Infrared Emissivity Data Research Articles

Multisensor Thermal Infrared and Microwave Land Surface Temperature Algorithm Intercomparison

To ensure optimal and consistent algorithm usage within climate studies utilizing satellite-derived Land Surface Temperature (LST) datasets, an algorithm intercomparison exercise was undertaken to assess the various operational and scientific LST retrieval algorithms in use. This study was focused on several LST products including single-sensor products for AATSR, Terra-MODIS, SEVIRI, SSM/I and SSMIS; a Climate Date Record (CDR), which is a combined dataset drawing from AATSR, SLSTR and MODIS; and finally a merged low Earth orbit/geostationary product using data from AATSR, MODIS and SEVIRI. Therefore, the analysis included 14 algorithms: seven thermal infrared algorithms and seven microwave algorithms. The thermal infrared algorithms include five split-window coefficient-based algorithms, one optimal estimation algorithm and one single-channel inversion algorithm, with the microwave focusing on linear regression and neural network methods. The algorithm intercomparison assessed the performance of the retrieval algorithms for all sensors using a benchmark database. This approach was chosen due to the lack of sufficient in situ validation sites globally and the bias this limited set engendered on the training of particular algorithms. A simulated approach has the ability to test all parameters in a consistent, fair manner at a global scale. The benchmark database was constructed from European Centre for Medium-Range Weather Forecasts Re-analysis 5 (ERA5) atmospheric data, Combined ASTER and MODIS Emissivity for Land (CAMEL) infrared emissivity data, and Tool to Estimate Land Surface Emissivities at Microwave frequencies (TELSEM) emissivity data for the period of 2013–2015. The best-performing algorithms had biases of under 0.2 K and standard deviations of approximately 0.7 K. These results were consistent across multiple sensors. Areas of improvement, such as coefficient banding, were found for all algorithms as well as lines for further inquiry that could improve the global and regional performance.

Radiometric calibration of thermal emission data from the Asteroid and Lunar Environment Chamber (ALEC).

The vacuum and thermal environment of airless planetary surfaces, particularly those dominated by a particulate regolith such as the Moon and asteroids, produces intense near-surface thermal gradients that can substantially alter their thermal emissivity spectra when compared with spectra collected at ambient terrestrial conditions. Therefore, spectroscopic measurements acquired under conditions designed to simulate the radiation environment in which remote measurements of airless bodies are made should be used as the basis for interpreting those data. As a foundation for this goal, we report the radiometric calibration of thermal infrared emission data collected with a Fourier transform infrared spectrometer integrated with the custom Asteroid and Lunar Environment Chamber (ALEC) at Brown University. This chamber is designed to simulate the environment of airless planetary bodies by evacuating the atmospheric gasses to vacuum (<10-4 mbar), cooling the chamber with a flow of liquid nitrogen, heating the base and sides of samples with temperature-controlled sample cups, and heating the top of samples with an external light source. We present a new method for deriving sample emissivity based on the absolute radiometry properties of our system, focusing on the 400-2000 cm-1 wavenumber range. This method produces calibrated radiance spectra from calibration targets, and particulate samples and those spectra are used to derive emissivity spectra. We demonstrate that the ALEC system and data reduction methods successfully replicate independently determined spectral properties of particulate samples under both ambient and cold, vacuum conditions. The ALEC system is shown to be capable of supporting ongoing and future planetary exploration of airless surfaces by facilitating careful investigation of meteorites, lunar samples, and planetary materials at an array of environmental conditions.

Integration and Visualization of Mineralogical and Topographical Information Derived from ASTER and DEM Data

This paper proposes a method of combining and visualizing multiple lithological indices derived from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data and topographical information derived from digital elevation model (DEM) data in a single color image that can be easily interpreted from a geological point of view. For the purposes of mapping silicate rocks, carbonate rocks, and clay minerals in hydrothermal alteration zones, two new indices derived from ASTER thermal infrared emissivity data were developed to identify silicate rocks, and existing indices were adopted to indicate the distribution of carbonate rocks and the species and amounts of clay mineral. In addition, another new method was developed to visualize the topography from DEM data. The lithological indices and topographical information were integrated using the hue–saturation–value (HSV) color model. The resultant integrated image was evaluated by field survey and through comparison with the results of previous studies in the Cuprite and Goldfield areas, Nevada, USA. It was confirmed that the proposed method can be used to visualize geological information and that the resulting images can easily be interpreted from a geological point of view.

