Long-wave Band Research Articles

Directional variation in surface emissivity inferred from the MYD21 product and its influence on estimated surface upwelling longwave radiation

The land surface emissivity (LSE) in the MYD21 product contains the effects of viewing zenith angle. The influence of the angular variation of LSE on the surface upwelling longwave radiation (SULR) estimation is still unexplored at the satellite scale. We performed statistical analyses of MYD21 emissivity retrievals over different land surface types for three longwave bands centred around 8.55 μm (Band 29), 11 μm (Band 31) and 12 μm (Band 32), respectively. A look-up table was generated to describe the angular variations for both single-band and broadband emissivities. The results showed that the angular variation of directional emissivity in Band 29 could reach up to 0.03, but was <0.01 for Bands 31 and 32. The angular variation in broadband emissivity was intermediate to that for individual bands. In all cases, the directional emissivity was greatest and symmetric around nadir. By integrating the directional broadband emissivity, the influence of angular variation of the LSE on estimated SULR was quantified using simulation and measurements at seven stations from the US surface radiation budget network (SURFRAD). The difference between the directional and integrated hemispheric broadband emissivity was within 0.01. As a result, the influence of angular variation of LSE on the SULR estimation was modest. For the SURFRAD stations, the differences of root-mean-square error (RMSE) before and after considering the angular variation of LSE were generally <1 W m−2. We conclude that the angular variation of broadband emissivity is not pronounced because of the small linear weight for Band 29 in the calculation of broadband emissivity. Ignoring the anisotropy of emissivity does not introduce large errors in SULR estimation generally.

Highly efficient K0.4Na3.6Co(MoO4)3 new alluaudite type structure for photocatalytic degradation of methylene blue and green diamine B dyes

A novel alluaudite framework K0.4Na3.6Co(MoO4)3 photocatalyst has been synthesized by a solid-state reaction for degradation of both methylene blue (MB) and green diamine B (GDB) organic pollutants under sunlight. The sample was characterized using X-ray diffraction (XRD), transmission electron microscope, infrared spectroscopy and Raman spectroscopy, as well as by means of photoluminescence probing, impedance spectroscopy and UV–vis–NIR spectrophotometry. The XRD analysis reveals that such alluaudite type structure crystallizes in the monoclinic system with space group C2/c. Emissions of this material have been observed in a visible region at 290 nm excitation with a broad long-wave luminescence band from oxygen vacancies. UV–vis absorption spectrum measurements showed an efficient optical absorption in UV–vis region with a direct band gap of 3.37 eV. The complex impedance spectra suggested that the ac conductivity is a power law (Aωs) derived by the correlated barrier hopping conduction mechanism. The efficiency of the dyes removal in the presence of K0.4Na3.6Co(MoO4)3 particles reaches 83% for MB and 53% for GDB under sunlight irradiation. The current studies establish interesting possibilities for investigating catalytic cycles of these solar light activated photocatalysts.

The Sensitivity of the Jet Stream Response to Climate Change to Radiative Assumptions

AbstractComprehensive climate models exhibit a large spread in the magnitude of projected poleward eddy‐driven jet shift in response to warming. The spread has been connected to the radiative response to warming. To understand how different radiative assumptions alone affect the jet shift in response to warming, we introduce a new clear‐sky longwave radiation hierarchy that spans idealized (gray versus four bands; without or with interactive water vapor) through comprehensive (correlated‐k) radiation in the same general circulation model. The new hierarchy is used in an aquaplanet configuration to explore the impact of radiation on the jet stream response to warming, independent of mean surface temperature and meridional surface temperature gradient responses. The gray radiation scheme produces a split jet and its eddy‐driven jet shifts equatorward as climate warms, whereas the storm track shifts equatorward then poleward. Including four longwave bands leads to a merged jet that shifts slightly poleward with warming, and the storm track shifts monotonically poleward. Including interactive water vapor makes the poleward jet shift comparable to the jet shift with comprehensive radiation and interactive water vapor. These jet and storm track differences are linked to the radiation response of the stratospheric temperature, the tropopause height, and the meridional gradient of the radiative forcing to warming. Dynamically, the equatorward jet shift with the gray scheme is consistent with reduced wave reflection on the poleward flank of the jet, whereas the poleward jet shift with the other schemes is consistent with increased eddy length scale that favors equatorward wave propagation.

