Search results for "Radiative Transfer"

Simultaneous retrieval of global scale Vegetation Optical Depth, surface roughness, and soil moisture using X-band AMSR-E observations

2019

Abstract The radiative transfer scheme implemented for the retrieval of soil moisture from passive microwaves is a function of scattering, polarization mixing and attenuation effects of soil and vegetation. Theses factors are usually represented by Vegetation Optical Depth (VOD), vegetation scattering albedo, and surface roughness parameter, along with soil moisture. The VOD is the degree to which vegetation attenuates the microwave radiation. It has generally the dominant effect from vegetation, whereas scattering is negligible and close to zero. The surface roughness (which varies in space but not much in time) is until recently, often assumed to be a global constant. In this work, we att…

In situ surface temperature retrieval in a boreal forest under variable cloudiness conditions

2005

Canopy temperature retrieval was one of the purposes during the Solar Induced FLuorescence EXperiment (SIFLEX‐2002) of the European Space Agency, carried out in a Finnish boreal forest. In this work, we describe the strategy used to determine this temperature from ground thermal infrared (TIR) data under skies with variable cloud cover. TIR radiance was measured by a CIMEL Electronique CE 312 radiometer. An analysis of the radiative transfer equation showed which terms were necessary to obtain accurate surface temperatures during the campaign. Atmospheric correction was considered negligible due to the small atmospheric path, but hemispheric downwelling sky radiance determination was needed…

Emissitivity spectra obtained from field and laboratory measurements using the temperature and emissivity separation algorithm.

2006

Surface emissivities play an important role in thermal remote sensing, since knowledge of them is required to estimate land surface temperature with enough accuracy. They are also important in other environmental or geological studies. We show the results obtained for the emissivity spectra of different natural surfaces (water, green, and senescent vegetation) by applying the temperature and emissivity separation (TES) algorithm to ground-based measurements collected at the field with a multiband thermal radiometer. The results have been tested with data included in spectral libraries, and rms errors lower than 0.01 have been found, except for senescent vegetation. Two methods are also prop…

Comparison of stereo vision techniques for cloud-top height retrieval

2007

This paper presents an ongoing study for the estimation of the cloud-top height by using only geometrical methods. In agreement with some recent studies showing that it is possible to achieve reliable height estimations not only with the classical methods based on radiative transfer, this article includes a comparison of performances of a selected set of vision algorithms devoted to extract dense disparity maps or motion fields from Infra Red stereo image pairs. This collection includes both area-based techniques and an optical flow-based method and the comparison is accomplished by using a set of cloudy scenes selected from the Along-Track Scanning Radiometer (ATSR2) database. The first gr…

Comparison between different sources of atmospheric profiles for land surface temperature retrieval from single channel thermal infrared data

2012

Abstract Different sources of atmospheric water vapor and temperature profiles were used with a radiative transfer model for retrieving land surface temperature (LST) from thermal infrared remote sensing data with the so-called single channel (SC) method. Retrieved LSTs were compared to concurrent ground measurements over homogeneous rice fields to assess the accuracy of the atmospheric profiles. These included radiosonde balloons launched at the test site near-concurrently to satellite overpasses, re-analysis profiles from the National Centers for Environmental Prediction (NCEP), and satellite sounder products from the Atmospheric Infrared Sounder (AIRS) and the Moderate Imaging Spectrorad…

Photoluminescence study of radiative transitions in ZnTe bulk crystals

1998

Abstract This paper focuses on photoluminescence (PL) and selective photoluminescence (SPL) of ZnTe bulk crystals grown by the cold traveling heater method. The crystals exhibit a PL response with a much more intense excitonic zone than the one due to free-to-bound and donor–acceptor bands, denoting a good sample quality. In particular, we have investigated the Y 1 and Y 2 peaks which, in epitaxial layers, have usually been associated with structural defects. On bulk samples they have not been detected so far because of different masked mechanisms. SPL measurements show that the electrons are the most likely involved carriers for this emission. Additionally, the analysis of the PL variation…

Radiative Improvement of the Lattice Nonrelativistic QCD Action Using the Background Field Method and Application to the Hyperfine Splitting of Quark…

2011

We present the first application of the background field method to nonrelativistic QCD (NRQCD) on the lattice in order to determine the one-loop radiative corrections to the coefficients of the NRQCD action in a manifestly gauge-covariant manner. The coefficients of the $\mathbit{\ensuremath{\sigma}}\ifmmode\cdot\else\textperiodcentered\fi{}\mathbit{B}$ term in the NRQCD action and the four-fermion spin-spin interaction are computed at the one-loop level; the resulting shift of the hyperfine splitting of bottomonium is found to bring the lattice predictions in line with experiment.

Fluorescence estimation in the framework of the CEFLES2 campaign

2011

International audience; Chlorophyll fluorescence (ChF) is a relevant indicator of the actual plant physiological status. In this article different methods to measure ChF from remote sensing are evaluated: The Fraunhofer Line Discrimination (FLD), theFluorescence Radiative Method (FRM) and the improved Fraunhofer Line Discrimination (iFLD). The three methods have been applied to data acquired in the framework of the CarboEurope, FLEX and Sentinel-2 (CEFLES2) campaign in Les Landes, France in September 2007. Comparing with in situ measurements, the results indicate that the methods that provide the best results are the FLD and the iFLD with root mean square errors (RMSEs) of 0.4 and 0.5 mW m-…

The HITRAN2016 molecular spectroscopic database

2017

This paper describes the contents of the 2016 edition of the HITRAN molecular spectroscopic compilation. The new edition replaces the previous HITRAN edition of 2012 and its updates during the intervening years. The HITRAN molecular absorption compilation is composed of five major components: the traditional line-by-line spectroscopic parameters required for high-resolution radiative-transfer codes, infrared absorption cross-sections for molecules not yet amenable to representation in a line-by-line form, collision-induced absorption data, aerosol indices of refraction, and general tables such as partition sums that apply globally to the data. The new HITRAN is greatly extended in terms of …

2018

Abstract. During the summertime, dust from the Sahara can be efficiently transported westwards within the Saharan air layer (SAL). This can lead to high aerosol loadings being observed above a relatively clean marine boundary layer (MBL) in the tropical Atlantic Ocean. These dust layers can impart significant radiative effects through strong visible and IR light absorption and scattering, and can also have indirect impacts by altering cloud properties. The processing of the dust aerosol can result in changes in both direct and indirect radiative effects, leading to significant uncertainty in climate prediction in this region. During August 2015, measurements of aerosol and cloud properties …