On the relationship between land surface infrared emissivity and soil moisture

The relationship between surface infrared (IR) emissivity and soil moisture content has been investigated based on satellite measurements. Surface soil moisture content can be estimated by IR remote sensing, namely using the surface parameters of IR emissivity, temperature, vegetation coverage, and soil texture. It is possible to separate IR emissivity from other parameters affecting surface soil moisture estimation. The main objective of this paper is to examine the correlation between land surface IR emissivity and soil moisture. To this end, we have developed a simple yet effective scheme to estimate volumetric soil moisture (VSM) using IR land surface emissivity retrieved from satellite IR spectral radiance measurements, assuming those other parameters impacting the radiative transfer (e.g., temperature, vegetation coverage, and surface roughness) are known for an acceptable time and space reference location. This scheme is applied to a decade of global IR emissivity data retrieved from MetOp-A infrared atmospheric sounding interferometer measurements. The VSM estimated from these IR emissivity data (denoted as IR-VSM) is used to demonstrate its measurement-to-measurement variations. Representative 0.25-deg spatially-gridded monthly-mean IR-VSM global datasets are then assembled to compare with those routinely provided from satellite microwave (MW) multisensor measurements (denoted as MW-VSM), demonstrating VSM spatial variations as well as seasonal-cycles and interannual variability. Initial positive agreement is shown to exist between IR- and MW-VSM (i.e., R(sup 2) = 0.85). IR land surface emissivity contains surface water content information. So, when IR measurements are used to estimate soil moisture, this correlation produces results that correspond with those customarily achievable from MW measurements. A decade-long monthly-gridded emissivity atlas is used to estimate IR-VSM, to demonstrate its seasonal-cycle and interannual variation, which is spatially coherent and consistent with that from MW measurements, and, moreover, to achieve our objective of investigating the relationship between land surface IR emissivity and soil moisture.

Thermal-based techniques for land cover change detection using a new dynamic MODIS multispectral emissivity product (MOD21)

Land Surface Temperature and Emissivity (LST&E) data determine the amount of net longwave radiation emitted from the Earth's surface and are therefore critical variables for studying a variety of surface–atmosphere processes over land such as evapotranspiration, land cover change, and surface composition. Because emissivity is an intrinsic property of the surface, multispectral thermal infrared emissivity data have the potential for enhancing our ability to monitor landscape changes in environmentally sensitive zones beyond what is currently possible from standard practices used today. The most common of these practices is the use of visible to short-wave infrared data, in particular the Normalized Difference Vegetation Index (NDVI). Two algorithms are currently used to generate the LST&E products from MODIS data, but studies have identified several issues with both these algorithms that limit their usefulness for land cover change detection. These issues have been recently addressed by applying the ASTER Temperature Emissivity Separation (TES) algorithm to MODIS thermal infrared data to generate LST and a dynamically varying multispectral emissivity product for bands 29, 31, and 32 at 1-km resolution. The new product (MOD21) will be released with MODIS Collection 6 during fall 2013. This study demonstrates the utility of the dynamic MOD21 multispectral emissivity product to detect land cover changes over a broad range of different Earth surface domains including land degradation in dryland regions, snow melt characteristics on glaciers and ice sheets, extreme ecosystem disturbances, and agricultural activities. The MOD21 spectral emissivity provided increased sensitivity to land cover change in a more consistent manner than is currently possible with other emissivity products and, depending on the application, standard visible to near infrared (VNIR) data. The results suggest that synergistic use of thermal and VNIR data will help us to better identify and understand changes in the Earth surface system, and reduce uncertainties in estimating their magnitudes and trends.