Квантово-химическое моделирование строения и свойств азопроизводных флороглюцина

The DFT/B3LYP quantum-chemical method has been used to simulate the structure of 2-((2-hydroxyphenyl) diazonyl) benzene-1,3,5-triol (L1) and 2-((2-hydroxy-4-nitrophenyl) diazonyl) benzene-1,3,5-triol (L2) molecules. The spatial and electronic structure of molecules in various tautomeric forms was determined. It was shown that the stability of these compounds is primarily due to the presence of strong intramolecular hydrogen bonds (IHB), which form six-membered cycles, and the isomerism of the molecule, which assume the formation of IHB. The structures where IHB form five-membered cycles, are less stable. In general, for the L1 and L2 molecules, azo-tautomers were found to be 4 and 3 kJ/mol more stable than the hydrazo-tautomers, respectively. Such a small difference in energy of molecules for the gas phase did not allow us to conclude about the form of existence of molecules in solutions or in the crystalline state. To assess the possibility of transition between tautomers, we used the DFT method to calculate the transition states (TS) between the azo and hydrazo tautomers of the L1 and L2 molecules. The barrier of the transition from the azo form to the hydrazo form was found to be 14 kJ/mol for the molecules L1 and L2, respectively. The interatomic distances, angles, charges on atoms, IR and electronic absorption spectra of tautomeric forms of L1 and L2 molecules were calculated. It has been established that the long-wave absorption band (LB) of the electronic absorption spectrum bathochromically shifts at transition from azo to hydrazo-tautomers by 41 nm for L1 and 40 nm for L2. The introduction of a nitro group also leads to a bathochromic shift of the LB by 22 nm at transition from azo-tautomer L1 to hydrazo-L1 L2 and by 21nm at transition from azo-L2 to hydrazo-L2.

Visualization example of the infrared image by high-speed infrared thermography

The development of high-performance infrared thermography has given rise to a wide variety of demanding thermal imaging applications that were previously not possible ranging from academics and research, industrial R&D, non-destructive testing and materials testing, aerospace and defence. High-speed infrared thermography is now available with spectral sensitivity, in the mid-wave and long-wave spectral bands.

Enhancing the Fast Radiative Transfer Model for FengYun‐4 GIIRS by Using Local Training Profiles

AbstractWith the successful launch of FengYun‐4A (FY‐4A), the first satellite in a new Chinese geostationary weather satellite series (FY‐4 series), which carries a high spectral resolution infrared (IR) sounder called GIIRS (Geosynchronous Interferometric Infrared Sounder), and vertical atmospheric profiles can be obtained frequently at the regional scale. A fast radiative transfer model is a key component for quantitative applications of GIIRS radiance measurements, including deriving soundings in near real time for situation awareness and radiance assimilation in numerical weather prediction models. The weighted least squares method on enhancing the accuracy of RTTOV (Radiative Transfer for TOVS) for GIIRS is developed. Besides, currently, fast radiative transfer models for IR sensors are based on global training profiles, since GIIRS is targeted for regional observations; it is beneficial for local weather related applications using local training profiles, which better represent the characteristics of that weather regime. A local training profile data set has been developed for GIIRS using the RTTOV approach, comparisons with line‐by‐line radiative transfer model indicate that weighted least squares method provides better accuracy (smaller root‐mean‐square error) in the brightness temperature simulation for the middlewave band of GIIRS than the ordinary least squares method, and the local training profiles have further remarkable improvements on brightness temperature simulation over the global training profiles, especially for GIIRS longwave band. The methods can be applied to RTTOV development for other IR sensors onboard the geostationary satellites.

Band optimization of passive methane gas leak detection based on uncooled infrared focal plane array.

