Search results for "Infrared window"
showing 10 items of 18 documents
Radiometric calibration of SeaWIFS in the near infrared
2005
The radiometric calibration of the Sea-Viewing Wide-Field-of-View Sensor (SeaWiFS) in the near infrared (band 8, centered on 865 nm) is evaluated by use of ground-based radiometer measurements of solar extinction and sky radiance in the Sun's principal plane at two sites, one located 13 km off Venice, Italy, and the other on the west coast of Lanai Island, Hawaii. The aerosol optical thickness determined from solar extinction is used in an iterative scheme to retrieve the pseudo aerosol phase function, i.e., the product of single-scattering albedo and phase function, in which sky radiance is corrected for multiple scattering effects. No assumption about the aerosol model is required. The ae…
Vicarious Calibration of Landsat-8 Thermal Data Collections and its Influence on Split-Window Algorithm Validation
2018
Landsat 8 (L8) satellite was launched on February 11, 2013 with two thermal bands located in the atmospheric window between $10-12\ \mu \mathrm{m}$ . Continuous monitoring of the Thermal Infrared Sensor (TIRS) onboard of L8 was performed over two Spanish test sites – Barrax and Donana – in order to contribute to the quality of TIRS data. In this work, a Vicarious Calibration (VC) of the TIRS bands was performed between years 2013–2016 in order to assess the new Stray Light (SL) data correction. The results of VC show us that band 10 and 11 provide accurate results (bias near to zero, and precision around 0.8 K) which is an improvement – especially for band 11 – in comparison to preprocessed…
On the angular variation of thermal infrared emissivity of inorganic soils
2012
[1] Land surface temperature (LST), a key parameter for many environmental studies, can be most readily estimated by using thermal infrared (TIR) sensors onboard satellites. Accurate LST are contingent upon simultaneously accurate estimates of land surface emissivity (e), which depend on sensor viewing angle and the anisotropy of optical and structural properties of surfaces. In the case of inorganic bare soils (IBS), there are still few data that quantify emissivity angular effects. The present work deals with the angular variation of TIR emissivity for twelve IBS types, representative of nine of the twelve soil textures found on Earth according to United States Department of Agriculture c…
Effects of ice crystal habit on thermal infrared radiative properties and forcing of cirrus
2007
[1] The impact of assumed ice crystal morphology on thermal infrared (IR) radiative properties of subtropical cirrus is quantified. In particular, the crystal-shape-dependent profiles of downwelling and upwelling thermal IR (broadband and spectral) irradiances and the radiative forcing of cirrus (at the top and bottom of the atmosphere) are investigated. For this purpose, airborne measurements of ice crystal size distribution (in terms of ice crystal maximum dimension) from the CRYSTAL-FACE campaign and a recently published library of thermal IR optical properties of nonspherical ice crystal habits are implemented into radiative transfer simulations. Two cirrus cases are studied in detail: …
A study on recovering the cloud top-height from infra-red video sequences
2004
In this paper we present some preliminary results on an opticalfow based technique aimed at recovering the cloud-top height from infra-red image sequences. The recovery of the cloud-top height from satellite infra-red images is an important topic in meteorological studies, and is traditionally based on the analysis of the temperature maps. In this work we explore the feasibility for this problem of a technique based on a robust multi-resolution opticalfow algorithm. The robustness is achieved adopting a Least Median of Squares paradigm. The algorithm has been tested on semi-synthetic data (i.e. real data that have been synthetically warped in order to have a reliable ground truth for the mo…
Estimation of Daily Solar Radiation from Measured Air Temperature Extremes in the Mid-Mediterranean Area
2012
AbstractDaily solar radiation Rs at ground level is a necessary input variable required for the evaluation of evapotranspiration and crop growth, development, and yield-simulation models. Nevertheless, it is measured in few weather stations and at many locations it is not observed; also, available Rs temporal series are generally no longer than a few years. A valid surrogate of Rs measurement is the diurnal air-temperature range (ΔT); indeed, ΔT is inversely proportional to cloudiness and therefore could be a good indicator of atmospheric transmittance. As opposed to Rs, daily maximum and minimum air temperatures are measured at many locations and their observations in developed countries b…
Near-infrared radiative transfer modelling with different CH4 spectroscopic databases to retrieve atmospheric methane total amount
2011
International audience; Atmospheric methane content can be retrieved from measurements of solar radiation attenuated by the atmosphere in the near infrared spectral region where the space-borne and ground-based spectrometers carry out regular measurements. It is shown, in the present work, that the different spectroscopic databases can give significantly different results for both forward simulations of the atmospheric transmittance and the inverse problem solution to retrieve the CH4 total content in the atmosphere using spectra measured by ground-based FTIR spectrometer in the near infrared spectral region. These discrepancies and the problem of the reduction of their influence on the atm…
Performance of a FieldSpec spectroradiometer for aerosol optical depth retrieval: method and preliminary results
2009
The performance of a FieldSpec spectroradiometer for retrieving aerosol optical depth (AOD) has been assessed after modifying its basic configuration in order to measure direct solar irradiance at ground level. The FieldSpec measurements were obtained during four summertime days in the years 2004 and 2005, over a Spanish agricultural site in Barrax, Albacete (30 degrees 3(') N, 2 degrees 6(') W, 700 m a.s.l.), in the framework of two European Space Agency mission remote sensing field campaigns. From the whole FieldSpec spectral domain (350-2500 nm) the AOD was extracted for channels within atmospheric windows. The instrument was calibrated by means of the standard Langley plot method, perfo…
Estimation of daily average values of the Ångström turbidity coefficient β using a Corrected Yang Hybrid Model
2013
This paper aims to test a method for estimating daily values of atmospheric turbidity from non-specialized data, such as those obtained from agro-meteorological stations. This method allows estimating the spatial and temporal evolution of aerosols concentration in more places than just those in which direct measurements are available. The method is based on the Corrected Yang Hybrid Model (CYHM). The data used in the determination of errors between measured and estimated values of the daily Angstrom turbidity coefficient β were recorded in Valencia, Spain, during 2009 and 2011. These data were global solar irradiance, direct solar irradiance, temperature, relative humidity and Aerosol Optic…
Impact of Crystal Habit on Cirrus Radiative Properties
2007
The impact of assumed ice crystal morphology of subtropical cirrus on the solar and thermal infrared (IR) radiative field above, within, and below the cirrus is quantified. For this purpose airborne measurements of ice crystal size distribution from the CRYSTAL-FACE campaign and a library of optical properties of nonspherical ice crystal habits are implemented into radiative transfer simulations.Two cirrus cases are studied in detail: a high (cold) cirrus cloud with small visible optical thickness (τ≈1), and a lower (warmer) cirrus cloud of relatively large visible optical thickness (τ≈7). For t+he solar wavelength range the impact of shape characteristics of the crystals was important for …