption separated). The derivatives, which are needed in the OE and DISMAS retrievals, are derived in a semi-analytical way from the adding formulae. DISAMAR uses plane-parallel homogeneous atmospheric layers with a pseudo-spherical correction for large solar zenith angles. DISAMAR has various novel features and diverse retrieval possibilities, such as retrieving aerosol layer heights and ozone vertical profiles. This paper provides an overview of the DISAMAR model version 4.1.5 without treating all the details. We focus on the principle of the layer-based orders of scattering method, the calculation of the semi-analytical derivatives, and the DISMAS retrieval method, and it is to our knowledge the first time that these methods are described. We demonstrate some applications of DISMAS and the derivatives.

Luminance Factor Modelling For An Arbitrary Surface

Reflection characteristics of asphalt pavements play one of the key roles in road lighting, as luminance is normalized and multiple reflections are absent. The values of the luminance factors of road surfaces can be found by carrying out measurements, but this is not always possible, since it requires the extraction of samples, or is laborious. Therefore, in this article it is proposed to model the spatialangular characteristics of reflection. The developed models (analytical and statistical) allow finding luminance factors for arbitrary angles of incidence and sighting. The models are based on a scattering planeparallel layer. The following optical properties of the medium serve as input data: single scattering albedo, optical thickness, phase function of the particles inside the layer. To validate the models, a comparison was made with the measurement results.

Поправка к статье Усиление электрической площади импульса при отражениях от движущегося зеркала" Оптика и спектроскопия 130 (9), 1402--1404 (2022)

It is indicated that sets of plane-parallel layers of linear materials do not reflect the zero-frequency component of the incident pulse and therefore cannot serve as mirrors for unipolar pulses. The amplification of the electric area is possible with Fresnel reflection from an unlimited medium with a refractive index lower than that of the medium in which the incident pulse propagates. The same is realized in the case of a thick layer of such a medium with the exclusion of the influence of reflection by its rear face due to the slope or roughness of the face. The movement of the boundary does not lead to an additional amplification of the electric area, since the increase in the peak amplitude of the wave upon reflection is compensated by a decrease in the pulse duration.

Fully developed anelastic convection with no-slip boundaries

Anelastic convection at high Rayleigh number in a plane parallel layer with no slip boundaries is considered. Energy and entropy balance equations are derived, and they are used to develop scaling laws for the heat transport and the Reynolds number. The appearance of an entropy structure consisting of a well-mixed uniform interior, bounded by thin layers with entropy jumps across them, makes it possible to derive explicit forms for these scaling laws. These are given in terms of the Rayleigh number, the Prandtl number and the bottom to top temperature ratio, which also measures how much the density varies across the layer. The top and bottom boundary layers are examined and they are found to be very different, unlike in the Boussinesq case. Elucidating the structure of these boundary layers plays a crucial part in determining the scaling laws. Physical arguments governing these boundary layers are presented, concentrating on the case in which the boundary layers are so thin that temperature and density vary little across them, even though there may be substantial temperature and density variations across the whole layer. Different scaling laws are found, depending on whether the viscous dissipation is primarily in the boundary layers or in the bulk. The cases of both high and low Prandtl number are considered. Numerical simulations of no-slip anelastic convection up to a Rayleigh number of $10^7$ have been performed and our theoretical predictions are compared with the numerical results.

Polarization Features of Diffraction of Light by Reflective Holographic Phase Gratings in a Plane-Parallel Layer

Polarization Features of Diffraction of Light by Reflective Holographic Phase Gratings in a Plane-Parallel Layer

ON THE INFLUENCE OF THE SIZE OF FLAKE GRAPHITE INCLUSIONS AND ITS VOLUME CONTENT ON THE ACOUSTIC PARAMETERS OF CAST IRON AND THE CHARACTERISTICS OF ULTRASONIC LONGITUDINAL WAVE SIGNALS