MetOp-A/IASI Observed Continental Thermal IR Emissivity Variations

<?Pub Dtl=""?> Satellite thermal infrared (IR) spectral emissivity data have been shown to be significant for atmospheric research and monitoring the Earth's environment. Long-term and large-scale observations that are needed for global monitoring and research can only be supplied by satellite-based remote sensing. Presented here is the global surface IR emissivity data retrieved from the last five and half years of Infrared Atmospheric Sounding Interferometer (IASI) measurements observed from the MetOp-A satellite. Monthly mean surface properties (i.e., skin temperature <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$T_{\rm s}$</tex></formula> and spectral emissivity <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$\varepsilon_{\nu}$</tex></formula> ) with a spatial resolution of 0.5 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\times$</tex></formula> 0.5-degrees latitude-longitude are produced to monitor seasonal and inter-annual variations. Continental IR spectral emissivity derived from satellite ultraspectral IR measurements reveals its variation depending on surface weather and climate conditions. Variation behaviors of continental IR spectral emissivity, associated with the seasonal change as well as weather and climate conditions are initially captured by IASI measurements and will be continuously monitored as provided by the satellite measurements. Surface <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\varepsilon_{\nu}$</tex></formula> retrieved with IASI measurements can be used to assist in monitoring surface weather and surface climate change. Surface <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\varepsilon_{\nu}$</tex> </formula> together with <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$T_{\rm s}$</tex></formula> from current and future operational weather satellites can be utilized as a means of long-term and large-scale monitoring of Earth's surface weather environment and associated changes.

Ionospheric VTEC and thermospheric infrared emission dynamics during corotating interaction region and high-speed stream intervals at solar minimum: 25 March to 26 April 2008

[1] We analyze a portion of the Whole Heliospheric Interval from 25 March to 26 April 2008 to identify the ionospheric and thermospheric responses to high-speed solar wind streams. This period during solar sunspot minimum is of moderate geomagnetic activity (with the minimum Dst ∼ −50 nT) with enhanced auroral activity seen in High-Intensity Long-Duration Continuous Auroral Activity events. The solar wind data show several corotating interaction regions (CIRs) and recurrent high-speed streams (HSSs). Using the infrared emission data obtained with Sounding of the Atmosphere using Broadband Emission Radiometry on Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics, we identify a distinct relationship between the infrared emission irradiated from the thermosphere and CIR-HSS intervals. Specifically, zonal flux of NO infrared radiation correlates well with AE indices. The most pronounced effects are found at high latitudes. We used Jet Propulsion Laboratory Global Ionospheric Maps (GIMs) software and the GPS total electron content (TEC) database to calculate the vertical total electron content (VTEC) and construct GIMs. It is shown that VTEC intensifies during HSSs periods. To illustrate the point, dynamics of daytime VTEC averaged over different latitude bands are presented. These results are compared to quiet time observations to contrast variations associated with geomagnetic activity. Data analyses show fast, global, and continuous ionospheric responses to external solar wind forcing. The largest variations are found in low-latitude (between −30° and 30°) VTEC. In conclusion, we suggest that CIRs/HSSs are external drivers for both thermospheric and ionospheric phenomena during the solar sunspot minimum. We discuss both prompt penetration electric fields and disturbance dynamos as possible mechanisms responsible for the observed VTEC effects. It is clear that efficient heliospheric-magnetospheric-ionospheric-thermospheric coupling occurs during CIR-HSS intervals even during solar sunspot minimum in 2008.

Identification of quartz and carbonate minerals across northern Nevada using ASTER thermal infrared emissivity data—Implications for geologic mapping and mineral resource investigations in well-studied and frontier areas

ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) thermal infrared imagery over a 389 km × 387 km area in northern Nevada (38.5°–42°N, 114°–118.5°W) was analyzed to evaluate its capability for accurate and cost-effective identification and mapping of quartz and carbonate minerals at regional to local scales. The geology of this area has been mapped at a wide range of scales and includes a diversity of rock types and unconsolidated surficial materials, many of which are composed primarily of quartz and carbonate minerals. This area is also endowed with a wide variety of economically and scientifically important ore deposit types that contain an array of commodities (Au, Ag, Pb, Zn, Cu, Mo, W, Sn, Be, F, Mn, Fe, Sb, Hg, and barite). The hydrothermal systems that generated these deposits frequently deposited large amounts of quartz where fluids cool, and generally smaller amounts of calcite or dolomite by other mechanisms. To identify and map quartz and carbonate minerals, band ratioing techniques were developed based on the shapes of laboratory reference spectra and applied to ASTER Level 2 surface emissivity products of 108 overlapping scenes. These mineral maps were mosaicked into a single coverage that was overlain with published, vector-format geologic maps of various scales to determine which geologic terranes, formations, and geomorphic features correspond to identified quartz or carbonate. Where quartz or carbonate minerals were mapped in rocks composed primarily of other minerals, they were inferred to be hydrothermal in origin and compared to known occurrences of hydrothermal alteration and mineralization. The ASTER-based quartz mapping identified thick sequences of quartzite, bedded radiolarian chert, quartz sandstone, conglomerates with clasts of quartzite and chert, silicic and/or altered rhyolites, and silicic welded tuffs. Alluvial fan surfaces, sand dunes, and beach deposits composed of quartz and/or carbonate are prominent, well-mapped features. Quartz was also identified in smaller bodies of jasperoid, quartz-alunite, and quartz-sericite-pyrite alteration, hot spring silica sinter terraces, and several diatomite and perlite mines and prospects. The ASTER-based carbonate mapping identified thick sequences of dolomite, limestone, and marble, as well as small hot spring travertine deposits. Eolian carbonate was identified in several playas. Dolomite exhibited a stronger carbonate response than calcite, as predicted based on their thermal spectral characteristics. Quartz was detected at lower concentrations than carbonates because of the greater strength of the quartz reststrahlen features in the thermal infrared compared to the bending-related spectral features of carbonates. The 90 m ground pixel size of the ASTER thermal imagery prevents the identification of small-scale features. Despite this limitation, numerous bodies of hydrothermal quartz were detected in or near known Carlin-type gold deposits, distal disseminated Au-Ag deposits, high- and low-sulfidation epithermal Au-Ag deposits, and geothermal areas. Detection of hydrothermal carbonate was rare and mainly in geothermal areas. The ASTER-based thermal quartz and carbonate mapping demonstrated here can be used in well-studied or frontier areas to verify the accuracy of existing geologic maps, guide future detailed stratigraphic and structural mapping in lithologically complex terranes and allochthons, and identify hydrothermal features for exploration and resource assessment purposes.

Monitoring Dielectric Thin-Film Production on Product Wafers Using Infrared Emission Spectroscopy

Monitoring of dielectric thin-film production in the microelectronics industry is generally accomplished by depositing a representative film on a monitor wafer and determining the film properties off line. One of the most important dielectric thin films in the manufacture of integrated circuits is borophosphosilicate glass (BPSG). The critical properties of BPSG thin films are the boron content, phosphorus content, and film thickness. We have completed an experimental study that demonstrates that infrared emission spectroscopy coupled with multivariate analysis can be used to simultaneously determine these properties directly from the spectra of product wafers, thus eliminating the need for producing monitor wafers. In addition, infrared emission data can be used to simultaneously determine the film temperature, which is an important film production parameter. The infrared data required to make these determinations can be collected on a time scale that is much faster than the film deposition time, hence infrared emission is an ideal candidate for an in situ process monitor for dielectric thin-film production.

Thermal infrared emission spectroscopy of anhydrous carbonates

The objective of this study is to present the thermal emission spectra of various anhydrous, calcite‐ and dolomite‐series carbonate minerals to illustrate the effect of the structural cation (Ca2+, Mg2+, Fe2+, Mn2+, Zn2+) on shifting the positions of the carbonate absorption bands. All of the carbonate mineral emission spectra included in this study exhibit three absorption features related to three specific vibrational modes of the carbonate anion (CO32−). These anion vibrations include the out‐of‐plane bend, the asymmetric stretch, and the in‐plane bend (i.e., the v2, v3, and v4 modes, respectively). The positions of the absorption‐band emissivity minima are unique for each carbonate chemistry and are thus diagnostic of mineralogy. The average v2, v3 and v4 wavenumber positions for the various carbonate minerals are as follows: calcite (CaCO3) 883, 1523, and 712 cm−1; magnesite (MgCO3) 901, 1572, and 748 cm−1; siderite (FeCO3) 876, 1523, and 736 cm−1; rhodochrosite (MnCO3) 877, 1535, and 726 cm−1; smithsonite (ZnCO3) 882, 1509, and 742 cm−1; dolomite (CaMg(CO3)2) 894, 1547, and 728 cm−1; and kutnahorite (CaMn(CO3)2) 882, 1526, and 716 cm−1. Carbonates as a general mineral class crystallize in a variety of geological environments; however, each specific carbonate mineralogy typically is limited to a narrow range of geologic settings in which it forms. Thermal infrared emission data to be received from the Mars Global Surveyor thermal emission spectrometer will contain the spectral signature of carbonates if they are present above the detectibility limit on the surface of Mars. This study presents the spectral information necessary to recognize carbonate as a mineral class as well as identify the specific type of carbonate from thermal emissivity data. Knowledge of distinct carbonate mineralogy will be useful for interpreting the environmental conditions that were present on Mars during the carbonate formation. The result of this study is that the major carbonate mineral species (calcite, dolomite, magnesite, siderite, and smithsonite) can be identified from thermal infrared emission data, provided moderate (10 cm−1) spectral sampling. Because of the similarity of absorption band positions between kutnahorite and calcite, high (2 cm−1) spectral sampling is required to distinguish kutnahorite. Moderate spectral sampling data are also sufficient to determine the amount of Mg and Fe in Mg‐Fe solid solution minerals to within 3–5% of the cation abundance.

