Search results for "EMISSIVITY"
showing 10 items of 136 documents
Temperature and emissivity separation from ASTER data for low spectral contrast surfaces
2007
Abstract The performance of Advanced Spaceborne Thermal Emission Reflection Radiometer (ASTER) thermal infrared (TIR) data product algorithms was evaluated for low spectral contrast surfaces (such as vegetation and water) in a test site close to Valencia, Spain. Concurrent ground measurements of surface temperature, emissivity, and atmospheric radiosonde profiles were collected at the test site, which is a thermally homogeneous area of rice crops with nearly full vegetation cover in summer. Using the ground data and the local radiosonde profiles, at-sensor radiances were simulated for the ASTER TIR channels and compared with L1B data (calibrated at-sensor radiances) showing discrepancies up…
Influence of soil water content on the thermal infrared emissivity of bare soils. Implication for land surface temperature determination.
2007
[1] The influence of soil water content in thermal infrared emissivity is a known fact but has been poorly studied in the past. A laboratory study for quantifying the dependence of emissivity on soil moisture was carried out. Six samples of surface horizons of different soil types were selected for the experiment. The gravimetric method was chosen for determining the soil moisture, whereas the emissivity was measured at different soil water contents using the two-lid variant of the box method. As a result, the study showed that emissivity increases from 1.7% to 16% when water content becomes higher, especially in sandy soils in the 8.2–9.2 μm range. Accordingly, a set of equations was deriv…
Temperature and Emissivity Separation From MSG/SEVIRI Data
2014
In this paper, we analyze the feasibility of applying the temperature and emissivity separation (TES) algorithm to thermal-infrared data acquired with three bands of the Spinning Enhanced Visible and Infrared Imager (SEVIRI) onboard the Meteosat Second Generation platform (SEVTES). The performance of the SEVTES algorithm was tested using data simulated over different atmospheric conditions and surface emissivities, with errors around 1.5% for emissivity and 1.5 K for temperature when atmospheric correction is accurate enough. In contrast, errors on land-leaving radiances higher than 2% or uncertainties on total atmospheric water vapor amount higher than 5% lead to errors on emissivity highe…
Theoretical split-window algorithms for determining the actual surface temperature
1993
Two split-window strategies for obtaining the actual surface temperature (AST) from an infra-red sensor system are investigated by means of simulations of radiometer signals for a wide range of different geophysical situations. The differences between strategies are closely related to the strong or weak presence of atmospheric effects in the split-window coefficient. It has been demonstrated that the strong presence makes it necessary to know the total atmospheric water vapour as well as the effective emissivities in the two thermal channels for applying the strong split-window method, whereas for the weak presence one only needs to know the emissivities. Simplified algorithms have been obt…
A physical model for interpreting the land surface temperature obtained by remote sensors over incomplete canopies
1992
Abstract At the present moment, land surface temperature cannot be obtained in a routine way from satellite data due, in part, to the nonexistence of a complete theoretical model that permits us to know the physical significance of land surface temperature obtained by remote sensors. In this article a relationship between the effective temperature of the radiative system vegetation-ground and the temperatures of each part of the system (top, sunny and shaded wall of vegetation, and sunny and shaded soil) has been derived. It depends on the proportions of each component observed by the sensor, on the ground and vegetation emissivities, and on the crop structure (mean height, width, and spaci…
Land surface temperature retrieval from LANDSAT TM 5
2004
In this paper, three methods to retrieve the land surface temperature (LST) from thermal infrared data supplied by band 6 of the Thematic Mapper (TM) sensor onboard the Landsat 5 satellite are compared. The first of them lies on the estimation of the land surface temperature from the radiative transfer equation using in situ radiosounding data. The others two are the mono-window algorithm developed by Qin et al. [International Journal of Remote Sensing 22 (2001) 3719] and the single-channel algorithm developed by Jime´nez-Mun˜oz and Sobrino [Journal of Geophysical Research 108 (2003)]. The land surface emissivity (LSE) values needed in order to apply these methods have been estimated from a…
Applications of a remote sensing-based two-source energy balance algorithm for mapping surface fluxes without in situ air temperature observations
2012
Abstract The two-source energy balance (TSEB) model uses remotely sensed maps of land–surface temperature (LST) along with local air temperature estimates at a nominal blending height to model heat and water fluxes across a landscape, partitioned between dual sources of canopy and soil. For operational implementation of TSEB, however, it is often difficult to obtain representative air temperature data that are compatible with the LST retrievals, which may themselves have residual errors due to atmospheric and emissivity corrections. To address this issue, two different strategies in applying the TSEB model without requiring local air temperature data were tested over a typical Mediterranean…
Foam effect on the sea surface emissivity in the 8–14μm region
2007
[1] The effect of foam on the sea surface emission has been studied in the microwave region, but its effect on thermal infrared emissivity and temperature has not been sufficiently analyzed in the literature. This paper presents thermal infrared measurements of foam-covered seawaters carried out under controlled conditions using a multichannel radiometer working in the 8–14 μm region. The experimental data show a negligible foam effect at low observation angles but a significant increase of emissivity with foam at angles above 45°. Differences between foam and foam-free emissivities are about +0.04 for observation angles of 65°, depending slightly on the radiometric spectral band. The effec…
Determination of the effective emissivity and temperature under vertical observation of a citrus orchard. Application to frost nowcasting
1988
Abstract In this work we use Becker's model for the determination of the effective temperature and emissivity under vertical observation of a citrus orchard. We apply this model to the particular case of a typically radiative night cooling (completely clear sky and calm wind) condition under which radiation frosts are normally produced which are damaging to the fruit and, consequently, to the Valencian economy. An attempt is made to establish a safety limit over which a frost cannot be produced. Ground and orange tree emissivity measurements were carried out by means of the box method. We were able to construct a hand-driven scanning system for the temperature measurement of the ground-oran…
Error sources on the land surface temperature retrieved from thermal infrared single channel remote sensing data
2006
In this paper, a theoretical study complementary to others given in the literature about the errors committed on the land surface temperature retrieved from the radiative transfer equation in the thermal infrared region by remote sensing techniques has been analysed. For this purpose, the MODTRAN 3.5 code has been used in order to simulate different conditions and evaluate the influence of several parameters on the land surface temperature accuracy: atmospheric correction, noise of the sensor, land surface emissivity, aerosols and other gaseous absorbers, angular effects, wavelength uncertainty, full‐width half‐maximum of the sensor and band‐pass effects. The results show that the most impo…