Search results for "Radiometry"
showing 10 items of 170 documents
Monthly Land Surface Temperature maps over European Zone using Advanced Along Track Scanning Radiometer data for 2007
2009
Land Surface Temperature (LST) monthly maps are necessary in climatic studies and remote sensing is a key tool used to obtain these maps. For this reason, we used the LST product of AATSR on board Envisat. This product uses a split-window algorithm which depends on vertical column water vapour content (W) and viewing angle. The algorithm proposed in Galve et al. [1] was also used, which is based on the Coll and Caselles [2] split-window model and depends explicitly on the emissivity and W. This algorithm was tested with concurrent ground measurements in the Valencia validation site, yielding an error of + 0.5 K. With both algorithms we perform LST maps over Europe with a spatial resolution …
A combined optical-microwave method to retrieve soil moisture over vegetated areas
2011
A simple approach for correcting for the effect of vegetation in the estimation of the surface soil moisture (wS) from L-band passive microwave observations is presented in this study. The approach is based on semi-empirical relationships between soil moisture and the polarized reflectivity including the effect of the vegetation optical depth which is parameterized as a function of the normalized vegetation difference index (NDVI). The method was tested against in situ measurements collected over a grass site from 2004 to 2007 (SMOSREX experiment). Two polarizations (horizontal/vertical) and five incidence angles (20◦, 30◦, 40◦, 50◦, and 60◦) were considered in the analysis. The best wS est…
Thermal-Infrared Spectral and Angular Characterization of Crude Oil and Seawater Emissivities for Oil Slick Identification
2014
Previous work has shown that the emissivity of crude oil is lower than that of the seawater in the thermal-infrared (TIR) spectrum. Thus, oil slicks cause an emissivity decrease relative to the seawater in that region. The aim of this paper was to carry out experimental measurements to characterize the spectral and angular variations of crude oil and seawater emissivities. The results showed that the crude oil emissivity is lower than the seawater emissivity and that it is essentially flat in the atmospheric window of 8-13 μm. The crude oil emissivity has a marked emissivity decrease with the angle (from 0.956 ± 0.005 at 15 ° to 0.873 ± 0.007 at 65 °), which is even higher than that of the …
Comparison of Thermal Infrared Emissivities Retrieved With the Two-Lid Box and the TES Methods With Laboratory Spectra
2009
Knowledge of surface emissivity in the thermal infrared (TIR) region is critical for determining the land surface temperature (LST) from remote-sensing measurements. If emissivity is not well determined, it can cause a significant systematic error in obtaining the LST. The main aim of this paper is to compare different methods for measuring accurate land surface emissivity in the field, namely, the box method and the temperature and emissivity separation (TES) algorithm. Field emissivities were compared with soil spectra from laboratory measurements. Emissivities were measured for the bands of a multispectral radiometer CE312-2 with effective wavelengths at 8.4, 8.7, 9.1, 10.6, and 11.3 mum…
Camera-based measurement of relative image contrast in projection displays
2013
International audience; This research investigated the measured contrast of projection displays based on pictures taken by un-calibrated digital cameras under typical viewing conditions. A high-end radiometer was employed as a reference to the physical response of projection luminance. Checkerboard, gray scale and color complex test images with a range of the projector's brightness and contrast settings were projected. Two local and two global contrast metrics were evaluated on the acquired pictures. We used contrast surface plots and Pearson correlation to investigate the measured contrast versus the projector's brightness and contrast settings. The results suggested, as expected, the proj…
Airborne observations of far-infrared upwelling radiance in the Arctic
2016
Abstract. The first airborne measurements of the Far-InfraRed Radiometer (FIRR) were performed in April 2015 during the panarctic NETCARE campaign. Vertical profiles of spectral upwelling radiance in the range 8–50 μm were measured in clear and cloudy conditions from the surface up to 6 km. The clear-sky profiles highlight the strong dependence of radiative fluxes to the temperature inversion typical of the Arctic. Measurements acquired for total column water vapor from 1.5 to 10.5 mm also underline the sensitivity of the far-infrared greenhouse effect to specific humidity. The cloudy cases show that optically thin ice clouds increase the cooling rate of the atmosphere by a factor up to thr…
A simple method for estimating downward longwave radiation from surface and satellite data by clear sky
1990
Abstract An attempt to derive downward longwave radiation at the surface in clear sky conditions is presented. A method that integrates satellite-measured infrared radiation temperatures with ground measurements of water vapour pressure is applied to Meteosat data. Satellite-derived fluxes are compared with corresponding ground-measured fluxes at three different sites in France and during various seasons. Comparison of the daily averaged fluxes shows a correlation coefficient of 0–88 and an r.m.s. difference between satellite estimates and ground measurements of 12 Wm-2.
The EuroSTARRS airborne campaign in support of the SMOS mission: first results over land surfaces
2004
A number of experiments using ground-based and airborne sensors have shown the high potential of L-band passive microwave radiometry for estimating and monitoring surface soil moisture. This has led to the Soil Moisture and Ocean Salinity (SMOS) mission, a European Space Agency (ESA) Earth Explorer Opportunity mission. SMOS has the objective to observe soil moisture over land and sea surface salinity over sea, both key parameters for atmospheric, oceanographic and hydrological predictive models. In preparation of SMOS, the EuroSTARRS airborne campaign was carried out in November 2001. Multi-angular measurements of the surface brightness temperature at L-band (1.4 GHz) at vertical polarizati…
Analysis of thermal infrared data from the Digital Airborne Imaging Spectrometer
2001
Thermal infrared data of the Digital Airborne Imaging Spectrometer (DAIS), whose channels 74-79 are in the 8-13 w m waveband region, were analysed with the aim of recovering land surface temperature (LST). DAIS images were acquired over an experimental site where field and laboratory emissivity measurements were performed, and these were used to recover the LST from the six DAIS thermal channels. Atmospheric correction of DAIS data was calculated by means of a nearby radiosounding and a radiative transfer model. DAIS derived LSTs were compared with ground measurements of LST made coincidentally for a few test fields, the central DAIS channels yielding temperatures up to 10°C higher than gro…
CAROLS campaigns 2009: First Results
2010
International audience; The CAROLS, L band radiometer, is built and designed as a copy of EMIRAD II radiometer of DTU team. It is a Correlation radiometer with direct sampling and fully polarimetric (i.e 4 Stockes). It will be used in conjunction with other airborne instruments (in particular the C-Band scatterometer (STORM) and IEEEC GPS system, Infrared CIMEL radiometer and one visible camera), in coordination with in situ field campaigns for SMOS CAL/VAL. The instruments are implemented on board the French research airplane ATR42. A scientific campaign with thirteen flights is realized over south-western France, Valencia site and Bay of Biscay (Atlantic Ocean) in spring 2009. In order to…