Current methane gas leak detection technology uses infrared imaging in the medium wave (MW) or long wave (LW) bands, essentially applying cooled infrared detectors. In this study, a simplified three-layer radiative transfer model is adopted based on methane gas detection theory, considering background radiation, atmospheric infrared absorption, gas absorption, and emission characteristics to analyze the contrast of methane gas thermography in different infrared bands. The analysis results suggest that under certain conditions, the 6.6-8.6μm LW band provides higher contrast compared to the 3-5μm MW band. The optimal imaging wavelength band is selected according to imaging contrast advantages and disadvantages, and infrared optical systems and infrared filters are designed and optimized. We build a passive methane gas leak detection system based on uncooled infrared focal plane array detectors. By collecting gas images under different conditions, the imaging detection capabilities for methane gas leaks in the MW and LW bands in a laboratory environment are compared. Finally, the developing trends in methane gas detection technology are analyzed.

Synthesis and properties of new heterocyclic betaines: 4-Aryl-5-(methoxycarbonyl)-2-oxo-3-(pyridin-1-ium-1-yl)-2,3-dihydro-1H-pyrrol-3-ides

New heterocyclic betaines, 4-aryl-5-(alkoxycarbonyl)-2-oxo-3-(pyridin-1-ium-1-yl)-2,3-dihydro-1H-pyrrol-3-ides, were synthesized in good yields by the reaction of alkyl 2H-azirine-2-carboxylates with 2-methoxy-2-oxo-1-(pyridin-1-ium-1-yl)ethan-1-ides, generated from the corresponding pyridinium salts. The betaines exist as the NH-tautomers both in solution and in the solid state. Two molecules of the betaine form a dimer by hydrogen bonds of the type NH⋯O in solid state. According to TD DFT calculations the long-wave absorption band in betaines mainly corresponds to the intramolecular charge transfer between the negatively charged pyrrole unit and the positively charged pyridinium group. The blue shift of the long-wave absorption in protic solvents was adequately described in terms of H-complex formation with the nucleophilic centre of the molecular skeleton.

SYNTHESIS, SPECTRAL AND QUANTUM CHEMICAL RESEARCHES OF (Z)-10-(2-(4-AMINO-5-THIOXO-4,5-DIHYDRO-1H-1,2,4-TRIAZOLE-3-IL)HYDRAZONO)-9-PHENANTHRONE

(Z)-10-(2-(4-amino-5-thioxo-4,5-dihydro-1H-1,2,4-triazole-3-il)hydrazono)-9-phenanthrone (I) was obtained by a condensation of 4-amino-5-hydrazino-4H-1,2,4-triazole-3-thiol with 9,10-phenanthrenequinone. The compound I was characterized by IR, UV-VIS, 1Н, 13С NMR and chromatography-mass spectrometry. The electronic absorption spectra of I in aproton solvents (DMF, DMSO) are characterized by the existence of an intensive long-wave band in the range of 468 - 485 nm. The absorption maximum of a freshly prepared solution of I (485 nm) after 48 h gradually undergoes hypsochromic shift to 474 nm, and after 72 h it shifts to 468 nm. In the UV-VIS spectrum of I, at addition of NaOH the batochromic shift of a long wave band to 511 nm with a significant increase in intensity is observed. The presence of one isobestic point in the spectrum indicates the formation of a mono-anion. In the UV-VIS spectrum of I at addition of HCl solution, the long wave absorption band undergoes hypsochromic shift to 376 nm with a small decrease in intensity. In the 1Н NMR spectrum of I, in the range of 15.08 ppm a singlet signal of a proton of a hydrazo-group is observed. In the 13С NMR spectrum of I, in the range of 180.80 ppm a signal which corresponds to carbonyl C-atom is observed. Quantum chemical modeling of the electronic structure of I as well as its ionic forms was performed in the frames of the density functional theory approach (DFT) using of a hybride tri-parametric exchange Becke functional with a correlational Lee-Yang-Parr functional (B3LYP) and basis sets def2-SV(P), def2-TZV(P). According to the spectral and quantum chemical studies, in the crystalline state and saturated solution the compound I exists in the form of the thione quinone hydrazone tautomer stabilized by intramolecular hydrogen bonds. The thione tautomer is 44 kJ/mol more stable than a thiol tautomer, the transition barrier is 135 kJ/mol. However, it is not possible to exclude possibility of transition of the thione form into the thiol one in the diluted solutions. Forcitation:Polyanskaya N.A., Ryabov M.A., Strashnov P.V., Linko R.V., Davydov V.V., Kobrakov K.I., Karavaeva E.B. synthesis, spectralandquantumchemicalresearchesof (Z)-10-(2-(4-amino-5-thioxo-4,5-dihydro-1H-1,2,4-triazole-3-il)hydrazono)-9-phenanthrone. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N 1. P. 55-65