Thermal studies of Martian channels and valleys using Termoskan data

The Termoskan instrument on board the Phobos '88 spacecraft acquired the highest spatial resolution thermal infrared emission data ever obtained for Mars. Included in the thermal images are 2 km/pixel, midday observations of several major channel and valley systems including significant portions of Shalbatana, Ravi, Al‐Qahira, and Ma'adim Valles, the channel connecting Valles Marineris with Hydraotes Chaos, and channel material in Eos Chasma. Termoskan also observed small portions of the southern beginnings of Simud, Tiu, and Ares Valles and some channel material in Gangis Chasma. Simultaneous broadband visible reflectance data were obtained for all but Ma'adim Vallis. We find that most of the channels and valleys have higher thermal inertias than their surroundings, consistent with previous thermal studies. We show for the first time that the thermal inertia boundaries closely match flat channel floor boundaries. Also, buttes within channels have inertias similar to the plains surrounding the channels, suggesting the buttes are remnants of a contiguous plains surface. Lower bounds on typical channel thermal inertias range from 8.4 to 12.5 (10−3 cal cm−2 s−1/2 K−1) (352 to 523 in SI units of J m−2 s−1/2 K−1). Lower bounds on inertia differences with the surrounding heavily cratered plains range from 1.1 to 3.5 (46 to 147 SI). Atmospheric and geometric effects are not sufficient to cause the observed channel inertia enhancements. We favor nonaeolian explanations of the overall channel inertia enhancements based primarily upon the channel floors' thermal homogeneity and the strong correlation of thermal boundaries with floor boundaries. However, localized, dark regions within some channels are likely aeolian in nature as reported previously. Most channels with increased inertias have fretted morphologies such as flat floors with steep walls. Eastern Ravi and southern Ares Valles, the only major channel sections observed that have obvious catastrophic flood bedforms, do not have enhanced inertias. Therefore, we favor fretting processes over catastrophic flooding for explaining the inertia enhancements. We postulate that the inertia enhancements were caused either by the original fretting process or by a process involving the bonding of fines due to an increased availability of water, either initially or secondarily.

IRAS OBSERVATIONS OF BINARIES WITH COMPACT OBJECTS.

ABSTRACT The infrared emission data, obtained on 260 binary systems by the all-sky IRAS survey in wavelengths between 12 and 100 microns, are reported. Of all the 260 sources, which contained compact objects including white dwarfs, neutron stars, or possibly black holes, only 32 contained detectable IR radiation. The X-ray emitting Be-type stars (gamma-Cas and X Per) were found to have their energy flux proportional to frequency in the range of the log nu values of 12.7-14.7. However, the GS304-1 flux distribution is unique, in that its flux rises by several orders of magnitude as the wavelength changes from 4000 A to 60 microns. A static dust cloud was detected, with a radius of about 1 AU, which has formed around the classical nova RR Pic since its 1925 eruption. The post-eruption far-IR light curve of a classical nova provides strong evidence for IR emissions from both dust grains formed during the eruption and dust grains existing from previous eruptions.

Nitric acid distribution in the stratosphere

The distribution of HNO3 in the lower stratosphere has been derived from atmospheric infrared emission data. In total, four flights of balloon-borne radiometers are analyzed. The derived mixing ratio profiles with altitude have on the average a low value of ∼2 × 10−9 g HNO3/g air at about 13-km altitude and a maximum value of ∼2 × 10−8 g HNO3/g air between 20 and 24 km. The profiles indicate definite HNO3 layers in the atmosphere.