Algorithms have been presented for calculating the velocity (in the approximation of a fine-layered model) and the attenuation coefficient of a longitudinal ultrasonic wave in cast iron, depending on the average size of graphite elements and its volume content, the calculation results for which are qualitatively confirmed experimentally. The calculation was performed using a fine-layered model of the structure, the graphite inclusions were described in the form of plane-parallel layers placed in an isotropic elastic medium (metal base). Computer simulation of acoustic paths for a mediumcast iron with flake graphite for standard direct converters is carried out in order to study the influence of such a medium on the characteristics of transmitted and received signals during ultrasonic testing. In the course of the research, a previously developed model was used to calculate the attenuation coefficient of longitudinal waves in cast iron with flake graphite due to their Rayleigh and phase scattering on graphite inclusions. Computer simulation of the acoustic characteristics of the signals of a direct linear probe with a phased array in cast iron with flake graphite was carried out, during which the shape of the acoustic pulses of the longitudinal wave was calculated, depending on the distance traveled by the wave and the value of the attenuation coefficient for various models of cast iron. The main modeled characteristics of the transducer include the directivity characteristic and the change in the signal amplitude along the acoustic axis. It is shown that for cast iron with flake graphite, there are cases when the directivity of the probe with a phased array transmitted into the cast iron is practically absent.

Free-Standing Composite Films Based on Thiol-Ene and PEDOT: PSS Layers for Optoelectronic Applications.

Free-standing composite films were fabricated by combining the plane parallel layers of thiol-ene based on pentaerythritol tetrakis(3-mercaptopropionate)-1,3,5-triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione (PETMP-TTT) UV curable polymer and poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) conductive polymer. A systematic analysis was performed with the focus on mechanical performance of the free-standing composite films. The PEDOT:PSS/PETMP-TTT composite exhibited higher values of adhesion force compared to the free-standing PETMP-TTT film due to hydrophilic nature of the PEDOT:PSS layer. The composite was found to be highly transparent in the range of 380–800 nm. The Young’s modulus and tensile strength of PETMP-TTT were found to be 3.6 ± 0.4 GPa and 19 ± 3 MPa, while for PEDOT:PSS/PETMP-TTT to be 3.5 ± 0.3 GPa and 20 ± 3 MPa, respectively. The sheet resistance values of the PEDOT:PSS layer in the composite film were found to be highly stable after a number of bending iterations with slight increase in sheet resistance from 108 to 118 ± 2 Ω/□. The resultant PEDOT:PSS/PETMP-TTT composite can be further used in optoelectronic applications.

Solar radiation budget in the atmosphere under broken cloudy sky. An analytical model

This study theoretically investigates the transport of broadband solar radiation in the Earth's cloudy atmosphere (extended and broken) by considering three plane parallel layers: i) thin bottom layer adjacent to the Earth's surface; ii) intermediate layer where clouds are most embedded; and iii) upper layer that is essentially cloud-free with possible occurrence of only thin clouds. These three layers are coupled by upwelling and downwelling radiation exchanges, including multiple retro-diffusion, and both direct beam and diffuse components are considered. The interrelation and relative magnitude of the solar radiation flux cascade across the atmosphere - αP, Ra, Rc, Rg and G/H – was established and explored as a tool for the present simulations. Two distinct radiation transport regimes through the inter-cloud gaps are identified, with the regime transition occurring when (AR*TAN(θ)+1)*CF = 1 where AR, θ and CF are the cloud aspect ratio, solar zenith angle, and cloud fraction, respectively. The variation of the solar radiation fluxes with CF and θ exhibit the transition between the two radiation transport regimes, as evidenced in the flux absorbed in the cloudy layer. The effect of AR upon the solar fluxes also exhibits the two radiation transport regimes, with one regime having linear dependence of the various fluxes on AR and the other one having fluxes stay at constant levels independent of AR. The shape factor SF of cloud top and bottom boundary “surfaces” is introduced to account for the self-irradiation effect for different cloud types. It is found that increased roughness of one or both boundaries increases the cloud absorptance in all cases whereas transmittance and reflectance for upwelling and downwelling can either be diminished or enhanced.With the proposed model the estimated impact of clouds on the enhancement of the shortwave radiation absorption in the atmospheric column was improved leading to results closer to the cloudy-sky absorptance observations reported in the literature. The ratio of the cloud radiative forcing at the surface to the cloud radiative forcing at the top of the atmosphere (Rnet), obtained by means of the present model, lead to Rnet = 1.3, closer to the estimate of 1.5 by Cess et al. than the values reported by other cloud radiative transfer models.