X-ray spectra of plasma radiation from laser induced low-power vacuum discharge

The x-ray spectra of plasma radiation in the wavelength range 30–300 Å are studied. The radiation is emitted from plasma of a vacuum discharge with storage energy less than 30 J that is initiated on an Al or Fe cathode by beam from neodymium laser with a power density up to 1012 W cm−2. It is shown that both the spectral composition and intensity of radiation of hot micropinch plasma that is formed in the cathodic jet are determined by the set of the discharge and the laser pulse characteristics. By optimizing these characteristics, a mode of the discharge operation is attainable, in which a significant portion of the radiation energy is located in the long-wave band of the quasi-continuum (230–270 Å and 160–200 Å for Al and Fe cathodes, respectively). That makes it possible to treat such a discharge as an intense source of narrow-band soft x-ray radiation.

Effect of methyl substituents on the electronic transitions in simple meso-aniline-BODIPY based dyes: RI-CC2 and TD-CAM-B3LYP computational investigation

The S0→Si, i=1–5 electronic transitions of four 8-(4-aniline)-BODIPY and four 8-(N,N-dimethyl)-BODIPY dyes, differ by number and position of methyl substituents in the BODIPY frame, were investigated theoretically using ab initio the coupled cluster doubles (CC2) and TD-CAM-B3LYP methods. Methyl substituents in the BODIPY frame and the aniline fragment at the meso position disturb energy of local excitations S0→S1, S0→S3, and S0→S4 weakly in comparison with the fully unsubstituted BODIPY molecule. These transitions in experimental spectra form the most long-wave absorption bands at ca. 500nm as well as absorption bands in the region of 300–400nm. At the same time, the presence of aniline fragments leads to the appearance of new S0→S2 transitions of the charge transfer character in electronic spectra of BODIPYs. We also found a linear relationship between vertical energy of these charge transfer transitions and the electron donating power of an aniline fragment and electron accepting power of the BODIPY core depending on the number and position of methyl groups. The CC2 method provides the best overall description of the excitation energies in line with the experimental observations. On average, the quality of TD-CAM-B3LYP is almost equal to that of CC2, however the TD method with the CAM-B3LYP functional slightly underestimates the CT excitation energy.

Bias-selectable mid-/long-wave dual band infrared focal plane array based on Type-II InAs/GaSb superlattice

In this paper, a mid-/long-wave dual-band detector which combined PπMN structure and unipolar barrier was developed based on type-II InAs/GaSb superlattice. A relevant 320×256 focal plane array (FPA) was fabricated. Unipolar barrier and PπMN structure in our dual band detector structure were used to suppress cross-talk and dark current, respectively. The two channels, with respective 50% cut-off wavelength at 4.5μm and 10μm were obtained. The peak quantum efficiency (QE) of mid wavelength infrared (MWIR) band and long wavelength infrared (LWIR) band are 53% at 3.2μm under no bias voltage and 40% at 6.4μm under bias voltage of −170mV, respectively. And the dark current density under 0 and −170mV of applied bias are 1.076×10−5A/cm2 and 2.16×10−4A/cm2. The specific detectivity of MWIR band and LWIR band are 2.15×1012cm·Hz1/2/W at 3.2μm and 2.31×1010cm·Hz1/2/W at 6.4μm, respectively, at 77K. The specific detectivity of LWIR band maintains above 1010cm·Hz1/2/W at the wavelength range from 4.3μm to 10.2μm under −170mV. The cross-talk, selectivity parameter at 3.0μm, about 0.14 was achieved under bias of −170mV. Finally, the thermal images were taken by the fabricated FPA at 77K.

