scholarly journals Radiative Transfer Modeling of a Coniferous Canopy Characterized by Airborne Remote Sensing

2008 ◽  
Vol 9 (2) ◽  
pp. 228-241 ◽  
Author(s):  
Richard Essery ◽  
Peter Bunting ◽  
Aled Rowlands ◽  
Nick Rutter ◽  
Janet Hardy ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Laser Scanning ◽  
Large Scale ◽  
Forest Canopy ◽  
Canopy Structure ◽  
Spatial Variations ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Temporal Averaging ◽  
Radiative Transfer Modeling

Abstract Solar radiation beneath a forest canopy can have large spatial variations, but this is frequently neglected in radiative transfer models for large-scale applications. To explicitly model spatial variations in subcanopy radiation, maps of canopy structure are required. Aerial photography and airborne laser scanning are used to map tree locations, heights, and crown diameters for a lodgepole pine forest in Colorado as inputs to a spatially explicit radiative transfer model. Statistics of subcanopy radiation simulated by the model are compared with measurements from radiometer arrays, and scaling of spatial statistics with temporal averaging and array size is discussed. Efficient parameterizations for spatial averages and standard deviations of subcanopy radiation are developed using parameters that can be obtained from the model or hemispherical photography.

scholarly journals UPSCALING OF SOLAR INDUCED CHLOROPHYLL FLUORESCENCE FROM LEAF TO CANOPY USING THE DART MODEL AND A REALISTIC 3D FOREST SCENE

2017 ◽  
Vol XLII-3/W3 ◽  
pp. 107-111 ◽  
Author(s):  
W. Liu ◽  
J. Atherton ◽  
M. Mõttus ◽  
A. MacArthur ◽  
H. Teemu ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Forest Canopy ◽  
Multiple Scales ◽  
Canopy Structure ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Fluorescence Signal ◽  
Forest Canopies ◽  
Vertical Heterogeneity ◽  
Leaf Level

Solar induced chlorophyll a fluorescence (SIF) has been shown to be an excellent proxy of photosynthesis at multiple scales. However, the mechanical linkages between fluorescence and photosynthesis at the leaf level cannot be directly applied at canopy or field scales, as the larger scale SIF emission depends on canopy structure. This is especially true for the forest canopies characterized by high horizontal and vertical heterogeneity. While most of the current studies on SIF radiative transfer in plant canopies are based on the assumption of a homogeneous canopy, recently codes have been developed capable of simulation of fluorescence signal in explicit 3-D forest canopies. Here we present a canopy SIF upscaling method consisting of the integration of the 3-D radiative transfer model DART and a 3-D object model BLENDER. Our aim was to better understand the effect of boreal forest canopy structure on SIF for a spatially explicit forest canopy.

scholarly journals Large-scale validation of SCIAMACHY reflectance in the ultraviolet

2005 ◽  
Vol 5 (2) ◽  
pp. 1771-1796 ◽  
Author(s):  
G. van Soest ◽  
L. G. Tilstra ◽  
P. Stammes
Keyword(s):  
Radiative Transfer ◽  
Validation Study ◽  
Large Scale ◽  
Scale Validation ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Time Level ◽  
Standard Calibration ◽  
Level 1 ◽  
Reflectance Data

Abstract. In this paper we present an extensive validation of calibrated SCIAMACHY nadir reflectance in the UV (240–400 nm) by comparison with spectra calculated with a fast radiative transfer model. We use operationally delivered near-real-time level 1 data, processed with 5 standard calibration tools. A total of 9 months of data has been analysed. This is the first reflectance validation study incorporating such a large amount of data. It is shown that this method is a valuable tool for spotting spatial and temporal anomalies. We conclude that SCIAMACHY reflectance data in this wavelength range are stable over the investigated period. In addition, we show an example of an 10 anomaly in the data due to an error in the processing chain that could be detected by our comparison. This validation method could be extremely useful too for validation of other satellite spectrometers, such as OMI and GOME-2.

scholarly journals Radiative Transfer Modeling of Phytoplankton Fluorescence Quenching Processes

2018 ◽  
Vol 10 (8) ◽  
pp. 1309 ◽  
Author(s):  
Peng-Wang Zhai ◽  
Emmanuel Boss ◽  
Bryan Franz ◽  
P. Werdell ◽  
Yongxiang Hu
Keyword(s):  
Quantum Yield ◽  
Radiative Transfer ◽  
Sensitivity Study ◽  
Radiative Transfer Model ◽  
Photochemical Quenching ◽  
Transfer Model ◽  
Fluorescence Signal ◽  
New Space ◽  
Non Photochemical Quenching ◽  
Radiative Transfer Modeling

