- SIMPLE RADIATIVE TRANSFER MODEL

AbstractThe advent of remote sensing from unmanned aerial systems (UAS) has opened the door to more affordable and effective methods of imaging and mapping of surface geophysical properties with many important applications in areas such as coastal zone management, ecology, agriculture, and defense. We describe a study to validate and improve soil moisture content retrieval and mapping from hyperspectral imagery collected by a UAS system. Our approach uses a recently developed model known as the multilayer radiative transfer model of soil reflectance (MARMIT). MARMIT partitions contributions due to water and the sediment surface into equivalent but separate layers and describes these layers using an equivalent slab model formalism. The model water layer thickness along with the fraction of wet surface become parameters that must be optimized in a calibration step, with extinction due to water absorption being applied in the model based on equivalent water layer thickness, while transmission and reflection coefficients follow the Fresnel formalism. In this work, we evaluate the model in both field settings, using UAS hyperspectral imagery, and laboratory settings, using hyperspectral spectra obtained with a goniometer. Sediment samples obtained from four different field sites representing disparate environmental settings comprised the laboratory analysis while field validation used hyperspectral UAS imagery and coordinated ground truth obtained on a barrier island shore during field campaigns in 2018 and 2019. Analysis of the most significant wavelengths for retrieval indicate a number of different wavelengths in the short-wave infra-red (SWIR) that provide accurate fits to measured soil moisture content in the laboratory with normalized root mean square error (NRMSE)< 0.145, while independent evaluation from sequestered test data from the hyperspectral UAS imagery obtained during the field campaign obtained an average NRMSE = 0.169 and median NRMSE = 0.152 in a bootstrap analysis.

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The radiative transfer model for the greenhouse effect

SeMA Journal ◽

10.1007/s40324-021-00265-y ◽

2021 ◽

Author(s):

Claude Bardos ◽

Olivier Pironneau

Keyword(s):

Radiative Transfer ◽

Greenhouse Effect ◽

Radiative Transfer Model ◽

Transfer Model

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Potential of Hyperspectral Thermal Infrared Spaceborne Measurements to Retrieve Ice Cloud Physical Properties: Case Study of IASI and IASI-NG

Remote Sensing ◽

10.3390/rs13010116 ◽

2020 ◽

Vol 13 (1) ◽

pp. 116

Author(s):

Lucie Leonarski ◽

Laurent C.-Labonnote ◽

Mathieu Compiègne ◽

Jérôme Vidot ◽

Anthony J. Baran ◽

...

Keyword(s):

Radiative Transfer ◽

Signal To Noise Ratio ◽

Thermal Infrared ◽

Radiative Transfer Model ◽

Retrieval Algorithm ◽

Transfer Model ◽

Water Path ◽

Ice Cloud ◽

Ice Water Path ◽

Ice Water

The present study aims to quantify the potential of hyperspectral thermal infrared sounders such as the Infrared Atmospheric Sounding Interferometer (IASI) and the future IASI next generation (IASI-NG) for retrieving the ice cloud layer altitude and thickness together with the ice water path. We employed the radiative transfer model Radiative Transfer for TOVS (RTTOV) to simulate cloudy radiances using parameterized ice cloud optical properties. The radiances have been computed from an ice cloud profile database coming from global operational short-range forecasts at the European Center for Medium-range Weather Forecasts (ECMWF) which encloses the normal conditions, typical variability, and extremes of the atmospheric properties over one year (Eresmaa and McNally (2014)). We performed an information content analysis based on Shannon’s formalism to determine the amount and spectral distribution of the information about ice cloud properties. Based on this analysis, a retrieval algorithm has been developed and tested on the profile database. We considered the signal-to-noise ratio of each specific instrument and the non-retrieved atmospheric and surface parameter errors. This study brings evidence that the observing system provides information on the ice water path (IWP) as well as on the layer altitude and thickness with a convergence rate up to 95% and expected errors that decrease with cloud opacity until the signal saturation is reached (satisfying retrievals are achieved for clouds whose IWP is between about 1 and 300 g/m2).

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

Remote Sensing ◽

10.3390/rs13030434 ◽

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.

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Retrieval of betalain contents based on the coupling of radiative transfer model and SVM model

International Journal of Applied Earth Observation and Geoinformation ◽

10.1016/j.jag.2021.102340 ◽

2021 ◽

Vol 100 ◽

pp. 102340

Author(s):

Rukeya Sawut ◽

Ying Li ◽

Yu Liu ◽

Nijat Kasim ◽

Umut Hasan ◽

...

Keyword(s):

Radiative Transfer ◽

Radiative Transfer Model ◽

Transfer Model ◽

Svm Model

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Radar altimeter waveform simulations in Antarctica with the Snow Microwave Radiative Transfer Model (SMRT)

Remote Sensing of Environment ◽

10.1016/j.rse.2021.112534 ◽

2021 ◽

Vol 263 ◽

pp. 112534

Author(s):

Fanny Larue ◽

Ghislain Picard ◽

Jérémie Aublanc ◽

Laurent Arnaud ◽

Alvaro Robledano-Perez ◽

...

Keyword(s):

Radiative Transfer ◽

Radiative Transfer Model ◽

Transfer Model ◽

Radar Altimeter

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Long-Term Observations of Microwave Brightness Temperatures over a Metropolitan Area: Comparison of Radiometric Data and Spectra Simulated with the Use of Radiosonde Measurements

Remote Sensing ◽

10.3390/rs13112061 ◽

2021 ◽

Vol 13 (11) ◽

pp. 2061

Author(s):

Mikhail V. Belikovich ◽

Mikhail Yu. Kulikov ◽

Dmitry S. Makarov ◽

Natalya K. Skalyga ◽

Vitaly G. Ryskin ◽

...

Keyword(s):

Radiative Transfer ◽

Elevation Angle ◽

Radiative Transfer Model ◽

Transfer Model ◽

Systematic Bias ◽

Tropospheric Temperature ◽

Absorption Model ◽

60 Ghz ◽

Error Budget ◽

The Difference

Ground-based microwave radiometers are increasingly used in operational meteorology and nowcasting. These instruments continuously measure the spectra of downwelling atmospheric radiation in the range 20–60 GHz used for the retrieval of tropospheric temperature and water vapor profiles. Spectroscopic uncertainty is an important part of the retrieval error budget, as it leads to systematic bias. In this study, we analyze the difference between observed and simulated microwave spectra obtained from more than four years of microwave and radiosonde observations over Nizhny Novgorod (56.2° N, 44° E). We focus on zenith-measured and elevation-scanning data in clear-sky conditions. The simulated spectra are calculated by a radiative transfer model with the use of radiosonde profiles and different absorption models, corresponding to the latest spectroscopy research. In the case of zenith-measurements, we found a systematic bias (up to ~2 K) of simulated spectra at 51–54 GHz. The sign of bias depends on the absorption model. A thorough investigation of the error budget points to a spectroscopic nature of the observed differences. The dependence of the results on the elevation angle and absorption model can be explained by the basic properties of radiative transfer and by cloud contamination at elevation angles.

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