Radiometric Characteristics of the Broadband Radiometer (BBR) Instrument for the EarthCARE Mission

AbstractThe Broadband Radiometer (BBR) is one of a suite of instruments to be flown on the Earth Clouds, Aerosol and Radiation Explorer (EarthCARE) space mission. Its role is to make broadband measurements of Earth radiance in terms of reflected solar radiation and emitted thermal infrared radiation for use with the other EarthCARE instruments for the study of Earth atmosphere processes. The Broadband Radiometer has its design based on the principles and heritage of previous instruments for studying the earth radiation budget (ERB). The radiometer has common features with those instruments: two measurement bands—shortwave (solar energy of 0.25–4 µm) and total wave (0.25 to &gt;50 µm)—with a longwave band (thermal emission of 4 to &gt;50 µm) being obtained by subtraction of the two measured bands. Multiple simultaneous views of Earth at three different view angles are used to account for angular variations in radiance. The radiometer requires an accuracy of 1% in each band, similar to those of the previous instruments, and detailed calibration measurements on ground and in orbit. This paper describes the instrument calibration algorithms and the corresponding requirements on the ground calibration of the flight instrument prior to launch. It includes a description of the main methods to be used and the error sources to be controlled, based on the design heritage and analysis results of the previous ERB instruments.

The Far Ultra-Violet imager on the ICON mission.

ICON Far UltraViolet (FUV) imager contributes to the ICON science objectives by providing remote sensing measurements of the daytime and nighttime atmosphere/ionosphere. During sunlit atmospheric conditions, ICON FUV images the limb altitude profile in the shortwave (SW) band at 135.6 nm and the longwave (LW) band at 157 nm perpendicular to the satellite motion to retrieve the atmospheric O/N2 ratio. In conditions of atmospheric darkness, ICON FUV measures the 135.6 nm recombination emission of O+ ions used to compute the nighttime ionospheric altitude distribution. ICON Far UltraViolet (FUV) imager is a CzernyTurner design Spectrographic Imager with two exit slits and corresponding back imager cameras that produce two independent images in separate wavelength bands on two detectors. All observations will be processed as limb altitude profiles. In addition, the ionospheric 135.6 nm data will be processed as longitude and latitude spatial maps to obtain images of ion distributions around regions of equatorial spread F. The ICON FUV optic axis is pointed 20 degrees below local horizontal and has a steering mirror that allows the field of view to be steered up to 30 degrees forward and aft, to keep the local magnetic meridian in the field of view. The detectors are micro channel plate (MCP) intensified FUV tubes with the phosphor fiber-optically coupled to Charge Coupled Devices (CCDs). The dual stack MCP-s amplify the photoelectron signals to dominate the CCD noise and the rapidly scanned frames are co-added to digitally create 12-second integrated images. Digital on-board signal processing is used to compensate for geometric distortion and satellite motion and to achieve data compression. The instrument was originally aligned in visible light by using a special grating and visible cameras. Final alignment, functional and environmental testing and calibration were performed in a large vacuum chamber with a UV source. The test and calibration program showed that ICON FUV meets its design requirements and is ready to be launched on the ICON spacecraft.

High Temperature Calibration of Thermal Imagers for Infrared Measurements on Military Platforms

&lt;p&gt;Calibration of thermal imaging system is not a straight forward process and hence manufacturers suggest re-calibration at factory itself. However, it is time consuming and expensive. A few research papers refer various approaches to perform low temperature calibration considering the wide requirement of low temperature measurements (typically less than 150 °C). However, no reference is available in open literature about high temperature calibration of thermal imagers. Hence, the possibility of high temperature calibration of thermal imaging systems has been explored using high temperature blackbody sources available at laboratory. With the use of neutral density filters, calibration has been performed in mid-wave (3.7 μm - 4.8 μm) and long-wave (7.7 μm - 9.5 μm) bands of imagers for IR measurements. The developed calibration has also been tested for field measurements.&lt;/p&gt;

Nano‐plasmonic chirped metal‐stripes polarimeter for dual‐band infrared detection