We report the first radiative transfer model that is able to simulate phytoplankton fluorescence with both photochemical and non-photochemical quenching included. The fluorescence source term in the inelastic radiative transfer equation is proportional to both the quantum yield and scalar irradiance at excitation wavelengths. The photochemical and nonphotochemical quenching processes change the quantum yield based on the photosynthetic active radiation. A sensitivity study was performed to demonstrate the dependence of the fluorescence signal on chlorophyll a concentration, aerosol optical depths and solar zenith angles. This work enables us to better model the phytoplankton fluorescence, which can be used in the design of new space-based sensors that can provide sufficient sensitivity to detect the phytoplankton fluorescence signal. It could also lead to more accurate remote sensing algorithms for the study of phytoplankton physiology.

scholarly journals Radiative Transfer Simulations Using Mesoscale Cloud Model Outputs: Comparisons with Passive Microwave and Infrared Satellite Observations for Midlatitudes

2007 ◽  
Vol 64 (5) ◽  
pp. 1550-1568 ◽  
Author(s):  
Ingo Meirold-Mautner ◽  
Catherine Prigent ◽  
Eric Defer ◽  
Juan R. Pardo ◽  
Jean-Pierre Chaboureau ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Large Scale ◽  
Mesoscale Model ◽  
Cloud Model ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Specific Situation ◽  
Dynamical Structure ◽  
Atmospheric Transmission ◽  
Brightness Temperatures

Abstract Real midlatitude meteorological cases are simulated over western Europe with the cloud mesoscale model Méso-NH, and the outputs are used to calculate brightness temperatures at microwave frequencies with the Atmospheric Transmission at Microwave (ATM) radiative transfer model. Satellite-observed brightness temperatures (TBs) from the Advanced Microwave Scanning Unit B (AMSU-B) and the Special Sensor Microwave Imager (SSM/I) are compared to the simulated ones. In this paper, one specific situation is examined in detail. The infrared responses have also been calculated and compared to the Meteosat coincident observations. Overall agreement is obtained between the simulated and the observed brightness temperatures in the microwave and in the infrared. The large-scale dynamical structure of the cloud system is well captured by Méso-NH. However, in regions with large quantities of frozen hydrometeors, the comparison shows that the simulated microwave TBs are higher than the measured ones in the window channels at high frequencies, indicating that the calculation does not predict enough scattering. The factors responsible for the scattering (frozen particle distribution, calculation of particle dielectric properties, and nonsphericity of the particles) are analyzed. To assess the quality of the cloud and precipitation simulations by Méso-NH, the microphysical fields predicted by the German Lokal-Modell are also considered. Results show that in these midlatitude situations, the treatment of the snow category has a high impact on the simulated brightness temperatures. The snow scattering parameters are tuned to match the discrete dipole approximation calculations and to obtain a good agreement between simulations and observations even in the areas with significant frozen particles. Analysis of the other meteorological simulations confirms these results. Comparing simulations and observations in the microwave provides a powerful evaluation of resolved clouds in mesoscale models, especially the precipitating ice phase.

scholarly journals A Novel GPU-Based Acceleration Algorithm for a Longwave Radiative Transfer Model

2020 ◽  
Vol 10 (2) ◽  
pp. 649 ◽  
Author(s):  
Yuzhu Wang ◽  
Yuan Zhao ◽  
Jinrong Jiang ◽  
He Zhang
Keyword(s):  
Radiative Transfer ◽  
General Circulation ◽  
Large Scale ◽  
General Circulation Models ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Processing Unit ◽  
Heating Rates ◽  
Area Of Interest ◽  
Intel Xeon

Graphics processing unit (GPU)-based computing for climate system models is a longstanding research area of interest. The rapid radiative transfer model for general circulation models (RRTMG), a popular atmospheric radiative transfer model, can calculate atmospheric radiative fluxes and heating rates. However, the RRTMG has a high calculation time, so it is urgent to study its GPU-based efficient acceleration algorithm to enable large-scale and long-term climatic simulations. To improve the calculative efficiency of radiation transfer, this paper proposes a GPU-based acceleration algorithm for the RRTMG longwave radiation scheme (RRTMG_LW). The algorithm concept is accelerating the RRTMG_LW in the g- p o i n t dimension. After implementing the algorithm in CUDA Fortran, the G-RRTMG_LW was developed. The experimental results indicated that the algorithm was effective. In the case without I/O transfer, the G-RRTMG_LW on one K40 GPU obtained a speedup of 30.98× over the baseline performance on one single Intel Xeon E5-2680 CPU core. When compared to its counterpart running on 10 CPU cores of an Intel Xeon E5-2680 v2, the G-RRTMG_LW on one K20 GPU in the case without I/O transfer achieved a speedup of 2.35×.