Holographic extraction of plane waves from an ultrasound beam for acoustic characterization of an absorbing layer of finite dimensions.

For the acoustic characterization of materials, a method is proposed for interpreting experiments with finite-sized transducers and test samples in terms of the idealized situation in which plane waves are transmitted through an infinite plane-parallel layer. The method uses acoustic holography, which experimentally provides complete knowledge of the wave field by recording pressure waveforms at points on a surface intersected by the acoustic beam. The measured hologram makes it possible to calculate the angular spectrum of the beam to decompose the field into a superposition of plane waves propagating in different directions. Because these waves cancel one another outside the beam, the idealized geometry of an infinite layer can be represented by a sample of finite size if its lateral dimensions exceed the width of the acoustic beam. The proposed method relies on holograms that represent the acoustic beam with and without the test sample in the transmission path. The method is described theoretically, and its capabilities are demonstrated experimentally for silicone rubber samples by measuring their frequency-dependent phase velocities and absorption coefficients in the megahertz frequency range.

Applying orbital multi-angle photopolarimetric observations to study properties of aerosols in the Earth's atmosphere: Implications of measurements in the 1.378 µm spectral channel to retrieve microphysical characteristics and composition of stratospheric aerosols

We analyze the possibilities of orbital photopolarimetric measurements to study properties of aerosols in the Earth's atmosphere. As an example, we consider the case when such measurements are performed within a narrow spectral channel centered at 1.378 µm that allows to retrieve microphysical characteristics of stratospheric aerosols separately from those of tropospheric aerosols. We consider the case of stratospheric aerosols caused by volcanic eruption, and adopt the model of the stratosphere in the form of a homogeneous plane-parallel layer composed of polydisperse spherical particles. We use numerically exact solutions of the vector radiative transfer equation to theoretically simulate measurements carried out at various numbers of scattering angles, including: (i) radiance measurements alone; (ii) polarization measurements alone; and (iii) radiance and polarization measurements together. The results of computations show that the simultaneous use of radiance and polarization measurements at a sufficiently large number of scattering angles enables one to retrieve the optical thickness, effective radius, and refractive index of aerosols with adequate accuracy. We demonstrate how the accuracy of the derived values of the optical parameters of aerosols depends on the accuracy of measurements of the intensity and polarization of the reflected light, optical thickness of aerosol layer itself, effective radius of aerosols, width of the particle size distribution, and number of viewing angles.

Stressed state of two-layer strip when interacting with rigid base

Relevance. In the calculation of multilayer bases, when the material of one or several layers has a pronounced anisotropy, the nature of the distribution of displacements and stresses depends on the direction of the anisotropy axes in each layer. Therefore, it is necessary to have an evaluation of the influence of this factor in the design and analysis of the operation of multilayer media. The aim of the work - to research the stress state in a strip composed of two anisotropic plane-parallel layers with different physical characteristics, lying without friction on a rigid base. Methods. The integration of the equations of the plane problem of the theory of elasticity of an anisotropic body is carried out by the symbolic method in combination with the method of initial functions. The initial functions on the contact line of the strip and the base are determined from the conditions of tight adhesion between the layers, the conditions of tight contact and the absence of friction between the strip and the base, the nature of the load applied to the upper plane of the strip. After transformations, the functions of displacements and stresses in each layer are written through the normal surface load in the form of improper integrals. Results. Plots of changes in stresses in the strip from the values of the characteristics of anisotropic materials, layer thicknesses are given. The maximum stresses on the interface line of the layers and on the line of contact with the base, depending on the direction of the anisotropy axes in each layer, are presented in the tables and shown in graphs. The effect of the elastic modules of materials on the nature of the stress distribution in a strip composed of two isotropic materials is estimated.