A novel chirped metal structure (CMS) is developed for polarimetric enhanced detection of both mid-wave (MW) (3–5 µm) and long-wave (LW) infrared (IR) wavelength bands (8–14 µm). The nano-scale structure consists of parallel sub-wavelength chirped-width stripes together with graded-width separating gaps. The CMS allows plasmonically enhanced polarisation-sensitive absorption of dual-bands simultaneously in underneath IR detection device. The finite-difference-time-domain method is utilised to numerically evaluate gold CMS structure on an IR detector. Simulations show an excellent performance with high plasmonic absorption enhancement and polarisation extinction-ratio over the continuous wavelength range 3–14 µm. The maximum recorded extinction-ratios are 2900:1 and 400:1 in the LW and MW bands, respectively. The maximum estimated plasmonic absorption enhancements for TM-polarisation in the LW and MW bands are 96 and 16%, respectively. The suppression of TE-polarisation absorption is almost 100% over both bands.

Influence of ligand donor-acceptor properties on the structure, optical, and electrochemical characteristics of Ir(III) complexes with cyclometallated 2-phenylbenzotiazole

The cis-C,C-structure of a series of cyclometallated Ir(III) complexes with 2-phenylbenzotiazole was determined by the methods of X-ray diffraction (XRD) analysis, 1H, 13C, 31P NMR, and IR spectroscopy. Long-wave absorption bands, phosphorescence, and processes of electrochemical oxidation and reduction of the complexes were assigned to the transfer of electrons presumably located on dπ and π* orbitals of cyclometallated 2-phenylbenzotiazole. The decrease in donor and acceptor properties of the ligands leads to the blue shift of absorption spectra and phosphorescence and to the anodic shift of oxidation and reduction potentials of the complexes.

Tunable Optical Properties of Ag–TiO2 Nanorod Composites Based on Interparticle Plasmon Coupling

The metal–semiconductor composites with unique optical properties are highly desirable. Here we report that Ag–TiO2 nanorod composites with two distinctive absorption peaks exhibit tunable plasmon coupling behaviors. The intensity of the long-wave absorption could be enhanced by modifying the geometry of TiO2 particles, while such absorption is due to the plasmon coupling between the Ag particles. The long-wave absorption bands can be tuned by varying the reaction time and changing the amount of silver acetate. Furthermore, the Ag–TiO2 composites were also prepared by photochemical reduction method which confirmed the previous properties. These results may help to design metal–semiconductor systems with desirable optical properties.

Recombination luminescence in alkali metal sulfates

In this paper we present the results of investigation of the nature of intrinsic luminescence caused by photon excitation in a wide spectral range from 10.3 eV to 4 eV at a temperature of 15–300 K. It is shown that in alkali metal sulfates the main emission band formed after excitation by X-rays and photons with an energy of 9–11 eV and 4–7.5 eV at 15–300 K is located in the spectral range of 3.65–3.9 eV. When the sulfates are excited by 4–7.75 eV photons, in addition to the emission band at 3.65–3.9 eV the other effective long-wave band at 3.1–2.5 eV appears. It is assumed that the 3.65–3.9 eV radiation results from the recombination of electrons with unevenly located holes of SO4− type. The long-wave emission bands in the alkali metal sulfates may be connected with the formation of electron-hole trapping centers after irradiation by photons with energies above 4.4 eV.

A generalized formulation for downscaling data based on Fourier Transform and inversion: Mathematical rationale and application to the Max-Planck-Institute aerosol climatology data

Occasionally, a need arises to downscale a time series of data from a coarse temporal resolution to a finer one, a typical example being from monthly means to daily means. For this case, daily means derived as such are used as inputs of climatic or atmospheric models so that the model results may exhibit variance on the daily time scale and retain the monthly mean of the original data set without an abrupt change from the end of one month to the beginning of the next. Different methods have been developed which often need assumptions, free parameters and the solution of simultaneous equations. Here we derive a generalized formulation by means of Fourier transform and inversion so that it can be used to directly compute daily means from a series of an arbitrary number of monthly means. The formulation can be used to transform any coarse temporal resolution to a finer one. From the derived results, the original data can be recovered almost identically. As a real application, we use this method to derive the daily counterpart of the MAC-v1 aerosol climatology that provides monthly mean aerosol properties for 18 shortwave bands and 12 longwave bands for the years from 1860 to 2100. The derived daily means are to be used as inputs of the shortwave and longwave algorithms of the NASA GEWEX SRB project.