scholarly journals Odin/OSIRIS observations of stratospheric NO<sub>3</sub> through sunrise and sunset

2008 ◽  
Vol 8 (18) ◽  
pp. 5529-5534 ◽  
Author(s):  
C. A. McLinden ◽  
C. S. Haley
Keyword(s):  
Radiative Transfer ◽  
Current Knowledge ◽  
Strong Dependence ◽  
Rapid Evolution ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Spectral Fitting ◽  
Infrared Imager ◽  
Fitting In ◽  
Radiative Transfer Modeling

Abstract. The nitrate radical (NO3) has been detected in visible limb-scattered spectra measured by the Optical Spectrograph and InfraRed Imager System (OSIRIS) on-board the Odin satellite when observing at large solar zenith angles (91–97°). Apparent slant column densities of NO3 at tangent heights between 10 and 45 km are derived via spectral fitting in the 610–680 nm window. Using observations from multiple scans spanning solar zenith angles of 91–97°, the rapid evolution of NO3 through sunrise and sunset can be traced. Slant column densities are found to be generally consistent with those simulated using a radiative transfer model with coupled photochemistry. In addition, a strong dependence of NO3 with temperature is observed. These results indicate that our current knowledge of NO3 photochemistry is generally consistent with OSIRIS observations to within the limitations of the radiative transfer modeling. Furthermore, they reveal that OSIRIS possesses signal-to-noise sufficient to make useful measurements of scattered sunlight out to solar zenith angles of 91–97° and suggest the possibility of retrieving profile information for NO3 and other species at large solar zenith angles.

scholarly journals Application of a Three-Dimensional Radiative Transfer Model to Retrieve the Species Composition of a Mixed Forest Stand from Canopy Reflected Radiation

2018 ◽  
Vol 10 (10) ◽  
pp. 1661 ◽  
Author(s):  
Natalia Levashova ◽  
Dmitry Lukyanenko ◽  
Yulia Mukhartova ◽  
Alexander Olchev
Keyword(s):  
Solar Radiation ◽  
Radiative Transfer ◽  
Tree Species ◽  
Forest Canopy ◽  
Mixed Forest ◽  
Three Dimensional ◽  
Forest Stand ◽  
Deciduous Tree ◽  
Radiative Transfer Model ◽  
Transfer Model

The paper introduces a three-dimensional model to derive the spatial patterns of photosynthetically active radiation (PAR) reflected and absorbed by a non-uniform forest canopy with a multi-species structure, as well as a model algorithm application to retrieve forest canopy composition from reflected PAR measured along some trajectory above the forest stand. This radiative transfer model is based on steady-state transport equations, initially suggested by Ross, and considers the radiative transfer as a function of the structure of individual trees and forest canopy, optical properties of photosynthesizing and non-photosynthesizing parts of the different tree species, soil reflection, and the ratio of incoming direct and diffuse solar radiation. Numerical experiments showed that reflected solar radiation of a typical mixed forest stand consisting of coniferous and deciduous tree species was strongly governed by canopy structure, soil properties and sun elevation. The suggested algorithm based on the developed model allows for retrieving the proportion of different tree species in a mixed forest stand from measured canopy reflection coefficients. The method accuracy strictly depends on the number of points for canopy reflection measurements.

scholarly journals Large-scale validation of SCIAMACHY reflectance in the ultraviolet

2005 ◽  
Vol 5 (8) ◽  
pp. 2171-2180 ◽  
Author(s):  
G. van Soest ◽  
L. G. Tilstra ◽  
P. Stammes
Keyword(s):  
Radiative Transfer ◽  
Validation Study ◽  
Large Scale ◽  
Scale Validation ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Time Level ◽  
Standard Calibration ◽  
Level 1 ◽  
Reflectance Data

Abstract. In this paper we present an extensive validation of calibrated SCIAMACHY nadir reflectance in the UV (240-400 nm) by comparison with spectra calculated with a fast radiative transfer model. We use operationally delivered near-real-time level 1 data, processed with standard calibration tools. A total of 9 months of data has been analysed. This is the first reflectance validation study incorporating such a large amount of data. It is shown that this method is a valuable tool for spotting spatial and temporal anomalies. We conclude that SCIAMACHY reflectance data in this wavelength range are stable over the investigated period. In addition, we show an example of an anomaly in the data due to an error in the processing chain that could be detected by our comparison. This validation method could be extremely useful too for validation of other satellite spectrometers, such as OMI and GOME-2.

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