FLiES-SIF version 1.0: three-dimensional radiative transfer model for estimating solar induced fluorescence

Abstract. Global terrestrial ecosystems control the atmospheric CO2 concentration through gross primary production (GPP) and ecosystem respiration processes. Chlorophyll fluorescence is one of the energy release pathways of excess incident light in the photosynthetic process. Over the last 10 years, extensive studies have revealed that canopy-scale Sun-induced chlorophyll fluorescence (SIF), which potentially provides a direct pathway to link leaf-level photosynthesis to global GPP, can be observed from satellites. SIF is used to infer photosynthetic capacity of plant canopy; however, it is not clear how the leaf-level SIF emission contributes to the top-of-canopy directional SIF. Plant canopy radiative transfer models are useful tools to understand the mechanism of anisotropic light interactions such as scattering and absorption in plant canopies. One-dimensional (1-D) plane-parallel layer models (e.g., the Soil Canopy Observation, Photochemistry and Energy fluxes (SCOPE) model) have been widely used and are useful to understand the general mechanisms behind the temporal and seasonal variations in SIF. However, a 1-D model does not explain the complexity of the actual canopy structures. Three-dimensional models (3-D) have a potential to delineate the realistic directional canopy SIFs. Forest Light Environmental Simulator for SIF (FLiES-SIF) version 1.0 is a 3-D Monte Carlo plant canopy radiative transfer model to understand the biological and physical mechanisms behind the SIF emission from complex forest canopies. The FLiES-SIF model is coupled with leaf-level fluorescence and a physiology module so that users are able to simulate how the changes in environmental and leaf traits as well as canopy structure affect the observed SIF at the top of the canopy. The FLiES-SIF model was designed as three-dimensional model, yet the entire modules are computationally efficient: FLiES-SIF can be easily run by moderate-level personal computers with lower memory demands and public software. In this model description paper, we focused on the model formulation and simulation schemes, and showed some sensitivity analysis against several major variables such as view angle and leaf area index (LAI). The simulation results show that SIF increases with LAI then saturated at LAI>2–4 depending on the spectral wavelength. The sensitivity analysis also shows that simulated SIF radiation may decrease with LAI at a higher LAI domain (LAI>5). These phenomena are seen in certain Sun and view angle conditions. This type of nonlinear and nonmonotonic SIF behavior towards LAI is also related to spatial forest structure patterns. FLiES-SIF version 1.0 can be used to quantify the canopy SIF in various view angles including the contribution of multiple scattering which is the important component in the near-infrared domain. The potential use of the model is to standardize the satellite SIF by correcting the bidirectional effect. This step will contribute to the improvement of the GPP estimation accuracy through SIF.

Diurnal Variability of the Radiative Impact of Atmospheric Aerosols in Ouagadougou, Burkina Faso: A Seasonal Approach

The objective of this work is to study the diurnal evolution of the radiative impact of atmospheric aerosols in an urban city located in the West African Sahel and the correlations with the main influencing factors of local climate dynamics. The simulation was performed using a treatment chain including the GAME code. In the methodology, the atmosphere is modeled by 33 plane parallel layers and the effects of absorption, multiple scattering by particles and gas are taken account. An hour-by-hour calculation of radiative forcing at the top of the atmosphere, in the atmospheric layer and at the earth’s surface was performed. The data used as input are the monthly averages of optical properties, radiosonde measurements, daily synoptic measurements and surface albedo. The results show a parabolic diurnal course of a negative radiative impact at the top of the atmosphere with an extremum at 12 o'clock. Maximum cooling is observed shortly after sunrise and shortly after sunset. The largest annual deviations are noted between the months of March and December with respective maximum cooling values of -34 W/m2 and -15.60 W/m2. On the earth’s surface, a cooling impact is observed with two diurnal peaks at sunrise and sunset, the greatest difference between the diurnal maximums is noted between March (-104.45 W/m2) and August (-54 W/m2). In the atmospheric layer, there is almost constant diurnal warming between 9 a.m. and 4 p.m. The maximum difference between the diurnal extremes is also noted between March (about 85 W/m2) and August (35 W/m2). Likewise, the study of the diurnal warming of the first atmospheric layer showed the extreme values in March (5.6°C) and August (2.4°C), these maximum values being always observed at around 12 o’clock. An analysis of similar works carried out in urban cities in various locations of the world has shown a relatively good accordance with the values obtained. This study highlights the radiative impact of Saharan desert dust, the effect of the local climate and the succession between dry season (November to May) and the rainy one (July to October), as well as the zenith solar angle and human activity.